安卓鎖屏音樂控件開發

             首先我個人先吐槽一下，這是一個吃力不討好的活。爲什麼？因爲現在安卓手機的各種定製rom五花八門，各種各樣，miui、樂蛙、emui、努比亞。。。我們今天要做的事情就是要在各種系統的鎖屏界面，出現一個音樂控件，用來做一些簡單的音樂播放的控制。

             做之前，習慣性的看了各大家的做法：酷我、多米等，這些家的做法的思路都一樣，都是在自己的應用中監聽power鎖屏事件，然後加一個“假鎖屏”，即每次鎖屏再打開的時候，首先顯示的是自己音樂的鎖屏，滑開以後再跳到系統的鎖屏。這樣做的好處是，通吃各種系統，弊端也是顯而易見：鎖屏太多了！！！尼瑪，對於普通用戶，究竟要滑幾次才能解開？

假鎖屏的方案棄置後，只能犧牲適配性，而考慮實用性，於是有了本文。本文做的是，針對安卓原生系統開發的音樂控件！因爲是建立在原生的keyguard上的，所以一些野路子第三方ROM不支持，也是正常。正文開始：

              基於原生android開發，需要用的一個很重要的類RemoteControlClient，RemoteControlClient是從API 14也就是android 4.0開始出現的類，用於在鎖屏狀態控制音樂播放。界面是系統提供的。

api doc文檔上附了一段註冊代碼

<pre class="prettyprint" name="code" style="white-space: pre-wrap; word-wrap: break-word; font-size: 14px; margin-top: 0px; margin-bottom: 1em; color: rgb(0, 102, 0); line-height: 1.5; font-family: 'courier new', courier, monospace; padding: 1em; overflow: auto; border: 1px solid rgb(221, 221, 221); background-color: rgb(247, 247, 247);"><span class="typ" style="color: rgb(102, 0, 102);">ComponentName</span><span class="pln" style="color: rgb(0, 0, 0);"> myEventReceiver </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">new</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">ComponentName</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">getPackageName</span><span class="pun" style="color: rgb(102, 102, 0);">(),</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">MyRemoteControlEventReceiver</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="kwd" style="color: rgb(0, 0, 136);">class</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">getName</span><span class="pun" style="color: rgb(102, 102, 0);">());</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="typ" style="color: rgb(102, 0, 102);">AudioManager</span><span class="pln" style="color: rgb(0, 0, 0);"> myAudioManager </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">AudioManager</span><span class="pun" style="color: rgb(102, 102, 0);">)</span><span class="pln" style="color: rgb(0, 0, 0);"> getSystemService</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">Context</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">AUDIO_SERVICE</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 myAudioManager</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">registerMediaButtonEventReceiver</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">myEventReceiver</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="com" style="color: rgb(136, 0, 0);">// build the PendingIntent for the remote control client</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="typ" style="color: rgb(102, 0, 102);">Intent</span><span class="pln" style="color: rgb(0, 0, 0);"> mediaButtonIntent </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">new</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">Intent</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="typ" style="color: rgb(102, 0, 102);">Intent</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">ACTION_MEDIA_BUTTON</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 mediaButtonIntent</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">setComponent</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">myEventReceiver</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="typ" style="color: rgb(102, 0, 102);">PendingIntent</span><span class="pln" style="color: rgb(0, 0, 0);"> mediaPendingIntent </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">PendingIntent</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">getBroadcast</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">getApplicationContext</span><span class="pun" style="color: rgb(102, 102, 0);">(),</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> mediaButtonIntent</span><span class="pun" style="color: rgb(102, 102, 0);">,</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="lit" style="color: rgb(0, 102, 102);">0</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="com" style="color: rgb(136, 0, 0);">// create and register the remote control client</span><span class="pln" style="color: rgb(0, 0, 0);">
 </span><span class="typ" style="color: rgb(102, 0, 102);">RemoteControlClient</span><span class="pln" style="color: rgb(0, 0, 0);"> myRemoteControlClient </span><span class="pun" style="color: rgb(102, 102, 0);">=</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="kwd" style="color: rgb(0, 0, 136);">new</span><span class="pln" style="color: rgb(0, 0, 0);"> </span><span class="typ" style="color: rgb(102, 0, 102);">RemoteControlClient</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">mediaPendingIntent</span><span class="pun" style="color: rgb(102, 102, 0);">);</span><span class="pln" style="color: rgb(0, 0, 0);">
 myAudioManager</span><span class="pun" style="color: rgb(102, 102, 0);">.</span><span class="pln" style="color: rgb(0, 0, 0);">registerRemoteControlClient</span><span class="pun" style="color: rgb(102, 102, 0);">(</span><span class="pln" style="color: rgb(0, 0, 0);">myRemoteControlClient</span><span class="pun" style="color: rgb(102, 102, 0);">);</span>

上面的代碼開始時註冊了耳機按鍵的事件，接着註冊了RemoteControlClient。

要想弄出RemoteControlClient的界面，上面的代碼還不夠，還需要把當前音樂狀態設置爲正在播放

mClient.setPlaybackState(RemoteControlClient.PLAYSTATE_PLAYING)

並且必須獲取當前的stream focus

am.requestAudioFocus(new OnAudioFocusChangeListener() {

    @Override
    public void onAudioFocusChange(int focusChange) {
        System.out.println("focusChange = " + focusChange);
    }
}, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);

這樣，在鎖屏狀態系統界面就能出現了，默認只有一個播放暫停按鈕。要想顯示額外的信息，使用editMetadata(boolean startEmpty)去put，如果想多顯示幾個控制按鈕，如下：

int flags = RemoteControlClient.FLAG_KEY_MEDIA_PREVIOUS
        | RemoteControlClient.FLAG_KEY_MEDIA_NEXT
        | RemoteControlClient.FLAG_KEY_MEDIA_PLAY
        | RemoteControlClient.FLAG_KEY_MEDIA_PAUSE
        | RemoteControlClient.FLAG_KEY_MEDIA_PLAY_PAUSE
        | RemoteControlClient.FLAG_KEY_MEDIA_STOP;
mClient.setTransportControlFlags(flags);

所有按鍵的響應事件都在註冊的receiver中。