Android Service（服务）

• 服务的定义
  服务是Android中实现后台运行的解决方案。
• android多线程
  定义线程：（两种方式）

class MyThread extends Thread{
    @Override
    public void run(){
       //处理的逻辑
    }
}

class MyThread implements Runnable{
    @Override
    public void run(){
       //处理的逻辑
    }
}

启动线程

MyThread myThread = new MyThread();
new Thread(myTread).start();

定义和启动线程

new Thread(new Runnable){
    @Override
    public void run(){
    
    }
}

利用线程改变Ui
MainActivity

package com.example.administrator.androidthreadtest;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView textView;
    public static final  int UPDATE_TEXT = 1;
    private Handler handler = new Handler(){
        public void handleMessage(Message message){
            switch (message.what){
                case UPDATE_TEXT:
                    textView.setText("Nice to meet you");
                    break;
                default:
                    break;
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView)findViewById(R.id.textview);
        Button changText = (Button)findViewById(R.id.change_text);
        changText.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.change_text:
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                       Message message = new Message();
                       message.what = UPDATE_TEXT;
                       handler.sendMessage(message);
                    }
                }).start();
                break;
            default:
                break;

        }
    }
}

activity_main_layout

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
   >

    <Button
        android:id="@+id/change_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Change Text"/>
    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textSize="20sp"
        android:text="Hello World!"
         />

</RelativeLayout>

运行效果

此处输入图片的描述

• 异步消息处理机制

  
  如图
  

  用AsyncTask更好地实现了子线程UI的操作。
  三个参数

• Params：执行时传入的参数。
• Progress：指定泛型的进度单位。
• Result：执行后返回的结果。

//自定义AsyncTask类
class DownloadTask extends AsyncTask<Void,Integer,Boolean>{
}

还需要重写一些方法：onPreExecute(),doInBackground(params...),onProgressUpdate(Progress...),
onPostExcute(Result).

class DownloadTask extends AsyncTask<Void,Integer,Boolean>{
    @Override
    protected void onPreExecute(){
        progressDialog.show();//显示进度条
    }
    @Override
    protected Boolean doInBackground <Void ...params){
       try{
         while(true){
          int downloadPercent = doDownload();
          publishProgress(downloadPercent);
          if(downloadPercent >= 100){
              break;
              }
         }
       }catch(Exception e){
           return false;
       }
       return true;
    }
      @Override
      protected void onProgressUpdate (Integer ...values){
          progressDialog.setMessage("Finish"+values[0]+"%");
      }
      @Override
      protected void onPostExecute(Boolean result){
         progressDialog.dismiss();
         if(result){
            Toast.makeText(context,"Download succeeded",Toast.LENGTH_SHORT).show();
            }else{
                  Toast.makeText(context,"Download failed",Toast.LENGTH_SHORT).show();
            }
      }
      
}

AsyncTask的核心是：doInBackground执行耗时的任务,onProgressUpdate进行UI操作，在onPostExecute执行返回结果的一些操作，如弹出下载完成对话框的动作。

new DownloadTask().execute()

启动任务（下载）

Service

定义一个服务，新建service

新建服务

重写onCreate,onStartCommand,onDestory方法。
我们在activity_main:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <Button
        android:id="@+id/start_service"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="启动服务"
        />
    <Button
        android:id="@+id/stop_service"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="停止服务"/>
    <Button
        android:id="@+id/bind_service"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="绑定服务"
        />
    <Button
        android:id="@+id/unbind_service"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="解绑服务"
        />


</LinearLayout>

这里我们定义四个按钮：启动，停止，绑定，解绑.
MainActivity

package com.example.administrator.servicetest;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private MyService.DownloadBinder downloadBinder;//这里是Myservice中的内部类
    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            downloadBinder = (MyService.DownloadBinder)service;
            downloadBinder.startDownload();//这是MyService中的方法。
            downloadBinder.getProgress();//这是MyService中的方法。
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
    //设置点击事件观察服务的一些信息
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button Start = (Button)findViewById(R.id.start_service);
        Button Stop = (Button)findViewById(R.id.stop_service);
        Button Bind = (Button)findViewById(R.id.bind_service);
        Button unBind = (Button)findViewById(R.id.unbind_service);
        Start.setOnClickListener(this);
        Stop.setOnClickListener(this);
        Bind.setOnClickListener(this);
        unBind.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.start_service:
                Intent intentOne = new Intent(this,MyService.class);
                startService(intentOne);//启动服务
                break;
            case R.id.stop_service:
                Intent intentTwo = new Intent(this,MyService.class);
                stopService(intentTwo);//停止服务
                break;
            case R.id.bind_service:
                Intent intentThree = new Intent(this,MyService.class);
                bindService(intentThree,connection,BIND_AUTO_CREATE);//绑定服务
                break;
            case R.id.unbind_service:
                Intent intentFour = new Intent(this,MyService.class);
                unbindService(connection);//解绑服务
                break;
            default:
                break;
        }
    }
}

MyService

package com.example.administrator.servicetest;

import android.app.DownloadManager;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {
    private DownloadBinder mBinder  = new DownloadBinder();
    class DownloadBinder extends Binder{
        public  void startDownload(){
            Log.d("MyService","开始下载");
        }
        public int getProgress(){
            Log.d("MyService","getProgress");
            return 0;
        }
    }
    //构造方法
    public MyService() {
    }
    //绑定服务
    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
       return mBinder;
    }
    //服务的创建
    @Override
    public void onCreate() {
        super.onCreate();
        Log.d("MyService","onCreate方法");//打印输出
    }
     //onCreate方法之后，多次执行，onCreate一次执行（观察logcat的打印）
    @Override
    public int onStartCommand(Intent intent, int flags, int startId)    {
        Log.d("MyService","onStartCommand方法");
        return super.onStartCommand(intent, flags, startId);
    }
    //服务的销毁，类似Activity的生命周期方法。
    @Override
    public void onDestroy() {
        Log.d("MyService","onDestroy方法");
        super.onDestroy();
    }

}

使用IntentService：运用Android多线程编程，给service新建一个子线程。
新建一个类继承于IntentService类：

package com.example.administrator.servicetest;

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

public class MyIntentService extends IntentService {
    public MyIntentService(){
        super("MyIntentService");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        Log.d("MyIntentService","Thread id is"+Thread.currentThread().getId());
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d("MyIntentService","onDestroy方法2");
    }
}

MainActivity中：

package com.example.administrator.servicetest;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private MyService.DownloadBinder downloadBinder;
    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            downloadBinder = (MyService.DownloadBinder)service;
            downloadBinder.startDownload();
            downloadBinder.getProgress();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button Start = (Button)findViewById(R.id.start_service);
        Button Stop = (Button)findViewById(R.id.stop_service);
        Button Bind = (Button)findViewById(R.id.bind_service);
        Button unBind = (Button)findViewById(R.id.unbind_service);
        Button StartIntentService = (Button) findViewById(R.id.start_intent_service);
        Start.setOnClickListener(this);
        Stop.setOnClickListener(this);
        Bind.setOnClickListener(this);
        unBind.setOnClickListener(this);
        StartIntentService.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.start_service:
                Intent intentOne = new Intent(this,MyService.class);
                startService(intentOne);//启动服务
                break;
            case R.id.stop_service:
                Intent intentTwo = new Intent(this,MyService.class);
                stopService(intentTwo);//停止服务
                break;
            case R.id.bind_service:
                Intent intentThree = new Intent(this,MyService.class);
                bindService(intentThree,connection,BIND_AUTO_CREATE);//绑定服务
                break;
            case R.id.unbind_service:
                Intent intentFour = new Intent(this,MyService.class);
                unbindService(connection);//解绑服务
                break;
            case R.id.start_intent_service:
                Log.d("Mainctivity","Thread id is" + Thread.currentThread().getId());
                Intent intentService = new Intent(this,MyIntentService.class);
                startService(intentService);
                break;
            default:
                break;
        }
    }
}