[android] Re-factor TextInputViews

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogFragment.java

@@ -19,7 +19,7 @@ import org.briarproject.briar.android.controller.handler.UiExceptionHandler;
 import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 
 import java.util.List;
 
@@ -32,10 +32,11 @@ import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
 import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
+import static org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class ReblogFragment extends BaseFragment implements TextInputListener {
+public class ReblogFragment extends BaseFragment implements SendListener {
 
 	public static final String TAG = ReblogFragment.class.getName();
 
@@ -80,7 +81,8 @@ public class ReblogFragment extends BaseFragment implements TextInputListener {
 		View v = inflater.inflate(R.layout.fragment_reblog, container, false);
 		ui = new ViewHolder(v);
 		ui.post.setTransitionName(postId);
-		ui.input.setSendButtonEnabled(false);
+		ui.input.setEnabled(false);
+		ui.input.setMaxTextLength(MAX_BLOG_POST_TEXT_LENGTH);
 		showProgressBar();
 
 		return v;
@@ -116,7 +118,7 @@ public class ReblogFragment extends BaseFragment implements TextInputListener {
 		ui.post.hideReblogButton();
 
 		ui.input.setListener(this);
-		ui.input.setSendButtonEnabled(true);
+		ui.input.setEnabled(true);
 		ui.scrollView.post(() -> ui.scrollView.fullScroll(FOCUS_DOWN));
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/blog/WriteBlogPostActivity.java

@@ -4,8 +4,6 @@ import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
-import android.text.Editable;
-import android.text.TextWatcher;
 import android.view.KeyEvent;
 import android.view.MenuItem;
 import android.widget.ProgressBar;
@@ -23,7 +21,7 @@ import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.view.TextInputView;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPost;
@@ -40,13 +38,12 @@ import static android.view.View.VISIBLE;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.bramble.util.StringUtils.truncateUtf8;
 import static org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class WriteBlogPostActivity extends BriarActivity
-		implements OnEditorActionListener, TextInputListener {
+		implements OnEditorActionListener, SendListener {
 
 	private static final Logger LOG =
 			Logger.getLogger(WriteBlogPostActivity.class.getName());
@@ -78,23 +75,7 @@ public class WriteBlogPostActivity extends BriarActivity
 		setContentView(R.layout.activity_write_blog_post);
 
 		input = findViewById(R.id.textInput);
-		input.setSendButtonEnabled(false);
-		input.addTextChangedListener(new TextWatcher() {
-			@Override
-			public void beforeTextChanged(CharSequence s, int start, int count,
-					int after) {
-			}
-
-			@Override
-			public void onTextChanged(CharSequence s, int start, int before,
-					int count) {
-			}
-
-			@Override
-			public void afterTextChanged(Editable s) {
-				enableOrDisablePublishButton();
-			}
-		});
+		input.setMaxTextLength(MAX_BLOG_POST_TEXT_LENGTH);
 		input.setListener(this);
 
 		progressBar = findViewById(R.id.progressBar);
@@ -134,20 +115,15 @@ public class WriteBlogPostActivity extends BriarActivity
 		return true;
 	}
 
-	private void enableOrDisablePublishButton() {
-		input.setSendButtonEnabled(!input.isEmpty());
-	}
-
 	@Override
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
-		if (isNullOrEmpty(text)) return;
+		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		// hide publish button, show progress bar
 		input.hideSoftKeyboard();
 		input.setVisibility(GONE);
 		progressBar.setVisibility(VISIBLE);
 
-		text = truncateUtf8(text, MAX_BLOG_POST_TEXT_LENGTH);
 		storePost(text);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -65,7 +65,7 @@ import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextInputView.AttachImageListener;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.BlogSharingManager;
 import org.briarproject.briar.api.client.ProtocolStateException;
@@ -118,7 +118,6 @@ import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.bramble.util.StringUtils.truncateUtf8;
 import static org.briarproject.briar.android.TestingConstants.FEATURE_FLAG_IMAGE_ATTACHMENTS;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_ATTACH_IMAGE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_INTRODUCTION;
@@ -136,7 +135,7 @@ import static uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt.S
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class ConversationActivity extends BriarActivity
-		implements EventListener, ConversationListener, TextInputListener,
+		implements EventListener, ConversationListener, SendListener,
 		TextCache, AttachmentCache, AttachImageListener {
 
 	public static final String CONTACT_ID = "briar.CONTACT_ID";
@@ -256,6 +255,8 @@ public class ConversationActivity extends BriarActivity
 		list.setEmptyText(getString(R.string.no_private_messages));
 
 		textInputView = findViewById(R.id.text_input_container);
+		textInputView.setMaxTextLength(MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
+		textInputView.setEnabled(false);
 		textInputView.setListener(this);
 		if (FEATURE_FLAG_IMAGE_ATTACHMENTS) {
 			textInputView.setAttachImageListener(this);
@@ -416,7 +417,7 @@ public class ConversationActivity extends BriarActivity
 		runOnUiThreadUnlessDestroyed(() -> {
 			if (revision == adapter.getRevision()) {
 				adapter.incrementRevision();
-				textInputView.setSendButtonEnabled(true);
+				textInputView.setEnabled(true);
 				List<ConversationItem> items = createItems(headers);
 				adapter.addAll(items);
 				list.showData();
@@ -592,16 +593,15 @@ public class ConversationActivity extends BriarActivity
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
 		if (!imageUris.isEmpty()) {
 			Toast.makeText(this, "Not yet implemented.", LENGTH_LONG).show();
-			textInputView.setText("");
+			textInputView.clearText();
 			return;
 		}
-		if (isNullOrEmpty(text)) return;
-		text = truncateUtf8(text, MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
+		if (isNullOrEmpty(text)) throw new AssertionError();
 		long timestamp = System.currentTimeMillis();
 		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
 		if (messagingGroupId == null) loadGroupId(text, timestamp);
 		else createMessage(text, timestamp);
-		textInputView.setText("");
+		textInputView.clearText();
 	}
 
 	private long getMinTimestampForNewMessage() {

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -23,7 +23,7 @@ import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 import org.briarproject.briar.api.introduction.IntroductionManager;
 
 import java.util.List;
@@ -40,14 +40,13 @@ import static android.view.View.VISIBLE;
 import static android.widget.Toast.LENGTH_SHORT;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.StringUtils.truncateUtf8;
 import static org.briarproject.briar.android.util.UiUtils.getContactDisplayName;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAX_INTRODUCTION_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class IntroductionMessageFragment extends BaseFragment
-		implements TextInputListener {
+		implements SendListener {
 
 	public static final String TAG =
 			IntroductionMessageFragment.class.getName();
@@ -103,7 +102,8 @@ public class IntroductionMessageFragment extends BaseFragment
 		View v = inflater.inflate(R.layout.introduction_message, container,
 				false);
 		ui = new ViewHolder(v);
-		ui.message.setSendButtonEnabled(false);
+		ui.message.setMaxTextLength(MAX_INTRODUCTION_TEXT_LENGTH);
+		ui.message.setEnabled(false);
 
 		return v;
 	}
@@ -168,7 +168,7 @@ public class IntroductionMessageFragment extends BaseFragment
 				// show views
 				ui.notPossible.setVisibility(GONE);
 				ui.message.setVisibility(VISIBLE);
-				ui.message.setSendButtonEnabled(true);
+				ui.message.setEnabled(true);
 				ui.message.showSoftKeyboard();
 			} else {
 				ui.notPossible.setVisibility(VISIBLE);
@@ -192,11 +192,8 @@ public class IntroductionMessageFragment extends BaseFragment
 	@Override
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
 		// disable button to prevent accidental double invitations
-		ui.message.setSendButtonEnabled(false);
+		ui.message.setEnabled(false);
 
-		if (text != null) {
-			text = truncateUtf8(text, MAX_INTRODUCTION_TEXT_LENGTH);
-		}
 		makeIntroduction(contact1, contact2, text);
 
 		// don't wait for the introduction to be made before finishing activity

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupActivity.java

@@ -196,7 +196,7 @@ public class GroupActivity extends
 
 	private void setGroupEnabled(boolean enabled) {
 		isDissolved = !enabled;
-		textInput.setSendButtonEnabled(enabled);
+		textInput.setEnabled(enabled);
 		list.getRecyclerView().setAlpha(enabled ? 1f : 0.5f);
 
 		if (!enabled) {

briar-android/src/main/java/org/briarproject/briar/android/privategroup/creation/CreateGroupController.java

@@ -1,5 +1,7 @@
 package org.briarproject.briar.android.privategroup.creation;
 
+import android.support.annotation.Nullable;
+
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
@@ -18,6 +20,7 @@ public interface CreateGroupController
 			ResultExceptionHandler<GroupId, DbException> result);
 
 	void sendInvitation(GroupId g, Collection<ContactId> contacts,
-			String text, ResultExceptionHandler<Void, DbException> result);
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> result);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/privategroup/creation/CreateGroupControllerImpl.java

@@ -1,5 +1,7 @@
 package org.briarproject.briar.android.privategroup.creation;
 
+import android.support.annotation.Nullable;
+
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
@@ -123,7 +125,8 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 
 	@Override
 	public void sendInvitation(GroupId g, Collection<ContactId> contactIds,
-			String text, ResultExceptionHandler<Void, DbException> handler) {
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
 		runOnDbThread(() -> {
 			try {
 				LocalAuthor localAuthor = identityManager.getLocalAuthor();
@@ -144,7 +147,7 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 	}
 
 	private void signInvitations(GroupId g, LocalAuthor localAuthor,
-			Collection<Contact> contacts, String text,
+			Collection<Contact> contacts, @Nullable String text,
 			ResultExceptionHandler<Void, DbException> handler) {
 		cryptoExecutor.execute(() -> {
 			long timestamp = clock.currentTimeMillis();
@@ -160,15 +163,14 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 	}
 
 	private void sendInvitations(GroupId g,
-			Collection<InvitationContext> contexts, String text,
+			Collection<InvitationContext> contexts, @Nullable String text,
 			ResultExceptionHandler<Void, DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				String txt = text.isEmpty() ? null : text;
 				for (InvitationContext context : contexts) {
 					try {
 						groupInvitationManager.sendInvitation(g,
-								context.contactId, txt, context.timestamp,
+								context.contactId, text, context.timestamp,
 								context.signature);
 					} catch (NoSuchContactException e) {
 						// Continue

briar-android/src/main/java/org/briarproject/briar/android/privategroup/creation/GroupInviteActivity.java

@@ -55,7 +55,7 @@ public class GroupInviteActivity extends ContactSelectorActivity
 	}
 
 	@Override
-	public boolean onButtonClick(String text) {
+	public void onButtonClick(@Nullable String text) {
 		if (groupId == null)
 			throw new IllegalStateException("GroupId was not initialized");
 		controller.sendInvitation(groupId, contacts, text,
@@ -72,7 +72,6 @@ public class GroupInviteActivity extends ContactSelectorActivity
 						handleDbException(exception);
 					}
 				});
-		return true;
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/sharing/BaseMessageFragment.java

@@ -6,7 +6,6 @@ import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
 import android.support.annotation.UiThread;
-import android.support.design.widget.Snackbar;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
 import android.view.View;
@@ -18,17 +17,14 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.LargeTextInputView;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 
 import java.util.List;
 
-import static android.support.design.widget.Snackbar.LENGTH_SHORT;
-import static org.briarproject.bramble.util.StringUtils.utf8IsTooLong;
-
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public abstract class BaseMessageFragment extends BaseFragment
-		implements TextInputListener {
+		implements SendListener {
 
 	protected LargeTextInputView message;
 	private MessageFragmentListener listener;
@@ -48,6 +44,7 @@ public abstract class BaseMessageFragment extends BaseFragment
 		View v = inflater.inflate(R.layout.fragment_message, container,
 				false);
 		message = v.findViewById(R.id.messageView);
+		message.setMaxTextLength(listener.getMaximumTextLength());
 		message.setButtonText(getString(getButtonText()));
 		message.setHint(getHintText());
 		message.setListener(this);
@@ -84,20 +81,11 @@ public abstract class BaseMessageFragment extends BaseFragment
 
 	@Override
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
-		if (text == null) return;
-		if (utf8IsTooLong(text, listener.getMaximumTextLength())) {
-			Snackbar.make(message, R.string.text_too_long, LENGTH_SHORT).show();
-			return;
-		}
-
 		// disable button to prevent accidental double actions
-		message.setSendButtonEnabled(false);
+		message.setEnabled(false);
 		message.hideSoftKeyboard();
 
-		if(!listener.onButtonClick(text)) {
-			message.setSendButtonEnabled(true);
-			message.showSoftKeyboard();
-		}
+		listener.onButtonClick(text);
 	}
 
 	@UiThread
@@ -108,8 +96,7 @@ public abstract class BaseMessageFragment extends BaseFragment
 
 		void setTitle(@StringRes int titleRes);
 
-		/** Returns true when the button click has been consumed. */
-		boolean onButtonClick(String text);
+		void onButtonClick(@Nullable String text);
 
 		int getMaximumTextLength();
 

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareActivity.java

@@ -41,13 +41,12 @@ public abstract class ShareActivity extends ContactSelectorActivity
 
 	@UiThread
 	@Override
-	public boolean onButtonClick(String text) {
+	public void onButtonClick(@Nullable String text) {
 		share(contacts, text);
 		setResult(RESULT_OK);
 		supportFinishAfterTransition();
-		return true;
 	}
 
-	abstract void share(Collection<ContactId> contacts, String text);
+	abstract void share(Collection<ContactId> contacts, @Nullable String text);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareBlogActivity.java

@@ -51,7 +51,7 @@ public class ShareBlogActivity extends ShareActivity {
 	}
 
 	@Override
-	void share(Collection<ContactId> contacts, String text) {
+	void share(Collection<ContactId> contacts, @Nullable String text) {
 		controller.share(groupId, contacts, text,
 				new UiExceptionHandler<DbException>(this) {
 					@Override

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareBlogController.java

@@ -9,10 +9,12 @@ import org.briarproject.briar.android.controller.handler.ExceptionHandler;
 
 import java.util.Collection;
 
+import javax.annotation.Nullable;
+
 public interface ShareBlogController
 		extends ContactSelectorController<SelectableContactItem> {
 
-	void share(GroupId g, Collection<ContactId> contacts, String text,
+	void share(GroupId g, Collection<ContactId> contacts, @Nullable String text,
 			ExceptionHandler<DbException> handler);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareBlogControllerImpl.java

@@ -20,12 +20,12 @@ import java.util.Collection;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @Immutable
 @NotNullByDefault
@@ -56,17 +56,16 @@ class ShareBlogControllerImpl extends ContactSelectorControllerImpl
 	}
 
 	@Override
-	public void share(GroupId g, Collection<ContactId> contacts, String text,
-			ExceptionHandler<DbException> handler) {
+	public void share(GroupId g, Collection<ContactId> contacts, @Nullable
+			String text, ExceptionHandler<DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				String txt = isNullOrEmpty(text) ? null : text;
 				for (ContactId c : contacts) {
 					try {
 						long time = Math.max(clock.currentTimeMillis(),
 								conversationManager.getGroupCount(c)
 										.getLatestMsgTime() + 1);
-						blogSharingManager.sendInvitation(g, c, txt, time);
+						blogSharingManager.sendInvitation(g, c, text, time);
 					} catch (NoSuchContactException | NoSuchGroupException e) {
 						logException(LOG, WARNING, e);
 					}

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareForumActivity.java

@@ -51,7 +51,7 @@ public class ShareForumActivity extends ShareActivity {
 	}
 
 	@Override
-	void share(Collection<ContactId> contacts, String text) {
+	void share(Collection<ContactId> contacts, @Nullable String text) {
 		controller.share(groupId, contacts, text,
 				new UiExceptionHandler<DbException>(this) {
 					@Override

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareForumController.java

@@ -9,10 +9,12 @@ import org.briarproject.briar.android.controller.handler.ExceptionHandler;
 
 import java.util.Collection;
 
+import javax.annotation.Nullable;
+
 public interface ShareForumController
 		extends ContactSelectorController<SelectableContactItem> {
 
-	void share(GroupId g, Collection<ContactId> contacts, String text,
+	void share(GroupId g, Collection<ContactId> contacts, @Nullable String text,
 			ExceptionHandler<DbException> handler);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareForumControllerImpl.java

@@ -13,19 +13,19 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
 import org.briarproject.briar.android.controller.handler.ExceptionHandler;
-import org.briarproject.briar.api.forum.ForumSharingManager;
 import org.briarproject.briar.api.conversation.ConversationManager;
+import org.briarproject.briar.api.forum.ForumSharingManager;
 
 import java.util.Collection;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @Immutable
 @NotNullByDefault
@@ -57,16 +57,15 @@ class ShareForumControllerImpl extends ContactSelectorControllerImpl
 
 	@Override
 	public void share(GroupId g, Collection<ContactId> contacts,
-			String text, ExceptionHandler<DbException> handler) {
+			@Nullable String text, ExceptionHandler<DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				String txt = isNullOrEmpty(text) ? null : text;
 				for (ContactId c : contacts) {
 					try {
 						long time = Math.max(clock.currentTimeMillis(),
 								conversationManager.getGroupCount(c)
 										.getLatestMsgTime() + 1);
-						forumSharingManager.sendInvitation(g, c, txt, time);
+						forumSharingManager.sendInvitation(g, c, text, time);
 					} catch (NoSuchContactException | NoSuchGroupException e) {
 						logException(LOG, WARNING, e);
 					}

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListActivity.java

@@ -28,7 +28,7 @@ import org.briarproject.briar.android.threaded.ThreadListController.ThreadListDa
 import org.briarproject.briar.android.threaded.ThreadListController.ThreadListListener;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.view.TextInputView;
-import org.briarproject.briar.android.view.TextInputView.TextInputListener;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
 import org.briarproject.briar.android.view.UnreadMessageButton;
 import org.briarproject.briar.api.client.NamedGroup;
 import org.thoughtcrime.securesms.components.KeyboardAwareLinearLayout;
@@ -44,14 +44,14 @@ import static android.support.design.widget.Snackbar.make;
 import static android.support.v7.widget.RecyclerView.NO_POSITION;
 import static android.support.v7.widget.RecyclerView.SCROLL_STATE_IDLE;
 import static java.util.logging.Level.INFO;
-import static org.briarproject.bramble.util.StringUtils.utf8IsTooLong;
+import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.briar.android.threaded.ThreadItemAdapter.UnreadCount;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadItem, A extends ThreadItemAdapter<I>>
 		extends BriarActivity
-		implements ThreadListListener<I>, TextInputListener, SharingListener,
+		implements ThreadListListener<I>, SendListener, SharingListener,
 		ThreadItemListener<I>, ThreadListDataSource {
 
 	protected static final String KEY_REPLY_ID = "replyId";
@@ -88,6 +88,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 		getController().setGroupId(groupId);
 
 		textInput = findViewById(R.id.text_input_container);
+		textInput.setMaxTextLength(getMaxTextLength());
 		textInput.setListener(this);
 		list = findViewById(R.id.list);
 		layoutManager = new LinearLayoutManager(this);
@@ -268,7 +269,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	@Override
 	public void onBackPressed() {
 		if (adapter.getHighlightedItem() != null) {
-			textInput.setText("");
+			textInput.clearText();
 			replyId = null;
 			updateTextInput();
 		} else {
@@ -351,12 +352,8 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 
 	@Override
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
-		if (text == null || text.trim().length() == 0)
-			return;
-		if (utf8IsTooLong(text, getMaxTextLength())) {
-			displaySnackbar(R.string.text_too_long);
-			return;
-		}
+		if (isNullOrEmpty(text)) throw new AssertionError();
+
 		I replyItem = adapter.getHighlightedItem();
 		UiResultExceptionHandler<I, DbException> handler =
 				new UiResultExceptionHandler<I, DbException>(this) {
@@ -372,7 +369,7 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 				};
 		getController().createAndStoreMessage(text, replyItem, handler);
 		textInput.hideSoftKeyboard();
-		textInput.setText("");
+		textInput.clearText();
 		replyId = null;
 		updateTextInput();
 	}

briar-android/src/main/java/org/briarproject/briar/android/view/TextAttachmentController.java

@@ -12,8 +12,6 @@ import android.support.design.widget.FloatingActionButton;
 import android.support.v4.view.AbsSavedState;
 import android.support.v7.graphics.Palette;
 import android.support.v7.widget.AppCompatImageButton;
-import android.text.Editable;
-import android.text.TextWatcher;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ImageView;
@@ -22,7 +20,6 @@ import com.bumptech.glide.load.DataSource;
 import com.bumptech.glide.load.engine.GlideException;
 import com.bumptech.glide.request.RequestListener;
 import com.bumptech.glide.request.target.Target;
-import com.vanniktech.emoji.EmojiEditText;
 
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.conversation.glide.GlideApp;
@@ -48,23 +45,24 @@ import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static com.bumptech.glide.load.resource.bitmap.DownsampleStrategy.FIT_CENTER;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
+import static java.util.Objects.requireNonNull;
 
 @UiThread
-class TextInputAttachmentController implements TextWatcher {
+class TextAttachmentController extends TextSendController {
 
-	private final EmojiEditText editText;
-	private final View sendButton;
 	private final AppCompatImageButton imageButton;
 	private final ViewGroup imageLayout;
 	private final ImageView imageView;
 
-	private final AttachImageListener listener;
+	@Nullable
+	private AttachImageListener imageListener;
 
-	private String textHint;
+	private CharSequence textHint;
 	private List<Uri> imageUris = emptyList();
 
-	public TextInputAttachmentController(View v, EmojiEditText editText,
-			View sendButton, AttachImageListener listener) {
+	TextAttachmentController(View v, View sendButton,
+			TextInputController textInput) {
+		super(sendButton, textInput, true);
 
 		imageLayout = v.findViewById(R.id.imageLayout);
 		imageView = v.findViewById(R.id.imageView);
@@ -72,20 +70,37 @@ class TextInputAttachmentController implements TextWatcher {
 				v.findViewById(R.id.imageCancelButton);
 		imageButton = v.findViewById(R.id.imageButton);
 
-		this.listener = listener;
-		this.sendButton = sendButton;
-		this.editText = editText;
-		this.textHint = editText.getHint().toString();
+		textHint = textInput.getHint();
 
-		editText.addTextChangedListener(this);
 		imageButton.setOnClickListener(view -> onImageButtonClicked());
 		imageCancelButton.setOnClickListener(view -> {
-			editText.setText(null);
+			textInput.clearText();
 			reset();
 		});
+	}
+
+	public void setAttachImageListener(AttachImageListener imageListener) {
+		this.imageListener = imageListener;
 		showImageButton(true);
 	}
 
+	@Override
+	public void onTextValidityChanged(boolean isEmpty) {
+		if (imageUris.isEmpty()) showImageButton(isEmpty);
+	}
+
+	@Override
+	void onSendButtonClicked() {
+		if (listener != null) {
+			if (textInput.isTooLong()) {
+				textInput.showError();
+				return;
+			}
+			listener.onSendClick(textInput.getText(), imageUris);
+		}
+		reset();
+	}
+
 	private void onImageButtonClicked() {
 		Intent intent = new Intent(SDK_INT >= 19 ?
 				ACTION_OPEN_DOCUMENT : ACTION_GET_CONTENT);
@@ -93,7 +108,7 @@ class TextInputAttachmentController implements TextWatcher {
 		intent.setType("image/*");
 		if (SDK_INT >= 18)  // TODO set true to allow attaching multiple images
 			intent.putExtra(EXTRA_ALLOW_MULTIPLE, false);
-		listener.onAttachImage(intent);
+		requireNonNull(imageListener).onAttachImage(intent);
 	}
 
 	void onImageReceived(@Nullable Intent resultData) {
@@ -114,7 +129,7 @@ class TextInputAttachmentController implements TextWatcher {
 	private void onNewUris() {
 		if (imageUris.isEmpty()) return;
 		showImageButton(false);
-		editText.setHint(R.string.image_caption_hint);
+		textInput.setHint(R.string.image_caption_hint);
 		imageLayout.setVisibility(VISIBLE);
 		GlideApp.with(imageView)
 				.asBitmap()
@@ -135,7 +150,7 @@ class TextInputAttachmentController implements TextWatcher {
 							Object model, Target<Bitmap> target,
 							DataSource dataSource, boolean isFirstResource) {
 						Palette.from(resource).generate(
-								TextInputAttachmentController.this::onPaletteGenerated);
+								TextAttachmentController.this::onPaletteGenerated);
 						return false;
 					}
 				})
@@ -158,11 +173,12 @@ class TextInputAttachmentController implements TextWatcher {
 	private void showImageButton(boolean showImageButton) {
 		if (showImageButton) {
 			imageButton.setVisibility(VISIBLE);
+			sendButton.setEnabled(false);
 			if (SDK_INT <= 15) {
 				sendButton.setVisibility(INVISIBLE);
+				imageButton.setEnabled(true);
 			} else {
 				sendButton.clearAnimation();
-				sendButton.setEnabled(false);
 				sendButton.animate().alpha(0f).withEndAction(() -> {
 					sendButton.setVisibility(INVISIBLE);
 					imageButton.setEnabled(true);
@@ -172,51 +188,25 @@ class TextInputAttachmentController implements TextWatcher {
 			}
 		} else {
 			sendButton.setVisibility(VISIBLE);
+			// enable/disable buttons right away to allow fast sending
+			sendButton.setEnabled(true);
+			imageButton.setEnabled(false);
 			if (SDK_INT <= 15) {
 				imageButton.setVisibility(INVISIBLE);
 			} else {
 				sendButton.clearAnimation();
 				sendButton.animate().alpha(1f).start();
 				imageButton.clearAnimation();
-				imageButton.setEnabled(false);
-				imageButton.animate().alpha(0f).withEndAction(() -> {
-					imageButton.setVisibility(INVISIBLE);
-					sendButton.setEnabled(true);
-				}).start();
+				imageButton.animate().alpha(0f).withEndAction(() ->
+						imageButton.setVisibility(INVISIBLE)
+				).start();
 			}
 		}
 	}
 
-	@Override
-	public void beforeTextChanged(CharSequence s, int start, int count,
-			int after) {
-		// noop
-	}
-
-	@Override
-	public void onTextChanged(CharSequence s, int start, int before,
-			int count) {
-		if (start != 0 || !imageUris.isEmpty()) return;
-		if (s.length() > 0) showImageButton(false);
-		else showImageButton(true);
-	}
-
-	@Override
-	public void afterTextChanged(Editable s) {
-		// noop
-	}
-
-	public List<Uri> getUris() {
-		return imageUris;
-	}
-
-	public void saveHint(String hint) {
-		textHint = hint;
-	}
-
-	void reset() {
+	private void reset() {
 		// restore hint
-		editText.setHint(textHint);
+		textInput.setHint(textHint);
 		// hide image layout
 		imageLayout.setVisibility(GONE);
 		// reset image URIs

briar-android/src/main/java/org/briarproject/briar/android/view/TextInputController.java

@@ -0,0 +1,165 @@
+package org.briarproject.briar.android.view;
+
+import android.content.Context;
+import android.graphics.Rect;
+import android.os.IBinder;
+import android.support.annotation.Nullable;
+import android.support.annotation.StringRes;
+import android.support.annotation.UiThread;
+import android.support.design.widget.Snackbar;
+import android.support.v7.widget.AppCompatImageButton;
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.view.View;
+import android.view.inputmethod.InputMethodManager;
+
+import com.vanniktech.emoji.EmojiEditText;
+import com.vanniktech.emoji.EmojiPopup;
+import com.vanniktech.emoji.RecentEmoji;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+
+import static android.content.Context.INPUT_METHOD_SERVICE;
+import static android.support.design.widget.Snackbar.LENGTH_SHORT;
+import static android.view.inputmethod.InputMethodManager.SHOW_IMPLICIT;
+import static java.util.Objects.requireNonNull;
+import static org.briarproject.briar.android.view.TextInputView.TextValidityListener;
+
+@UiThread
+@NotNullByDefault
+class TextInputController implements TextWatcher {
+
+	private final Context ctx;
+	private final AppCompatImageButton emojiToggle;
+	private final EmojiPopup emojiPopup;
+	private final EmojiEditText editText;
+
+	private @Nullable TextValidityListener listener;
+	private int maxLength = Integer.MAX_VALUE;
+	private final boolean emptyTextAllowed;
+	private boolean isEmpty = true;
+
+	TextInputController(View rootView, AppCompatImageButton emojiToggle,
+			EmojiEditText editText, RecentEmoji recentEmoji,
+			boolean emptyTextAllowed) {
+		ctx = rootView.getContext();
+		this.emojiToggle = emojiToggle;
+		this.editText = editText;
+		this.editText.addTextChangedListener(this);
+		this.editText.setOnClickListener(v -> showSoftKeyboard());
+		emojiPopup = EmojiPopup.Builder
+				.fromRootView(rootView)
+				.setRecentEmoji(recentEmoji)
+				.setOnEmojiPopupShownListener(this::showKeyboardIcon)
+				.setOnEmojiPopupDismissListener(this::showEmojiIcon)
+				.build(this.editText);
+		this.emojiToggle.setOnClickListener(v -> emojiPopup.toggle());
+		this.emptyTextAllowed = emptyTextAllowed;
+	}
+
+	@Override
+	public void beforeTextChanged(CharSequence s, int start, int count,
+			int after) {
+	}
+
+	@Override
+	public void onTextChanged(CharSequence s, int start, int before,
+			int count) {
+		if (emptyTextAllowed || listener == null) return;
+		if (s.toString().trim().length() == 0) {
+			if (!isEmpty) {
+				isEmpty = true;
+				listener.onTextValidityChanged(true);
+			}
+		} else if (isEmpty) {
+			isEmpty = false;
+			listener.onTextValidityChanged(false);
+		}
+	}
+
+	@Override
+	public void afterTextChanged(Editable s) {
+	}
+
+	void setMaxLength(int maxLength) {
+		this.maxLength = maxLength;
+	}
+
+	boolean isTooLong() {
+		return editText.getText() != null &&
+				editText.getText().toString().trim().length() > maxLength;
+	}
+
+	/**
+	 * Returns the current text or {@code null},
+	 * if it is empty or only consists of white-spaces.
+	 */
+	@Nullable
+	String getText() {
+		Editable editable = editText.getText();
+		if (editable == null || editable.toString().trim().length() == 0)
+			return null;
+		return editable.toString().trim();
+	}
+
+	void clearText() {
+		editText.setText(null);
+	}
+
+	CharSequence getHint() {
+		return editText.getHint();
+	}
+
+	void setHint(@StringRes int res) {
+		setHint(ctx.getString(res));
+	}
+
+	void setHint(CharSequence hint) {
+		editText.setHint(hint);
+	}
+
+	void setTextValidityListener(@Nullable TextValidityListener listener) {
+		this.listener = listener;
+	}
+
+	void showError() {
+		Snackbar.make(editText, R.string.text_too_long, LENGTH_SHORT).show();
+	}
+
+	boolean requestFocus(int direction, Rect previouslyFocusedRect) {
+		return editText.requestFocus(direction, previouslyFocusedRect);
+	}
+
+	void onDetachedFromWindow() {
+		if (emojiPopup.isShowing()) emojiPopup.dismiss();
+	}
+
+	void showSoftKeyboard() {
+		Object o = ctx.getSystemService(INPUT_METHOD_SERVICE);
+		InputMethodManager imm = (InputMethodManager) requireNonNull(o);
+		imm.showSoftInput(editText, SHOW_IMPLICIT);
+	}
+
+	void hideSoftKeyboard() {
+		if (emojiPopup.isShowing()) emojiPopup.dismiss();
+		IBinder token = editText.getWindowToken();
+		Object o = ctx.getSystemService(INPUT_METHOD_SERVICE);
+		InputMethodManager imm = (InputMethodManager) requireNonNull(o);
+		imm.hideSoftInputFromWindow(token, 0);
+	}
+
+	private void showEmojiIcon() {
+		emojiToggle.setImageResource(R.drawable.ic_emoji_toggle);
+	}
+
+	private void showKeyboardIcon() {
+		emojiToggle.setImageResource(R.drawable.ic_keyboard);
+	}
+
+	public void setEnabled(boolean enabled) {
+		editText.setEnabled(enabled);
+		emojiToggle.setEnabled(enabled);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/view/TextInputView.java

@@ -6,22 +6,17 @@ import android.content.Intent;
 import android.content.res.TypedArray;
 import android.graphics.Rect;
 import android.net.Uri;
-import android.os.IBinder;
 import android.os.Parcelable;
 import android.support.annotation.CallSuper;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
 import android.support.annotation.UiThread;
 import android.support.v7.widget.AppCompatImageButton;
-import android.text.Editable;
-import android.text.TextWatcher;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.View;
-import android.view.inputmethod.InputMethodManager;
 
 import com.vanniktech.emoji.EmojiEditText;
-import com.vanniktech.emoji.EmojiPopup;
 import com.vanniktech.emoji.RecentEmoji;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
@@ -34,11 +29,8 @@ import java.util.List;
 
 import javax.inject.Inject;
 
-import static android.content.Context.INPUT_METHOD_SERVICE;
 import static android.content.Context.LAYOUT_INFLATER_SERVICE;
 import static android.view.KeyEvent.KEYCODE_ENTER;
-import static android.view.inputmethod.InputMethodManager.SHOW_IMPLICIT;
-import static java.util.Collections.emptyList;
 import static java.util.Objects.requireNonNull;
 
 @UiThread
@@ -49,16 +41,14 @@ public class TextInputView extends KeyboardAwareLinearLayout {
 	@Inject
 	RecentEmoji recentEmoji;
 
-	@Nullable
-	TextInputListener listener;
-	@Nullable
-	TextInputAttachmentController attachmentController;
-
-	AppCompatImageButton emojiToggle;
+	TextInputController textInputController;
+	TextSendController textSendController;
 	EmojiEditText editText;
-	EmojiPopup emojiPopup;
 	View sendButton;
 
+	@Nullable
+	TextAttachmentController attachmentController;
+
 	public TextInputView(Context context) {
 		this(context, null);
 	}
@@ -90,34 +80,42 @@ public class TextInputView extends KeyboardAwareLinearLayout {
 
 	@CallSuper
 	protected void setUpViews(Context context, @Nullable AttributeSet attrs) {
-		emojiToggle = findViewById(R.id.emoji_toggle);
-		editText = findViewById(R.id.input_text);
-		emojiPopup = EmojiPopup.Builder
-				.fromRootView(this)
-				.setRecentEmoji(recentEmoji)
-				.setOnEmojiPopupShownListener(this::showKeyboardIcon)
-				.setOnEmojiPopupDismissListener(this::showEmojiIcon)
-				.build(editText);
-		sendButton = findViewById(R.id.btn_send);
-
 		// get attributes
 		TypedArray attributes = context.obtainStyledAttributes(attrs,
 				R.styleable.TextInputView);
 		String hint = attributes.getString(R.styleable.TextInputView_hint);
+		boolean allowEmptyText = attributes
+				.getBoolean(R.styleable.TextInputView_allowEmptyText, false);
+		boolean supportsAttachments = attributes
+				.getBoolean(R.styleable.TextInputView_supportsAttachments, false);
 		attributes.recycle();
 
-		if (hint != null) setHint(hint);
+		// set up input controller
+		AppCompatImageButton emojiToggle = findViewById(R.id.emoji_toggle);
+		editText = findViewById(R.id.input_text);
+		textInputController = new TextInputController(this, emojiToggle,
+				editText, recentEmoji, allowEmptyText);
+		if (hint != null) textInputController.setHint(hint);
 
-		emojiToggle.setOnClickListener(v -> emojiPopup.toggle());
-		editText.setOnClickListener(v -> showSoftKeyboard());
+		// set up sending controller
+		sendButton = findViewById(R.id.btn_send);
+		if (supportsAttachments) {
+			textSendController = new TextAttachmentController(this, sendButton,
+					textInputController);
+		} else {
+			textSendController = new TextSendController(sendButton,
+					textInputController, allowEmptyText);
+		}
+		textInputController.setTextValidityListener(textSendController);
+
+		// support sending with Ctrl+Enter
 		editText.setOnKeyListener((v, keyCode, event) -> {
 			if (keyCode == KEYCODE_ENTER && event.isCtrlPressed()) {
-				onSendButtonClicked();
+				textSendController.onSendButtonClicked();
 				return true;
 			}
 			return false;
 		});
-		sendButton.setOnClickListener(v -> onSendButtonClicked());
 	}
 
 	@Nullable
@@ -141,41 +139,13 @@ public class TextInputView extends KeyboardAwareLinearLayout {
 		}
 	}
 
-	public void setListener(TextInputListener listener) {
-		this.listener = listener;
+	public void setListener(SendListener listener) {
+		textSendController.setSendListener(listener);
 	}
 
-	/**
-	 * Call this during onCreate() to enable image attachment support.
-	 * Do not call it twice!
-	 */
 	public void setAttachImageListener(AttachImageListener imageListener) {
-		if (attachmentController != null) throw new IllegalStateException();
-		attachmentController = new TextInputAttachmentController(getRootView(),
-				editText, sendButton, imageListener
-		);
-	}
-
-	private void showEmojiIcon() {
-		emojiToggle.setImageResource(R.drawable.ic_emoji_toggle);
-	}
-
-	private void showKeyboardIcon() {
-		emojiToggle.setImageResource(R.drawable.ic_keyboard);
-	}
-
-	private void onSendButtonClicked() {
-		if (listener != null) {
-			Editable editable = editText.getText();
-			String text = editable == null || editable.length() == 0 ?
-					null : editable.toString();
-			List<Uri> imageUris = attachmentController == null ? emptyList() :
-					attachmentController.getUris();
-			listener.onSendClick(text, imageUris);
-		}
-		if (attachmentController != null) {
-			attachmentController.reset();
-		}
+		attachmentController = (TextAttachmentController) textSendController;
+		attachmentController.setAttachImageListener(imageListener);
 	}
 
 	public void onImageReceived(@Nullable Intent resultData) {
@@ -183,61 +153,54 @@ public class TextInputView extends KeyboardAwareLinearLayout {
 		attachmentController.onImageReceived(resultData);
 	}
 
+	@Override
+	public void setEnabled(boolean enabled) {
+		super.setEnabled(enabled);
+		textInputController.setEnabled(enabled);
+		textSendController.setEnabled(enabled);
+	}
+
 	@Override
 	public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
-		return editText.requestFocus(direction, previouslyFocusedRect);
+		return textInputController
+				.requestFocus(direction, previouslyFocusedRect);
 	}
 
 	@Override
 	public void onDetachedFromWindow() {
 		super.onDetachedFromWindow();
-		if (emojiPopup.isShowing()) emojiPopup.dismiss();
+		textInputController.onDetachedFromWindow();
 	}
 
-	public void setText(String text) {
-		editText.setText(text);
-	}
-
-	public boolean isEmpty() {
-		return editText.getText() == null || editText.getText().length() == 0;
+	public void clearText() {
+		textInputController.clearText();
 	}
 
 	public void setHint(@StringRes int res) {
-		setHint(getContext().getString(res));
+		textInputController.setHint(getContext().getString(res));
 	}
 
-	public void setHint(String hint) {
-		if (attachmentController != null) attachmentController.saveHint(hint);
-		editText.setHint(hint);
-	}
-
-	public void setSendButtonEnabled(boolean enabled) {
-		sendButton.setEnabled(enabled);
-	}
-
-	public void addTextChangedListener(TextWatcher watcher) {
-		editText.addTextChangedListener(watcher);
+	public void setMaxTextLength(int maxLength) {
+		textInputController.setMaxLength(maxLength);
 	}
 
 	public void showSoftKeyboard() {
-		Object o = getContext().getSystemService(INPUT_METHOD_SERVICE);
-		InputMethodManager imm = (InputMethodManager) requireNonNull(o);
-		imm.showSoftInput(editText, SHOW_IMPLICIT);
+		textInputController.showSoftKeyboard();
 	}
 
 	public void hideSoftKeyboard() {
-		if (emojiPopup.isShowing()) emojiPopup.dismiss();
-		IBinder token = editText.getWindowToken();
-		Object o = getContext().getSystemService(INPUT_METHOD_SERVICE);
-		InputMethodManager imm = (InputMethodManager) requireNonNull(o);
-		imm.hideSoftInputFromWindow(token, 0);
+		textInputController.hideSoftKeyboard();
+	}
+
+	interface TextValidityListener {
+		void onTextValidityChanged(boolean isEmpty);
 	}
 
 	public interface AttachImageListener {
 		void onAttachImage(Intent intent);
 	}
 
-	public interface TextInputListener {
+	public interface SendListener {
 		void onSendClick(@Nullable String text, List<Uri> imageUris);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/view/TextSendController.java

@@ -0,0 +1,62 @@
+package org.briarproject.briar.android.view;
+
+import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
+import android.view.View;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.android.view.TextInputView.SendListener;
+import org.briarproject.briar.android.view.TextInputView.TextValidityListener;
+
+import static java.util.Collections.emptyList;
+
+@UiThread
+@NotNullByDefault
+class TextSendController implements TextValidityListener {
+
+	protected final TextInputController textInput;
+	protected final View sendButton;
+	@Nullable
+	protected SendListener listener;
+	protected boolean enabled = true;
+
+	private final boolean allowEmptyText;
+	private boolean wasEmpty = true;
+
+	TextSendController(View sendButton, TextInputController textInput,
+			boolean allowEmptyText) {
+		this.sendButton = sendButton;
+		this.sendButton.setOnClickListener(v -> onSendButtonClicked());
+		this.sendButton.setEnabled(allowEmptyText);
+		this.textInput = textInput;
+		this.allowEmptyText = allowEmptyText;
+	}
+
+	@Override
+	public void onTextValidityChanged(boolean isEmpty) {
+		sendButton.setEnabled(enabled && !isEmpty);
+		wasEmpty = isEmpty;
+	}
+
+	public void setEnabled(boolean enabled) {
+		sendButton.setOnClickListener(
+				enabled ? v -> onSendButtonClicked() : null);
+		sendButton.setEnabled(!wasEmpty || allowEmptyText);
+		this.enabled = enabled;
+	}
+
+	void setSendListener(SendListener listener) {
+		this.listener = listener;
+	}
+
+	void onSendButtonClicked() {
+		if (listener != null) {
+			if (textInput.isTooLong()) {
+				textInput.showError();
+				return;
+			}
+			listener.onSendClick(textInput.getText(), emptyList());
+		}
+	}
+
+}