Android Service
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1.首先来了解Service
service就是一个服务的后勤人员,就像(快递员不停的收快递,发快递,来保证顾客的需求)
Service,看名字就知道跟正常理解的“服务”差不多,后台运行,可交互这样的一个东西。它跟Activity的级别差不多,但是他不能自己运行,
需要通过某一个Activity或者其他Context对象来调用, Context.startService() 和Context.bindService()。
两种启动Service的方式有所不同。这里要说明一下的是如果你在Service的onCreate或者onStart做一些很耗时间的事情,
最好在Service里启动一个线程来完成,因为Service是跑在主线程中,会影响到你的UI操作或者阻塞主线程中的其他事情。
什么时候需要Service呢?比如播放多媒体的时候用户启动了其他Activity这个时候程序要在后台继续播放,比如检测网络的变化,
再或者在后台记录你地理信息位置的改变等等,总之服务就是你看不见的但是能感受到的而且很重要的东西.
2.看看看service的生命周期(即从创建到销毁的过程)
3.具体代码演示
首先要创建一个类并继承Srvice 自然要实现父类的方法
public class MyService extends Service {
private static final String TAG = "MyService";
private NotificationManager _nm;
@Override
public void onCreate() {
Log.e(TAG, "============> TestService.onCreate");
_nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
showNotification();
}
@Override
public IBinder onBind(Intent i) {
Log.e(TAG, "============> MyService.onBind");
return null;
}
public class LocalBinder extends Binder {
TestService getService() {
return TestService.this;
}
}
@Override
public boolean onUnbind(Intent i) {
Log.e(TAG, "============> MyService.onUnbind");
return false;
}
@Override
public void onRebind(Intent i) {
Log.e(TAG, "============> TestService.onRebind");
}
@Override
public void onCreate() {
Log.e(TAG, "============> MyService.onCreate");
_nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
showNotification();
}
@Override
public void onStart(Intent intent, int startId) {
Log.e(TAG, "============> MyService.onStart");
}
@Override
public void onDestroy() {
_nm.cancel(R.string.service_started);
Log.e(TAG, "============> MyService.onDestroy");
}
private void showNotification() {
Notification notification = new Notification(R.drawable.face_1,
"Service started", System.currentTimeMillis());
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, TestServiceHolder.class), 0);
// must set this for content view, or will throw a exception
notification.setLatestEventInfo(this, "Test Service",
"Service started", contentIntent);
_nm.notify(R.string.service_started, notification);
}
}
其中用到Notification是为了明显地表明Service存活的状
public class LocalBinder extends Binder {
TestService getService() {
return TestService.this;
}
}
这个方法是为了让调用者得到这个Service并操作它。Service本身就这样简单了,你需要做什么就在onCreate和onStart里做好了,起个线程什么的。
在Activity中调用service
public class TestServiceHolder extends Activity {
private boolean _isBound;
private TestService _boundService;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test_service_holder);
setTitle("Service Test");
initButtons();
}
//构造服务连接对象
private ServiceConnection _connection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
_boundService = ((TestService.LocalBinder)service).getService();
Toast.makeText(TestServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName className) {
// unexpectedly disconnected,we should never see this happen.
_boundService = null;
Toast.makeText(TestServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
};
private void initButtons() {
Button buttonStart = (Button) findViewById(R.id.start_service);
buttonStart.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
startService();
}
});
Button buttonStop = (Button) findViewById(R.id.stop_service);
buttonStop.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
stopService();
}
});
Button buttonBind = (Button) findViewById(R.id.bind_service);
buttonBind.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
bindService();
}
});
Button buttonUnbind = (Button) findViewById(R.id.unbind_service);
buttonUnbind.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
unbindService();
}
});
}
private void startService() {
Intent i = new Intent(this, TestService.class);
this.startService(i);
}
private void stopService() {
Intent i = new Intent(this, TestService.class);
this.stopService(i);
}
private void bindService() {
Intent i = new Intent(this, TestService.class);
bindService(i, _connection, Context.BIND_AUTO_CREATE);
_isBound = true;
}
private void unbindService() {
if (_isBound) {
unbindService(_connection);
_isBound = false;
}
}
}
这里可以看到两种启动方法,start和bind,当然也是通过intent调用的,在intent中指明指定要启动的Service的名字,stop也一样 :
private void startService() {
Intent i = new Intent(this, MyService.class);
this.startService(i);
}
private void stopService() {
Intent i = new Intent(this, MyService.class);
this.stopService(i);
}
对于bind的话,需要一个ServiceConnection对象
private ServiceConnection _connection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
_boundService = ((MyService.LocalBinder)service).getService();
Toast.makeText(MyServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName className) {
// unexpectedly disconnected,we should never see this happen.
_boundService = null;
Toast.makeText(MyServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
};
用来把Activity和特定的Service连接在一起,共同存亡。
service就是一个服务的后勤人员,就像(快递员不停的收快递,发快递,来保证顾客的需求)
Service,看名字就知道跟正常理解的“服务”差不多,后台运行,可交互这样的一个东西。它跟Activity的级别差不多,但是他不能自己运行,
需要通过某一个Activity或者其他Context对象来调用, Context.startService() 和Context.bindService()。
两种启动Service的方式有所不同。这里要说明一下的是如果你在Service的onCreate或者onStart做一些很耗时间的事情,
最好在Service里启动一个线程来完成,因为Service是跑在主线程中,会影响到你的UI操作或者阻塞主线程中的其他事情。
什么时候需要Service呢?比如播放多媒体的时候用户启动了其他Activity这个时候程序要在后台继续播放,比如检测网络的变化,
再或者在后台记录你地理信息位置的改变等等,总之服务就是你看不见的但是能感受到的而且很重要的东西.
2.看看看service的生命周期(即从创建到销毁的过程)
3.具体代码演示
首先要创建一个类并继承Srvice 自然要实现父类的方法
public class MyService extends Service {
private static final String TAG = "MyService";
private NotificationManager _nm;
@Override
public void onCreate() {
Log.e(TAG, "============> TestService.onCreate");
_nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
showNotification();
}
@Override
public IBinder onBind(Intent i) {
Log.e(TAG, "============> MyService.onBind");
return null;
}
public class LocalBinder extends Binder {
TestService getService() {
return TestService.this;
}
}
@Override
public boolean onUnbind(Intent i) {
Log.e(TAG, "============> MyService.onUnbind");
return false;
}
@Override
public void onRebind(Intent i) {
Log.e(TAG, "============> TestService.onRebind");
}
@Override
public void onCreate() {
Log.e(TAG, "============> MyService.onCreate");
_nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
showNotification();
}
@Override
public void onStart(Intent intent, int startId) {
Log.e(TAG, "============> MyService.onStart");
}
@Override
public void onDestroy() {
_nm.cancel(R.string.service_started);
Log.e(TAG, "============> MyService.onDestroy");
}
private void showNotification() {
Notification notification = new Notification(R.drawable.face_1,
"Service started", System.currentTimeMillis());
PendingIntent contentIntent = PendingIntent.getActivity(this, 0,
new Intent(this, TestServiceHolder.class), 0);
// must set this for content view, or will throw a exception
notification.setLatestEventInfo(this, "Test Service",
"Service started", contentIntent);
_nm.notify(R.string.service_started, notification);
}
}
其中用到Notification是为了明显地表明Service存活的状
public class LocalBinder extends Binder {
TestService getService() {
return TestService.this;
}
}
这个方法是为了让调用者得到这个Service并操作它。Service本身就这样简单了,你需要做什么就在onCreate和onStart里做好了,起个线程什么的。
在Activity中调用service
public class TestServiceHolder extends Activity {
private boolean _isBound;
private TestService _boundService;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test_service_holder);
setTitle("Service Test");
initButtons();
}
//构造服务连接对象
private ServiceConnection _connection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
_boundService = ((TestService.LocalBinder)service).getService();
Toast.makeText(TestServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName className) {
// unexpectedly disconnected,we should never see this happen.
_boundService = null;
Toast.makeText(TestServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
};
private void initButtons() {
Button buttonStart = (Button) findViewById(R.id.start_service);
buttonStart.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
startService();
}
});
Button buttonStop = (Button) findViewById(R.id.stop_service);
buttonStop.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
stopService();
}
});
Button buttonBind = (Button) findViewById(R.id.bind_service);
buttonBind.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
bindService();
}
});
Button buttonUnbind = (Button) findViewById(R.id.unbind_service);
buttonUnbind.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
unbindService();
}
});
}
private void startService() {
Intent i = new Intent(this, TestService.class);
this.startService(i);
}
private void stopService() {
Intent i = new Intent(this, TestService.class);
this.stopService(i);
}
private void bindService() {
Intent i = new Intent(this, TestService.class);
bindService(i, _connection, Context.BIND_AUTO_CREATE);
_isBound = true;
}
private void unbindService() {
if (_isBound) {
unbindService(_connection);
_isBound = false;
}
}
}
这里可以看到两种启动方法,start和bind,当然也是通过intent调用的,在intent中指明指定要启动的Service的名字,stop也一样 :
private void startService() {
Intent i = new Intent(this, MyService.class);
this.startService(i);
}
private void stopService() {
Intent i = new Intent(this, MyService.class);
this.stopService(i);
}
对于bind的话,需要一个ServiceConnection对象
private ServiceConnection _connection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
_boundService = ((MyService.LocalBinder)service).getService();
Toast.makeText(MyServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName className) {
// unexpectedly disconnected,we should never see this happen.
_boundService = null;
Toast.makeText(MyServiceHolder.this, "Service connected",
Toast.LENGTH_SHORT).show();
}
};
用来把Activity和特定的Service连接在一起,共同存亡。
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