安卓音频焦点(AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK)

Question

我用的是AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK，但安卓系统叫AUDIOFOCUS_LOSS_TRANSIENT。

我不知道为什么系统不调用AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK。

正常操作如下

AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK到AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK

请给我一些建议。

谢谢。

// MainActivity.java
package com.example.af_test;

import android.app.Activity;
import android.media.AudioManager;
import android.media.AudioManager.OnAudioFocusChangeListener;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

    private AudioManager am;
    private MediaPlayer mp;
    private MediaPlayer mp_alarm;

    private String LOG = "Seo";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mp = MediaPlayer.create(this, R.raw.explosion);
        mp_alarm = MediaPlayer.create(this, R.raw.caution);     // test



        Button btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {

                    am = (AudioManager) getSystemService(AUDIO_SERVICE);
                    int requestResult = am.requestAudioFocus(
                            mAudioFocusListener, AudioManager.STREAM_MUSIC,
                            //AudioManager.AUDIOFOCUS_GAIN);
                            //AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);
                            AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK);

                    if (requestResult == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
                        mp.start();

                        Log.d(LOG, "Successfull to request audioFocus listener");

                    }

                        else if(requestResult == AudioManager.AUDIOFOCUS_REQUEST_FAILED)
                        {
                             mp.stop();
                            //mp_alarm.stop();
                        }

                     else {
                        Log.d(LOG, "Failure to request focus listener");
                    }

                    //mp.start();
//                  am.abandonAudioFocus(mAudioFocusListener);
//                  Log.d(LOG, "Abandon focus");

            }

        });


        // 동영상 재생이 완료된걸 알수있는 리스너
         mp.setOnCompletionListener(new OnCompletionListener() {

               // 동영상 재생이 완료된후 호출되는 메서드
               public void onCompletion(MediaPlayer player) {
                   am.abandonAudioFocus(mAudioFocusListener);
               }
              });

    }



    @Override
    // onDestroy()는 해당 Activity가 화면에서 사라진 후에 호출된다.
    protected void onDestroy() {
        mp.stop();
        am.abandonAudioFocus(mAudioFocusListener);
        Log.d(LOG, "Abandon focus");
        super.onDestroy();

    }

    public void abandonAudioFocus() {
        //Abandon audio focus
        int result = am.abandonAudioFocus(mAudioFocusListener);
        if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            Log.d(LOG, "Audio focus abandoned");
        } else {
            Log.e(LOG, "Audio focus failed to abandon");
        }

    }


    public void stop() {
        mp.stop();
        abandonAudioFocus();
    }

    private OnAudioFocusChangeListener mAudioFocusListener = new OnAudioFocusChangeListener() {
        public void onAudioFocusChange(int focusChange) {
            // AudioFocus is a new feature: focus updates are made verbose on
            // purpose
            switch (focusChange) {
            case AudioManager.AUDIOFOCUS_LOSS:
                mp.stop();
                //stop();
                Log.d(LOG, "AudioFocus: received AUDIOFOCUS_LOSS");
//              mp.release();
//              mp = null;
                break;

            case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
//              if (mp.isPlaying())
                mp.pause();

                Log.d(LOG, "AudioFocus: received AUDIOFOCUS_LOSS_TRANSIENT");

                break;

            case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                mp.setVolume(0.5f, 0.5f);
                Log.d(LOG,  "AudioFocus: received AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK");
                break;

            case AudioManager.AUDIOFOCUS_GAIN:
                mp.start();
                mp.setVolume(1.0f, 1.0f);
                Log.d(LOG, "AudioFocus: received AUDIOFOCUS_GAIN");
                break;

            default:
                Log.e(LOG, "Unknown audio focus change code");
            }

        }
    };
}

<!-- activity_main.xml -->

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${relativePackage}.${activityClass}" >

    <Button
        android:id="@+id/btn"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="Audio Focus Test" />

</RelativeLayout>

Logcat信息

08-05 16:46:00.115: I/AudioService(2429):  AudioFocus  requestAudioFocus() from 11622 focusChangeHint:3 
08-05 16:46:00.115: V/CorePlayerService(20934): AudioFocus: received AUDIOFOCUS_LOSS_TRANSIENT 
08-05 16:46:00.165: D/Seo(11622): Successfull to request audioFocus listener 
08-05 16:46:03.400: I/AudioService(2429):  AudioFocus  abandonAudioFocus() from 11622 
08-05 16:46:03.405: V/CorePlayerService(20934): AudioFocus: received AUDIOFOCUS_GAIN 
08-05 16:46:03.435: I/AudioService(2429):  AudioFocus  requestAudioFocus() from 20934 focusChangeHint:1

Answer 1

你对音频焦点的解释似乎有点不正确。当您失去音频焦点时，您不会得到基于您先前请求的LOSS (例如，请求AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK并不意味着当您失去音频焦点时会得到AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK )。

相反，音频焦点的丢失取决于另一个应用程序请求的音频焦点类型。因此，例如，如果其他应用程序请求并获得了AUDIOFOCUS_GAIN_TRANSIENT，那么您的应用程序将接收AUDIOFOCUS_LOSS_TRANSIENT (或者，在某些情况下，接收AUDIOFOCUS_LOSS)。

如果您对如何完成从GAIN到LOSS的映射感兴趣，可以在安卓源代码中的FocusRequester.java中找到它。