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      1 /*
      2  * Copyright (C) 2013 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.example.android.pictureviewer;
     18 
     19 import android.app.Activity;
     20 import android.graphics.Bitmap;
     21 import android.graphics.BitmapFactory;
     22 import android.graphics.Color;
     23 import android.graphics.drawable.BitmapDrawable;
     24 import android.os.Bundle;
     25 import android.view.View;
     26 import android.widget.ImageView;
     27 
     28 /**
     29  * This example shows how to use ViewPropertyAnimator to get a cross-fade effect as new
     30  * bitmaps get installed in an ImageView.
     31  *
     32  * Watch the associated video for this demo on the DevBytes channel of developer.android.com
     33  * or on YouTube at https://www.youtube.com/watch?v=9XbKMUtVnJA.
     34  */
     35 public class PictureViewer extends Activity {
     36 
     37     int mCurrentDrawable = 0;
     38     int drawableIDs[] = {
     39             R.drawable.p1,
     40             R.drawable.p2,
     41             R.drawable.p3,
     42             R.drawable.p4,
     43     };
     44 
     45     @Override
     46     public void onCreate(Bundle savedInstanceState) {
     47         super.onCreate(savedInstanceState);
     48         setContentView(R.layout.activity_picture_viewer);
     49 
     50         // This app works by having two views, which get faded in/out for the cross-fade effect
     51         final ImageView prevImageView = (ImageView) findViewById(R.id.prevImageView);
     52         final ImageView nextImageView = (ImageView) findViewById(R.id.nextImageView);
     53         prevImageView.setBackgroundColor(Color.TRANSPARENT);
     54         nextImageView.setBackgroundColor(Color.TRANSPARENT);
     55 
     56         // Setup default ViewPropertyAnimator durations for the two ImageViews
     57         prevImageView.animate().setDuration(1000);
     58         nextImageView.animate().setDuration(1000);
     59 
     60         // NOte that a real app would do this more robustly, and not just load all possible
     61         // bitmaps at onCreate() time.
     62         final BitmapDrawable drawables[] = new BitmapDrawable[drawableIDs.length];
     63         for (int i = 0; i < drawableIDs.length; ++i) {
     64             Bitmap bitmap = BitmapFactory.decodeResource(getResources(),
     65                     drawableIDs[i]);
     66             drawables[i] = new BitmapDrawable(getResources(), bitmap);
     67         }
     68         prevImageView.setImageDrawable(drawables[0]);
     69         nextImageView.setImageDrawable(drawables[1]);
     70 
     71         prevImageView.setOnClickListener(new View.OnClickListener() {
     72 
     73             @Override
     74             public void onClick(View v) {
     75                 // Use ViewPropertyAnimator to fade the previous imageView out and the next one in
     76                 prevImageView.animate().alpha(0).withLayer();
     77                 nextImageView.animate().alpha(1).withLayer().
     78                         withEndAction(new Runnable() {
     79                     // When the animation ends, set up references to change the prev/next
     80                     // associations
     81                     @Override
     82                     public void run() {
     83                         mCurrentDrawable =
     84                                 (mCurrentDrawable + 1) % drawables.length;
     85                         int nextDrawableIndex =
     86                                 (mCurrentDrawable + 1) % drawables.length;
     87                         prevImageView.setImageDrawable(drawables[mCurrentDrawable]);
     88                         nextImageView.setImageDrawable(drawables[nextDrawableIndex]);
     89                         nextImageView.setAlpha(0f);
     90                         prevImageView.setAlpha(1f);
     91                     }
     92                 });
     93             }
     94         });
     95     }
     96 
     97 }
     98