Android Service 组件

Service是Androd系统提供的四种组件之一，它的地位和Activity是并列的，只不过没有Activity的使用频率高。顾名思义Service就是运行在后台的一种服务程序，一般很少和用户交互，因此没有可视化界面。

下面我们演示一下如何创建一个Service：

1：我们通过布局文件layout/main.xml创建一个启动、停止、及绑定一个Service

<?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/startButton01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="启动Service"
/>
<Button
android:id="@+id/stopButton02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="停止Service"
/>
<Button
android:id="@+id/bindButton03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="绑定Service"
/>
<Button
android:id="@+id/unbindButton04"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="解除绑定"
/>
</LinearLayout>

2：我们创建一个MainActivity.java来实现Service

package com.android.test;

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.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

private Button startBtn, stopBtn, bindBtn, unbindBtn;

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//实例化Button
startBtn = (Button)findViewById(R.id.startButton01);
stopBtn = (Button)findViewById(R.id.stopButton02);
bindBtn = (Button)findViewById(R.id.bindButton03);
unbindBtn = (Button)findViewById(R.id.unbindButton04);
//添加监听器
startBtn.setOnClickListener(startListener);
stopBtn.setOnClickListener(stopListener);
bindBtn.setOnClickListener(bindListener);
unbindBtn.setOnClickListener(unBindListener);
}
//启动Service监听器
private OnClickListener startListener = new OnClickListener() {

public void onClick(View v) {
Intent intent = new Intent();
//设置Action属性
intent.setAction("com.android.test.action.MY_SERVICE");
startService(intent);
}

};
//停止Service监听器
private OnClickListener stopListener = new OnClickListener() {

public void onClick(View v) {
Intent intent = new Intent();
intent.setAction("com.android.test.action.MY_SERVICE");
stopService(intent);
}
};
//绑定Service监听器
private OnClickListener bindListener = new OnClickListener() {

public void onClick(View v) {
Intent intent = new Intent();
intent.setAction("com.android.test.action.MY_SERVICE");
//绑定Service
bindService(intent, conn, Service.BIND_AUTO_CREATE);
}
};
//解除Service监听器
private OnClickListener unBindListener = new OnClickListener() {

public void onClick(View v) {
Intent intent = new Intent();
intent.setAction("com.android.test.action.MY_SERVICE");
//解除绑定
unbindService(conn);
}
};

private ServiceConnection conn = new ServiceConnection() {

public void onServiceConnected(ComponentName name, IBinder service) {
Log.i("SERVICE", "连接成功！");
Toast.makeText(MainActivity.this, "连接成功！", Toast.LENGTH_LONG).show();
}

public void onServiceDisconnected(ComponentName name) {
Log.i("SERVICE", "断开连接！");
Toast.makeText(MainActivity.this, "断开连接！", Toast.LENGTH_LONG).show();
}
};

3：创建一个MyService.java继承Service，覆盖其声明周期中的方法，并在各个方法中显示信息

package com.android.test;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import android.widget.Toast;

public class MyService extends Service {
//可以返回null,通常返回一个aidl定义的接口
public IBinder onBind(Intent intent) {
Log.i("SERVICE", "onBind......");
Toast.makeText(MyService.this, "onBind......", Toast.LENGTH_LONG).show();
return null;
}
//Service创建时调用
public void onCreate() {
Log.i("SERVICE", "onCreate......");
}
//当客户端调用startService()方法启动Service时，该方法被调用
public void onStart(Intent intent, int startId) {
Log.i("SERVICE", "onStart......");
Toast.makeText(MyService.this, "onStart......", Toast.LENGTH_LONG).show();
}
//当Service不再使用时调用
public void onDestroy() {
Log.i("SERVICE", "onDestroy......");
Toast.makeText(MyService.this, "onDestroy......", Toast.LENGTH_LONG).show();
}
}

4：在AndroidManifest.xml配置文件中声明Activity和Service

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.android.test"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<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">
<intent-filter>
<action android:name="com.android.test.action.MY_SERVICE"/>
</intent-filter>
</service>
</application>
<uses-sdk android:minSdkVersion="4" />

</manifest>

运行如图：











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