AsyncTask的方块UI线程，并显示进度延迟 [英] AsyncTask block UI thread and show progressbar with delay
问题描述
我的AsyncTask阻止块按钮元素，而下载的图像，并显示进度对话框延迟 - 它显示的图像之前显示了一段时间，但下载需要很长的时间，按钮被阻塞（橙色）和对话框不显示。
My AsyncTask is blocking block button element while downloading image and progress dialog is shown with delay - its shows for a while before image is shown, but downloading takes long time and button is blocked (orange) and dialog is not shown.
public Bitmap download(String url, ProgressBar progressbar) throws InterruptedException, ExecutionException {
BitmapDownloaderTask task = new BitmapDownloaderTask(progressbar);
task.execute(url);
return task.get();
}
class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> {
public BitmapDownloaderTask(ProgressBar progressbar) {
}
@Override
protected void onPreExecute() {
dialog = new ProgressDialog(ShowActivity.this);
dialog.setMessage("Loading");
dialog.setIndeterminate(true);
dialog.setCancelable(false);
dialog.show();
}
@Override
protected Bitmap doInBackground(String... Params) {
return imageLoader.getBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
dialog.dismiss();
}
}
在按钮监听器，只需调用下载功能，进度参数是因为我有进度条圈的ImageView - 对话框仅用于测试，以发现为什么会出现延迟和块。在另一个应用程序，我使用的可运行和线程和元素没有被阻塞，但在教程中AsyncTask的提到这个更好的解决方案。
In button listener, simply call download function, the progress parameter is because I have progress bar circle in imageview - the dialog is for testing only, to found why is there the delay and block. In another app I use runable and thread and element is not blocked, but in tutorials is AsyncTask mentioned as better solution for this.
推荐答案
图片下载确实执行在后台线程，但返回task.get（）; 你只是等待它完成，这是什么阻止你的主线程。
The image download is indeed executed in the background thread, but with return task.get(); you're just waiting for it to finish, and that's what's blocking your main thread.
您应该使用 onPostExecute（）作为回调的当任务完成，所以不只是关闭对话框还要做你需要与返回的位图通过 doInBackground（）。
You should use onPostExecute() as a callback for when the task has finished, so not just to dismiss the dialog but also to do what you need with the bitmap returned by doInBackground().
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