Android Studio开发基础之Service
1、Service的使用
Activity可以呈现一个用户界面，但是Service确实运行在后台，新建一个Myservice.java，会在AndroidManifest中自动配置<Service>标签。
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.lhb.service" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
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=".MyService"
android:enabled="true"
android:exported="true" >
</service>
</application>
</manifest>
在新建的Service中重写onStartCommand()函数，创建一个线程，点击启动线程按钮，让它在后台循环打印，注意按后退键退出Activity，服务仍在进行。
package com.example.lhb.service;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
public class MyService extends Service {
public MyService() {
}
@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
throw new UnsupportedOperationException("Not yet implemented");
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
new Thread(){
@Override
public void run() {
super.run();
do {
System.out.println("Service is running......");
try {
sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
} while (true);
}
}.start();
return super.onStartCommand(intent, flags, startId);
}
}
主代码如下：
package com.example.lhb.service;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends Activity implements View.OnClickListener{
private TextView textView;
private Intent intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
InitView();
}
private void InitView(){
textView=new TextView(this);
textView.setText(R.string.hello_world);
findViewById(R.id.btnStartService).setOnClickListener(this);
findViewById(R.id.btnStopService).setOnClickListener(this);
intent=new Intent(MainActivity.this,MyService.class);
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.btnStartService:
startService(intent);
break;
case R.id.btnStopService:
stopService(intent);
break;
}
}
}
2、绑定Service
可以以绑定的方式启动MyService，再添加一个绑定Service和解除绑定Service的按钮。
<LinearLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="启动服务"
android:id="@+id/btnStartService" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="停止服务"
android:id="@+id/btnStopService" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="绑定服务"
android:id="@+id/btnBindService" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="解除绑定服务"
android:id="@+id/btnUnBindService" />
</LinearLayout>
主程序：
package com.example.lhb.service;
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.view.View;
import android.widget.TextView;
public class MainActivity extends Activity implements View.OnClickListener, ServiceConnection {
private TextView textView;
private Intent intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
InitView();
}
private void InitView(){
textView=new TextView(this);
textView.setText(R.string.hello_world);
findViewById(R.id.btnStartService).setOnClickListener(this);
findViewById(R.id.btnStopService).setOnClickListener(this);
findViewById(R.id.btnBindService).setOnClickListener(this);
findViewById(R.id.btnUnBindService).setOnClickListener(this);
intent=new Intent(MainActivity.this,MyService.class);
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.btnStartService:
startService(intent);
break;
case R.id.btnStopService:
stopService(intent);
break;
case R.id.btnBindService:
bindService(intent,this, Context.BIND_AUTO_CREATE);
//直接用this连接会出错，按Alt+Enter,创建下面的onServiceConnected()
break;
case R.id.btnUnBindService:
unbindService(this);
break;
}
}
@Override
//服务绑定后执行
public void onServiceConnected(ComponentName name, IBinder service) {
System.out.println("Service connected");
}
@Override
//进程奔溃时执行
public void onServiceDisconnected(ComponentName name) {
}
}
注意：完成上述代码之后，要将MyService.java中的IBinder改为return new Binder();，否则会出现错误！
@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
//throw new UnsupportedOperationException("Not yet implemented");
return new Binder();
}
java.lang.RuntimeException: Unable to bind to service com.example.lhb.service.MyService@d3a4c20 with Intent { cmp=com.example.lhb.service/.MyService }: java.lang.UnsupportedOperationException: Not yet implemented
at android.app.ActivityThread.handleBindService(ActivityThread.java:2771)
at android.app.ActivityThread.access$1900(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1366)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.UnsupportedOperationException: Not yet implemented
at com.example.lhb.service.MyService.onBind(MyService.java:14)
3、Service生命周期
package com.example.lhb.service;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
public class MyService extends Service {
public MyService() {
}
@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
//throw new UnsupportedOperationException("Not yet implemented");
return new Binder();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onCreate() {
super.onCreate();
System.out.println("onCreate");
}
@Override
public void onDestroy() {
super.onDestroy();
System.out.println("onDestroy");
}
}
运行时发现，同时点击了启动服务和绑定服务，需同时点击停止服务和解除绑定服务才能将服务停下来，点击绑定服务，再退出Activity，程序会抛出异常，然后会执行解除绑定服务，整个程序界面如下图：
