具有图像更改功能的Android小部件

我正在尝试制作一个小部件，它可以改变SD卡中特定计时器中的图像。我的onUpdate函数如下所示：

public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.main);
ComponentName thisWidget = new ComponentName(context, PhotoWidgetProvider.class);
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) 
    mExternalStorageWriteable = true;

if(mExternalStorageWriteable) {
    BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 2;
    //of course it's a sample filename
String fileName = Environment.getExternalStorageDirectory().getPath() + "/DCIM/100MEDIA/IMAG0159.jpg";
Bitmap bitmap = BitmapFactory.decodeFile(fileName, options);
remoteViews.setImageViewBitmap(R.id.widget_imageview, bitmap);
    appWidgetManager.updateAppWidget(thisWidget, remoteViews);
}

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但是我在我的小部件上看不到任何照片。文件当然存在。

试试这个。经过一些修改后，它运行良好，对我来说更好