异步调用任务 [英] Calling Async Task
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问题描述
我流收音机流。欲产生一通知时，在流的变化的乐曲。我使用streamscraper（HTTP：//$c$c.google.com/p/streamscraper）来获得当前流的元数据，我尝试生成通知的元数据发生变化时。
I am streaming a radio Stream. I want to generate a notification when the song in the stream changes. I am using streamscraper (http://code.google.com/p/streamscraper) to get the metadata of the current stream, and I try to generate a notification when the metadata changes.
下面是异步任务，我创建实现这一点。
Here is the Async Task that I created to implement this.
public class updateMetadata extends
AsyncTask<String, Void, PlaylistSong<BaseArtist, BaseAlbum>> {
private static final String TAG = updateMetadata.class.getSimpleName();
private PlaylistSong<BaseArtist, BaseAlbum> oldSong = null;
private PlaylistSong<BaseArtist, BaseAlbum> newSong = null;
private metadataHarvester fetchMetadata = new metadataHarvester();
private String streamUrl = null;
@Override
protected PlaylistSong<BaseArtist, BaseAlbum> doInBackground(String... urls) {
for (String url : urls) {
try {
oldSong = fetchMetadata.prepareRadioSong(url);
} catch (Exception e) {
e.printStackTrace();
}
streamUrl = url;
}
newSong = oldSong;
while (newSong == oldSong) {
try {
newSong = fetchMetadata.prepareRadioSong(streamUrl);
} catch (Exception e) {
e.printStackTrace();
}
}
return newSong;
}
@Override
protected void onPostExecute(PlaylistSong<BaseArtist, BaseAlbum> song) {
Log.v(TAG, "New Song: " + song.getTitle());
}
}
该应用程序是建立在两个相连的项目。项目A是应用程序被初始化和项目B包含集合和播放逻辑。我想用在项目B.这个任务下面是播放功能（项目B）。
The application is built on two linked projects. Project A is where the Application is initialised and Project B contains the collections and the playing logic. I want to use this task in Project B. Here is the play function (in project B).
protected synchronized void play(final IMediaPlayerWrapper mp) {
streamURL = streamFetcher.getStreamUrl();
Log.i(TAG, "Stream URL: " + streamURL);
try {
Log.i(TAG, "Testing metadata harvester");
radioSong = metadata.prepareRadioSong(streamURL);
} catch (Exception e) {
Log.w(TAG, e);
}
updateMetadata(radioSong);
currentPlaylistManager.clearPlaylist();
currentPlaylistManager.appendSongAtEnd(radioSong);
listenerInformer.informCurrentSongChangeListener(radioSong);
try {
mp.setSong(radioSong, streamURL);
mp.play();
if (mp.isPlaying()) {
setPlayerState(PlayerState.PLAY);
}
} catch (Exception e) {
Log.w(TAG, e);
setPlayerState(PlayerState.ERROR);
}
updateMetadata metadataChecker = new updateMetadata();
metadataChecker.execute(streamURL);
}
当我尝试执行它，应用程序崩溃。
When I try to execute it, the application crashes.
下面是完整的错误跟踪：
Here, is the complete error trace:
04-04 23:34:34.975: E/WindowManager(18080): Activity ch.ethz.dcg.pancho2.view.radioplayer.RadioPlayerActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@4053e8f0 that was originally added here
04-04 23:34:34.975: E/WindowManager(18080): android.view.WindowLeaked: Activity ch.ethz.dcg.pancho2.view.radioplayer.RadioPlayerActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@4053e8f0 that was originally added here
04-04 23:34:34.975: E/WindowManager(18080): at android.view.ViewRoot.<init>(ViewRoot.java:258)
04-04 23:34:34.975: E/WindowManager(18080): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
04-04 23:34:34.975: E/WindowManager(18080): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
04-04 23:34:34.975: E/WindowManager(18080): at android.view.Window$LocalWindowManager.addView(Window.java:424)
04-04 23:34:34.975: E/WindowManager(18080): at android.app.Dialog.show(Dialog.java:241)
04-04 23:34:34.975: E/WindowManager(18080): at android.app.ProgressDialog.show(ProgressDialog.java:107)
04-04 23:34:34.975: E/WindowManager(18080): at android.app.ProgressDialog.show(ProgressDialog.java:90)
04-04 23:34:34.975: E/WindowManager(18080): at ch.ethz.dcg.pancho2.view.radioplayer.RadioPlayerActivity$5.onClick(RadioPlayerActivity.java:276)
04-04 23:34:34.975: E/WindowManager(18080): at android.view.View.performClick(View.java:2485)
04-04 23:34:34.975: E/WindowManager(18080): at android.view.View$PerformClick.run(View.java:9080)
04-04 23:34:34.975: E/WindowManager(18080): at android.os.Handler.handleCallback(Handler.java:587)
04-04 23:34:34.975: E/WindowManager(18080): at android.os.Handler.dispatchMessage(Handler.java:92)
04-04 23:34:34.975: E/WindowManager(18080): at android.os.Looper.loop(Looper.java:130)
04-04 23:34:34.975: E/WindowManager(18080): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-04 23:34:34.975: E/WindowManager(18080): at java.lang.reflect.Method.invokeNative(Native Method)
04-04 23:34:34.975: E/WindowManager(18080): at java.lang.reflect.Method.invoke(Method.java:507)
04-04 23:34:34.975: E/WindowManager(18080): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-04 23:34:34.975: E/WindowManager(18080): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-04 23:34:34.975: E/WindowManager(18080): at dalvik.system.NativeStart.main(Native Method)
我在我的异步任务的理解混淆。这是不使用它们的正确方法是什么？
I am confused in my understanding of Async Tasks. Is this not the correct way to use them?
编辑：答案分别加入。
Answer added separately.
推荐答案
使用TimerTask的解决。
Solved using TimerTask.
private void pollMetadata() {
lastSong = radioSong;
newSong = lastSong;
Log.i(TAG, "Old Song: " + lastSong.getTitle());
Log.i(TAG, "New Song: " + newSong.getTitle());
updateMetadataTask = new TimerTask() {
@Override
public void run() {
try {
newSong = metadata.prepareRadioSong(streamURL);
} catch (Exception e) {
e.printStackTrace();
}
Log.i(TAG, "Old Song: " + lastSong.getTitle());
Log.i(TAG, "New Song: " + newSong.getTitle());
if (newSong.getTitle().equals(lastSong.getTitle())) {
Log.v(TAG, "SAME SONG");
}
else {
Log.v(TAG, "SONG CHANGED");
lastSong = newSong;
currentPlaylistManager.clearPlaylist();
currentPlaylistManager.appendSongAtEnd(newSong);
listenerInformer.informCurrentSongChangeListener(newSong);
}
}
};
t.schedule(updateMetadataTask, 300, 30000);
}
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