调用异步任务

Question

我正在播放一段广播流。当流中的歌曲更改时，我希望生成一个通知。我使用streamscraper（http://code.google.com/p/streamscraper）获取当前流的元数据，并尝试在元数据更改时生成通知。

以下是我创建的异步任务以实现此目的。

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());
    }
}

该应用程序由两个相关项目构建而成。项目A是初始化应用程序的地方，而项目B包含集合和播放逻辑。我想在项目B中使用此任务。以下是项目B中的播放函数。

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);
    }

当我尝试执行它时，应用程序崩溃了。

这里是完整的错误跟踪：

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)

我对异步任务的理解感到困惑。这不是使用它们的正确方式吗？

编辑：答案单独添加。

- rahulthewall

---

基本上，您正在尝试在退出活动后显示对话框。以上情况发生的原因有很多，但我在您的代码中没有看到任何关于对话框的内容。您是否使用对话框？ - Marcos

不，我想要在当前歌曲改变后记录新歌曲。目前没有对话框或任何其他内容。我已经设置了一个onSongChanged监听器。当我确定检查新歌曲的部分正在工作时，我可以直接调用它。 - rahulthewall

你的RadioPlayerActivity中的onclick方法中是否尝试显示任何对话框或进度对话框？ - Ads

如果TimerTask解决了您的问题，请将解决方案作为答案添加并接受它。这样，这个问题就不会再显示为未回答了。 - Dirk Jäckel

Answer 1

使用TimerTask解决。

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);
}

- rahulthewall