Android进度条设置可见不工作

我无法在异步任务中设置Progressbar的可见性

这是我的代码：

public class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {

ImageView IV;
FullImageActivity MA;
ProgressBar lp1;

public DownloadImageTask(ImageView IV,
        FullImageActivity fullImageActivity) {
    this.IV = IV;
    this.MA = fullImageActivity;
    lp1 = (ProgressBar) MA.findViewById(R.id.progressBar1);
}

protected Bitmap doInBackground(String... p) {
    String url = "...";
    Bitmap BI = null;
    try {
        InputStream in = new java.net.URL(url).openStream();
        BI = BitmapFactory.decodeStream(in);
    } catch (Exception e) {
        Log.e("Error", e.getMessage());
        e.printStackTrace();
    }
    return BI;
}

@Override
protected void onPreExecute() {
    lp1.setVisibility(1);
    super.onPreExecute();
}

protected void onPostExecute(Bitmap result) {
    IV.setImageBitmap(result);
    lp1.setVisibility(0);
}
}

或

或

或

我的进度条仍然可见

 lp1.setVisibility(0);

0是View.VISIBILE的值

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文档

为什么您使用进度条而不是使用进度对话框，并在onPostExecute上关闭它……tanx@SimplePlan我使用它

 lp1.setVisibility(0);

 lp1.setVisibility(ProgressBar.GONE); 

lp1.setVisibility(View.GONE);

lp1.setVisibility(View.INVISIBLE);

 lp1.setVisibility(0);