Android关于view按键音的修改

最新推荐文章于 2024-07-08 03:04:05 发布

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最新推荐文章于 2024-07-08 03:04:05 发布 · 5.8k 阅读

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CC 4.0 BY-SA版权

文章标签：

#android #stream #audio #system #null #float

本文探讨了Android系统中View的按键音，揭示了按键音实际上是与媒体音量（STREAM_MUSIC）绑定的。通过分析源码，从View的点击事件开始，追踪到AudioService，发现按键音的STREAM_TYPE为STREAM_SYSTEM，但其音量受媒体音量控制。

首先简单介绍下预备知识：

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) {