Android多进程之Binder解绑监听的问题
Android多进程系列
接上一篇文章《Android多进程之手动编写Binder类》中向服务端注册监听事件的问题，在扩展了Binder类后，我们还需要改造对应的服务端和客户端
客户端和服务端的改造
服务端改造
- 增加注册监听接口的功能
private CopyOnWriteArrayList<IOnNewBookArrivedListener> mListenerList = new CopyOnWriteArrayList<IOnNewBookArrivedListener>();
private Binder mBinder = new BookManagerImpl(){
@Override
public List<Book> getBookList() throws RemoteException {
Log.e(TAG, "getBookList-->"+ System.currentTimeMillis());
return mBookList;
}
@Override
public void addBook(Book book) throws RemoteException {
Log.e(TAG, "addBook-->");
mBookList.add(book);
}
@Override
public void registerListener(IOnNewBookArrivedListener listener) {
if (!mListenerList.contains(listener)) {
mListenerList.add(listener);
}else {
Log.e(TAG, "already exists");
}
Log.e(TAG, "registerListener, size:"+mListenerList.size());
}
@Override
public void unRegisterListener(IOnNewBookArrivedListener listener) {
if (mListenerList.contains(listener)) {
mListenerList.remove(listener);
Log.e(TAG, "unRegisterListener listener succeed");
}else {
Log.e(TAG, "not found, can not unregister");
}
Log.e(TAG, "unRegisterListener, current size:"+mListenerList.size());
}
};- 添加一个任务，定时像书籍列表中添加一本书，并触发通知客户端的操作
@Override
public void onCreate() {
super.onCreate();
Log.e(TAG, "onCreate-->"+ System.currentTimeMillis());
mBookList.add(new Book(1, "Android"));
mBookList.add(new Book(2, "IOS"));
new Thread(new ServiceWorker()).start();
}
private void onNewBookArrived(Book book) throws RemoteException{
mBookList.add(book);
Log.e(TAG, "new book arrived, notify listeners:" + mListenerList.size());
for (int i=0; i<mListenerList.size(); i++) {
IOnNewBookArrivedListener listener = mListenerList.get(i);
Log.e(TAG, "new book arrived, notify listener:" + listener);
listener.onNewBookArrived(book);
}
}
private class ServiceWorker implements Runnable {
@Override
public void run() {
while (!mIsServiceDestoryed.get()) {
try {
Thread.sleep(5000);
}catch (InterruptedException e) {
e.printStackTrace();
}
int bookId = mBookList.size() + 1;
Book newBook = new Book(bookId, "new book#" + bookId);
try {
onNewBookArrived(newBook);
}catch (RemoteException e) {
e.printStackTrace();
}
}
}
}- 通知客户端的过程就是调用每个注册的监听接口的onNewBookArrived方法，也就是一个服务端调用客户端的过程，分别是调用onNewBookArrived-->onTransact-->Proxy的onNewBookArrived-->客户端
客户端改造
- 首先要声明一个IOnNewBookArrivedListener对象，并注册到服务端中
private IBookManager mRemoteBookManager;
private ServiceConnection mConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
Log.e(TAG, "ServiceConnection-->"+ System.currentTimeMillis());
IBookManager bookManager = BookManagerImpl.asInterface(iBinder);
mRemoteBookManager = bookManager;
try {
List<Book> list = bookManager.getBookList();
Log.e(TAG, "query book list, list type:" + list.getClass().getCanonicalName());
Log.e(TAG, "query book list:" + list.toString());
Book newBook = new Book(3, "Android 进阶");
bookManager.addBook(newBook);
Log.e(TAG, "add book:" + newBook);
List<Book> newList = bookManager.getBookList();
Log.e(TAG, "query book list:" + newList.toString());
bookManager.registerListener(mOnNewBookArrivedListener);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mRemoteBookManager = null;
Log.e(TAG, "binder died");
}
};
/**
* 这个方法运行在客户端的binder线程池中，不能直接进行UI操作
*/
private IOnNewBookArrivedListener mOnNewBookArrivedListener = new OnNewBookArrivedListenerImpl(){
@Override
public void onNewBookArrived(Book book) {
mHandler.obtainMessage(MESSAGE_NEW_BOOK_ARRIVED, book).sendToTarget();
}
};- 然后由于客户端的IOnNewBookArrivedListener回调方法onNewBookArrived运行在Binder线程池中，所以需要一个Handler来切换到UI线程
private static final int MESSAGE_NEW_BOOK_ARRIVED = 1;
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message message) {
switch (message.what) {
case MESSAGE_NEW_BOOK_ARRIVED:
Log.e(TAG, "receive new book:" + message.obj);
break;
default:
super.handleMessage(message);
}
}
};- 最后需要在客户端退出时解除服务端的注册监听
@Override
protected void onDestroy() {
if (mRemoteBookManager != null && mRemoteBookManager.asBinder().isBinderAlive()) {
try {
Log.e(TAG, "unRegister listener:" + mOnNewBookArrivedListener);
mRemoteBookManager.unRegisterListener(mOnNewBookArrivedListener);
}catch (RemoteException e) {
e.printStackTrace();
}
}
unbindService(mConnection);
super.onDestroy();
}改造结果
- 通过上图我们可以看到，我们已经成功实现了预期的功能，并且服务端通知客户端的调用过程也如我们上面所说的那样
- 接下去我们退出应用，这样可以测试解绑监听的功能
![解除绑定失败]( "解除绑定失败")
- 从上图我们可以看到，服务端调用解绑失败了，提示找不到接口，这是咋回事呢？
利用Binder进行进程间通信，Binder会把客户端传递的参数AIDL接口和Parcelable对象，重新转化并生成一个新的对象。因为对象是不能跨进程传输的，对象的跨进程传输本质上就是序列化和反序列化的过程。所以上述情况服务端根本就没有客户端的那个对象，那肯定找不到会解绑失败。那咋办呢？
RemoteCallBackList
RemoteCallBackList是啥
public class RemoteCallbackList<E extends IInterface> {
/*package*/ ArrayMap<IBinder, Callback> mCallbacks
= new ArrayMap<IBinder, Callback>();
...
}- RemoteCallBackList的内部有一个Map结构用来保存所有的AIDL回调，这个Map的key是IBinder类型，value是CallBack类型
public boolean register(E callback, Object cookie) {
synchronized (mCallbacks) {
if (mKilled) {
return false;
}
IBinder binder = callback.asBinder();
try {
Callback cb = new Callback(callback, cookie);
binder.linkToDeath(cb, 0);
mCallbacks.put(binder, cb);
return true;
} catch (RemoteException e) {
return false;
}
}
}- 每次有新的接口来，就调用register方法注册，添加到mCallbacks中
- 通过上面的源码我们可以看到，由于客户端跨进程传输的对象的底层的Binder对象都是同一个，所以我们可以通过这一点，当需要解除注册监听时，就可以通过遍历RemoteCallBackList找到与解绑客户端Binder对象相同的listener并删除即可
- 而且我们可以看到RemoteCallBackList中实现了线程同步，我们在利用它进行注册和解注册时不需要处理同步问题。
- 特别的是，客户端进程终止后，RemoteCallBackList能够自动解除客户端所注册的listener
用RemoteCallBackList实现实现解绑注册
private RemoteCallbackList<IOnNewBookArrivedListener> mListenerList = new RemoteCallbackList<IOnNewBookArrivedListener>();
private Binder mBinder = new BookManagerImpl(){
@Override
public List<Book> getBookList() throws RemoteException {
Log.e(TAG, "getBookList-->"+ System.currentTimeMillis());
return mBookList;
}
@Override
public void addBook(Book book) throws RemoteException {
Log.e(TAG, "addBook-->");
mBookList.add(book);
}
@Override
public void registerListener(IOnNewBookArrivedListener listener) {
//注册接口
mListenerList.register(listener);
}
@Override
public void unRegisterListener(IOnNewBookArrivedListener listener) {
//解注册接口
mListenerList.unregister(listener);
}
};
//通知客户端
private void onNewBookArrived(Book book) throws RemoteException{
mBookList.add(book);
final int N = mListenerList.beginBroadcast();
for (int i=0; i<N; i++) {
IOnNewBookArrivedListener listener = mListenerList.getBroadcastItem(i);
if (listener != null) {
try {
listener.onNewBookArrived(book);
}catch (RemoteException e) {
e.printStackTrace();
}
}
}
mListenerList.finishBroadcast();
}- 通过RemoteCallBackList的改造，我们就可以成功解注册客户端的listener了
注意点
- RemoteCallBackList并不是一个List，我们无法像操作list一样操作它，比如调用size方法
- 遍历RemoteCallBackList必须按照上面代码中的方式进行，beginBroadcast方法和finishBroadcast方法必须配对使用
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