ClassCastException當使用自定義顯示器

Question

我想在我的項目中使用UIL gridview佈局。出於測試目的，我修改了項目本身的代碼。我的要求是顯示一個TransitionDrawable與原始位圖作爲基礎圖像在零層和第一層的刻度線。這裏是自定義的BitmapDisplayer代碼。

public class customBitmapDisplayer implements BitmapDisplayer 
{ 

public static Drawable tick; 
Drawable[] layers = new Drawable[2]; 
TransitionDrawable mytransition; 

@Override 
public Bitmap display(Bitmap bitmap, ImageView imageView) 
{ 
BitmapDrawable base_image = new BitmapDrawable(imageView.getResources(), bitmap); 
layers[0] = base_image; 
layers[1] = tick; 

mytransition = new TransitionDrawable(layers); 
imageView.setImageDrawable(mytransition); 
return bitmap; 
} 

public customBitmapDisplayer(Drawable tick_mark) 
{ 
tick = tick_mark; 
} 
} 

我也修改了getView稍微。這是代碼。

if(selected[position]) //selected is a boolean array 
{ 
TransitionDrawable quickTransition = (TransitionDrawable)imageView.getDrawable(); 
quickTransition.startTransition(0); 
} 

通過我使用UIL 1.8.0的方式，默認ImageConfiguration，DisplayImageOptions修改與自定義BitmapDisplayer，其代碼是上面使用。我在android 2.3.4上測試，發現沒有問題，但在android 4.0.4上，我在getView方法中得到一個ClassCastException，說當我選擇每個圖像後，當我滾動整個gridview時，BitmapDrawable不能轉換爲TransitionDrawable。

這裏是堆棧跟蹤。

03-20 20:46:40.797: E/AndroidRuntime(11943): FATAL EXCEPTION: main 
03-20 20:46:40.797: E/AndroidRuntime(11943): java.lang.ClassCastException: android.graphics.drawable.BitmapDrawable cannot be cast to android.graphics.drawable.TransitionDrawable 
03-20 20:46:40.797: E/AndroidRuntime(11943): at com.nostra13.example.universalimageloader.ImageGridActivity$ImageAdapter.getView(ImageGridActivity.java:219) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.AbsListView.obtainView(AbsListView.java:2019) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.GridView.makeAndAddView(GridView.java:1338) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.GridView.makeRow(GridView.java:343) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.GridView.fillUp(GridView.java:384) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.GridView.fillGap(GridView.java:260) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.AbsListView.trackMotionScroll(AbsListView.java:4567) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.widget.AbsListView$FlingRunnable.run(AbsListView.java:3834) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.os.Handler.handleCallback(Handler.java:605) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.os.Handler.dispatchMessage(Handler.java:92) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.os.Looper.loop(Looper.java:137) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at android.app.ActivityThread.main(ActivityThread.java:4448) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at java.lang.reflect.Method.invokeNative(Native Method) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at java.lang.reflect.Method.invoke(Method.java:511) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
03-20 20:46:40.797: E/AndroidRuntime(11943): at dalvik.system.NativeStart.main(Native Method) 
03-20 20:46:44.377: I/Process(11943): Sending signal. PID: 11943 SIG: 9 

ImageGridActivity.java在線路219

TransitionDrawable quickTransition = (TransitionDrawable)imageView.getDrawable(); 

這裏是我getView代碼下面的代碼。

@Override 
public View getView(int position, View convertView, ViewGroup parent) 
{ 
    final ImageView imageView; 
    if (convertView == null) 
    { 
     imageView = (ImageView) getLayoutInflater().inflate(R.layout.item_grid_image, parent, false); 
    } 
    else 
    { 
     imageView = (ImageView) convertView; 
    } 

    imageLoader.displayImage(imageUrls[position], imageView, options); 

    if(selected[position]) 
    { 

     TransitionDrawable quickTransition = (TransitionDrawable)imageView.getDrawable(); 
     quickTransition.startTransition(0); 

    } 
    return imageView; 
} 

Answer 1

我想你應該改變你的getView()方法如下：

@Override 
public View getView(final int position, View convertView, ViewGroup parent) 
{ 
    final ImageView imageView; 
    if (convertView == null) { 
     imageView = (ImageView) getLayoutInflater().inflate(R.layout.item_grid_image, parent, false); 
    } else { 
     imageView = (ImageView) convertView; 
    } 

    imageLoader.displayImage(imageUrls[position], imageView, options, new SimpleImageLoadingListener() { 
      @Override 
      public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) { 
       if(selected[position]) { 
        TransitionDrawable quickTransition = (TransitionDrawable)imageView.getDrawable(); 
        quickTransition.startTransition(0); 
       } 
      } 
     }); 
    return imageView; 
}