本文主要是介绍android AudioManager AUDIOFOCUS，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
现在开始做音乐播放器的模块，遇到了几个问题
当播放音乐的过程中，去调节音量或者情景模式中的铃声设置，结果会有两种声音同时响起。引起此问题的原因是音乐焦点问题没弄清
现分析一下音乐焦点的几个属性：源码在frameworks/base/media/java/andorid/media/AudioManager.java中
public static final int AUDIOFOCUS_NONE = 0;
指示申请得到的Audio Focus不知道会持续多久，一般是长期占有；获得了Audio Focus；
public static final int AUDIOFOCUS_GAIN = 1;
指示要申请的AudioFocus是暂时性的，会很快用完释放的；
public static final int AUDIOFOCUS_GAIN_TRANSIENT = 2;
不但说要申请的AudioFocus是暂时性的，还指示当前正在使用AudioFocus的可以继续播放，只是要“duck”一下（降低音量）。
public static final int AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK = 3;
public static final int AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE = 4;
AudioManager.OnAudioFocusChangeListener是申请成功之后监听AudioFocus使用情况的Listener，后续如果有别的程序要竞争AudioFocus，都是通过这个Listener的onAudioFocusChange()方法来通知这个Audio Focus的使用者的。
失去了Audio Focus，并将会持续很长的时间
public static final int AUDIOFOCUS_LOSS = -1 * AUDIOFOCUS_GAIN;
暂时失去Audio Focus，并会很快再次获得。必须停止Audio的播放，但是因为可能会很快再次获得AudioFocus，这里可以不释放Media资源；
public static final int AUDIOFOCUS_LOSS_TRANSIENT = -1 * AUDIOFOCUS_GAIN_TRANSIENT;
暂时失去AudioFocus，但是可以继续播放，不过要在降低音量。
public static final int AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK =
-1 * AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK;
看看刚才修改的一个问题：
问题描述：播放音乐时闹钟到来，把闹钟放在后台时进入文件管理器播放音频，闹钟仍然在响应，闹钟和音乐同时响起；
问题分析：在闹钟铃声响起时，没有去做音频焦点的处理
解决方案：在packages/apps/deskclock/src/com/android/deskclock/alarms/AlarmKlaxon.java文件中加上焦点处理
修改后的源码：
package com.android.deskclock.alarms;import android.content.Context;
import android.content.res.AssetFileDescriptor;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnErrorListener;
import android.media.RingtoneManager;
import android.net.Uri;
import android.os.Vibrator;import com.android.deskclock.Log;
import com.android.deskclock.R;
import com.android.deskclock.provider.AlarmInstance;import java.io.IOException;
/*add by leo.tan 20140717 for bugzilla 20064 start */
import android.os.Handler;
import android.media.AudioManager.OnAudioFocusChangeListener;
import android.os.Message;
/*add by <span id="summary_alias_container"><span id="short_desc_nonedit_display"></span></span> leo.tan 20140717 for bugzilla 20064 end */
/*** Manages playing ringtone and vibrating the device.*/
public class AlarmKlaxon {private static final long[] sVibratePattern = new long[] { 500, 500 };// Volume suggested by media team for in-call alarms.private static final float IN_CALL_VOLUME = 0.125f;private static boolean sStarted = false;private static MediaPlayer sMediaPlayer = null;
/*add by leo.tan 20140717 for bugzilla 20064 start */private static final int FOCUSCHANGE = 3000;private static final int FADEDOWN = 5;private static final int FADEUP = 6;private static final int RETRY_REQUEST_FOCUS = 7;private static final int OVER_SHORT_VIBRATOR = 8;private static OnAudioFocusChangeListener mAudioFocusListener = new OnAudioFocusChangeListener() {public void onAudioFocusChange(int focusChange) {android.util.Log.v("AlarmKlaxon", "mAudioFocusListener::focusChange-->" + focusChange);mHandler.obtainMessage(FOCUSCHANGE, focusChange, 0).sendToTarget();}};
/*add by leo.tan 20140717 for bugzilla 20064 end */public static void stop(Context context) {Log.v("AlarmKlaxon.stop()");if (sStarted) {sStarted = false;// Stop audio playingif (sMediaPlayer != null) {sMediaPlayer.stop();AudioManager audioManager = (AudioManager)context.getSystemService(Context.AUDIO_SERVICE);audioManager.abandonAudioFocus(null);sMediaPlayer.release();sMediaPlayer = null;}/*add by leo.tan 20140717 for bugzilla 20064 start */final AudioManager audioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);audioManager.abandonAudioFocus(mAudioFocusListener);/*add by leo.tan 20140717 for bugzilla 20064 end */((Vibrator)context.getSystemService(Context.VIBRATOR_SERVICE)).cancel();}}public static void start(final Context context, AlarmInstance instance,boolean inTelephoneCall) {Log.v("AlarmKlaxon.start()");// Make sure we are stop before startingstop(context);if (!AlarmInstance.NO_RINGTONE_URI.equals(instance.mRingtone)) {Uri alarmNoise = instance.mRingtone;// Fall back on the default alarm if the database does not have an// alarm stored.if (alarmNoise == null) {alarmNoise = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);if (Log.LOGV) {Log.v("Using default alarm: " + alarmNoise.toString());}}
TODO: Reuse mMediaPlayer instead of creating a new one and/or use RingtoneManager.sMediaPlayer = new MediaPlayer();sMediaPlayer.setOnErrorListener(new OnErrorListener() {@Overridepublic boolean onError(MediaPlayer mp, int what, int extra) {Log.e("Error occurred while playing audio. Stopping AlarmKlaxon.");AlarmKlaxon.stop(context);return true;}});try {// Check if we are in a call. If we are, use the in-call alarm// resource at a low volume to not disrupt the call.if (inTelephoneCall) {Log.v("Using the in-call alarm");sMediaPlayer.setVolume(IN_CALL_VOLUME, IN_CALL_VOLUME);setDataSourceFromResource(context, sMediaPlayer, R.raw.in_call_alarm);} else {sMediaPlayer.setDataSource(context, alarmNoise);}startAlarm(context, sMediaPlayer);}catch (Exception ex) {Log.v("Using the fallback ringtone");// The alarmNoise may be on the sd card which could be busy right// now. Use the fallback ringtone.try {// Must reset the media player to clear the error state.sMediaPlayer.reset();setDataSourceFromResource(context, sMediaPlayer, R.raw.fallbackring);startAlarm(context, sMediaPlayer);} catch (Exception ex2) {// At this point we just don't play anything.Log.e("Failed to play fallback ringtone", ex2);}}}if (instance.mVibrate && !inTelephoneCall) {Vibrator vibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);vibrator.vibrate(sVibratePattern, 0);}sStarted = true;}// Do the common stuff when starting the alarm.private static void startAlarm(Context context, MediaPlayer player) throws IOException {AudioManager audioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);// do not play alarms if stream volume is 0 (typically because ringer mode is silent).if (audioManager.getStreamVolume(AudioManager.STREAM_ALARM) != 0) {player.setAudioStreamType(AudioManager.STREAM_ALARM);player.setLooping(true);player.prepare();audioManager.requestAudioFocus(null,AudioManager.STREAM_ALARM, AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);player.start();}/*add by leo.tan 20140717 for bugzilla 20064 start */
//在这个地方进行焦点的请求
final int requestResult = audioManager.requestAudioFocus(mAudioFocusListener,AudioManager.STREAM_ALARM,AudioManager.AUDIOFOCUS_GAIN_TRANSIENT);/*add by leo.tan 20140717 for bugzilla 20064 end */}private static void setDataSourceFromResource(Context context, MediaPlayer player, int res)throws IOException {AssetFileDescriptor afd = context.getResources().openRawResourceFd(res);if (afd != null) {player.setDataSource(afd.getFileDescriptor(), afd.getStartOffset(), afd.getLength());afd.close();}}/*add by leo.tan 20140717 for bugzilla 20064 start */private static void setVolume(float vol) {if(sMediaPlayer != null){sMediaPlayer.setVolume(vol, vol);}}//用handler来对焦点进行处理private static Handler mHandler = new Handler() {public void handleMessage(Message msg) {switch (msg.what) {case FOCUSCHANGE: {switch (msg.arg1) {case AudioManager.AUDIOFOCUS_LOSS:case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:mHandler.removeMessages(FADEUP);mHandler.sendEmptyMessage(FADEDOWN);break;case AudioManager.AUDIOFOCUS_GAIN:mHandler.removeMessages(FADEDOWN);mHandler.sendEmptyMessage(FADEUP);break;}break;}case FADEDOWN:// Turn off the soundsetVolume(0.0f);break;case FADEUP:// Turn on the soundsetVolume(1.0f);break;}}};/*add by leo.tan 20140717 for bugzilla 20064 end */
}
<span id="summary_alias_container"></span>
这篇关于android AudioManager AUDIOFOCUS的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
