上一篇水文介绍了IPC的几种方式,几乎都是一对一的方式。本节,再次探讨AIDL的使用,例如多个业务都需要使用AIDL时,我们不能对每个都写一个Service吧,10个也许能写,那100个呢?所以,换种思路。
前方高能,又是一篇“水”文,O(∩_∩)O哈哈~,主要是简单的Binder线程池用法和IPC各种方式的优缺点。
详细代码见Binder线程池
线程池机制
大致流程
每个业务模块创建自己的AIDL接口并实现此接口,这个时候不同业务模块之间不能有耦合,所有实现细节单独开来,然后向服务端提供自己的唯一标识和其对应的Binder对象;对于服务端而言,只需要一个Service就可以了,服务端提供一个queryBinder接口,这个接口能够根据业务模块的特征来返回相应的Binder对象给它们,不同的业务模块拿到所需的Binder对象后就可以进程远程方法调用了。由此可见,Binder线程池的主要作用就是将每个业务模块的Binder请求统一转发到远程Servie中去执行,从而避免了重复创建Service的过程,工作原理如图
下面用代码模拟实现下。
我们创建两个AIDL接口(ISecurityCenter和ICompute)来模拟两个业务,多个时类似,增加对应接口即可。
ISecurityCenter.aidl
// ISecurityCenter.aidl
package com.breezehan.ipc.binderpool;
interface ISecurityCenter {
String encrypt(String content);
String decrypt(String password);
}
ICompute.aidl
// ICompute.aidl
package com.breezehan.ipc.binderpool;
interface ICompute {
int add(int a,int b);
}
简单实现实现上述接口:
public class SecurityCenterImpl extends ISecurityCenter.Stub {
private static final char SECRET_CODE = '^';
@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);
}
}
public class ComputeImpl extends ICompute.Stub {
@Override
public int add(int a, int b) throws RemoteException {
return a + b;
}
}
业务模块都有了,我们要创建一个Binder连接池需要的AIDL,这里是一个代理或工厂,根据标识返回对应Binder
// IBinderPool.aidl
package com.breezehan.ipc.binderpool;
interface IBinderPool {
IBinder queryBinder(int binderCode);
}
在连接池中实现,根据标识返回不同Binder
static class BinderPoolImpl extends IBinderPool.Stub {
@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;
}
return binder;
}
}
Service比较简单,逻辑处理都放在Binder线程池中
package com.breezehan.ipc.binderpool;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class BinderPoolService extends Service {
private static final String TAG = "BinderPoolService";
private IBinder binderPool = new BinderPool.BinderPoolImpl();
public BinderPoolService() {
}
@Override
public IBinder onBind(Intent intent) {
Log.d(TAG, "onBind");
return binderPool;
}
@Override
public void onDestroy() {
super.onDestroy();
}
}
Binder线程池的具体实现,同时需处理Binder死亡代理问题。
public class BinderPool {
private static final String TAG = "BinderPool";
public static final int BINDER_NONE = -1;
public static final int BINDER_COMPUTE = 0;
public static final int BINDER_SECURITY_CENTER = 1;
private static volatile BinderPool sInstance;//确保并发取值正确性
private final Context mContext;
//控制多个线程时,某一线程中代码执行顺序;是一个同步工具类,它允许一个或多个线程一直等待,直到其他线程的操作执行完后再执行
private CountDownLatch mConnectBinderPoolCountDownLatch;
private IBinderPool mBinderPool;
public BinderPool(Context context) {
mContext = context.getApplicationContext();
connectBinderPoolService();
}
private void connectBinderPoolService() {
mConnectBinderPoolCountDownLatch = new CountDownLatch(1);
Intent service = new Intent(mContext, BinderPoolService.class);
mContext.bindService(service, mServiceConnection, Context.BIND_AUTO_CREATE);
try {
mConnectBinderPoolCountDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static BinderPool getInstance(Context context) {
if (sInstance == null) {
synchronized (BinderPool.class) {
if (sInstance == null) {
sInstance = new BinderPool(context);
}
}
}
return sInstance;
}
private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
mBinderPool = IBinderPool.Stub.asInterface(service);
try {
mBinderPool.asBinder().linkToDeath(mBinderDeathRecipient, 0);
} catch (RemoteException e) {
e.printStackTrace();
}
mConnectBinderPoolCountDownLatch.countDown();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
private IBinder.DeathRecipient mBinderDeathRecipient = new IBinder.DeathRecipient() {
@Override
public void binderDied() {
Log.w(TAG, "binderDied: ");
mBinderPool.asBinder().unlinkToDeath(mBinderDeathRecipient, 0);
mBinderPool = null;
connectBinderPoolService();
}
};
public IBinder queryBinder(int bindCode) {
IBinder binder = null;
try {
binder = mBinderPool.queryBinder(bindCode);
} catch (RemoteException e) {
e.printStackTrace();
}
return binder;
}
static class BinderPoolImpl extends IBinderPool.Stub {
@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;
}
return binder;
}
}
}
Activity中模拟使用。此处我只使用了其中一个Binder。
public class BinderPoolActivity extends AppCompatActivity {
private static final String TAG = "BinderPoolActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_binder_pool);
new Thread(new Runnable() {
@Override
public void run() {
doWork();
}
}).start();
}
private void doWork() {
BinderPool binderPool = BinderPool.getInstance(BinderPoolActivity.this);
IBinder securityBinder = binderPool.queryBinder(BinderPool.BINDER_SECURITY_CENTER);
// ISecurityCenter iSecurityCenter = ISecurityCenter.Stub.asInterface(securityBinder);
ISecurityCenter iSecurityCenter = SecurityCenterImpl.asInterface(securityBinder);
Log.d(TAG, "visit ISecurityCenter");
String msg = "helloworld-安卓";
try {
String encrypt = iSecurityCenter.encrypt(msg);
Log.d(TAG, "doWork,encrypt:"+encrypt);
Log.d(TAG, "doWork,decrypt:"+iSecurityCenter.decrypt(encrypt));
} catch (RemoteException e) {
e.printStackTrace();
}
IBinder computeBinder = binderPool.queryBinder(BinderPool.BINDER_COMPUTE);
ICompute iCompute = ComputeImpl.asInterface(computeBinder);
try {
Log.d(TAG, "doWork,compute: "+iCompute.add(1,2));
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
protected void onDestroy() {
super.onDestroy();
}
}
基本思想如上,改进或者多个Binder根本不变,添枝加叶即可。
选中合适的IPC方式
每种IPC方式都有优缺点和适用场景。
名称 | 优点 | 缺点 | 适用场景 |
---|---|---|---|
Bundle | 简单易用 | 只能传输Bundle支持的数据类型 | 四大组件间的进程间通信 |
文件共享 | 简单易用 | 不适合高并发场景,并且无法做到进程间的即时通信 | 无并发访问情形,交换简单的数据,实时性不高的场景 |
AIDL | 功能强大,支持一对多并发通信,支持实时通信 | 使用稍复杂,需要处理好线程同步 | 一对多通信且有RPC需求 |
Messenger | 功能一般,支持一对多串行通信,支持实时通信 | 不能很好处理高并发情形,不支持RPC,数据通过Message进行传输,因此只能传输Bundle支持的数据类型 | 低并发的一对多即时通信,无RPC需求,或者无需要返回结果的RPC请求 |
ContentProvider | 在数据源访问方便功能强大,支持一对多并发数据共享,可通过Call方法扩展其他操作 | 可以理解为受约束的AIDL,主要提供数据源的CRUD操作 | 一对多的进程间的数据共享 |
Socket | 功能强大,可以通过网络传输字节流,支持一对多并发实时通信 | 实现细节稍微有点儿繁琐,不支持直接的RPC | 网络数据交换 |