情境
在如何使用Messenger(IPC)中簡單介紹怎麼透過Messenger來進行IPC(跨行程溝通),
這邊就實際做個範例來呈現。
跟如何使用AIDL-非同步實作一樣, 會有兩個app被安裝,
一個用來遠端啟動Service, 另外一邊就是Client端。
程式碼說明
Remote Side
只需要建立一個Service即可。
public class RemoteService extends Service {
private Messenger mMessenger;
private HandlerThread mHandlerThread;
private Handler mHandler;
@Override
public void onCreate() {
super.onCreate();
mHandlerThread = new HandlerThread("remote service");
mHandlerThread.start();
mHandler = new Handler(mHandlerThread.getLooper()){
@Override
public void handleMessage(Message msg) {
try {
int rand = (int) Math.random()*3 + 1;
Thread.sleep(rand * 1000);
int what = msg.what;
Bundle b = new Bundle();
b.putString("remote", "task " + what + " is done\n");
Message m = new Message();
m.setData(b);
msg.replyTo.send(m);
} catch (RemoteException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
mMessenger = new Messenger(mHandler);
}
@Override
public void onDestroy() {
mHandlerThread.quit();
super.onDestroy();
}
@Override
public IBinder onBind(Intent intent) {
return mMessenger.getBinder();
}
}Service做的事情非常簡單, 利用HandlerThread以及Looper跟Messenger進行聯繫。
mHandlerThread = new HandlerThread("remote service");
mHandlerThread.start();
mHandler = new Handler(mHandlerThread.getLooper());聯繫的時候, 將Messenger的Binder回傳出去。
@Override
public IBinder onBind(Intent intent) {
return mMessenger.getBinder();
}而當結束聯繫的時候, 則關閉Thread。
mHandlerThread.quit();而假設你需要雙向溝通的時候, 其實可以透過Message.replyTo這個方法再將Message回傳。
int what = msg.what;
Bundle b = new Bundle();
b.putString("remote", "task " + what + " is done\n");
Message m = new Message();
m.setData(b);
msg.replyTo.send(m);記得在AndroidMenifest加入process
<service
android:name=".RemoteService"
android:process=":remote">
<intent-filter>
<action android:name="service.remote" />
</intent-filter>
</service>這樣Remote Side就講解的差不多了。
Client Side
一開始宣告兩個Button用來處理連接跟中斷Remote端的Service,
TextView用來呈現連接以及中斷的結果。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="example.givemepass.messengerclientdemo.MainActivity">
<Button
android:id="@+id/connect_remote"
android:text="connect to remote"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/disconnect_remote"
android:text="disconnect"
android:layout_toRightOf="@id/connect_remote"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/result"
android:layout_below="@id/connect_remote"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!" />
</RelativeLayout>主程式
public class MainActivity extends AppCompatActivity {
private Button connectRemote;
private Button disconnectRemote;
private ServiceConnection mServiceConnection;
private Messenger messenger;
private boolean isBound;
private TextView result;
private StringBuffer sb;
private int index = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initData();
initView();
}
private void clearText(String msg){
sb.delete(0, sb.length());
if(msg != null) {
sb.append(msg);
sb.append("\n");
}
result.setText(sb);
}
private void initData(){
sb = new StringBuffer();
}
private void initView(){
result = (TextView) findViewById(R.id.result);
connectRemote = (Button) findViewById(R.id.connect_remote);
disconnectRemote = (Button) findViewById(R.id.disconnect_remote);
connectRemote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(!isBound) {
clearText(null);
mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
messenger = new Messenger(service);
isBound = true;
clearText("remote is connected");
}
@Override
public void onServiceDisconnected(ComponentName name) {
messenger = null;
isBound = false;
clearText("remote is disconnected.");
}
};
Intent intent = new Intent();
intent.setAction("service.remote");
intent.setPackage("example.givemepass.messengerremotedemo");
bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);
} else{
try {
Message m = new Message();
m.what = index;
m.replyTo = new Messenger(new Handler(getMainLooper()){
@Override
public void handleMessage(Message msg) {
String msgStr = msg.getData().getString("remote");
if(msgStr != null){
sb.append(msgStr);
result.setText(sb);
}
}
});
messenger.send(m);
} catch (RemoteException e) {
e.printStackTrace();
}
index++;
}
}
});
disconnectRemote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
messenger = null;
isBound = false;
index = 1;
clearText("remote is disconnected.");
}
});
}
}雖然看起來很長, 但是其實處理的事情很單純,
一開始會透過ServiceConnection來判斷是否已經連接,
如果連接就會顯示已連結,
接著把傳過來的IBinder物件丟進Messenger就完成初始化了。
mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
messenger = new Messenger(service);
isBound = true;
clearText("remote is connected");
}
@Override
public void onServiceDisconnected(ComponentName name) {
messenger = null;
isBound = false;
clearText("remote is disconnected.");
}
};接著對Remote的Service真實連接。
Intent intent = new Intent();
intent.setAction("service.remote");
intent.setPackage("example.givemepass.messengerremotedemo");
bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);如果已經連接了,
由於可以透過replyTo雙向溝通,
我們就可以透過Messenger來取得Handler傳過來的Message物件,
將物件打開塞進我們的TextView。
try {
Message m = new Message();
m.what = index;
m.replyTo = new Messenger(new Handler(getMainLooper()){
@Override
public void handleMessage(Message msg) {
String msgStr = msg.getData().getString("remote");
if(msgStr != null){
sb.append(msgStr);
result.setText(sb);
}
}
});
messenger.send(m);
} catch (RemoteException e) {
e.printStackTrace();
}
index++;那當中斷連線, 我們就可以把數值再次的全部初始化, 並且顯示已斷線。
messenger = null;
isBound = false;
index = 1;
clearText("remote is disconnected.");這樣就完成IPC的串接了。
我們來看結果,
連續按下connect to remote的Button, 第一次會進行連接,
如果已經連接remote則會送出任務,
而按下disconnect則會中斷連接,
然後就重複以上的行為。
