Service知识

1. Service的两种启动模式

• startService()

Intent intent = new Intent(this, MyService.class);
startService(intent);

• bindService

        Intent  intent = new Intent(this, MyService.class);
        startService(intent);
        ServiceConnection conn = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
                Log.d("TAG", "onServiceConnected");
                MyService.MyBinder myBinder = (MyService.MyBinder) iBinder;
                service = myBinder.getService();
                isBind = true;
            }

            @Override
            public void onServiceDisconnected(ComponentName componentName) {
                Log.d("TAG", "onServiceDisconnected");
            }
        };
        bindService(intent, conn, Service.BIND_AUTO_CREATE);

2. 自定义Service

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

    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("TAG", "MyService---->onCreate");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d("TAG", "MyService---->onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.d("TAG", "MyService---->onBind");
        return new MyBinder();
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.d("TAG","MyService---->onUnbind");
        return super.onUnbind(intent);
    }

    public class MyBinder extends Binder {
        public MyService getService() {
            return MyService.this;
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("TAG", "MyService---->onDestroy");
    }
}

既startService又bindService

从中可以看出onCreate只执行一次,onCreate不管startService或者bindService多少次都只执行一次onCreate()

3. startService和bindService的区别
   startService没有和Activity绑定，Activity销毁了之后service还是能够运行；bindService启动时Service和Activity进行了绑定，如果Activity销毁了，那么Service会自动进行解绑和调用Service的onDestroy()方法
4. IntentService

• IntentService的定义

package com.example.ulabor.testproject;

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

import java.util.concurrent.Executors;

/**
 * An {@link IntentService} subclass for handling asynchronous task requests in
 * a service on a separate handler thread.
 * 

 * helper methods.
 */
public class MyIntentService extends IntentService {
    private static final String ACTION_FOO = "com.example.ulabor.testproject.action.FOO";
    private static final String ACTION_BAZ = "com.example.ulabor.testproject.action.BAZ";

    private static final String EXTRA_PARAM1 = "com.example.ulabor.testproject.extra.PARAM1";
    private static final String EXTRA_PARAM2 = "com.example.ulabor.testproject.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
     */
    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);
    }

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


    /**
     * 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
     */
    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);
            }
        }
    }

    /**
     * Handle action Foo in the provided background thread with the provided
     * parameters.
     */
    private void handleActionFoo(String param1, String param2) {
        try {
            try {
                for (int i = 0; i < 10; i++) {
                    Thread.sleep(1000);
                    Log.d("TAG", "i---》" + i);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 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");
    }
}

最主要的就是onHandleIntent()方法对传入的参数进行处理；从中可以看出在handleActionFoo方法中，调用 Thread.sleep(1000);来进行耗时操作模拟，Service自己循环了10次之后自动销毁。能够在onHandleIntent（）方法中进行耗时操作。因为Service的onCreate（）和onStartCommand方法是在主线程运行的，所以不能够在这里进行耗时操作。IntentService是窜行操作，不是并行操作，也就是任务是一步一步完成的，如下图

执行如下代码:

        for (int j = 0; j < 2; j++) {
            MyIntentService.startActionFoo(this, "a", "b");
        }

运行结果

image.png