FlipAsyncContentActivity.java

/*
Copyright 2012 Aphid Mobile

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 
	 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

 */

package com.duguang.baseanimation.ui.flip;

import java.lang.ref.WeakReference;
import java.util.Random;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.res.AssetManager;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.aphidmobile.flip.FlipViewController;
import com.aphidmobile.utils.AphidLog;
import com.aphidmobile.utils.IO;
import com.aphidmobile.utils.UI;
import com.duguang.baseanimation.R;
import com.duguang.baseanimation.ui.flip.data.Travels;

public class FlipAsyncContentActivity extends Activity {

  private FlipViewController flipView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setTitle(R.string.activity_title);

    flipView = new FlipViewController(this);
    flipView.setAdapter(new MyBaseAdapter(this, flipView));

    setContentView(flipView);
  }

  @Override
  protected void onResume() {
    super.onResume();
    flipView.onResume();
  }

  @Override
  protected void onPause() {
    super.onPause();
    flipView.onPause();
  }

  private static class MyBaseAdapter extends BaseAdapter {

    private FlipViewController controller;

    private Context context;

    private LayoutInflater inflater;

    private Bitmap placeholderBitmap;

    private MyBaseAdapter(Context context, FlipViewController controller) {
      inflater = LayoutInflater.from(context);
      this.context = context;
      this.controller = controller;

      //Use a system resource as the placeholder
      placeholderBitmap =
          BitmapFactory.decodeResource(context.getResources(), android.R.drawable.dark_header);
    }

    @Override
    public int getCount() {
      return Travels.IMG_DESCRIPTIONS.size();
    }

    @Override
    public Object getItem(int position) {
      return position;
    }

    @Override
    public long getItemId(int position) {
      return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
      View layout = convertView;
      if (convertView == null) {
        layout = inflater.inflate(R.layout.activity_flip_complex, null);
      }

      final Travels.Data data = Travels.IMG_DESCRIPTIONS.get(position);

      UI
          .<TextView>findViewById(layout, R.id.title)
          .setText(AphidLog.format("%d. %s", position, data.title));

      UI
          .<TextView>findViewById(layout, R.id.description)
          .setText(Html.fromHtml(data.description));

      UI
          .<Button>findViewById(layout, R.id.wikipedia)
          .setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
              Intent intent = new Intent(
                  Intent.ACTION_VIEW,
                  Uri.parse(data.link)
              );
              inflater.getContext().startActivity(intent);
            }
          });

      ImageView photoView = UI.findViewById(layout, R.id.photo);
      //Use an async task to load the bitmap
      boolean needReload = true;
      AsyncImageTask previousTask = AsyncDrawable.getTask(photoView);
      if (previousTask != null) {
        if (previousTask.getPageIndex() == position && previousTask.getImageName()
            .equals(data.imageFilename)) //check if the convertView happens to be previously used
        {
          needReload = false;
        } else {
          previousTask.cancel(true);
        }
      }

      if (needReload) {
        AsyncImageTask
            task =
            new AsyncImageTask(layout.getContext().getAssets(), photoView, controller, position,
                               data.imageFilename);
        photoView
            .setImageDrawable(new AsyncDrawable(context.getResources(), placeholderBitmap, task));

        task.execute();
      }

      return layout;
    }
  }

  /**
   * Borrowed from the official BitmapFun tutorial: http://developer.android.com/training/displaying-bitmaps/index.html
   */
  private static final class AsyncDrawable extends BitmapDrawable {

    private final WeakReference<AsyncImageTask> taskRef;

    public AsyncDrawable(Resources res, Bitmap bitmap, AsyncImageTask task) {
      super(res, bitmap);
      this.taskRef = new WeakReference<AsyncImageTask>(task);
    }

    public static AsyncImageTask getTask(ImageView imageView) {
      Drawable drawable = imageView.getDrawable();
      if (drawable instanceof AsyncDrawable) {
        return ((AsyncDrawable) drawable).taskRef.get();
      }

      return null;
    }
  }

  private static final class AsyncImageTask extends AsyncTask<Void, Void, Bitmap> {

    private static final Random RANDOM = new Random();

    private final AssetManager assetManager;

    private final WeakReference<ImageView> imageViewRef;
    private final WeakReference<FlipViewController> controllerRef;
    private final int pageIndex;
    private final String imageName;

    public AsyncImageTask(AssetManager assetManager, ImageView imageView,
                          FlipViewController controller, int pageIndex, String imageName) {
      this.assetManager = assetManager;
      imageViewRef = new WeakReference<ImageView>(imageView);
      controllerRef = new WeakReference<FlipViewController>(controller);
      this.pageIndex = pageIndex;
      this.imageName = imageName;
    }

    public int getPageIndex() {
      return pageIndex;
    }

    public String getImageName() {
      return imageName;
    }

    @Override
    protected Bitmap doInBackground(Void... params) {
      try {
        Thread.sleep(500 + RANDOM.nextInt(2000)); //wait for a random time
      } catch (InterruptedException e) {
      }

      return IO.readBitmap(assetManager, imageName);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
      if (isCancelled()) {
        return;
      }

      ImageView imageView = imageViewRef.get();
      if (imageView != null && AsyncDrawable.getTask(imageView)
                               == this) { //the imageView can be reused for another page, so it's necessary to check its consistence
        imageView.setImageBitmap(bitmap);
        FlipViewController controller = controllerRef.get();
        if (controller != null) {
          controller.refreshPage(pageIndex);
        }
      }
    }
  }
}