Binder作为AIDL通信的核心, 在使用中经常需要重复利用, 动态管理AIDL接口. Binder连接池的主要作用是把Binder请求统一发送至Service执行, 即动态管理Binder操作, 避免重复创建Service. 本文使用两种简单的AIDL服务, 使用Binder连接池动态切换, 含有演示Demo.

Binder

本文源码的GitHub下载地址

AIDL

模拟Binder连接池, 使用两个简单的AIDL接口与实现, 一个是加解密, 一个是加法.

加解密, AIDL提供两个方法, 即加密字符串和解密字符串.

package org.wangchenlong.binderpooldemo;interface ISecurityCenter {String encrypt(String content);String decrypt(String password);
}

加密和解密的实现, 使用简单的异或运算处理.

public class SecurityCenterImpl extends ISecurityCenter.Stub {private static final char SECRET_CODE = 'w';@Override public String encrypt(String content) throws RemoteException {char[] chars = content.toCharArray();for (int i = 0; i < chars.length; i++) {chars[i] ^= SECRET_CODE;}return new String(chars);}@Override public String decrypt(String password) throws RemoteException {return encrypt(password);}
}

AIDL的实现方法都需要设置RemoteException的异常抛出, 防止连接异常.

求和的AIDL接口

package org.wangchenlong.binderpooldemo;interface ICompute {int add(int a, int b);
}

求和的实现, 非常简单.

public class ComputeImpl extends ICompute.Stub {@Override public int add(int a, int b) throws RemoteException {return a + b;}
}

Binder连接池通过ID查找Bidner, 查询并返回匹配的Binder.

package org.wangchenlong.binderpooldemo;interface IBinderPool {IBinder queryBinder(int binderCode);
}

Binder 连接池

Service服务通过Binder连接池动态选择Binder请求.

private Binder mBinderPool = new BinderPool.BinderPoolImpl(); // 动态选择Binder@Nullable @Override public IBinder onBind(Intent intent) {Log.e(TAG, "onBind");return mBinderPool;
}

Binder连接池的具体实现, 创建BinderPool单例, 连接服务.

private BinderPool(Context context) {mContext = context.getApplicationContext();connectBinderPoolService(); // 连接服务
}public static BinderPool getInstance(Context context) {if (sInstance == null) {synchronized (BinderPool.class) {if (sInstance == null) {sInstance = new BinderPool(context);}}}return sInstance;
}

绑定服务, 通过CountDownLatch类, 把异步操作转换为同步操作, 防止绑定冲突.

private synchronized void connectBinderPoolService() {mCountDownLatch = new CountDownLatch(1); // 只保持一个绑定服务Intent service = new Intent(mContext, BinderPoolService.class);mContext.bindService(service, mBinderPoolConnection, Context.BIND_AUTO_CREATE);try {mCountDownLatch.await();} catch (InterruptedException e) {e.printStackTrace();}
}

通过DeathRecipient处理Binder连接池死亡重联机制.

// 失效重联机制, 当Binder死亡时, 重新连接
private IBinder.DeathRecipient mDeathRecipient = new IBinder.DeathRecipient() {@Override public void binderDied() {Log.e(TAG, "Binder失效");mBinderPool.asBinder().unlinkToDeath(mDeathRecipient, 0);mBinderPool = null;connectBinderPoolService();}
};// Binder的服务连接
private ServiceConnection mBinderPoolConnection = new ServiceConnection() {@Override public void onServiceConnected(ComponentName name, IBinder service) {mBinderPool = IBinderPool.Stub.asInterface(service);try {mBinderPool.asBinder().linkToDeath(mDeathRecipient, 0);} catch (RemoteException e) {e.printStackTrace();}mCountDownLatch.countDown();}@Override public void onServiceDisconnected(ComponentName name) {}
};

通过ID连接不同的Binder请求.

public IBinder queryBinder(int binderCode) {IBinder binder = null;try {if (mBinderPool != null) {binder = mBinderPool.queryBinder(binderCode);}} catch (RemoteException e) {e.printStackTrace();}return binder;
}

Binder连接池AIDL的具体实现, 通过ID选择Binder.

public static class BinderPoolImpl extends IBinderPool.Stub {public BinderPoolImpl() {super();}@Override public IBinder queryBinder(int binderCode) throws RemoteException {IBinder binder = null;switch (binderCode) {case BINDER_COMPUTE:binder = new ComputeImpl();break;case BINDER_SECURITY_CENTER:binder = new SecurityCenterImpl();break;default:break;}return binder;}
}

AIDL并不会直接生成, 使用AS的Build -> Make Project即可.

客户端

通过AIDL接口, 把耗时任务移到Service进行. 操作Binder需要在其他线程中执行, 使用Handler回调至主线程, 并更新页面.

public void encryptMsg(View view) {new Thread(new Runnable() {@Override public void run() {doEncrypt();}}).start();
}private void doEncrypt() {BinderPool binderPool = BinderPool.getInstance(getApplicationContext());IBinder securityBinder = binderPool.queryBinder(BinderPool.BINDER_SECURITY_CENTER);mISecurityCenter = SecurityCenterImpl.asInterface(securityBinder);String msg = "Hello, I am Spike!";try {String encryptMsg = mISecurityCenter.encrypt(msg);Log.e(TAG, "加密信息: " + encryptMsg);String decryptMsg = mISecurityCenter.decrypt(encryptMsg);Log.e(TAG, "解密信息: " + decryptMsg);Message hm = new Message();hm.what = 0;hm.obj = encryptMsg + "\n" + decryptMsg;mHandler.sendMessage(hm);} catch (RemoteException e) {e.printStackTrace();}
}

其他线程使用Handler向主线程传递数据, 在界面中显示效果.

加法操作类似.

public void addNumbers(View view) {new Thread(new Runnable() {@Override public void run() {doAddition();}}).start();
}private void doAddition() {BinderPool binderPool = BinderPool.getInstance(getApplicationContext());IBinder computeBinder = binderPool.queryBinder(BinderPool.BINDER_COMPUTE);mICompute = ComputeImpl.asInterface(computeBinder);try {int result = mICompute.add(12, 12);Log.e(TAG, "12 + 12 = " + result);Message hm = new Message();hm.what = 1;hm.obj = result + "";mHandler.sendMessage(hm);} catch (RemoteException e) {e.printStackTrace();}
}

注意AIDL需要捕获RemoteException的异常.

效果

效果

AIDL是较为高效的跨进程通信方式, 也是很多方式的低层实现; Binder连接池可以在同一服务中处理多个Binder请求, 节省资源, 因此需要熟练掌握.

OK, that's all! Enjoy it!

原文地址： http://www.jianshu.com/p/39c1c2bf39c6