Service简介

  新建一个ServiceTest项目，然后右击com.example.servicetest→New→Service→Service。

  每个Service中最常用到onCreate()、onStartCommand()和onDestroy()这3个方法其中onCreate()方法会在Service创建的时候调用，onStartCommand()方法会在每次Service启动的时候调用，onDestroy()方法会在Service销毁的时候调用。

  另外需要注意，每一个Service都需要在AndroidManifest.xml文件中进行注册才能生效。

启动和停止Service

  修改activity_main.xml中的代码。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent">
 <Button
 android:id="@+id/startServiceBtn"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:text="Start Service" />
 <Button
 android:id="@+id/stopServiceBtn"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:text="Stop Service" />
</LinearLayout>

  修改MainActivity中的代码。

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button startService = (Button) findViewById(R.id.startServiceBtn);
        Button stopService = (Button) findViewById(R.id.stopServiceBtn);
        startService.setOnClickListener(this);
        stopService.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.startServiceBtn:
                Intent startIntent = new Intent(this, MyService.class);
                startService(startIntent); // 启动服务
                break;
            case R.id.stopServiceBtn:
                Intent stopIntent = new Intent(this, MyService.class);
                stopService(stopIntent); // 停止服务
                break;
            default:
                break;
        }
    }
}

  修改MyService.java中的代码。

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

Activity和Service进行通信

  修改MyService中的代码。

public class MyService extends Service {
    private DownloadBinder mBinder = new DownloadBinder();

    class DownloadBinder extends Binder {
        public void startDownload() {
            Log.d("MyService", "startDownload executed");
        }
        public int getProgress() {
            Log.d("MyService", "getProgress executed");
            return 0;
        }
    }
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

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

  修改activity_main.xml中的代码，在布局文件里新增两个按钮用于调用Service。这两个按钮分别是用于绑定和取消绑定Service的，当一个Activity和Service绑定了之后，就可以调用该Service里的Binder提供的方法了。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/startServiceBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start Service" />
    <Button
        android:id="@+id/stopServiceBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Stop Service" />
    <Button
        android:id="@+id/bindServiceBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Bind Service" />
    <Button
        android:id="@+id/unbindServiceBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Unbind Service" />
</LinearLayout>

  修改MainActivity中的代码。

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private MyService.DownloadBinder downloadBinder;

    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            downloadBinder = (MyService.DownloadBinder) service;
            downloadBinder.startDownload();
            downloadBinder.getProgress();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button startService = (Button) findViewById(R.id.startServiceBtn);
        Button stopService = (Button) findViewById(R.id.stopServiceBtn);
        startService.setOnClickListener(this);
        stopService.setOnClickListener(this);

        Button bindService = (Button) findViewById(R.id.bindServiceBtn);
        Button unbindService = (Button) findViewById(R.id.unbindServiceBtn);
        bindService.setOnClickListener(this);
        unbindService.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.startServiceBtn:
                Intent startIntent = new Intent(this, MyService.class);
                startService(startIntent); // 启动服务
                break;
            case R.id.stopServiceBtn:
                Intent stopIntent = new Intent(this, MyService.class);
                stopService(stopIntent); // 停止服务
                break;
            case R.id.bindServiceBtn:
                Intent bindIntent = new Intent(this, MyService.class);
                bindService(bindIntent, connection, BIND_AUTO_CREATE); // 绑定服务
                break;
            case R.id.unbindServiceBtn:
                unbindService(connection);  // 解绑服务
                break;
            default:
                break;
        }
    }
}