IntentService源码分析

IntentService继承Service，它包含了Service的全部特性，当然也包含service的生命周期，那么与service不同的是，IntentService在执行onCreate操作的时候，内部开了一个线程，去执行你的耗时操作。
IntentService源码：

import android.app.Service;import android.content.Intent;import android.os.Handler;import android.os.HandlerThread;import android.os.IBinder;import android.os.Looper;import android.os.Message;import android.util.Log;import static android.app.Service.START_NOT_STICKY;import static android.app.Service.START_REDELIVER_INTENT;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() {        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);}

从源码中可以看出，IntentService在onCreate操作的时候，通过HandlerThread开启了一个内部线程，耗时操作可以放在onHandleIntent(Intent intent)的重载函数中。
为了便于理解，写了一个上传图片的demo。
继承于IntentService的上传图片的Service：

package com.zrp.myintentservice;import android.content.Context;import android.content.Intent;import android.util.Log;import static android.os.Build.VERSION_CODES.M;public class UploadImgService extends IntentService{    private static final String ACTION_UPLOAD_IMG = "com.zhy.blogcodes.intentservice.action.UPLOAD_IMAGE";    public static final String EXTRA_IMG_PATH = "com.zhy.blogcodes.intentservice.extra.IMG_PATH";    public static void startUploadImg(Context context, String path)    {        Intent intent = new Intent(context, UploadImgService.class);        intent.setAction(ACTION_UPLOAD_IMG);        intent.putExtra(EXTRA_IMG_PATH, path);        context.startService(intent);    }    public UploadImgService()    {        super("UploadImgService");    }    @Override    protected void onHandleIntent(Intent intent)    {        if (intent != null)        {            final String action = intent.getAction();            if (ACTION_UPLOAD_IMG.equals(action))            {                final String path = intent.getStringExtra(EXTRA_IMG_PATH);                handleUploadImg(path);            }        }    }    private void handleUploadImg(String path)    {        try        {            //模拟上传耗时            Thread.sleep(3000);            Intent intent = new Intent(MainActivity.UPLOAD_RESULT);            intent.putExtra(EXTRA_IMG_PATH, path);            sendBroadcast(intent);        } catch (InterruptedException e)        {            e.printStackTrace();        }    }    @Override    public void onCreate()    {        super.onCreate();        Log.e("TAG","onCreate");    }    @Override    public void onDestroy()    {        super.onDestroy();        Log.e("TAG","onDestroy");    }}

MainAcitivity:

package com.zrp.myintentservice;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.LinearLayout;import android.widget.TextView;public class MainActivity extends AppCompatActivity {    public static final String UPLOAD_RESULT = "com.zhy.blogcodes.intentservice.UPLOAD_RESULT";    private LinearLayout mLyTaskContainer;    private BroadcastReceiver uploadImgReceiver = new BroadcastReceiver() {        @Override        public void onReceive(Context context, Intent intent) {            if (intent.getAction() == UPLOAD_RESULT) {                String path = intent.getStringExtra(UploadImgService.EXTRA_IMG_PATH);                handleResult(path);                Log.d("zeng","MainActivity BroadcastReceiver Thread Name: " + Thread.currentThread().getName());            }        }    };    private void handleResult(String path) {        TextView tv = (TextView) mLyTaskContainer.findViewWithTag(path);        tv.setText(path + " upload success ~~~ ");    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mLyTaskContainer = (LinearLayout) findViewById(R.id.id_ll_taskcontainer);        Log.d("zeng","MainActivity Thread Name: " + Thread.currentThread().getName());        registerReceiver();    }    private void registerReceiver() {        IntentFilter filter = new IntentFilter();        filter.addAction(UPLOAD_RESULT);        registerReceiver(uploadImgReceiver, filter);    }    int i = 0;    public void addTask(View view) {        //模拟路径        String path = "/sdcard/imgs/" + (++i) + ".png";        UploadImgService.startUploadImg(this, path);        TextView tv = new TextView(this);        mLyTaskContainer.addView(tv);        tv.setText(path + " is uploading ...");        tv.setTag(path);    }    @Override    protected void onDestroy() {        super.onDestroy();        unregisterReceiver(uploadImgReceiver);    }}

MainActivity的布局：

<?xml version="1.0" encoding="utf-8"?><LinearLayout android:id="@+id/id_ll_taskcontainer"    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    >    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"        android:onClick="addTask" android:text="add Task"/></LinearLayout>

Menifest.xml中注册UploadImgService

<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=".UploadImgService"/>    </application>