Make the blog post pager usable for the feed and individual blogs

briar-android/src/org/briarproject/android/blogs/BasePostPagerFragment.java

@@ -0,0 +1,187 @@
+package org.briarproject.android.blogs;
+
+import android.os.Bundle;
+import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentManager;
+import android.support.v4.app.FragmentStatePagerAdapter;
+import android.support.v4.view.ViewPager;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.briarproject.R;
+import org.briarproject.android.blogs.BaseController.OnBlogPostAddedListener;
+import org.briarproject.android.controller.handler.UiResultExceptionHandler;
+import org.briarproject.android.fragment.BaseFragment;
+import org.briarproject.api.blogs.BlogPostHeader;
+import org.briarproject.api.db.DbException;
+import org.briarproject.api.sync.MessageId;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+import static org.briarproject.android.blogs.BasePostPagerFragment.BlogPostPagerAdapter.INVALID_POSITION;
+import static org.briarproject.android.blogs.BlogActivity.POST_ID;
+
+abstract class BasePostPagerFragment extends BaseFragment
+		implements OnBlogPostAddedListener {
+
+	private ViewPager pager;
+	private BlogPostPagerAdapter postPagerAdapter;
+	private MessageId postId;
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater, ViewGroup container,
+			Bundle state) {
+
+		Bundle args;
+		if (state == null) args = getArguments();
+		else args = state;
+		byte[] p = args.getByteArray(POST_ID);
+		if (p == null)
+			throw new IllegalStateException("No post ID in args");
+		postId = new MessageId(p);
+
+		View v = inflater.inflate(R.layout.fragment_blog_post_pager, container,
+				false);
+		pager = (ViewPager) v.findViewById(R.id.pager);
+		postPagerAdapter = new BlogPostPagerAdapter(getChildFragmentManager());
+		listener.showLoadingScreen(false, R.string.progress_title_please_wait);
+
+		return v;
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		if (postId == null) {
+			MessageId selected = getSelectedPost();
+			if (selected != null) loadBlogPosts(selected);
+		} else {
+			loadBlogPosts(postId);
+		}
+	}
+
+	@Override
+	public void onSaveInstanceState(Bundle outState) {
+		super.onSaveInstanceState(outState);
+		MessageId selected = getSelectedPost();
+		if (selected != null)
+			outState.putByteArray(POST_ID, selected.getBytes());
+	}
+
+	@Override
+	public void onBlogPostAdded(BlogPostHeader header, boolean local) {
+		loadBlogPost(header);
+	}
+
+	abstract void loadBlogPosts(final MessageId select);
+
+	abstract BaseController getController();
+
+	protected void onBlogPostsLoaded(MessageId select,
+			Collection<BlogPostItem> posts) {
+
+		postId = null;
+		postPagerAdapter.setPosts(posts);
+		selectPost(select);
+	}
+
+	protected void onBlogPostsLoadedException(DbException exception) {
+		// TODO: Decide how to handle errors in the UI
+		finish();
+	}
+
+	private void loadBlogPost(BlogPostHeader header) {
+		getController().loadBlogPost(header,
+				new UiResultExceptionHandler<BlogPostItem, DbException>(
+						getActivity()) {
+					@Override
+					public void onResultUi(BlogPostItem post) {
+						addPost(post);
+					}
+
+					@Override
+					public void onExceptionUi(DbException exception) {
+						// TODO: Decide how to handle errors in the UI
+						finish();
+					}
+				});
+	}
+
+	@Nullable
+	private MessageId getSelectedPost() {
+		if (postPagerAdapter.getCount() == 0) return null;
+		int position = pager.getCurrentItem();
+		return postPagerAdapter.getPost(position).getId();
+	}
+
+	private void selectPost(MessageId m) {
+		int pos = postPagerAdapter.getPostPosition(m);
+		if (pos != INVALID_POSITION) {
+			pager.setAdapter(postPagerAdapter);
+			pager.setCurrentItem(pos);
+		}
+	}
+
+	protected void addPost(BlogPostItem post) {
+		MessageId selected = getSelectedPost();
+		postPagerAdapter.addPost(post);
+		if (selected != null) selectPost(selected);
+	}
+
+	@UiThread
+	static class BlogPostPagerAdapter extends FragmentStatePagerAdapter {
+
+		static final int INVALID_POSITION = -1;
+		private final List<BlogPostItem> posts = new ArrayList<>();
+
+		private BlogPostPagerAdapter(FragmentManager fm) {
+			super(fm);
+		}
+
+		@Override
+		public int getCount() {
+			return posts.size();
+		}
+
+		@Override
+		public Fragment getItem(int position) {
+			BlogPostItem post = posts.get(position);
+			return FeedPostFragment.newInstance(post.getGroupId(), post.getId());
+		}
+
+		private BlogPostItem getPost(int position) {
+			return posts.get(position);
+		}
+
+		private void setPosts(Collection<BlogPostItem> posts) {
+			this.posts.clear();
+			this.posts.addAll(posts);
+			Collections.sort(this.posts);
+			notifyDataSetChanged();
+		}
+
+		private void addPost(BlogPostItem post) {
+			posts.add(post);
+			Collections.sort(posts);
+			notifyDataSetChanged();
+		}
+
+		private int getPostPosition(MessageId m) {
+			int count = getCount();
+			for (int i = 0; i < count; i++) {
+				if (getPost(i).getId().equals(m)) {
+					return i;
+				}
+			}
+			return INVALID_POSITION;
+		}
+	}
+
+}