android 按键声音
https://www.360doc.com/content/13/1217/19/1698092_337948357.shtml
1.Android的audio流的类型有以下12种:
- /* The audio stream for phone calls */
- public static final int STREAM_VOICE_CALL = 0;//通话连接时的音频流(通话声)
- /* The audio stream for system sounds */
- public static final int STREAM_SYSTEM = 1;//系统音频流
- /* The audio stream for the phone ring and message alerts */
- public static final int STREAM_RING = 2;//来电铃声
- /* The audio stream for music playback */
- public static final int STREAM_MUSIC = 3;//媒体音频流
- /* The audio stream for alarms */
- public static final int STREAM_ALARM = 4;//闹钟音频流
- /* The audio stream for notifications */
- public static final int STREAM_NOTIFICATION = 5;//通知音频流
- /* @hide The audio stream for phone calls when connected on bluetooth */
- public static final int STREAM_BLUETOOTH_SCO = 6;//从注释上看时使用蓝牙耳机通话的音频流
- /* @hide The audio stream for enforced system sounds in certain countries (e.g camera in Japan) */
- public static final int STREAM_SYSTEM_ENFORCED = 7;//一些国家强制使用的音频流??不太明白
- /* @hide The audio stream for DTMF tones */
- public static final int STREAM_DTMF = 8;//DTMF音频流
- /* @hide The audio stream for text to speech (TTS) */
- public static final int STREAM_TTS = 9;//TTS: Text to Speech:文件到语言的音频流,即机器说话
- /* @hide The audio stream for Fm */
- public static final int STREAM_FM = 10;//FM的音频流
- /* @hide The audio stream for MATV */
- public static final int STREAM_MATV = 11;//TV的音频流
每种音频流所规定的最大值:
- /** @hide Maximum volume index values for audio streams */
- private int[] MAX_STREAM_VOLUME = new int[] {
- 6, // STREAM_VOICE_CALL
- 7, // STREAM_SYSTEM
- 7, // STREAM_RING
- 12, // STREAM_MUSIC
- 7, // STREAM_ALARM
- 7, // STREAM_NOTIFICATION
- 15, // STREAM_BLUETOOTH_SCO
- 7, // STREAM_SYSTEM_ENFORCED
- 15, // STREAM_DTMF
- 15, // STREAM_TTS
- 13, //STREAM_FM
- 13 //stream_MATV
- };
2.所有的按键事件都是touch事件,这部分我会另外开篇博文介绍。
开始本文正文,Anndroid系统中所有View带有按键音,用户可以通过Settings>Sound>勾选Audible Selection即可开启按键音。但是有个奇怪的地方:此按键音是与媒体音量(即STREAM_MUSIC)绑定的,难道按键音的STREAM TYPE就是STREAM_MUSIC吗?我们从代码中寻找一下。
首先所有的View点击的时候都有按键音,我们从View.java的点击事件找起,在view的响应的onTouchEvent()方法中有如下代码:
- switch (event.getAction()) {
- case MotionEvent.ACTION_UP:
- boolean prepressed = (mPrivateFlags & PREPRESSED) != 0;
- if ((mPrivateFlags & PRESSED) != 0 || prepressed) {
- // take focus if we don't have it already and we should in
- // touch mode.
- boolean focusTaken = false;
- if (isFocusable() && isFocusableInTouchMode() && !isFocused()) {
- focusTaken = requestFocus();
- }
- if (!mHasPerformedLongPress) {
- // This is a tap, so remove the longpress check
- removeLongPressCallback();
- // Only perform take click actions if we were in the pressed state
- if (!focusTaken) {
- // Use a Runnable and post this rather than calling
- // performClick directly. This lets other visual state
- // of the view update before click actions start.
- if (mPerformClick == null) {
- mPerformClick = new PerformClick();
- }
- if (!post(mPerformClick)) {
- performClick();//这里响应click事件
- }
- }
- }
- if (mUnsetPressedState == null) {
- mUnsetPressedState = new UnsetPressedState();
- }
- if (prepressed) {
- mPrivateFlags |= PRESSED;
- refreshDrawableState();
- postDelayed(mUnsetPressedState,
- ViewConfiguration.getPressedStateDuration());
- } else if (!post(mUnsetPressedState)) {
- // If the post failed, unpress right now
- mUnsetPressedState.run();
- }
- removeTapCallback();
- }
- break;
- public boolean performClick() {
- sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
- if (mOnClickListener != null) {
- playSoundEffect(SoundEffectConstants.CLICK);
- mOnClickListener.onClick(this);
- return true;
- }
- return false;
- }
- public class SoundEffectConstants
- {
- SoundEffectConstants() { throw new RuntimeException("Stub!"); }
- public static int getContantForFocusDirection(int direction) { throw new RuntimeException("Stub!"); }
- public static final int CLICK = 0;
- public static final int NAVIGATION_LEFT = 1;
- public static final int NAVIGATION_UP = 2;
- public static final int NAVIGATION_RIGHT = 3;
- public static final int NAVIGATION_DOWN = 4;
- }
playSoundEffect ()的具体内容如下:
- public void playSoundEffect(int soundConstant) {
- if (mAttachInfo == null || mAttachInfo.mRootCallbacks == null || !isSoundEffectsEnabled()) {
- return;
- }
- mAttachInfo.mRootCallbacks.playSoundEffect(soundConstant);
- }
真正调用的是AttachInfo Callbacks接口的playSoundEffect()函数:
- /**
- * A set of information given to a view when it is attached to its parent
- * window.
- */
- static class AttachInfo {
- interface Callbacks {
- void playSoundEffect(int effectId);
- boolean performHapticFeedback(int effectId, boolean always);
- }
看注释可知其真正的方法写在parent window中,那parent window是哪个呢?ViewRoot的实现该回调接口:
- public final class ViewRoot extends Handler implements ViewParent,
- View.AttachInfo.Callbacks {
具体的playSoundEffect()函数内容:
- public void playSoundEffect(int effectId) {
- checkThread();
- try {
- final AudioManager audioManager = getAudioManager();
- switch (effectId) {
- case SoundEffectConstants.CLICK:
- audioManager.playSoundEffect(AudioManager.FX_KEY_CLICK);
- return;
- case SoundEffectConstants.NAVIGATION_DOWN:
- audioManager.playSoundEffect(AudioManager.FX_FOCUS_NAVIGATION_DOWN);
- return;
- case SoundEffectConstants.NAVIGATION_LEFT:
- audioManager.playSoundEffect(AudioManager.FX_FOCUS_NAVIGATION_LEFT);
- return;
- case SoundEffectConstants.NAVIGATION_RIGHT:
- audioManager.playSoundEffect(AudioManager.FX_FOCUS_NAVIGATION_RIGHT);
- return;
- case SoundEffectConstants.NAVIGATION_UP:
- audioManager.playSoundEffect(AudioManager.FX_FOCUS_NAVIGATION_UP);
- return;
- default:
- throw new IllegalArgumentException("unknown effect id " + effectId +
- " not defined in " + SoundEffectConstants.class.getCanonicalName());
- }
- } catch (IllegalStateException e) {
- // Exception thrown by getAudioManager() when mView is null
- Log.e(TAG, "FATAL EXCEPTION when attempting to play sound effect: " + e);
- e.printStackTrace();
- }
- }
我们传入的参数为SoundEffectContants.CLICK,调用AudioManager的playSoundEffect()方法,参数为AudioManger.FX_KEY_CLICK,继续往下看,在AudioManager.java中playSoundEffect()方法:
- public void playSoundEffect(int effectType) {
- if (effectType < 0 || effectType >= NUM_SOUND_EFFECTS) {
- return;
- }
- if (!querySoundEffectsEnabled()) {
- return;
- }
- IAudioService service = getService();
- try {
- service.playSoundEffect(effectType);
- } catch (RemoteException e) {
- Log.e(TAG, "Dead object in playSoundEffect"+e);
- }
- }
- /** @see AudioManager#playSoundEffect(int) */
- public void playSoundEffect(int effectType) {
- sendMsg(mAudioHandler, MSG_PLAY_SOUND_EFFECT, SHARED_MSG, SENDMSG_NOOP,
- effectType, -1, null, 0);
- }
- private static void sendMsg(Handler handler, int baseMsg, int streamType,
- int existingMsgPolicy, int arg1, int arg2, Object obj, int delay) {
- int msg = (streamType == SHARED_MSG) ? baseMsg : getMsg(baseMsg, streamType);
- if (existingMsgPolicy == SENDMSG_REPLACE) {
- handler.removeMessages(msg);
- } else if (existingMsgPolicy == SENDMSG_NOOP && handler.hasMessages(msg)) {
- Log.d(TAG, "sendMsg: Msg " + msg + " existed!");
- return;
- }
- handler
- .sendMessageDelayed(handler.obtainMessage(msg, arg1, arg2, obj), delay);
- }
该方法就是将传入的参数经过计算,obtain一个message,message的what = 7 arg1 = 0 arg2 = -1 object = null; 处理该消息的地方handleMessage
():
- @Override
- public void handleMessage(Message msg) {
- int baseMsgWhat = getMsgBase(msg.what);
- switch (baseMsgWhat) {
- ...
- case MSG_PLAY_SOUND_EFFECT:
- playSoundEffect(msg.arg1, msg.arg2);
- break;
- ...
- }
调用了带两个参数的playSoundEffect()函数,传入参数 0,-1:
- private void playSoundEffect(int effectType, int volume) {
- synchronized (mSoundEffectsLock) {
- if (mSoundPool == null) {
- return;
- }
- float volFloat;
- // use STREAM_MUSIC volume attenuated by 3 dB if volume is not specified by caller
- if (volume < 0) {
- //以下计算播放的音量大小:
- // Same linear to log conversion as in native AudioSystem::linearToLog() (AudioSystem.cpp)
- float dBPerStep = (float)((0.5 * 100) / MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC]);
- int musicVolIndex = (mStreamStates[AudioSystem.STREAM_MUSIC].mIndex + 5) / 10;
- float musicVoldB = dBPerStep * (musicVolIndex - MAX_STREAM_VOLUME[AudioSystem.STREAM_MUSIC]);
- volFloat = (float)Math.pow(10, (musicVoldB - 3)/20);
- } else {
- volFloat = (float) volume / 1000.0f;
- }
- if (SOUND_EFFECT_FILES_MAP[effectType][1] > 0) {
- mSoundPool.play(SOUND_EFFECT_FILES_MAP[effectType][1], volFloat, volFloat, 0, 0, 1.0f);//调用该函数播放按键音
- } else {
- MediaPlayer mediaPlayer = new MediaPlayer();
- if (mediaPlayer != null) {
- try {
- String filePath = Environment.getRootDirectory() + SOUND_EFFECTS_PATH + SOUND_EFFECT_FILES[SOUND_EFFECT_FILES_MAP[effectType][0]];
- mediaPlayer.setDataSource(filePath);
- mediaPlayer.setAudioStreamType(AudioSystem.STREAM_RING);
- mediaPlayer.prepare();
- mediaPlayer.setVolume(volFloat, volFloat);
- mediaPlayer.setOnCompletionListener(new OnCompletionListener() {
- public void onCompletion(MediaPlayer mp) {
- cleanupPlayer(mp);
- }
- });
- mediaPlayer.setOnErrorListener(new OnErrorListener() {
- public boolean onError(MediaPlayer mp, int what, int extra) {
- cleanupPlayer(mp);
- return true;
- }
- });
- mediaPlayer.start();
- } catch (IOException ex) {
- Log.w(TAG, "MediaPlayer IOException: "+ex);
- } catch (IllegalArgumentException ex) {
- Log.w(TAG, "MediaPlayer IllegalArgumentException: "+ex);
- } catch (IllegalStateException ex) {
- Log.w(TAG, "MediaPlayer IllegalStateException: "+ex);
- }
- }
- }
- }
- }
因为传入的参数volume为-1,按键音大小的值走if(volume < 0)内,函数中此部分计算的是按键音的大小volFloat,可以看出,整个计算过程都跟媒体音量STREAM_MUSIC有关,这里就看出,按键音的音量大小是与STREAM_MUSIC绑定的,那按键音的类型呢?继续看下去,函数 mSoundPool.play(SOUND_EFFECT_FILES_MAP[effectType][1],
volFloat, volFloat, 0, 0, 1.0f);中使用了SoundPool来播放按键音,我们看看该SoundPool初始化步骤,在AudioService初始化时,调用了loadSoundEffects()函数:
- public AudioService(Context context) {
- ......
- loadSoundEffects();
- .......
- }
loadSoundEffects()函数的具体实现如下:
- public boolean loadSoundEffects() {
- synchronized (mSoundEffectsLock) {
- if (mSoundPool != null) {
- return true;
- }
- mSoundPool = new SoundPool(NUM_SOUNDPOOL_CHANNELS, AudioSystem.STREAM_SYSTEM, 0);
- ......
- return true;
- }
在此函数中,初始化了该SoundPool,类型为STREAM_SYSTEM。
到这里,结果出来了,android中,view的按键音类型为系统音频(STREAM_SYSTEM),而音量的大小与媒体音量(STREAM_MUSIC)绑定了起来。
最后更新:2017-04-03 12:53:47