如今開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一时候响起。
引起此问题的解决办法是音乐焦点问题没弄清
现分析一下音乐焦点的几个属性:源代码在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,通常是长期占有。获得了Audio Focus;
public static final int AUDIOFOCUS_GAIN = 1;
指示要申请的AudioFocus是临时性的,会非常快用完释放的;
public static final int AUDIOFOCUS_GAIN_TRANSIENT = 2;
不但说要申请的AudioFocus是临时性的。还指示当前正在使用AudioFocus的能够继续播放,仅仅是要“duck”一下(减少音量)。
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,兴许假设有别的程序要竞争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,并将会持续非常长的时间
public static final int AUDIOFOCUS_LOSS = -1 * AUDIOFOCUS_GAIN;
临时失去Audio Focus,并会非常快再次获得。必须停止Audio的播放。可是由于可能会非常快再次获得AudioFocus。这里能够不释放Media资源;
public static final int AUDIOFOCUS_LOSS_TRANSIENT = -1 * AUDIOFOCUS_GAIN_TRANSIENT;
临时失去AudioFocus,可是能够继续播放,只是要在减少音量。
public static final int AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK =
-1 * AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK;
看看刚才改动的一个问题:
问题描写叙述: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,闹钟和音乐同一时候响起;
问题分析:在闹钟铃声响起时,没有去做音频焦点的处理
解决方式:在packages/apps/deskclock/src/com/android/deskclock/alarms/AlarmKlaxon.java文件里加上焦点处理
改动后的源代码:
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 playing if (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 starting stop(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() { @Override public 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 sound setVolume(0.0f); break; case FADEUP: // Turn on the sound setVolume(1.0f); break; } } }; /*add by leo.tan 20140717 for bugzilla 20064 end */ } <span id="summary_alias_container"></span>