Binder
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Android
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.
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!
