Android 控制车载蓝牙播放音乐详解流程
作者：路过独木桥！！
需求：手机端音乐暂停和播放状态从服务端告诉客户端、设备端实现暂停、播放、上一首、下一首等功能
代码路径：
packages/apps/Bluetooth/src/com/android/bluetooth/avrcpcontroller/AvrcpControllerService.java
packages/apps/Bluetooth/src/com/android/bluetooth/avrcpcontroller/AvrcpControllerStateMachine.java
packages/apps/Bluetooth/src/com/android/bluetooth/a2dpsink/A2dpSinkService.java
packages/apps/Bluetooth/src/com/android/bluetooth/avrcpcontroller/AvrcpControllerService.java
packages/apps/Bluetooth/jni/com_android_bluetooth_avrcp_controller.cpp
一、蓝牙音乐播放状态
1、在AvrcpControllerService.java文件中onPlayStatusChanged()方法就是音乐播放状态改变，该方法是由JNI层中com_android_bluetooth_avrcp_controller.cpp中调用java层的
private synchronized void onPlayStatusChanged(byte[] address, byte playStatus) {
if (DBG) {
Log.d(TAG, "onPlayStatusChanged " + playStatus);
}
int playbackState = PlaybackState.STATE_NONE;
switch (playStatus) {
case JNI_PLAY_STATUS_STOPPED:
playbackState = PlaybackState.STATE_STOPPED;
break;
case JNI_PLAY_STATUS_PLAYING:
playbackState = PlaybackState.STATE_PLAYING;
break;
case JNI_PLAY_STATUS_PAUSED:
playbackState = PlaybackState.STATE_PAUSED;
break;
case JNI_PLAY_STATUS_FWD_SEEK:
playbackState = PlaybackState.STATE_FAST_FORWARDING;
break;
case JNI_PLAY_STATUS_REV_SEEK:
playbackState = PlaybackState.STATE_REWINDING;
break;
default:
playbackState = PlaybackState.STATE_NONE;
}
BluetoothDevice device = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(address);
AvrcpControllerStateMachine stateMachine = getStateMachine(device);
if (stateMachine != null) {
stateMachine.sendMessage(
AvrcpControllerStateMachine.MESSAGE_PROCESS_PLAY_STATUS_CHANGED, playbackState);
}
}
2、在AvrcpControllerStateMachine.java文件中Connected类中
MESSAGE_PROCESS_PLAY_STATUS_CHANGED消息就是处理播放状态的，然后通过广播方式把该状态发送出去
case MESSAGE_PROCESS_PLAY_STATUS_CHANGED:
if (SystemProperties.get("persist.ivi.feature", "0").equals("1")) {
A2dpSinkService a2dpSinkService = A2dpSinkService.getA2dpSinkService();
Log.d(TAG, "the state: " + msg.arg1);
if (a2dpSinkService != null && msg.arg1 != preAudioStatus) {
preAudioStatus = msg.arg1;
Log.d(TAG, "preAudioStatus: " + msg.arg1);
if (msg.arg1 == PlaybackState.STATE_PLAYING) {
//播放
a2dpSinkService.informPlayState(mDevice, true);
} else if (msg.arg1 == PlaybackState.STATE_PAUSED) {
//暂停
a2dpSinkService.informPlayState(mDevice, false);
}
}
}
Intent intent = new Intent("zqc.bluetooth.PLAY_STATUS_CHANGED");
intent.putExtra("zqc.bluetooth.PLAYBACK", msg.arg1);
mService.sendBroadcast(intent);
mAddressedPlayer.setPlayStatus(msg.arg1);
BluetoothMediaBrowserService.notifyChanged(mAddressedPlayer.getPlaybackState());
if (mAddressedPlayer.getPlaybackState().getState()
== PlaybackState.STATE_PLAYING
&& A2dpSinkService.getFocusState() == AudioManager.AUDIOFOCUS_NONE
&& !shouldRequestFocus()) {
sendMessage(MSG_AVRCP_PASSTHRU,
AvrcpControllerService.PASS_THRU_CMD_ID_PAUSE);
}
return true;
二、蓝牙音乐中怎么获取音乐信息
1、在AvrcpControllerService.java文件中onTrackChanged()方法中是获取JNI层上报的音乐信息，该方法是由JNI层中com_android_bluetooth_avrcp_controller.cpp中调用java层的
private synchronized void onTrackChanged(byte[] address, byte numAttributes, int[] attributes,
String[] attribVals) {
if (DBG) {
Log.d(TAG, "onTrackChanged");
}
BluetoothDevice device = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(address);
AvrcpControllerStateMachine stateMachine = getStateMachine(device);
//该方法就是把蓝牙音乐的信息传递给java层
getElementAttrRsp(attributes,attribVals,numAttributes);
if (stateMachine != null) {
stateMachine.sendMessage(AvrcpControllerStateMachine.MESSAGE_PROCESS_TRACK_CHANGED,
TrackInfo.getMetadata(attributes, attribVals));
}
}
2、在AvrcpControllerService.java文件中getElementAttrRsp()中，然后通过该方法中通过广播告诉出去
private void getElementAttrRsp(int[] attr_id,String[] textArray,byte num_attr){
String artist = null;
String trackTitle = null;
String album = null;
for (int i = 0; i < num_attr; i++){
switch (attr_id[i]) {
case JNI_MEDIA_ATTR_ID_TITLE:
trackTitle = textArray[i];
if (trackTitle == null){
trackTitle = "Unknown";
}
break;
case JNI_MEDIA_ATTR_ID_ARTIST:
artist = textArray[i];
if (artist == null){
artist = "Unknown";
}
break;
case JNI_MEDIA_ATTR_ID_ALBUM:
album = textArray[i];
if (album == null){
album = "Unknown";
}
break;
}
}
Intent intent = new Intent("com.android.getelementattrrsp");
intent.putExtra("artist", artist);
intent.putExtra("trackTitle",trackTitle);
intent.putExtra("album",album);
Log.d(TAG,"getElementAttrRsp,artist: " + artist + ",trackTitle: " + trackTitle + ",album: " + album);
intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);
sendBroadcast(intent, ProfileService.BLUETOOTH_PERM);
}
三、设备蓝牙音乐中上一首、下一首、暂停功能控制手机端
1、在AvrcpControllerService.java文件中sendPassThroughCmd()方法来控制暂停、播放、上一首、下一首等功能
public synchronized void sendPassThroughCmd(BluetoothDevice device, int keyCode, int keyState) {
Log.v(TAG, "sendPassThroughCmd keyCode: " + keyCode + " keyState: " + keyState);
if (device == null) {
Log.e(TAG, "sendPassThroughCmd Device is null");
return;
}
AvrcpControllerStateMachine stateMachine = getStateMachine(device);
if (stateMachine != null) {
stateMachine.sendMessage(AvrcpControllerStateMachine.MESSAGE_SEND_PASS_THROUGH_CMD,
keyCode, keyState, device);
}
}
2、在AvrcpControllerStateMachine.java文件中MESSAGE_SEND_PASS_THROUGH_CMD变量中通过JNI层来实现功能
case MESSAGE_SEND_PASS_THROUGH_CMD:
BluetoothDevice device = (BluetoothDevice) msg.obj;
mService.sendPassThroughCommandNative(Utils.getByteAddress(device), msg.arg1,
msg.arg2);
return true;
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