1、后臺音樂保活
（1）、前后臺管理

public class ForegroundCallbacks implements Application.ActivityLifecycleCallbacks {
    public static final long CHECK_DELAY = 500;
    public static final String TAG = ForegroundCallbacks.class.getName();
    public interface Listener {
        public void onBecameForeground(Activity activity);
        public void onBecameBackground(Activity activity);
    }
    private static ForegroundCallbacks instance;
    private boolean foreground = false, paused = true;
    private Handler handler = new Handler();
    private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
    private Runnable check;
    public static ForegroundCallbacks init(Application application){
        if (instance == null) {
            instance = new ForegroundCallbacks();
            application.registerActivityLifecycleCallbacks(instance);
        }
        return instance;
    }
    public static ForegroundCallbacks get(Application application){
        if (instance == null) {
            init(application);
        }
        return instance;
    }
    public static ForegroundCallbacks get(Context ctx){
        if (instance == null) {
            Context appCtx = ctx.getApplicationContext();
            if (appCtx instanceof Application) {
                init((Application)appCtx);
            }
            throw new IllegalStateException(
                    "Foreground is not initialised and " +
                            "cannot obtain the Application object");
        }
        return instance;
    }
    public static ForegroundCallbacks get(){
        if (instance == null) {
            throw new IllegalStateException(
                    "Foreground is not initialised - invoke " +
                            "at least once with parameterised init/get");
        }
        return instance;
    }
    public boolean isForeground(){
        return foreground;
    }
    public boolean isBackground(){
        return !foreground;
    }
    public void addListener(Listener listener){
        listeners.add(listener);
    }
    public void removeListener(Listener listener){
        listeners.remove(listener);
    }
    @Override
    public void onActivityResumed(final Activity activity) {
        paused = false;
        boolean wasBackground = !foreground;
        foreground = true;
        if (check != null)
            handler.removeCallbacks(check);
        if (wasBackground){
            for (Listener l : listeners) {
                try {
                    l.onBecameForeground(activity);
                } catch (Exception exc) { }
            }
        } else {

        }
    }
    @Override
    public void onActivityPaused(final Activity activity) {
        paused = true;
        if (check != null)
            handler.removeCallbacks(check);
        handler.postDelayed(check = new Runnable(){
            @Override
            public void run() {
                if (foreground && paused) {
                    foreground = false;
                    for (Listener l : listeners) {
                        try {
                            l.onBecameBackground(activity);
                        } catch (Exception exc) {
                        }
                    }
                } else {
                }
            }
        }, CHECK_DELAY);
    }
    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {}
    @Override
    public void onActivityStarted(Activity activity) {}
    @Override
    public void onActivityStopped(Activity activity) {}
    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {}
    @Override
    public void onActivityDestroyed(Activity activity) {}
}

在Application使用

 private MediaPlayer mediaPlayer = null;
 ForegroundCallbacks.init(this);
 ForegroundCallbacks.get().addListener(new ForegroundCallbacks.Listener() {
                @Override
                public void onBecameForeground(Activity activity) {
                    //在前臺
                    //todo 保活1
                    if (null!=mediaPlayer) {
                        mediaPlayer.stop();
                        mediaPlayer.release();
                        mediaPlayer=null;
                    }
                }
                @Override
                public void onBecameBackground(Activity activity) {
                    //在后臺
                    // todo 保活1 根據音樂資源文件創建MediaPlayer對象 設置循環播放屬性 開始播放
                    if (null == mediaPlayer) {
                        mediaPlayer = MediaPlayer.create(activity, R.raw.no_notice);
                        mediaPlayer.setLooping(true);
                    }
                    if (!mediaPlayer.isPlaying()) {
                       mediaPlayer.start();
                    }
                }
            });

通知權限保活
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