第 16 章 Service

			
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.netkiller.service">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <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>			
			
			

這段代碼不是手工加入的，只需在 Android Studio 中選擇 File - New - Service - Service 創建 Service 會自動加入下面代碼

			
<service
            android:name=".MyService"
            android:enabled="true"
            android:exported="true"></service>			
			
			

在 Android Studio 中選擇 File - New - Service - Service 創建 Service

MyService繼承自Service，並重寫父類的onCreate()、onStartCommand()和onDestroy()方法

			
package cn.netkiller.service;

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

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("Service", "onCreate() executed");
        Log.d("Service", "MyService thread id is " + Thread.currentThread().getId());
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d("Service", "onStartCommand() executed");
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("Service", "onDestroy() executed");
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

			
			

onCreate() Service 創建的時候執行，已經創建的Service不會再執行

onStartCommand() 任何時候，只要執行 startService(intent); 便會執行

onDestroy() 停止的時候執行

在佈局檔案中加入了兩個按鈕，一個用於啟動Service，一個用於停止Service

			
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="368dp"
        android:layout_height="229dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0">

        <Button
            android:id="@+id/startService"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Start service" />

        <Button
            android:id="@+id/stopService"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Stop service" />
    </LinearLayout>

</android.support.constraint.ConstraintLayout>			
			
			

			
package cn.netkiller.service;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button startService;
    private Button stopService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        startService = (Button) findViewById(R.id.startService);
        stopService = (Button) findViewById(R.id.stopService);
        startService.setOnClickListener(this);
        stopService.setOnClickListener(this);

        Log.d("Service", "MainActivity thread id is " + Thread.currentThread().getId());

    }

    @Override
    public void onClick(View v) {
        Intent intent;
        switch (v.getId()) {
            case R.id.startService:
                intent = new Intent(this, MyService.class);
                startService(intent);
                break;
            case R.id.stopService:
                intent = new Intent(this, MyService.class);
                stopService(intent);
                break;
            default:
                break;
        }
    }
}