Android中AIDL详解
16lz
2022-03-11
欢迎转载，转载请注明出处http://blog.csdn.net/l664675249/article/details/50649676
介绍
Android Interface Definition Language (AIDL)， Android接口定义语言。系统中的进程之间不能共享内存，因此，需要提供一些机制在不同进程之间进行数据通信Interprocess communication (IPC)。AIDL就是解决这个问题的。
阅读本文需要了解Service的相关知识，关于Service的讲解请参考http://blog.csdn.net/l664675249/article/details/48899323
创建.aidl文件
aidl是用Java语法编写的，后缀为.aidl的文件。
- 每一个aidl文件必须定义一个接口，在这个接口里声明方法
- 在aidl里不能有static属性（field）
- aidl支持基本的数据类型，当你需要使用额外的数据类型时需要把它们import进来，即使它们跟这个文件在同一个包中。
示例
// IRemoteService.aidlpackage com.example.android;// Declare any non-default types here with import statements/** Example service interface */interface IRemoteService { /** Request the process ID of this service, to do evil things with it. */ int getPid(); /** Demonstrates some basic types that you can use as parameters * and return values in AIDL. */ void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString);}把aidl文件存在src/目录下，当你build项目的时候，SDK工具会在gen/目录下生成一个与.aidl文件名字相同的.java文件。
实现接口
生成的IRemoteService.java如下
public interface IRemoteService extends android.os.IInterface {/** Local-side IPC implementation stub class. */public static abstract class Stub extends android.os.Binder implements com.spark.meizi.IRemoteService {private static final java.lang.String DESCRIPTOR = "com.spark.meizi.IRemoteService";/** Construct the stub at attach it to the interface. */public Stub(){this.attachInterface(this, DESCRIPTOR);}/** * Cast an IBinder object into an com.spark.meizi.IRemoteService interface, * generating a proxy if needed. */public static com.spark.meizi.IRemoteService asInterface(android.os.IBinder obj){if ((obj==null)) {return null;}android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);if (((iin!=null)&&(iin instanceof com.spark.meizi.IRemoteService))) {return ((com.spark.meizi.IRemoteService)iin);}return new com.spark.meizi.IRemoteService.Stub.Proxy(obj);}@Override public android.os.IBinder asBinder(){return this;}@Override public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags) throws android.os.RemoteException{switch (code){case INTERFACE_TRANSACTION:{reply.writeString(DESCRIPTOR);return true;}case TRANSACTION_basicTypes:{data.enforceInterface(DESCRIPTOR);int _arg0;_arg0 = data.readInt();long _arg1;_arg1 = data.readLong();boolean _arg2;_arg2 = (0!=data.readInt());float _arg3;_arg3 = data.readFloat();double _arg4;_arg4 = data.readDouble();java.lang.String _arg5;_arg5 = data.readString();this.basicTypes(_arg0, _arg1, _arg2, _arg3, _arg4, _arg5);reply.writeNoException();return true;}}return super.onTransact(code, data, reply, flags);}private static class Proxy implements com.spark.meizi.IRemoteService {private android.os.IBinder mRemote;Proxy(android.os.IBinder remote){mRemote = remote;}@Override public android.os.IBinder asBinder(){return mRemote;}public java.lang.String getInterfaceDescriptor(){return DESCRIPTOR;}/** * Demonstrates some basic types that you can use as parameters * and return values in AIDL. */@Override public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) throws android.os.RemoteException{android.os.Parcel _data = android.os.Parcel.obtain();android.os.Parcel _reply = android.os.Parcel.obtain();try {_data.writeInterfaceToken(DESCRIPTOR);_data.writeInt(anInt);_data.writeLong(aLong);_data.writeInt(((aBoolean)?(1):(0)));_data.writeFloat(aFloat);_data.writeDouble(aDouble);_data.writeString(aString);mRemote.transact(Stub.TRANSACTION_basicTypes, _data, _reply, 0);_reply.readException();}finally {_reply.recycle();_data.recycle();}}}static final int TRANSACTION_basicTypes = (android.os.IBinder.FIRST_CALL_TRANSACTION + 0);}/** * Demonstrates some basic types that you can use as parameters * and return values in AIDL. */public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, java.lang.String aString) throws android.os.RemoteException;}在这个文件中有一个内部类Stub，这是父接口的一个抽象实现，并声明了aidl中的所有方法。为了实现由aidl生成的接口，我们需要继承Stub并实现从aidl继承过来的方法。下面是一个使用匿名类的例子
private final IRemoteService.Stub mBinder = new IRemoteService.Stub() { public int getPid(){ return Process.myPid(); } public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) { // Does nothing }};这样mBinder就是一个Stub的实例了，下一步就是如何在client端使用，与service端产生交互了。
注：
- 不能保证请求是在主线程被执行的，所以从构建到使用要考虑Service线程的安全性
- 默认情况下，请求是同步的，所以尽量不要在主线程中发出请求
- 所有的异常都不会返回给请求者（Caller）
在Client中使用接口
当你已经实现你的Service之后，你需把它暴露在Client中使Client可以绑定它。继承Service并实现onBind()方法，来返回一个实现了Stub的实例。下面就是一个把IRemoteService暴露给Client的例子：
public class RemoteService extends Service { @Override public void onCreate() { super.onCreate(); } @Override public IBinder onBind(Intent intent) { // Return the interface return mBinder; } private final IRemoteService.Stub mBinder = new IRemoteService.Stub() { public int getPid(){ return Process.myPid(); } public void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat, double aDouble, String aString) { // Does nothing } };}现在client（比如是一个Activity）可以调用bindService()来连接这个Service，通过onServiceConnected()来接收Service中 onBind() 返回的mBinder，最后使用YourServiceInterface.Stub.asInterface(service)来把返回的mBinder转换成YourServiceInterface类型。例子如下：
IRemoteService mIRemoteService;private ServiceConnection mConnection = new ServiceConnection() { // Called when the connection with the service is established public void onServiceConnected(ComponentName className, IBinder service) { // Following the example above for an AIDL interface, // this gets an instance of the IRemoteInterface, which we can use to call on the service mIRemoteService = IRemoteService.Stub.asInterface(service); } // Called when the connection with the service disconnects unexpectedly public void onServiceDisconnected(ComponentName className) { Log.e(TAG, "Service has unexpectedly disconnected"); mIRemoteService = null; }};注：
如果Service和Client在两个不同的Application中，Client的Application的src/目录下必须也有对应的.aidl文件。
一个Client的例子
public static class Binding extends Activity { /** The primary interface we will be calling on the service. */ IRemoteService mService = null; /** Another interface we use on the service. */ ISecondary mSecondaryService = null; Button mKillButton; TextView mCallbackText; private boolean mIsBound; /** * Standard initialization of this activity. Set up the UI, then wait * for the user to poke it before doing anything. */ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.remote_service_binding); // Watch for button clicks. Button button = (Button)findViewById(R.id.bind); button.setOnClickListener(mBindListener); button = (Button)findViewById(R.id.unbind); button.setOnClickListener(mUnbindListener); mKillButton = (Button)findViewById(R.id.kill); mKillButton.setOnClickListener(mKillListener); mKillButton.setEnabled(false); mCallbackText = (TextView)findViewById(R.id.callback); mCallbackText.setText("Not attached."); } /** * Class for interacting with the main interface of the service. */ private ServiceConnection mConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { // This is called when the connection with the service has been // established, giving us the service object we can use to // interact with the service. We are communicating with our // service through an IDL interface, so get a client-side // representation of that from the raw service object. mService = IRemoteService.Stub.asInterface(service); mKillButton.setEnabled(true); mCallbackText.setText("Attached."); // We want to monitor the service for as long as we are // connected to it. try { mService.registerCallback(mCallback); } catch (RemoteException e) { // In this case the service has crashed before we could even // do anything with it; we can count on soon being // disconnected (and then reconnected if it can be restarted) // so there is no need to do anything here. } // As part of the sample, tell the user what happened. Toast.makeText(Binding.this, R.string.remote_service_connected, Toast.LENGTH_SHORT).show(); } public void onServiceDisconnected(ComponentName className) { // This is called when the connection with the service has been // unexpectedly disconnected -- that is, its process crashed. mService = null; mKillButton.setEnabled(false); mCallbackText.setText("Disconnected."); // As part of the sample, tell the user what happened. Toast.makeText(Binding.this, R.string.remote_service_disconnected, Toast.LENGTH_SHORT).show(); } }; /** * Class for interacting with the secondary interface of the service. */ private ServiceConnection mSecondaryConnection = new ServiceConnection() { public void onServiceConnected(ComponentName className, IBinder service) { // Connecting to a secondary interface is the same as any // other interface. mSecondaryService = ISecondary.Stub.asInterface(service); mKillButton.setEnabled(true); } public void onServiceDisconnected(ComponentName className) { mSecondaryService = null; mKillButton.setEnabled(false); } }; private OnClickListener mBindListener = new OnClickListener() { public void onClick(View v) { // Establish a couple connections with the service, binding // by interface names. This allows other applications to be // installed that replace the remote service by implementing // the same interface. Intent intent = new Intent(Binding.this, RemoteService.class); intent.setAction(IRemoteService.class.getName()); bindService(intent, mConnection, Context.BIND_AUTO_CREATE); intent.setAction(ISecondary.class.getName()); bindService(intent, mSecondaryConnection, Context.BIND_AUTO_CREATE); mIsBound = true; mCallbackText.setText("Binding."); } }; private OnClickListener mUnbindListener = new OnClickListener() { public void onClick(View v) { if (mIsBound) { // If we have received the service, and hence registered with // it, then now is the time to unregister. if (mService != null) { try { mService.unregisterCallback(mCallback); } catch (RemoteException e) { // There is nothing special we need to do if the service // has crashed. } } // Detach our existing connection. unbindService(mConnection); unbindService(mSecondaryConnection); mKillButton.setEnabled(false); mIsBound = false; mCallbackText.setText("Unbinding."); } } }; private OnClickListener mKillListener = new OnClickListener() { public void onClick(View v) { // To kill the process hosting our service, we need to know its // PID. Conveniently our service has a call that will return // to us that information. if (mSecondaryService != null) { try { int pid = mSecondaryService.getPid(); // Note that, though this API allows us to request to // kill any process based on its PID, the kernel will // still impose standard restrictions on which PIDs you // are actually able to kill. Typically this means only // the process running your application and any additional // processes created by that app as shown here; packages // sharing a common UID will also be able to kill each // other's processes. Process.killProcess(pid); mCallbackText.setText("Killed service process."); } catch (RemoteException ex) { // Recover gracefully from the process hosting the // server dying. // Just for purposes of the sample, put up a notification. Toast.makeText(Binding.this, R.string.remote_call_failed, Toast.LENGTH_SHORT).show(); } } } }; // ---------------------------------------------------------------------- // Code showing how to deal with callbacks. // ---------------------------------------------------------------------- /** * This implementation is used to receive callbacks from the remote * service. */ private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() { /** * This is called by the remote service regularly to tell us about * new values. Note that IPC calls are dispatched through a thread * pool running in each process, so the code executing here will * NOT be running in our main thread like most other things -- so, * to update the UI, we need to use a Handler to hop over there. */ public void valueChanged(int value) { mHandler.sendMessage(mHandler.obtainMessage(BUMP_MSG, value, 0)); } }; private static final int BUMP_MSG = 1; private Handler mHandler = new Handler() { @Override public void handleMessage(Message msg) { switch (msg.what) { case BUMP_MSG: mCallbackText.setText("Received from service: " + msg.arg1); break; default: super.handleMessage(msg); } } };}欢迎转载，转载请注明出处http://blog.csdn.net/l664675249/article/details/50649676
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