如果把Activity比喻为前台程序，那么Service就是后台程序，Service的整个生命周期都只会在后台执行。Service跟Activity一样也由Intent调用。在工程里想要添加一个Service，先新建继承Service的类，然后到AndroidManifest.xml -> Application ->Application Nodes中的Service标签中添加。
Service要由Activity通过startService 或者 bindService来启动，Intent负责传递参数。先贴出本应用运行截图：
本文主要讲解Service的调用，以及其生命周期。
下图是startService之后再stopService的Service状态变化。
下图是bindService之后再unbindService的Service状态变化。
startService与bindService都可以启动Service，那么它们之间有什么区别呢？它们两者的区别就是使Service的周期改变。由startService启动的Service必须要有stopService来结束Service，不调用stopService则会造成Activity结束了而Service还运行着。bindService启动的Service可以由unbindService来结束，也可以在Activity结束之后(onDestroy)自动结束。
下图是startService之后再Activity.finish()的Service状态变化，Service还在跑着。
下图是bindService之后再Activity.finish()的Service状态变化，Service最后自动unbindService。
main.xml代码
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<Button
android:id="@+id/btnStartMyService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="StartMyService"
/>
<Button
android:id="@+id/btnStopMyService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="StopMyService"
/>
<Button
android:id="@+id/btnBindMyService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="BindMyService"
/>
<Button
android:id="@+id/btnUnbindMyService"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="UnbindMyService"
/>
<Button
android:id="@+id/btnExit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="退出程序"
/>
</LinearLayout>
testService.java的源码
package com.testService;
import android.app.Activity;
import android.app.Service;
import android.content.ComponentName;
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.Button;
public class testService extends Activity {
Button btnStartMyService, btnStopMyService, btnBindMyService,
btnUnbindMyService, btnExit;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btnStartMyService = (Button)this.findViewById(R.id.btnStartMyService);
btnStartMyService.setOnClickListener(new ClickEvent());
btnStopMyService = (Button) this.findViewById(R.id.btnStopMyService);
btnStopMyService.setOnClickListener(new ClickEvent());
btnBindMyService = (Button) this.findViewById(R.id.btnBindMyService);
btnBindMyService.setOnClickListener(new ClickEvent());
btnUnbindMyService = (Button) this
.findViewById(R.id.btnUnbindMyService);
btnUnbindMyService.setOnClickListener(new ClickEvent());
btnExit = (Button) this.findViewById(R.id.btnExit);
btnExit.setOnClickListener(new ClickEvent());
}
@Override
public void onDestroy() {
super.onDestroy();
Log.e("Activity", "onDestroy");
}
private ServiceConnection _connection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName arg0, IBinder arg1) {
// TODO Auto-generated method stub
}
@Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
}
};
class ClickEvent implements View.OnClickListener {
@Override
public void onClick(View v) {
Intent intent = new Intent(testService.this, MyService.class);
if (v == btnStartMyService) {
testService.this.startService(intent);
} else if (v == btnStopMyService) {
testService.this.stopService(intent);
} else if (v == btnBindMyService) {
testService.this.bindService(intent, _connection,
Service.BIND_AUTO_CREATE);
} else if (v == btnUnbindMyService) {
if (MyService.ServiceState == "onBind")// Service绑定了之后才能解绑
testService.this.unbindService(_connection);
} else if (v == btnExit) {
testService.this.finish();
}
}
}
}
MyService.java的源码
package com.testService;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
public class MyService extends Service {
static public String ServiceState = "";
@Override
public IBinder onBind(Intent arg0) {
Log.e("Service", "onBind");
ServiceState = "onBind";
return null;
}
@Override
public boolean onUnbind(Intent intent) {
super.onUnbind(intent);
Log.e("Service", "onUnbind");
ServiceState = "onUnbind";
return false;
}
@Override
public void onCreate() {
super.onCreate();
Log.e("Service", "onCreate");
ServiceState = "onCreate";
}
@Override
public void onDestroy() {
super.onDestroy();
Log.e("Service", "onDestroy");
ServiceState = "onDestroy";
}
@Override
public void onStart(Intent intent, int startid) {
super.onStart(intent, startid);
Log.e("Service", "onStart");
ServiceState = "onStart";
}
}
