1 废话不多说，Tower的连接方式之一是通过android通过手机自带蓝牙模块，和遥控器蓝牙通信，最后在连接飞空，飞空是一块单片机，里面也有一套程序处理逻辑，然后遥控器坐传输媒介
这样做的好处就是把一些用户操作放到android上面，比如航点规划，客服端控制飞机的起飞，降落等，最后飞空来控制无人机玩成一系列的操作
连接方式如图
2 今天主要说一下Mavlink的连接首先在Tower的源码里构建了一个类
public class MAVLinkClient implements MAVLinkStreams.MAVLinkOutputStream {
public MAVLinkClient(Context context, MAVLinkStreams.MavlinkInputStream listener) {
this.listener = listener;
}
private void connectMAVConnection() {
}
public void sendMavPacket(MAVLinkPacket pack) {
}
@Override
public void toggleConnectionState() {
if (isConnected()) {
closeConnection();
} else {
openConnection();
}
}
}
这个了主要实习了 连接，切换连接，发送数据包，和注入一个listener ， 这个listener主要是接受到数据的时候回调，所以这个类主要就是实习这个几个功能，Tower向无人机发送数据基本都是通过这个sendMavPacket方法去实现的
3 我们看看listener是个什么东西
public interface MavlinkInputStream {
void notifyConnected();
void notifyDisconnected();
void notifyReceivedData(MAVLinkMessage m);
}
这个listener的声明 ，他是用来处理收到消息的 ，调用notifyReceivedData 接受一个MavLinkmessage
4 接来我们看MavLinkClient的初始化，差看源码可以看到，在Application的初始化OnCreatef 方法里面 MAVLinkClient MAVClient = new MAVLinkClient(this, this); 可以看到Application 实现了MavlinkInputStream 接口，并且实现了 notifyReceivedData 方法
@Override
public void notifyReceivedData(MAVLinkMessage msg) {
mavLinkMsgHandler.receiveData(msg);
}
5 这样你就很容易看到在哪里处理 MAVLinkMessage 了，so ， MavLinkMsgHandler 就是 MAVLinkMessage 的处类了，你可以看到关于多种MAVLinkMessage 的处理，这些消息有心跳消息，事件消息等。。。
6 现在条理是不是很清楚了，那我们就来看android如果通过蓝牙连接飞控的，首先你必须会蓝牙连接的基础知识，网上资料很多
7 我们看连接函数
private void connectMAVConnection() {
bluetoothConnection.addMavLinkConnectionListener("blue",mConnectionListener);
Toast.makeText(parent, R.string.status_connecting, Toast.LENGTH_SHORT).show();
if (bluetoothConnection.getConnectionStatus() == MavLinkConnection.MAVLINK_DISCONNECTED) {
bluetoothConnection.connect();
}
}
直接调用了bluetoothConnection.connect(), MavLinkConnection bluetoothConnection是一个抽象类，也住无人机地面站里面的一个比较核心的类，
/**
* Listen for incoming data on the mavlink connection.
*/
private final Runnable mConnectingTask = new Runnable() {
@Override
public void run() {
Thread sendingThread = null, loggingThread = null;
try {
// Open the connection
openConnection();
mConnectionStatus.set(MAVLINK_CONNECTED);
// Launch the ‘Sending‘, and ‘Logging‘ threads
sendingThread = new Thread(mSendingTask, "MavLinkConnection-Sending Thread");
sendingThread.start();
final Parser parser = new Parser();
parser.stats.mavlinkResetStats();
final byte[] readBuffer = new byte[READ_BUFFER_SIZE];
while (mConnectionStatus.get() == MAVLINK_CONNECTED&&!isAndroidfor4_4()) {
int bufferSize = readDataBlock(readBuffer);
if (readBuffer==null||readBuffer.length==0){
continue;
}
handleData(parser, bufferSize, readBuffer);
}
} catch (Exception e) {
Log.i("===>>","disconent");
if (loggingThread != null && loggingThread.isAlive()) {
loggingThread.interrupt();
}
if (sendingThread != null && sendingThread.isAlive()) {
sendingThread.interrupt();
}
mConnectionStatus.set(MAVLINK_DISCONNECTED);
disconnect();
}
}
8 这个类有几个核心的方法 1打开连接 openConnection（），2 sendingThread不停地发送数据 3 handleData（）处理数据，在其实现类里面主要也是完成这3个方法，
public Bluetoothfor2_0Connection(Context parentContext) {
prefs = new DroidPlannerPrefs(parentContext);
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (mBluetoothAdapter == null) {
Log.d(BLUE, "Null adapters");
}
}
protected void openAndroidConnection() throws IOException {
Log.d(BLUE, "Connect");
// Reset the bluetooth connection
resetConnection();
// Retrieve the stored device
BluetoothDevice device = null;
final String addressName = prefs.getBluetoothDeviceAddress();
if (addressName != null) {
// strip name, use address part - stored as <address>;<name>
final String part[] = addressName.split(";");
try {
device = mBluetoothAdapter.getRemoteDevice(part[0]);
} catch (IllegalArgumentException ex) {
// invalid configuration (device may have been removed)
// NOP fall through to ‘no device‘
}
}
// no device
if (device == null)
device = findSerialBluetoothBoard();
Log.d(BLUE, "Trying to connect to device with address " + device.getAddress());
Log.d(BLUE, "BT Create Socket Call...");
bluetoothSocket = device.createInsecureRfcommSocketToServiceRecord(UUID
.fromString(UUID_SPP_DEVICE));
Log.d(BLUE, "BT Cancel Discovery Call...");
mBluetoothAdapter.cancelDiscovery();
Log.d(BLUE, "BT Connect Call...");
bluetoothSocket.connect(); // Here the IOException will rise on BT
// protocol/handshake error.
Log.d(BLUE, "## BT Connected ##");
out = bluetoothSocket.getOutputStream();
in = bluetoothSocket.getInputStream();
}
@Override
protected int readDataBlock(byte[] buffer) throws IOException {
return in.read(buffer);
}
@Override
protected void sendBuffer(byte[] buffer) throws IOException {
if (out != null) {
out.write(buffer);
}
}
9 handledata 方法就是回调之前的 listener.notifydatareceiver(),是不是之前地方了，至于发送数据
private final Runnable mSendingTask = new Runnable() {
@Override
public void run() {
int msgSeqNumber = 0;
try {
while (mConnectionStatus.get() == MAVLINK_CONNECTED) {
final MAVLinkPacket packet = mPacketsToSend.take();
packet.seq = msgSeqNumber;
byte[] buffer = packet.encodePacket();
if (buffer==null|| buffer.length==0){
continue;
}
try {
sendBuffer(buffer);
queueToLog(packet);
} catch (IOException e) {
reportComError(e.getMessage());
mLogger.logErr(TAG, e);
}
msgSeqNumber = (msgSeqNumber + 1) % (MAX_PACKET_SEQUENCE + 1);
}
} catch (InterruptedException e) {
};
发送数据其实也是Mavclient的 sendMavPacket方法，里面有一个阻塞队列的东西，线程安全的双端队列，可能需要你看看，思路很清晰，2可能会讲 MavlinkMessage
@Override
public void sendMavPacket(MAVLinkPacket pack) {
if (!isConnected()) {
return;
}
bluetoothConnection.sendMavPacket(pack);
}