Android播放GIF动画

Android支持GIF动画，但是如果利用ImageView标签直接写在布局文件中：

Xml代码

1. <ImageView android:id="@+id/gifpicture"  
2. android:layout_width="fill_parent"  
3. android:layout_height="wrap_content"  
4. android:src="@drawable/animation"    /> 

程序只能加载GIF动画的第一帧。效果如下：


如果想要正常播放GIF动画，需要借助Movie实现。写了一个简单示例，程序目录结构如下：


animation.gif是需要播放的GIF动画。
MainActivity实现了加载GIF动画的功能。

Java代码  



public class MainActivity extends Activity {   

      
    private Movie mMovie;   
    private long mMovieStart;  
    /** Called when the activity is first created. */   
    @Override   
    public void onCreate(Bundle savedInstanceState) {   
        super.onCreate(savedInstanceState);   
       setContentView(new CustomGifView(this));   
          }  
    class CustomGifView extends View {  
        public CustomGifView(Context context) {   
            super(context);   
            mMovie = Movie.decodeStream(getResources().openRawResource(   
                    R.drawable.animation));  
        }   
          
        public void onDraw(Canvas canvas) {  
            long now = android.os.SystemClock.uptimeMillis();   
              
            if (mMovieStart == 0) { // first time   
                mMovieStart = now;   
            }   
            if (mMovie != null) {   
                  
                int dur = mMovie.duration();   
                if (dur == 0) {   
                    dur = 1000;   
                }   
                int relTime = (int) ((now – mMovieStart) % dur);                  
                mMovie.setTime(relTime);   
                mMovie.draw(canvas, 0, 0);   
                invalidate();   
            }   
        }  
    }  
}  


public class MainActivity extends Activity { 
    
    private Movie mMovie; 
    private long mMovieStart;
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
       setContentView(new CustomGifView(this)); 
          }
    class CustomGifView extends View {
        public CustomGifView(Context context) { 
            super(context); 
            mMovie = Movie.decodeStream(getResources().openRawResource( 
                    R.drawable.animation));
        } 
        
        public void onDraw(Canvas canvas) {
            long now = android.os.SystemClock.uptimeMillis(); 
            
            if (mMovieStart == 0) { // first time 
                mMovieStart = now; 
            } 
            if (mMovie != null) { 
                
                int dur = mMovie.duration(); 
                if (dur == 0) { 
                    dur = 1000; 
                } 
                int relTime = (int) ((now – mMovieStart) % dur);                
                mMovie.setTime(relTime); 
                mMovie.draw(canvas, 0, 0); 
                invalidate(); 
            } 
        }
    }
}


内部类CustomGifView 利用Movie播放GIF动画。解释一下：

Java代码  

mMovie = Movie.decodeStream(getResources().openRawResource(R.drawable.animation));  

mMovie = Movie.decodeStream(getResources().openRawResource(R.drawable.animation));

将GIF动画以文件流的形式转换成Movie。

Java代码  



public void onDraw(Canvas canvas) {  

        long now = android.os.SystemClock.uptimeMillis();   
          
        if (mMovieStart == 0) { // first time   
            mMovieStart = now;   
        }   
        if (mMovie != null) {   
              
            int dur = mMovie.duration();   
            if (dur == 0) {   
                dur = 1000;   
            }   
            int relTime = (int) ((now – mMovieStart) % dur);                  
            mMovie.setTime(relTime);   
            mMovie.draw(canvas, 0, 0);   
            invalidate();   
        }   
    }  


public void onDraw(Canvas canvas) {
        long now = android.os.SystemClock.uptimeMillis(); 
        
        if (mMovieStart == 0) { // first time 
            mMovieStart = now; 
        } 
        if (mMovie != null) { 
            
            int dur = mMovie.duration(); 
            if (dur == 0) { 
                dur = 1000; 
            } 
            int relTime = (int) ((now – mMovieStart) % dur);                
            mMovie.setTime(relTime); 
            mMovie.draw(canvas, 0, 0); 
            invalidate(); 
        } 
    }


   invalidate();作用是刷新当前View，这样onDraw方法重复执行，Movie就能画出GIF动画的每一帧。到此，GIF动画就能正常播放了。



源代码见：http://bigcateasymorse.googlecode.com/svn/trunk/android_gif_demo/