IntentService解析

IntentService中内置了一个HandlerThread，能够对数据进行处理。相比于普通的Service，IntentService有以下优点：

1. 不用在Service创建线程。

2. 不用考虑什么时候关闭Service。

IntentService使用示例

CountService类

package com.fxb.intentservicetest;

import android.app.IntentService;

import android.content.Intent;

import android.util.Log;

public class CountService extends IntentService{

    private volatile boolean isRunning = true;

    public CountService(String name) {

        super(name);

    }

    public CountService(){

        super("CountService");

    }

    @Override

    protected void onHandleIntent(Intent intent) {

        Log.i(MainActivity.TAG, "StartCount");

        int count = intent.getIntExtra("StartCount", 0);

        startCount(count);

    }

    private void startCount(int count){

        isRunning = true;

        while(isRunning){

            try {

                Thread.sleep(1000);

            } catch (InterruptedException e) {

                e.printStackTrace();

            }

            count++;

            Intent intent = new Intent("MY_COUNTER");

            intent.putExtra("count", count);

            sendBroadcast(intent);

        }

    }

}

测试Activity

package com.fxb.intentservicetest;

import android.app.Activity;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.content.IntentFilter;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

public class MainActivity extends Activity implements View.OnClickListener{

    public static final String TAG = "IntentServiceTest";

    private TextView tvShow;

    private Button btnStart;

    private BroadcastReceiver receiver;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initView();

        receiver = new BroadcastReceiver() {

            @Override

            public void onReceive(Context context, Intent intent) {

                int count = intent.getIntExtra("count", 0);

                tvShow.setText("count:"+count);

            }

        };

        IntentFilter filter = new IntentFilter();

        filter.addAction("MY_COUNTER");

        registerReceiver(receiver, filter);

    }

    private void initView(){

        tvShow = (TextView)findViewById(R.id.tvShow);

        btnStart = (Button)findViewById(R.id.btnStart);

        btnStart.setOnClickListener(this);

    }

    @Override

    public void onClick(View v) {

        if(v == btnStart){

            Intent intent = new Intent(this, CountService.class);

            intent.putExtra("StartCount", 5);

            startService(intent);

            Log.i(MainActivity.TAG, "my click");

        }

    }

    @Override

    protected void onDestroy() {

        super.onDestroy();

        unregisterReceiver(receiver);

    }

}

点击Start按钮后，tvShow依次递增变化，从5开始。

IntentService源码

package android.app;

import android.content.Intent;

import android.os.Handler;

import android.os.HandlerThread;

import android.os.IBinder;

import android.os.Looper;

import android.os.Message;

public abstract class IntentService extends Service {

    private volatile Looper mServiceLooper;

    private volatile ServiceHandler mServiceHandler;

    private String mName;

    private boolean mRedelivery;

    private final class ServiceHandler extends Handler {

        public ServiceHandler(Looper looper) {

            super(looper);

        }

        @Override

        public void handleMessage(Message msg) {

            onHandleIntent((Intent)msg.obj);

            stopSelf(msg.arg1);

        }

    }

    public IntentService(String name) {

        super();

        mName = name;

    }

    public void setIntentRedelivery(boolean enabled) {

        mRedelivery = enabled;

    }

    @Override

    public void onCreate() {

        // TODO: It would be nice to have an option to hold a partial wakelock

        // during processing, and to have a static startService(Context, Intent)

        // method that would launch the service & hand off a wakelock.

        super.onCreate();

        HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");

        thread.start();

        mServiceLooper = thread.getLooper();

        mServiceHandler = new ServiceHandler(mServiceLooper);

    }

    @Override

    public void onStart(Intent intent, int startId) {

        Message msg = mServiceHandler.obtainMessage();

        msg.arg1 = startId;

        msg.obj = intent;

        mServiceHandler.sendMessage(msg);

    }

    @Override

    public int onStartCommand(Intent intent, int flags, int startId) {

        onStart(intent, startId);

        return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;

    }

    @Override

    public void onDestroy() {

        mServiceLooper.quit();

    }

    @Override

    public IBinder onBind(Intent intent) {

        return null;

    }

    protected abstract void onHandleIntent(Intent intent);

}