Android服務Service

一、普通服務

1 . 定義服務

package com.ysy.mythreaddemo;

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

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


    @Override
    public void onCreate () {
        super.onCreate ();
    }

    @Override
    public int onStartCommand (Intent intent, int flags, int startId) {
        return super.onStartCommand (intent, flags, startId);
    }

    @Override
    public IBinder onBind (Intent intent) {
        throw new UnsupportedOperationException ("Not yet implemented");
    }

    @Override
    public void onDestroy () {
        super.onDestroy ();
    }

}

2 . 啟動和停止服務

  • 啟動服務
            Intent service = new Intent (this,MyService.class);
            startService (service);
  • 停止服務
    stopService (service);

3 . 綁定和解綁服務、調用服務中的方法。

  • 綁定服務前的準備
    在服務中定義一個公共的繼承Binder類,并實現一個自定義的接口(為了調用服務中的方法)的MyBinder類,在服務的onBind()方法中創建MyBinder對象并返回。
    public class MyBinder extends Binder implements IService{

        @Override
        public void startDownload () {
            Log.d ("ysy","start download!");
        }

        @Override
        public int getProgress () {
            Log.d ("ysy","get progress!");
            return 0;
        }
    }
    @Override
    public IBinder onBind (Intent intent) {
        return new MyBinder ();
    }

在活動中創建實現ServiceConnection接口的類,用于綁定服務。

 public class MyConnection implements ServiceConnection{

        @Override
        public void onServiceConnected (ComponentName name, IBinder service) {
            MyService.MyBinder mService = (MyService.MyBinder) service;
            mService.startDownload ();
            int progress = mService.getProgress ();
            Log.d ("ysy","progress "+progress);
        }

        @Override
        public void onServiceDisconnected (ComponentName name) {

        }
    }
  • 綁定服務
       conn = new MyConnection ();
       Intent service = new Intent (this,MyService.class);
       bindService (service,conn,BIND_AUTO_CREATE);
  • 解綁服務
    unbindService (conn);

  • 調用服務中的方法

        @Override
        public void onServiceConnected (ComponentName name, IBinder service) {
            MyService.MyBinder mService = (MyService.MyBinder) service;
            mService.startDownload ();
            int progress = mService.getProgress ();
            Log.d ("ysy","progress "+progress);
        }

4 . 服務的幾個規則

  • 服務可以被多次啟動,每次啟動都會執行onStartCommand()方法
  • 服務可以多次綁定,但只會執行一次onBind()方法。
  • 服務只能解綁一次,解綁多次會出錯
  • 服務的onCreate()方法只會在第一次啟動或者第一次綁定時調用。
  • 服務的onDestory()方法只會在停止服務的時候,或者在未啟動但綁定狀態下,解綁時調用。

二、前臺服務

  • 前臺服務與普通服務的區別是,前臺服務啟動起來之后,會在系統的狀態欄一直有個圖標顯示,下拉狀態之后會看到更詳細的信息。
  • 前臺服務的定義與普通服務定義的不同是,前臺服務會在普通服務的onCreate()方法中添加以下代碼。
        Intent intent = new Intent (this,MainActivity.class);
        PendingIntent pi = PendingIntent.getActivity (this,0,intent,0);
        Notification build = new NotificationCompat.Builder (this)
                .setContentTitle ("this is title")
                .setContentText ("this is content")
                .setSmallIcon (R.mipmap.ic_launcher)
                .setWhen (System.currentTimeMillis ())
                .setContentIntent (pi)
                .build ();
        startForeground (1,build);
  • 前臺服務的啟動與普通服務的啟動相同。

三、在服務中做耗時操作

  • 服務是運行在主線程中的,android規定不能在主線程中做耗時操作。
  • 使用IntentService可以在服務中做耗時操作,定義如下:
package com.ysy.mythreaddemo;

import android.app.IntentService;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

/**
 * An {@link IntentService} subclass for handling asynchronous task requests in
 * a service on a separate handler thread.
 * <p>
 * TODO: Customize class - update intent actions, extra parameters and static
 * helper methods.
 */
public class MyIntentService extends IntentService {
    // TODO: Rename actions, choose action names that describe tasks that this
    // IntentService can perform, e.g. ACTION_FETCH_NEW_ITEMS
    private static final String ACTION_FOO = "com.ysy.mythreaddemo.action.FOO";
    private static final String ACTION_BAZ = "com.ysy.mythreaddemo.action.BAZ";

    // TODO: Rename parameters
    private static final String EXTRA_PARAM1 = "com.ysy.mythreaddemo.extra.PARAM1";
    private static final String EXTRA_PARAM2 = "com.ysy.mythreaddemo.extra.PARAM2";

    public MyIntentService () {
        super ("MyIntentService");
    }

    /**
     * Starts this service to perform action Foo with the given parameters. If
     * the service is already performing a task this action will be queued.
     *
     * @see IntentService
     */
    // TODO: Customize helper method
    public static void startActionFoo (Context context, String param1, String param2) {
        Intent intent = new Intent (context, MyIntentService.class);
        intent.setAction (ACTION_FOO);
        intent.putExtra (EXTRA_PARAM1, param1);
        intent.putExtra (EXTRA_PARAM2, param2);
        context.startService (intent);
    }

    /**
     * Starts this service to perform action Baz with the given parameters. If
     * the service is already performing a task this action will be queued.
     *
     * @see IntentService
     */
    // TODO: Customize helper method
    public static void startActionBaz (Context context, String param1, String param2) {
        Intent intent = new Intent (context, MyIntentService.class);
        intent.setAction (ACTION_BAZ);
        intent.putExtra (EXTRA_PARAM1, param1);
        intent.putExtra (EXTRA_PARAM2, param2);
        context.startService (intent);
    }

    @Override
    protected void onHandleIntent (Intent intent) {
        if (intent != null) {
            final String action = intent.getAction ();
            if (ACTION_FOO.equals (action)) {
                final String param1 = intent.getStringExtra (EXTRA_PARAM1);
                final String param2 = intent.getStringExtra (EXTRA_PARAM2);
                handleActionFoo (param1, param2);
            } else if (ACTION_BAZ.equals (action)) {
                final String param1 = intent.getStringExtra (EXTRA_PARAM1);
                final String param2 = intent.getStringExtra (EXTRA_PARAM2);
                handleActionBaz (param1, param2);
            }
        }
        Log.d ("ysy","Thread is "+Thread.currentThread ().getId ());
    }

    /**
     * Handle action Foo in the provided background thread with the provided
     * parameters.
     */
    private void handleActionFoo (String param1, String param2) {
        // TODO: Handle action Foo
        throw new UnsupportedOperationException ("Not yet implemented");
    }

    /**
     * Handle action Baz in the provided background thread with the provided
     * parameters.
     */
    private void handleActionBaz (String param1, String param2) {
        // TODO: Handle action Baz
        throw new UnsupportedOperationException ("Not yet implemented");
    }

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


}

  • 可以將耗時操作放在MyIntentService的onHandleIntent ()方法中,這個方法中的代碼是運行在子線程中。
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