binder机制是贯穿整个android系统的进程间访问机制,经常被用来访问service,我们结合代码看一下binder在访问service的情形下是怎么具体使用的。
service 你可以理解成没有的界面的activity,它是跑在后台的程序,所谓后台是相对于可以被看得到的程序的,后台程序是不能直接交互的程序。
binder主要是用来进程间通信的,但也可用在和本地service通信。
1. 我们先来看一个与本地service通信的例子。
- package com.ckt.wangxin;
- import android.app.Service;
- import android.content.Intent;
- import android.os.Binder;
- import android.os.IBinder;
- import android.widget.Toast;
- /**
- * This is a service stub for both LocalBinderClient
- * and RemoteBinderClient
- * @author Wang Xin
- * @email springnap@163.com
- *
- */
- public class LocalService extends Service {
- @Override
- public IBinder onBind(Intent intent) {
- return new LocalBinder();
- }
- public void sayHelloWorld(){
- Toast.makeText(this.getApplicationContext(), "Hello World Local Service!", Toast.LENGTH_SHORT).show();
- }
- public class LocalBinder extends Binder {
- LocalService getService() {
- // Return this instance of LocalService so clients can call public methods
- return LocalService.this;
- }
- }
- }
package com.ckt.wangxin; import android.app.Service; import android.content.Intent; import android.os.Binder; import android.os.IBinder; import android.widget.Toast; /** * This is a service stub for both LocalBinderClient * and RemoteBinderClient * @author Wang Xin * @email springnap@163.com * */ public class LocalService extends Service { @Override public IBinder onBind(Intent intent) { return new LocalBinder(); } public void sayHelloWorld(){ Toast.makeText(this.getApplicationContext(), "Hello World Local Service!", Toast.LENGTH_SHORT).show(); } public class LocalBinder extends Binder { LocalService getService() { // Return this instance of LocalService so clients can call public methods return LocalService.this; } } }
local servcie 的代码如上,在onBinder方法中返回binder,binder包含了service的句柄,客户端得到句柄以后就可以调用servcie的公共方法了,这种调用方式是最常见的。
客户端代码
- package com.ckt.wangxin;
- 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 com.ckt.wangxin.LocalService.LocalBinder;
- public class LocalServiceTestActivity extends Activity {
- static final String TAG = "LocalBinderTestActivity";
- ServiceConnection mSc;
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- mSc = new ServiceConnection(){
- @Override
- public void onServiceConnected(ComponentName name, IBinder service) {
- Log.d(TAG, "service connected");
- LocalService ss = ((LocalBinder)service).getService();
- ss.sayHelloWorld();
- }
- @Override
- public void onServiceDisconnected(ComponentName name) {
- Log.d(TAG, "service disconnected");
- }
- };
- }
- @Override
- protected void onStart() {
- super.onStart();
- Log.d(TAG, this.getApplicationContext().getPackageCodePath());
- Intent service = new Intent(this.getApplicationContext(),LocalService.class);
- this.bindService(service, mSc, Context.BIND_AUTO_CREATE);
- }
- @Override
- protected void onStop() {
- super.onStop();
- //must unbind the service otherwise the ServiceConnection will be leaked.
- <span style="color: rgb(255, 0, 0); ">this.unbindService(mSc);</span>
- }
- }
package com.ckt.wangxin; 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 com.ckt.wangxin.LocalService.LocalBinder; public class LocalServiceTestActivity extends Activity { static final String TAG = "LocalBinderTestActivity"; ServiceConnection mSc; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mSc = new ServiceConnection(){ @Override public void onServiceConnected(ComponentName name, IBinder service) { Log.d(TAG, "service connected"); LocalService ss = ((LocalBinder)service).getService(); ss.sayHelloWorld(); } @Override public void onServiceDisconnected(ComponentName name) { Log.d(TAG, "service disconnected"); } }; } @Override protected void onStart() { super.onStart(); Log.d(TAG, this.getApplicationContext().getPackageCodePath()); Intent service = new Intent(this.getApplicationContext(),LocalService.class); this.bindService(service, mSc, Context.BIND_AUTO_CREATE); } @Override protected void onStop() { super.onStop(); //must unbind the service otherwise the ServiceConnection will be leaked. <span style="color: rgb(255, 0, 0); ">this.unbindService(mSc);</span> } }
需要注意的是在onStop中要解绑定service, 否则会造成内存泄露的问题。
2. 我们再看一下与另外一个进程中的service进行通信的问题(跨进程通信!)。
如何将servcie运行在另外一个进程呢?在manifest 里面配置个属性就行了。
android:process=":remote" , 代表这个service运行在同一个应用程序的不同进程中。
- <?xml version="1.0" encoding="utf-8"?>
- <manifest xmlns:android="http://schemas.android.com/apk/res/android"
- package="com.ckt.wangxin"
- android:versionCode="1"
- android:versionName="1.0" >
- <uses-sdk android:minSdkVersion="15" />
- <application
- android:icon="@drawable/ic_launcher"
- android:label="@string/app_name" >
- <activity
- android:name=".LocalServiceTestActivity"
- android:label="@string/app_name" >
- <!-- <intent-filter>
- <action android:name="android.intent.action.MAIN" />
- <category android:name="android.intent.category.LAUNCHER" />
- </intent-filter> -->
- </activity>
- <service android:name=".LocalService"></service>
- <!-- android:process=":remote" specify this service run in
- another process in the same application. -->
- <service android:name=".RemoteService" android:process=":remote"></service>
- <activity android:name="RemoteServiceTestActivity">
- <intent-filter>
- <action android:name="android.intent.action.MAIN" />
- <category android:name="android.intent.category.LAUNCHER" />
- </intent-filter>
- </activity>
- </application>
- </manifest>
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.ckt.wangxin" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="15" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <activity android:name=".LocalServiceTestActivity" android:label="@string/app_name" > <!-- <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> --> </activity> <service android:name=".LocalService"></service> <!-- android:process=":remote" specify this service run in another process in the same application. --> <service android:name=".RemoteService" android:process=":remote"></service> <activity android:name="RemoteServiceTestActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
客户端可以使用Messenger发送消息到service。
客户端代码:
- package com.ckt.wangxin;
- 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.Handler;
- import android.os.IBinder;
- import android.os.Message;
- import android.os.Messenger;
- import android.os.RemoteException;
- import android.util.Log;
- import android.widget.Toast;
- public class RemoteServiceTestActivity extends Activity {
- static final String TAG = "RemoteServiceTestActivity";
- ServiceConnection mSc;
- public static final int SAY_HELLO_TO_CLIENT = 0;
- /**
- * Handler of incoming messages from service.
- */
- class IncomingHandler extends Handler {
- @Override
- public void handleMessage(Message msg) {
- switch (msg.what) {
- case SAY_HELLO_TO_CLIENT:
- Toast.makeText(RemoteServiceTestActivity.this.getApplicationContext(), "Hello World Remote Client!",
- Toast.LENGTH_SHORT).show();
- break;
- default:
- super.handleMessage(msg);
- }
- }
- }
- Messenger messenger_reciever = new Messenger(new IncomingHandler());
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- mSc = new ServiceConnection(){
- @Override
- public void onServiceConnected(ComponentName name, IBinder service) {
- Log.d(TAG, "service connected");
- <span style="color: rgb(204, 0, 0); ">Messenger messenger = new Messenger(service);
- Message msg = new Message();
- msg.what = RemoteService.MSG_SAY_HELLO;</span>
- msg.replyTo = messenger_reciever;
- try {
- <span style="color: rgb(255, 0, 0); ">messenger.send(msg);</span>
- } catch (RemoteException e) {
- e.printStackTrace();
- }
- }
- @Override
- public void onServiceDisconnected(ComponentName name) {
- Log.d(TAG, "service disconnected");
- }
- };
- }
- @Override
- protected void onStart() {
- super.onStart();
- Log.d(TAG, this.getApplicationContext().getPackageCodePath());
- Intent service = new Intent(this.getApplicationContext(),RemoteService.class);
- this.bindService(service, mSc, Context.BIND_AUTO_CREATE);
- }
- @Override
- protected void onStop() {
- super.onStop();
- //must unbind the service otherwise the ServiceConnection will be leaked.
- this.unbindService(mSc);
- }
- }
package com.ckt.wangxin; 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.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.util.Log; import android.widget.Toast; public class RemoteServiceTestActivity extends Activity { static final String TAG = "RemoteServiceTestActivity"; ServiceConnection mSc; public static final int SAY_HELLO_TO_CLIENT = 0; /** * Handler of incoming messages from service. */ class IncomingHandler extends Handler { @Override public void handleMessage(Message msg) { switch (msg.what) { case SAY_HELLO_TO_CLIENT: Toast.makeText(RemoteServiceTestActivity.this.getApplicationContext(), "Hello World Remote Client!", Toast.LENGTH_SHORT).show(); break; default: super.handleMessage(msg); } } } Messenger messenger_reciever = new Messenger(new IncomingHandler()); /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mSc = new ServiceConnection(){ @Override public void onServiceConnected(ComponentName name, IBinder service) { Log.d(TAG, "service connected"); <span style="color: rgb(204, 0, 0); ">Messenger messenger = new Messenger(service); Message msg = new Message(); msg.what = RemoteService.MSG_SAY_HELLO;</span> msg.replyTo = messenger_reciever; try { <span style="color: rgb(255, 0, 0); ">messenger.send(msg);</span> } catch (RemoteException e) { e.printStackTrace(); } } @Override public void onServiceDisconnected(ComponentName name) { Log.d(TAG, "service disconnected"); } }; } @Override protected void onStart() { super.onStart(); Log.d(TAG, this.getApplicationContext().getPackageCodePath()); Intent service = new Intent(this.getApplicationContext(),RemoteService.class); this.bindService(service, mSc, Context.BIND_AUTO_CREATE); } @Override protected void onStop() { super.onStop(); //must unbind the service otherwise the ServiceConnection will be leaked. this.unbindService(mSc); } }
获得service端传来的binder,用来构建一个Messenger向service发送消息。
service端代码:
- package com.ckt.wangxin;
- import android.app.Service;
- import android.content.Intent;
- import android.os.Handler;
- import android.os.IBinder;
- import android.os.Message;
- import android.os.Messenger;
- import android.os.RemoteException;
- import android.widget.Toast;
- public class RemoteService extends Service {
- public static final int MSG_SAY_HELLO = 0;
- @Override
- public IBinder onBind(Intent intent) {
- <span style="color: rgb(204, 0, 0); "> return messager.getBinder();</span>
- }
- Handler IncomingHandler = new Handler() {
- @Override
- public void handleMessage(Message msg) {
- if(msg.replyTo != null){
- Message msg_client = this.obtainMessage();
- msg_client.what = RemoteServiceTestActivity.SAY_HELLO_TO_CLIENT;
- try {
- ((Messenger)msg.replyTo).send(msg_client);
- } catch (RemoteException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- switch (msg.what) {
- case MSG_SAY_HELLO:
- Toast.makeText(RemoteService.this.getApplicationContext(), "Hello World Remote Service!",
- Toast.LENGTH_SHORT).show();
- break;
- default:
- super.handleMessage(msg);
- }
- }
- };
- Messenger messager = new Messenger (IncomingHandler);
- }
package com.ckt.wangxin; import android.app.Service; import android.content.Intent; import android.os.Handler; import android.os.IBinder; import android.os.Message; import android.os.Messenger; import android.os.RemoteException; import android.widget.Toast; public class RemoteService extends Service { public static final int MSG_SAY_HELLO = 0; @Override public IBinder onBind(Intent intent) { <span style="color: rgb(204, 0, 0); "> return messager.getBinder();</span> } Handler IncomingHandler = new Handler() { @Override public void handleMessage(Message msg) { if(msg.replyTo != null){ Message msg_client = this.obtainMessage(); msg_client.what = RemoteServiceTestActivity.SAY_HELLO_TO_CLIENT; try { ((Messenger)msg.replyTo).send(msg_client); } catch (RemoteException e) { // TODO Auto-generated catch block e.printStackTrace(); } } switch (msg.what) { case MSG_SAY_HELLO: Toast.makeText(RemoteService.this.getApplicationContext(), "Hello World Remote Service!", Toast.LENGTH_SHORT).show(); break; default: super.handleMessage(msg); } } }; Messenger messager = new Messenger (IncomingHandler); }
构建一个Messenger,包含一个handler,然后将messenger的binder传给客户端,客户端可以通过handler再构造一个messenger与service通信,消息在handler里面被处理。
现在是service端单向响应客户端的消息,同理可以做成双向发送消息,实现双向通信。