Android(安卓)控制车载蓝牙播放音乐详解流程
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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