void onDestroy() { super.onDestroy();

    try {
        trimCache(this);
       // Toast.makeText(this,"onDestroy ",Toast.LENGTH_LONG).show();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

public static void trimCache(Context context) {
    try {
       File dir = context.getCacheDir();
       if (dir != null && dir.isDirectory()) {
          deleteDir(dir);
       }
    } catch (Exception e) {
       // TODO: handle exception
    }
 }

 public static boolean deleteDir(File dir) {
    if (dir != null && dir.isDirectory()) {
       String[] children = dir.list();
       for (int i = 0; i < children.length; i++) {
          boolean success = deleteDir(new File(dir,children[i]));
          if (!success) {
             return false;
          }
       }
    }

    // The directory is now empty so delete it
    return dir.delete();
 }