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Android BLE 总结－源码篇(BluetoothLeAdvertiser)
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在做Android BLE的应用程序时，我们发出广播数据是调用BluetoothLeAdvertiser的startAdvertising方法，如下所示： mBluetoothLeAdvertiser.startAdvertising(advertiseSettings,
advertiseData, myAdvertiseCallback); 那么我打算写的BLE总结之源码篇就以此为线索来分析Android BLE FrameWork方面的东西。 public void startAdvertising(AdvertiseSettings settings,
AdvertiseData advertiseData, final AdvertiseCallback callback) {
startAdvertising(settings, advertiseData, null, callback);
}
public void startAdvertising(AdvertiseSettings settings,
AdvertiseData advertiseData, AdvertiseData scanResponse,
final AdvertiseCallback callback) {
synchronized (mLeAdvertisers) { //该check只是检查mBluetoothAdater是否为null和其状态是否为State_ON BluetoothLeUtils.checkAdapterStateOn(mBluetoothAdapter);
if (callback == null) {
throw new IllegalArgumentException("callback cannot be null");
} if (!mBluetoothAdapter.isMultipleAdvertisementSupported() &&
!mBluetoothAdapter.isPeripheralModeSupported()) {//是否支持广播和作为外围设备
postStartFailure(callback,
AdvertiseCallback.ADVERTISE_FAILED_FEATURE_UNSUPPORTED);
return;
}
boolean isConnectable = settings.isConnectable();
if (totalBytes(advertiseData, isConnectable) > MAX_ADVERTISING_DATA_BYTES ||
totalBytes(scanResponse, false) > MAX_ADVERTISING_DATA_BYTES) {
postStartFailure(callback, AdvertiseCallback.ADVERTISE_FAILED_DATA_TOO_LARGE);
return;
}
if (mLeAdvertisers.containsKey(callback)) {
postStartFailure(callback, AdvertiseCallback.ADVERTISE_FAILED_ALREADY_STARTED);
return;
}
IBluetoothGatt gatt;
try {
gatt = mBluetoothManager.getBluetoothGatt();
} catch (RemoteException e) {
Log.e(TAG, "Failed to get Bluetooth gatt - ", e);
postStartFailure(callback, AdvertiseCallback.ADVERTISE_FAILED_INTERNAL_ERROR);
return;
}
AdvertiseCallbackWrapper wrapper = new AdvertiseCallbackWrapper(callback, advertiseData,
scanResponse, settings, gatt);
wrapper.startRegisteration();
}
} 大家可以看到在startAdvertising内部，首先经过了一系列的判断，然后包装了一个叫作AdvertiseCallbackWrapper的类来做发广播数据的行为。 我们先看一下startAdvertising内部都是做了哪些判断：
1.判断蓝牙是否已经打开，否则抛出异常。 2.判断回调callback是否为空 3.判断当前设备是否支持广播数据和作为外围设备 4.判断广播数据包的长度是否超过了31字节 5.判断广播是否已经开始 经过了这５步初步的判断，下面来到了最重要的地方，mBluetoothManager.getBluetoothGatt();获取一个引用，最终的发送广播和停止广播都是通过这个引用来进行实现的。这里不进行展开，因为本文主要是对BluetoothLeAdvertiser的解读。 下面我们就来看看刚才提到的AdvertiseCallbackWrapper，代码如下： /**
* Bluetooth GATT interface callbacks for advertising.
*/
private class AdvertiseCallbackWrapper extends BluetoothGattCallbackWrapper {
private static final int LE_CALLBACK_TIMEOUT_MILLIS = 2000;
private final AdvertiseCallback mAdvertiseCallback;
private final AdvertiseData mAdvertisement;
private final AdvertiseData mScanResponse;
private final AdvertiseSettings mSettings;
private final IBluetoothGatt mBluetoothGatt;
// mClientIf 0: not registered
// -1: advertise stopped or registration timeout
// >0: registered and advertising started
private int mClientIf;
private boolean mIsAdvertising = false;
public AdvertiseCallbackWrapper(AdvertiseCallback advertiseCallback,
AdvertiseData advertiseData, AdvertiseData scanResponse,
AdvertiseSettings settings,
IBluetoothGatt bluetoothGatt) {
mAdvertiseCallback = advertiseCallback;
mAdvertisement = advertiseData;
mScanResponse = scanResponse;
mSettings = settings;
mBluetoothGatt = bluetoothGatt;
mClientIf = 0;
}
public void startRegisteration() {
synchronized (this) {
if (mClientIf == -1) return;//这个就不解释了
try {
UUID uuid = UUID.randomUUID();
mBluetoothGatt.registerClient(new ParcelUuid(uuid), this);//注册
wait(LE_CALLBACK_TIMEOUT_MILLIS);//等待２秒,在过程中会依次回调onClientRegistered和onMultiAdvertiseCallback
} catch (InterruptedException | RemoteException e) {
Log.e(TAG, "Failed to start registeration", e);
} //注册成功并且广播成功，加入广播缓存，以callback为key的Hashmap,callback为用户自己定义的Callback if (mClientIf > 0 && mIsAdvertising) {
mLeAdvertisers.put(mAdvertiseCallback, this);
} else if (mClientIf <= 0) {//注册失败
// Registration timeout, reset mClientIf to -1 so no subsequent operations can
// proceed.
if (mClientIf == 0) mClientIf = -1;
// Post internal error if registration failed.
postStartFailure(mAdvertiseCallback,
AdvertiseCallback.ADVERTISE_FAILED_INTERNAL_ERROR);
} else {//注册成功但广播开启失败
// Unregister application if it's already registered but advertise failed.
try {
mBluetoothGatt.unregisterClient(mClientIf);
mClientIf = -1;
} catch (RemoteException e) {
Log.e(TAG, "remote exception when unregistering", e);
}
}
}
}
public void stopAdvertising() {
synchronized (this) {
try {
mBluetoothGatt.stopMultiAdvertising(mClientIf);
wait(LE_CALLBACK_TIMEOUT_MILLIS);
} catch (InterruptedException | RemoteException e) {
Log.e(TAG, "Failed to stop advertising", e);
}
// Advertise callback should have been removed from LeAdvertisers when
// onMultiAdvertiseCallback was called. In case onMultiAdvertiseCallback is never
// invoked and wait timeout expires, remove callback here.
if (mLeAdvertisers.containsKey(mAdvertiseCallback)) {
mLeAdvertisers.remove(mAdvertiseCallback);
}
}
}
/**
* Application interface registered - app is ready to go
*/
@Override
public void onClientRegistered(int status, int clientIf) {
Log.d(TAG, "onClientRegistered() - status=" + status + " clientIf=" + clientIf);
synchronized (this) {
if (status == BluetoothGatt.GATT_SUCCESS) {
try {
if (mClientIf == -1) {//在２秒内未完成注册，超时
// Registration succeeds after timeout, unregister client.
mBluetoothGatt.unregisterClient(clientIf);
} else {//完成注册，并开始广播
mClientIf = clientIf;
mBluetoothGatt.startMultiAdvertising(mClientIf, mAdvertisement,
mScanResponse, mSettings);
}
return;
} catch (RemoteException e) {
Log.e(TAG, "failed to start advertising", e);
}
}
// Registration failed.
mClientIf = -1;
notifyAll();
}
}
@Override
public void onMultiAdvertiseCallback(int status, boolean isStart,
AdvertiseSettings settings) {
synchronized (this) {
if (isStart) {//广播成功时的回调
if (status == AdvertiseCallback.ADVERTISE_SUCCESS) {
// Start success
mIsAdvertising = true;
postStartSuccess(mAdvertiseCallback, settings);
} else {
// Start failure.
postStartFailure(mAdvertiseCallback, status);
}
} else {//stop 时的回调，用来反注册和清除缓存的callback
// unregister client for stop.
try {
mBluetoothGatt.unregisterClient(mClientIf);
mClientIf = -1;
mIsAdvertising = false;
mLeAdvertisers.remove(mAdvertiseCallback);
} catch (RemoteException e) {
Log.e(TAG, "remote exception when unregistering", e);
}
}
notifyAll();
}
}
}
private void postStartFailure(final AdvertiseCallback callback, final int error) {
mHandler.post(new Runnable() {
@Override
public void run() {
callback.onStartFailure(error);
}
});
}
private void postStartSuccess(final AdvertiseCallback callback,
final AdvertiseSettings settings) {
mHandler.post(new Runnable() {
@Override
public void run() {
callback.onStartSuccess(settings);
}
});
} AdvertiseCallbackWrapper的成员变量mClientIf非常重要，在广播发送和停止的过程中起着重要的作用。这里先简单的记住该属性的以下特征： mClientIf=0——>未注册 mClinetIf=-1——>广播停止或注册超时 mClientIf>0——>已注册并且已经广播成功 mClientIf默认值为0 这时我们追踪到startRegisteration这个方法了，该方法里面调用了registerClient方法，经过IPC通信后会回调到onClientRegistered方法，继续调用到了startMultiAdvertising方法，接着触发onMultiAdvertiseCallback，成功发送广播后，将该AdvertiseCallbackWrapper对象加入mLeAdvertisers。 这里我们需要注意和了解以下几点： 1.在调用startRegisteration的2秒的时间内，如果没有注册成功且广播成功，这次广播数据的行为均为失败。 2.即使2秒之后onClientRegistered回调，也将视为注册未成功，并进行解注册操作。 startAdvertising方法就到这，至于更底层的细节后续的文章会展开，下面我们看一下其对应的stopAdvertising方法 /**
* Stop Bluetooth LE advertising. The {@code callback} must be the same one use in
* {@link BluetoothLeAdvertiser#startAdvertising}.
* <p>
* Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission.
*
* @param callback {@link AdvertiseCallback} identifies the advertising instance to stop.
*/
public void stopAdvertising(final AdvertiseCallback callback) {
synchronized (mLeAdvertisers) {
if (callback == null) {
throw new IllegalArgumentException("callback cannot be null");
}
AdvertiseCallbackWrapper wrapper = mLeAdvertisers.get(callback);
if (wrapper == null) return;
wrapper.stopAdvertising();
}
} 大家可以看到，stopAdvertising方法内部是调用AdvertiseCallbackWrapper.stopAdvertising方法。这里必须注意stopAdvertising方法的callback必须和start时传入的callback参数是同一个。否则在mLeAdvertisers缓存里是找不到相应的AdvertiseCallbackWrapper的实例的，就无法正常停止广播。
转载请注明：http://blog.csdn.net/android_jiangjun/article/details/77946857
