一、 Binder概述
1.1 爲什麼要用binder
- 出於安全性、穩定性和內存管理的考慮,Android的應用和系統服務運行在分離的進程中,但是它們之間需要通信和共享數據
- 避免傳統IPC開銷和服務拒絕的問題
- android的庫不支持System V 的IPC
- Binder加入了對象引用的引用計數器,消亡提醒機制。當一個Binder服務沒有任何終端引用時,它的所有者可以自動提醒它去處理自己
- Binder通過UID/PID來分辨發送者和接受者(對於安全很重要)
但是:
- Binder不支持RPC,只有本地
- 客戶端和服務端基於消息通信,不適用於流
- 不符合POSIX標準
1.2 binder通信流程
客戶端使用服務
進程之間無法進行直接通信,所以通過Binder驅動
客戶端和服務端不需要了解binder協議,所以使用代理和存根
客戶端不想要知道正在使用IPC,也不關心binder和代理,所以,需要管理對象進行抽象
但是客戶端怎樣獲取它想要通信的服務的handle,只需要問問sevicemanager(Context Manager),服務是否已經註冊
最後,我們看下總體的架構
二 、 AIDL示例
使用aidl實現跨進程的加減法
2.1 服務端
新建android工程,創建包com.realize.calc.aidl,新建文件ICalcAIDL.aidl,內容如下
package com.realize.calc.aidl;
interface ICalcAIDL
{
int add(int x , int y);
int min(int x , int y );
}
創建包com.realize.lizijun.binder_server,新建服務CalcService.java,內容如下
package com.realize.lizijun.binder_server;
import com.realize.calc.aidl.ICalcAIDL;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
public class CalcService extends Service
{
private static final String TAG = "server";
public void onCreate()
{
Log.e(TAG, "onCreate");
}
public IBinder onBind(Intent t)
{
Log.e(TAG, "onBind");
return mBinder;
}
public void onDestroy()
{
Log.e(TAG, "onDestroy");
super.onDestroy();
}
public boolean onUnbind(Intent intent)
{
Log.e(TAG, "onUnbind");
return super.onUnbind(intent);
}
public void onRebind(Intent intent)
{
Log.e(TAG, "onRebind");
super.onRebind(intent);
}
private final ICalcAIDL.Stub mBinder = new ICalcAIDL.Stub()
{
@Override
public int add(int x, int y) throws RemoteException
{
return x + y;
}
@Override
public int min(int x, int y) throws RemoteException
{
return x - y;
}
};
}
AndroidManifest.xml中註冊服務
<service android:name="com.realize.lizijun.binder_server.CalcService" >
<intent-filter>
<action android:name="com.realize.calc.aidl" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</service>
2.2 客戶端
新建android工程,創建包com.realize.calc.aidl,新建文件ICalcAIDL.aidl(與服務端是一樣的),內容如下
package com.realize.calc.aidl;
interface ICalcAIDL
{
int add(int x , int y);
int min(int x , int y );
}
主activity內容如下
package com.realize.lizijun.binder_client;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
import com.realize.calc.aidl.ICalcAIDL;
public class MainActivity extends Activity
{
private static final String TAG = "client";
private ICalcAIDL mCalcAidl;
private ServiceConnection mServiceConn = new ServiceConnection()
{
@Override
public void onServiceDisconnected(ComponentName name)
{
Log.e(TAG, "onServiceDisconnected");
mCalcAidl = null;
}
@Override
public void onServiceConnected(ComponentName name, IBinder service)
{
Log.e(TAG, "onServiceConnected");
mCalcAidl = ICalcAIDL.Stub.asInterface(service);
}
};
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/**
* 點擊BindService按鈕時調用
* @param view
*/
public void bindService(View view)
{
Intent intent = new Intent();
intent.setAction("com.realize.calc.aidl");
bindService(intent, mServiceConn, Context.BIND_AUTO_CREATE);
}
/**
* 點擊unBindService按鈕時調用
* @param view
*/
public void unbindService(View view)
{
unbindService(mServiceConn);
}
/**
* 點擊12+12按鈕時調用
* @param view
*/
public void addInvoked(View view) throws Exception
{
if (mCalcAidl != null)
{
int addRes = mCalcAidl.add(12, 12);
Toast.makeText(this, addRes + "", Toast.LENGTH_SHORT).show();
} else
{
Toast.makeText(this, "服務器被異常殺死,請重新綁定服務端", Toast.LENGTH_SHORT)
.show();
}
}
/**
* 點擊50-12按鈕時調用
* @param view
*/
public void minInvoked(View view) throws Exception
{
if (mCalcAidl != null)
{
int addRes = mCalcAidl.min(50, 12);
Toast.makeText(this, addRes + "", Toast.LENGTH_SHORT).show();
} else
{
Toast.makeText(this, "服務器未綁定或被異常殺死,請重新綁定服務端", Toast.LENGTH_SHORT)
.show();
}
}
}
界面如下:
2.3 結果說明
- 點擊BindService之後,服務端執行了onCreate和onBind的方法, 客戶端執行onServiceConnected方法
- 然後點擊12+12,50-12可以成功的調用服務端的代碼並返回正確的結果
- 再點擊unBindService, Service調用了onUnbind和onDestory
- 然後點擊12+12,50-12,仍然能夠看到正確的結果,說明客戶端與服務端的連接仍然存在
- 我們通過後臺,把服務強制停止掉,可以看到調用了onServiceDisconnected方法,此時,再點擊12+12,50-12,就獲取不到結果了
三、 分析AIDL生成的接口代碼
上面創建ICalcAIDL.aidl之後,在gen目錄下回生成文件ICalcAIDL.java, 該文件實現了客戶端和服務端的代理(proxy)和存根(stub)
3.1 服務端
服務端代碼中調用ICalcAIDL.Stub
private final ICalcAIDL.Stub mBinder = new ICalcAIDL.Stub()
{
@Override
public int add(int x, int y) throws RemoteException
{
return x + y;
}
@Override
public int min(int x, int y) throws RemoteException
{
return x - y;
}
};
而在CalcService.java中,很明顯Stub就是Binder的子類
public static abstract class Stub extends android.os.Binder implements com.realize.calc.aidl.ICalcAIDL
接着看看Stub下面的方法onTransact,該方法內部實現了加減法的操作
@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_add:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.add(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case TRANSACTION_min:
{
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = this.min(_arg0, _arg1);
reply.writeNoException();
reply.writeInt(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
服務端會根據客戶端發送來的消息執行onTransact方法,該方法有四個參數
code 是一個整形的唯一標識,用於區分執行哪個方法
data 客戶端傳遞過來的參數
reply 服務器返回的值
flags 標明是否有返回值,0爲有(雙向),1爲沒有(單向)
3.2 客戶端
客戶端代碼中,調用了ICalcAIDL.Stub.asInterface
private ServiceConnection mServiceConn = new ServiceConnection()
{
@Override
public void onServiceDisconnected(ComponentName name)
{
Log.e(TAG, "onServiceDisconnected");
mCalcAidl = null;
}
@Override
public void onServiceConnected(ComponentName name, IBinder service)
{
Log.e(TAG, "onServiceConnected");
mCalcAidl = ICalcAIDL.Stub.asInterface(service);
}
};
而ICalcAIDL.java文件中,asInterface,最終是調用到Proxy
public static com.realize.calc.aidl.ICalcAIDL asInterface(android.os.IBinder obj)
{
if ((obj==null)) {
return null;
}
android.os.IInterface iin = obj.queryLocalInterface(DESCRIPTOR);
if (((iin!=null)&&(iin instanceof com.realize.calc.aidl.ICalcAIDL))) {
return ((com.realize.calc.aidl.ICalcAIDL)iin);
}
return new com.realize.calc.aidl.ICalcAIDL.Stub.Proxy(obj);
}
所以,我們看下Proxy的add方法
@Override public int add(int x, int y) throws android.os.RemoteException
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result;
try {
_data.writeInterfaceToken(DESCRIPTOR);
_data.writeInt(x);
_data.writeInt(y);
mRemote.transact(Stub.TRANSACTION_add, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
}
finally {
_reply.recycle();
_data.recycle();
}
return _result;
}
聲明瞭兩個android.os.Parcel對象,_data用於傳遞數據,_replay用於接收返回的數據
最後調用transact方法,與服務端進行通信
四、不依賴AIDL的示例
怎樣不通過AIDL文件,實現跨進程通信呢,從上面的分析中,我們可以知道,不通過AIDL文件,實現跨進程通信,那麼實際上,就是要實現自動生成的AIDL文件中的接口功能, 下面我們實現跨進程的乘除調用
4.1 服務端
創建工程,實現CalcService.java,代碼如下
package com.realize.lizijun.noaidl_binder_server;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.os.Parcel;
import android.os.RemoteException;
import android.util.Log;
public class CalcService extends Service
{
private static final String DESCRIPTOR = "CalcService";
private static final String TAG = "server";
public void onCreate()
{
Log.e(TAG, "onCreate");
}
@Override
public int onStartCommand(Intent intent, int flags, int startId)
{
Log.e(TAG, "onStartCommand");
return super.onStartCommand(intent, flags, startId);
}
public IBinder onBind(Intent t)
{
Log.e(TAG, "onBind");
return mBinder;
}
public void onDestroy()
{
Log.e(TAG, "onDestroy");
super.onDestroy();
}
public boolean onUnbind(Intent intent)
{
Log.e(TAG, "onUnbind");
return super.onUnbind(intent);
}
public void onRebind(Intent intent)
{
Log.e(TAG, "onRebind");
super.onRebind(intent);
}
private MyBinder mBinder = new MyBinder();
private class MyBinder extends Binder
{
@Override
protected boolean onTransact(int code, Parcel data, Parcel reply,
int flags) throws RemoteException
{
switch (code)
{
case 0x110:
{
Log.e(TAG, "0x110");
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = _arg0 * _arg1;
reply.writeNoException();
reply.writeInt(_result);
return true;
}
case 0x111:
{
Log.e(TAG, "0x111");
data.enforceInterface(DESCRIPTOR);
int _arg0;
_arg0 = data.readInt();
int _arg1;
_arg1 = data.readInt();
int _result = _arg0 / _arg1;
reply.writeNoException();
reply.writeInt(_result);
return true;
}
}
return super.onTransact(code, data, reply, flags);
}
};
}
自定義了一個Binder子類,然後複寫了其onTransact方法
AndroidManifest.xml中註冊服務
<service android:name="com.realize.lizijun.noaidl_binder_server.CalcService" >
<intent-filter>
<action android:name="com.realize.noaidl.calc" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</service>
4.2 客戶端
創建工程,其主activity內容如下所示:
package com.realize.lizijun.noaidl_binder_client;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends Activity
{
private static final String TAG = "client";
private IBinder mPlusBinder = null;
private ServiceConnection mServiceConnPlus = new ServiceConnection()
{
// 只有當servie異常退出時,系統纔會調用onServiceDisconnected()
@Override
public void onServiceDisconnected(ComponentName name)
{
Log.e(TAG, "mServiceConnPlus onServiceDisconnected");
mPlusBinder = null;
}
@Override
public void onServiceConnected(ComponentName name, IBinder service)
{
Log.e(TAG, " mServiceConnPlus onServiceConnected");
mPlusBinder = service;
}
};
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void bindService(View view)
{
Intent intentPlus = new Intent();
intentPlus.setAction("com.realize.noaidl.calc");
boolean result = bindService(intentPlus, mServiceConnPlus,
Context.BIND_AUTO_CREATE);
Log.e(TAG, result + "");
}
public void unbindService(View view)
{
if (mServiceConnPlus != null)
{
Log.e(TAG, "unbindService");
unbindService(mServiceConnPlus);
//mServiceConnPlus = null;
}
}
public void mulInvoked(View view)
{
if (mPlusBinder == null)
{
Toast.makeText(this, "未連接服務端或服務端被異常殺死", Toast.LENGTH_SHORT).show();
} else
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result = 0;
try
{
_data.writeInterfaceToken("CalcService");
_data.writeInt(50);
_data.writeInt(12);
mPlusBinder.transact(0x110, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
Toast.makeText(this, _result + "", Toast.LENGTH_SHORT).show();
} catch (RemoteException e)
{
e.printStackTrace();
} finally
{
_reply.recycle();
_data.recycle();
}
}
}
public void divInvoked(View view)
{
if (mPlusBinder == null)
{
Toast.makeText(this, "未連接服務端或服務端被異常殺死", Toast.LENGTH_SHORT).show();
} else
{
android.os.Parcel _data = android.os.Parcel.obtain();
android.os.Parcel _reply = android.os.Parcel.obtain();
int _result = 0;
try
{
_data.writeInterfaceToken("CalcService");
_data.writeInt(36);
_data.writeInt(12);
mPlusBinder.transact(0x111, _data, _reply, 0);
_reply.readException();
_result = _reply.readInt();
Toast.makeText(this, _result + "", Toast.LENGTH_SHORT).show();
} catch (RemoteException e)
{
e.printStackTrace();
} finally
{
_reply.recycle();
_data.recycle();
}
}
}
}
界面如下: