使用线程持续产生随机数

功能描述：

        点击'启动service’按钮后启动后台线程，点击“停止service”按钮后关闭线程。后台线程每一秒产生一个随机数，并通过Handler将产生的随机数显示在用户界面上。

activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="wrap_content"
    android:layout_width="fill_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="      "
        android:textSize="30sp"/>

    <Button
        android:id="@+id/btnstart"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="启动service"/>

    <Button
        android:id="@+id/btnstop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="停止service"/>

</LinearLayout>

MainActivity.java文件

package com.example.pprp.myapplication2_lh;

import android.app.Activity;
import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.support.annotation.Nullable;
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 Activity {

    private static TextView tv01=null;
    Button btnstart;
    Button btnstop;
    private static Handler handler=new Handler();
    private static double randomnum;

    public static void UpdateGUI(double refreshDouble){
        randomnum=refreshDouble;
        handler.post(RefreshLable);
    }

    private static Runnable RefreshLable=new Runnable() {
        @Override
        public void run() {
            tv01.setText(String.valueOf(randomnum));
        }
    };

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

        tv01=(TextView)findViewById(R.id.tv01);
        btnstart=(Button)findViewById(R.id.btnstart);
        btnstop=(Button)findViewById(R.id.btnstop);

        final Intent serviceintent=new Intent(this,ThreadActivity.class); //连接两个java文件的媒介


        btnstart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startService(serviceintent); //开始线程
            }
        });

        btnstop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                stopService(serviceintent); //停止线程
            }
        });
    }

}

ThreadActivity .java文件

package com.example.pprp.myapplication2_lh;

import android.app.Activity;
import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.widget.TextView; 

/**
 * Created by lh on 2018/11/21.
 */

public class ThreadActivity extends Service{

    private Thread thread;

    @Override
    public void onCreate() {
        super.onCreate();
        thread=new Thread(null,backgroundwork,"thread"); //创建线程,将Runnable对象作为参数传递给thread,第三个参数是线程的名称

    }

    @Override
    public void onStart(Intent intent, int startId) {
        super.onStart(intent, startId);
        if(!thread.isAlive()){
            thread.start();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        thread.interrupt();
    }

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

    private Runnable backgroundwork=new Runnable() { //在run（）中放置代码的主体部分
        @Override
        public void run() {
            try {
                while(!thread.interrupted()){
                    double randomnum=Math.random();
                    MainActivity.UpdateGUI(randomnum);
                    Thread.sleep(1000);
                }
            }catch (InterruptedException e){
                e.printStackTrace();
            }
        }
    };
}

AndroidManifest.xml文件：新建立的threadactivity.java文件是service类型，所以在AndroidManifest.xml中注册时需注意写成service.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.pprp.myapplication2_lh">

    <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=".ThreadActivity">

        </service>
    </application>

</manifest>