我从这里改编了一个教程，通过 JSON 从 YouTube 频道检索视频。一切正常，但我想在后台线程中加载视频时添加一个 ProgressDialog。如果后台线程由 AsyncTask 处理，我知道如何添加 ProgressDialog，但我不知道如何在这种情况下执行此操作。
这是代码的重要部分：
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_video);
listView = (VideosListView) findViewById(R.id.videosListView);
listView.setOnVideoClickListener(this);
getUserYouTubeFeed((VideosListView) findViewById(R.id.videosListView));
}
// This is the XML onClick listener to retreive a users video feed
public void getUserYouTubeFeed(View v){
// We start a new task that does its work on its own thread
// We pass in a handler that will be called when the task has finished
// We also pass in the name of the user we are searching YouTube for
new GetYouTubeUserVideosTask(responseHandler, "videoslusofona").run();
}
// This is the handler that receives the response when the YouTube task has finished
Handler responseHandler = new Handler() {
public void handleMessage(Message msg) {
populateListWithVideos(msg);
};
};
所以我有一个活动列出打开的视频，最重要的是，我android:onClick=getUserYouTubeFeed在 XML 布局中有一个按钮，以便用户可以在需要时刷新。想法是将 ProgressDialog 放在某个位置，以便在活动启动以及用户按下刷新按钮时将其激活。
如果您能告诉我应该将 ProgressDialog 放在哪里，我将不胜感激。
提前致谢。
编辑：
整个活动的代码以及 Pratik Sharma 建议的修改：
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import com.example.igestao.youtube.GetYouTubeUserVideosTask;
import com.example.igestao.R;
import com.example.igestao.youtube.Library;
import com.example.igestao.youtube.Video;
import com.example.igestao.youtube.VideoClickListener;
import com.example.igestao.youtube.VideosListView;
/**
* The Activity can retrieve Videos for a specific username from YouTube</br>
* It then displays them into a list including the Thumbnail preview and the title</br>
* There is a reference to each video on YouTube as well but this isn't used in this tutorial</br>
* </br>
* <b>Note<b/> orientation change isn't covered in this tutorial, you will want to override
* onSaveInstanceState() and onRestoreInstanceState() when you come to this
* </br>
* @author paul.blundell
*/
public class MainVideoActivity extends Activity implements VideoClickListener {
// A reference to our list that will hold the video details
private VideosListView listView;
ProgressDialog dialog = new ProgressDialog(MainVideoActivity.this);
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_video);
listView = (VideosListView) findViewById(R.id.videosListView);
listView.setOnVideoClickListener(this);
getUserYouTubeFeed((VideosListView) findViewById(R.id.videosListView));
}
// This is the XML onClick listener to retreive a users video feed
public void getUserYouTubeFeed(View v){
// We start a new task that does its work on its own thread
// We pass in a handler that will be called when the task has finished
// We also pass in the name of the user we are searching YouTube for
new VideosLoad().execute();
}
// This is the handler that receives the response when the YouTube task has finished
Handler responseHandler = new Handler() {
public void handleMessage(Message msg) {
if (dialog.isShowing()){
dialog.dismiss();
}
populateListWithVideos(msg);
};
};
/**
* This method retrieves the Library of videos from the task and passes them to our ListView
* @param msg
*/
private void populateListWithVideos(Message msg) {
// Retreive the videos are task found from the data bundle sent back
Library lib = (Library) msg.getData().get(GetYouTubeUserVideosTask.LIBRARY);
// Because we have created a custom ListView we don't have to worry about setting the adapter in the activity
// we can just call our custom method with the list of items we want to display
listView.setVideos(lib.getVideos());
}
@Override
protected void onStop() {
// Make sure we null our handler when the activity has stopped
// because who cares if we get a callback once the activity has stopped? not me!
responseHandler = null;
super.onStop();
}
@Override
public void onVideoClicked(Video video) {
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setData(Uri.parse(video.getUrl()));
startActivity(intent);
}
private class VideosLoad extends AsyncTask<Void, Void, String>{
@Override
protected String doInBackground(Void... arg0){
new GetYouTubeUserVideosTask(responseHandler, "videoslusofona").run();
return "Executed";
}
@Override
protected void onPreExecute() {
dialog.setMessage("Carregando Videos");
dialog.show();
}
}
}