详解Android中IntentService的使用方法

package com.ispring.startservicedemo;

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

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class DownloadIntentService extends IntentService {

 public DownloadIntentService(){
  super("Download");
  Log.i("DemoLog", "DownloadIntentService构造函数, Thread: " + Thread.currentThread().getName());
 }

 @Override
 public void onCreate() {
  super.onCreate();
  Log.i("DemoLog", "DownloadIntentService -> onCreate, Thread: " + Thread.currentThread().getName());
 }

 @Override
 public int onStartCommand(Intent intent, int flags, int startId) {
  Log.i("DemoLog", "DownloadIntentService -> onStartCommand, Thread: " + Thread.currentThread().getName() + " , startId: " + startId);
  return super.onStartCommand(intent, flags, startId);
 }

 @Override
 protected void onHandleIntent(Intent intent) {
  HttpURLConnection conn = null;
  InputStream is = null;
  String blogUrl = intent.getStringExtra("url");
  String blogName = intent.getStringExtra("name");
  try{
   //下载指定的文件
   URL url = new URL(blogUrl);
   conn = (HttpURLConnection)url.openConnection();
   if(conn != null){
    //我们在此处得到所下载文章的输入流，可以将其以文件的形式写入到存储卡上面或
    //将其读取出文本显示在App中
    is = conn.getInputStream();
   }
  }catch (MalformedURLException e){
   e.printStackTrace();
  }catch (IOException e){
   e.printStackTrace();
  }finally {
   if(conn != null){
    conn.disconnect();
   }
  }
  Log.i("DemoLog", "DownloadIntentService -> onHandleIntent, Thread: " + Thread.currentThread().getName() + ", 《" + blogName + "》下载完成");
 }

 @Override
 public void onDestroy() {
  super.onDestroy();
  Log.i("DemoLog", "DownloadIntentService -> onDestroy, Thread: " + Thread.currentThread().getName());
 }
}

package com.ispring.startservicedemo;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


public class DownloadActivity extends Activity implements Button.OnClickListener {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_download);
 }

 @Override
 public void onClick(View v) {
  List<String> list = new ArrayList<>();
  list.add("Android通过startService播放背景音乐;https://www.jb51.net/article/76479.htm");
  Iterator iterator = list.iterator();

  while (iterator.hasNext()){
   String str = (String)iterator.next();
   String[] splits = str.split(";");
   String name = splits[0];
   String url = splits[1];
   Intent intent = new Intent(this, DownloadIntentService.class);
   intent.putExtra("name", name);
   intent.putExtra("url", url);
   //启动IntentService
   startService(intent);
  }
 }
}

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) {
   //在工作线程中调用onHandleIntent，确保onHandleIntent不会阻塞主线程
   onHandleIntent((Intent)msg.obj);
   //在执行完了onHandleIntent之后，我们需要调用stopSelf(startId)声明某个job完成了
   //当所有job完成的时候，Android就会回调onDestroy方法，销毁IntentService
   stopSelf(msg.arg1);
  }
 }

 public IntentService(String name) {
  //此处的name将用作线程名称
  super();
  mName = name;
 }

 public void setIntentRedelivery(boolean enabled) {
  mRedelivery = enabled;
 }

 @Override
 public void onCreate() {
  super.onCreate();
  //创建HandlerThread，利用mName作为线程名称，HandlerThread是IntentService的工作线程
  HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
  thread.start();

  mServiceLooper = thread.getLooper();
  //将创建的HandlerThread所绑定的looper对象传递给ServiceHandler，
  //这样我们创建的Handler就和HandlerThread通过消息队列绑定在了一起
  mServiceHandler = new ServiceHandler(mServiceLooper);
 }

 @Override
 public void onStart(Intent intent, int startId) {
  //在此方法中创建Message对象，并将intent作为Message的obj参数,
  //这样Message与Intent就关联起来了
  Message msg = mServiceHandler.obtainMessage();
  msg.arg1 = startId;
  msg.obj = intent;
  //将关联了Intent信息的Message发送给Handler
  mServiceHandler.sendMessage(msg);
 }

 @Override
 public int onStartCommand(Intent intent, int flags, int startId) {
  //IntentService重写了onStartCommand回调方法:在内部调用onStart回调方法
  //所以我们在继承IntentService时，不应该再覆写该方法，即便覆盖该方法，我们也应该调用super.onStartCommand()
  onStart(intent, startId);
  return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
 }

 @Override
 public void onDestroy() {
  //在onDestroy方法中调用了Handler的quit方法，该方法会终止消息循环
  mServiceLooper.quit();
 }

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

 protected abstract void onHandleIntent(Intent intent);
}