Activity与Service之间的数据通信
我们知道启动Service有两种方法：在Activity里调用startService或者BindService方法。
那二者之间的不同之处是什么呢？用代码来说话吧。
Activity:
public class MainActivity extends BaseActivity implements HandlerCallback {
private TextView mTextView;
private Button mBtn;
private Button mBindBtn;
private Button mUnBindBtn;
private Button mStartBtn;
private Button mStopBtn;
private Intent mIntent;
private MyServiceConnection mMyServiceConnection;
private MyService.MyBinder myBinder;
private MyService myService;
private NoLeakHandler mHandler;
private View.OnClickListener mListener = new View.OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn:
if (myBinder != null) {
myBinder.setData("DEMO");
}
break;
case R.id.bind_btn:
bindService(mIntent, mMyServiceConnection, BIND_AUTO_CREATE);
break;
case R.id.unbind_btn:
unbindService(mMyServiceConnection);
break;
case R.id.start_btn:
mIntent.putExtra("data", "data");
startService(mIntent);
break;
case R.id.stop_btn:
stopService(mIntent);
break;
default:
break;
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = (TextView) findViewById(R.id.textview);
mBtn = (Button) findViewById(R.id.btn);
mBtn.setOnClickListener(mListener);
mBindBtn = (Button) findViewById(R.id.bind_btn);
mBindBtn.setOnClickListener(mListener);
mUnBindBtn = (Button) findViewById(R.id.unbind_btn);
mUnBindBtn.setOnClickListener(mListener);
mStartBtn = (Button) findViewById(R.id.start_btn);
mStopBtn = (Button) findViewById(R.id.stop_btn);
mStartBtn.setOnClickListener(mListener);
mStopBtn.setOnClickListener(mListener);
mHandler = new NoLeakHandler(this);
mIntent = new Intent(this, MyService.class);
mMyServiceConnection = new MyServiceConnection();
}
@Override
public void callback(Message message) {
mTextView.setText((String) message.getData().get("data"));
}
@Override
protected void onDestroy() {
super.onDestroy();
mHandler.removeCallbacksAndMessages(null);
}
private static class NoLeakHandler extends Handler {
private WeakReference mWeakReference;
public NoLeakHandler(T t) {
mWeakReference = new WeakReference(t);
}
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
T t = mWeakReference.get();
if (null != t) {
t.callback(msg);
}
}
}
private class MyServiceConnection implements ServiceConnection {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
myBinder = (MyService.MyBinder) service;
myService = myBinder.getMyService();
myService.setCallback(new MyService.Callback() {
@Override
public void receive(String rec) {
Message msg = new Message();
Bundle bundle = new Bundle();
bundle.putString("data", rec);
msg.setData(bundle);
mHandler.sendMessage(msg);
}
});
}
@Override
public void onServiceDisconnected(ComponentName name) {
myBinder = null;
}
@Override
public void onBindingDied(ComponentName name) {
}
}
}
Service：
public class MyService extends Service {
private String mStr;
private Callback callback;
private int i = 0;
private boolean stop = false;
@Nullable
@Override
public IBinder onBind(Intent intent) {
Log.w("onBind");
return new MyBinder();
}
@Override
public void onCreate() {
super.onCreate();
Log.w("onCreate()");
Thread thread = new Thread() {
@Override
public void run() {
super.run();
while (!stop) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Log.i("999");
if (null != callback) {
callback.receive(mStr + (i++));
}
}
}
};
thread.start();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.w("onStartCommand");
mStr = intent.getStringExtra("data");
return super.onStartCommand(intent, flags, startId);
}
public void setCallback(Callback callback) {
this.callback = callback;
}
@Override
public void onDestroy() {
Log.w("onDestroy()");
stop = true;
super.onDestroy();
}
@Override
public boolean onUnbind(Intent intent) {
Log.w("onUnbind");
return super.onUnbind(intent);
}
@Override
public void onRebind(Intent intent) {
Log.w("onRebind");
super.onRebind(intent);
}
public interface Callback {
void receive(String rec);
}
public class MyBinder extends Binder {
public MyService getMyService() {
return MyService.this;
}
public void setData(String s) {
mStr = s;
}
}
}
（1）通过startService来启动Service
Log:
10-21 15:42:47.705 6821-6821/gryl.client W/GRYL: onCreate()
10-21 15:42:47.706 6821-6821/gryl.client W/GRYL: onStartCommand
10-21 15:42:48.706 6821-20260/gryl.client I/GRYL: 999
10-21 15:42:49.707 6821-20260/gryl.client I/GRYL: 999
调用stopService后：
10-21 15:42:56.844 6821-6821/gryl.client W/GRYL: onDestroy()
10-21 15:42:57.709 6821-20260/gryl.client I/GRYL: 999
说明停止并销毁了当前启动的service.
若未调用stopService或stopSelf，按返回键后销毁当前Activity后，Log依然打印
10-21 15:42:49.707 6821-20260/gryl.client I/GRYL: 999
说明Service一直在后台运行，没有销毁。
需要注意的是：（a）如果service没有被创建，当调用startService后会执行onCreate回调，service创建后没有被销毁onDestroy，会一直运行，多次调用startService也不会反复的执行onCreate回调，因此在这个回调函数中可以执行一些初始化的工作。
(b)多次执行startService方法，onStartCommand方法会相应的被多次调用。在onStartCommand中可根据传入的Intent参数执行一些工作。
（2）通过BindService来启动Service
Log:
10-21 15:56:15.737 22681-22681/gryl.client W/GRYL: onCreate()
10-21 15:56:15.738 22681-22681/gryl.client W/GRYL: onBind
10-21 15:56:16.739 22681-1908/gryl.client I/GRYL: 999
10-21 15:56:17.740 22681-1908/gryl.client I/GRYL: 999
10-21 15:56:18.740 22681-1908/gryl.client I/GRYL: 999
10-21 15:56:19.741 22681-1908/gryl.client I/GRYL: 999
10-21 15:56:20.229 22681-22681/gryl.client W/GRYL: onUnbind
10-21 15:56:20.229 22681-22681/gryl.client W/GRYL: onDestroy()
10-21 15:56:20.741 22681-1908/gryl.client I/GRYL: 999
我个人对这种方式的理解是这样的：（a）service与启动它的组件如Activity是关联的，和Activity的生命周期相关联的。当Activity被销毁onDestroy时，Service与之绑定的Activity会解除绑定关系。
MainActivity执行BindService后，按Back键后打印的Log:
10-21 16:05:02.340 10760-10760/gryl.client W/GRYL: MyService: onCreate()
10-21 16:05:02.342 10760-10760/gryl.client W/GRYL: MyService: onBind
10-21 16:05:03.345 10760-10890/gryl.client I/GRYL: 999
10-21 16:05:04.345 10760-10890/gryl.client I/GRYL: 999
10-21 16:05:05.346 10760-10890/gryl.client I/GRYL: 999
10-21 16:05:06.346 10760-10890/gryl.client I/GRYL: 999
10-21 16:05:07.178 10760-10760/gryl.client W/GRYL: MainActivity: onDestroy()
10-21 16:05:07.182 10760-10760/gryl.client W/GRYL: MyService: onUnbind
10-21 16:05:07.182 10760-10760/gryl.client W/GRYL: MyService: onDestroy()
10-21 16:05:07.347 10760-10890/gryl.client I/GRYL: 999
当然可以调用unbindService解除绑定关系。Log:
10-21 16:08:19.976 10760-10760/gryl.client W/GRYL: MyService: onCreate()
10-21 16:08:19.976 10760-10760/gryl.client W/GRYL: MyService: onBind
10-21 16:08:20.978 10760-14105/gryl.client I/GRYL: 999
10-21 16:08:21.979 10760-14105/gryl.client I/GRYL: 999
10-21 16:08:22.979 10760-14105/gryl.client I/GRYL: 999
10-21 16:08:23.498 10760-10760/gryl.client W/GRYL: MyService: onUnbind
10-21 16:08:23.498 10760-10760/gryl.client W/GRYL: MyService: onDestroy()
10-21 16:08:23.980 10760-14105/gryl.client I/GRYL: 999
(b)可通过IBinder接口获取Service的实例，从而可实现在Activity中直接调用Service中的各种方法，实现Activity与Service的各种交互，而这是startService无法做到的。
如本文中在MyService的OnBind中执行了
public IBinder onBind(Intent intent) {
Log.w(getClass().getSimpleName()+": onBind");
return new MyBinder();
}
public class MyBinder extends Binder {
public MyService getMyService() {
return MyService.this;
}
public void setData(String s) {
mStr = s;
}
}
在MainActivity中implements ServiceConnection:
private class MyServiceConnection implements ServiceConnection {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
myBinder = (MyService.MyBinder) service;
myService = myBinder.getMyService();
myService.setCallback(new MyService.Callback() {
@Override
public void receive(String rec) {
Message msg = new Message();
Bundle bundle = new Bundle();
bundle.putString("data", rec);
msg.setData(bundle);
mHandler.sendMessage(msg);
}
});
}
@Override
public void onServiceDisconnected(ComponentName name) {
myBinder = null;
}
@Override
public void onBindingDied(ComponentName name) {
}
}
获取到Service实例，这样的话就实现了再Activity中通过Service实例调用Service中设计的各种方法了。
好了，就到这，可能表述的不是特别准确。