Runnable的作用及使用方式

前言

Java中实现多线程主要由以下两种方式:继承Thread类和实现Runnable接口，本文主要说明Runnable接口实现多线程。

Runnable接口简介

(1)定义
Runnable接口是线程辅助类，仅定义了一个方法run()方法
(2)作用
实现多线程
(3)优点
灵活：Runnable可以继承其他类实现对Runnable实现类的增强，避免了Thread类由于继承Thread类而无法继承其他类的问题
共享资源:Runnable接口的run()方法可以被多个线程共享，适用于多个进程处理一种资源的问题

使用方法

(1) 实现Runnable接口
(2) 重写run()方法
(3) 创建runnable实例
(4) 创建Thread实例
(5) 将Runnable实例放入Thread实例中
(6) 通过线程实例控制线程的行为(运行，停止)，在运行时会调用Runnable接口中的run方法。

注意:Java中真正能创建新线程的只有Thread类对象
通过实现Runnable的方式，最终还是通过Thread类对象来创建线程

Runnable方式也分为标准方式和匿名方式
(1)标准方式

public class MainActivity extends AppCompatActivity {
    Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = findViewById(R.id.btn);
        //2.创建MyRunnable实例
        MyRunnable runnable=new MyRunnable();
        //3.创建Thread对象
        //4.将MyRunnable放入Thread实例中
        Thread thread=new Thread(runnable);
        //5.通过线程对象操作线程(运行、停止)
        thread.start();

    }
    //1.实现runnable接口并重写run方法
    class MyRunnable implements Runnable{

        @Override
        public void run() {

        }
    }
}

(2)匿名方式

public class MainActivity extends AppCompatActivity {
    Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //1.匿名实现Runnable接口并重写run方法
        Runnable runnable = new Runnable() {
            @Override
            public void run() {

            }
        };
        //2.创建线程对象
        //3.将runnable实例放入线程对象中
        Thread thread=new Thread(runnable);
        //4.由线程实例控制线程的行为(运行，停止)
        thread.start();

    }

}

实际用例

现在假设有两个窗口卖车票，每一秒卖出一张车票，每个窗口有100张票
activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.zhqy.threaddemo.MainActivity">

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:text="售票"
        />

</android.support.constraint.ConstraintLayout>

MainActivity.java:

package com.zhqy.threaddemo;

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 {
    Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn=findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //创建runnnable实例
                TicketRunnable run1=new TicketRunnable();
                TicketRunnable run2=new TicketRunnable();
                //创建Thread实例并将runnable实例放入
                Thread th1=new Thread(run1,"th1");
                Thread th2=new Thread(run2,"th2");
                //通过线程实例控制线程的行为(运行、停止)
                th1.start();
                th2.start();
            }
        });
    }
     //实现Runnable接口并重写run方法
    class TicketRunnable implements  Runnable{
        int ticket=100;
        @Override
        public void run() {
            //卖票
            while (ticket>0){
                Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket));
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}

测试结果:

08-26 10:52:21.954 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:99
08-26 10:52:21.954 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:99
08-26 10:52:22.955 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:98
08-26 10:52:22.955 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:98
08-26 10:52:23.955 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:97
08-26 10:52:23.955 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:97
08-26 10:52:24.956 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:96
08-26 10:52:24.956 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:96
08-26 10:52:25.956 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:95
08-26 10:52:25.956 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:95
08-26 10:52:26.957 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:94
08-26 10:52:26.957 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:94
08-26 10:52:27.958 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:93
08-26 10:52:27.958 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:93
08-26 10:52:28.958 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:92
08-26 10:52:28.958 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:92

那么如何让两个窗口共享“车票”呢？

package com.zhqy.threaddemo;

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 {
    Button btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn=findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //创建runnnable实例
                TicketRunnable run1=new TicketRunnable();

                //创建Thread实例并将runnable实例放入
                Thread th1=new Thread(run1,"th1");
                Thread th2=new Thread(run1,"th2");
                //通过线程实例控制线程的行为(运行、停止)
                th1.start();
                th2.start();
            }
        });
    }
     //实现Runnable接口并重写run方法
    class TicketRunnable implements  Runnable{
        int ticket=100;
        @Override
        public void run() {
            //卖票
            while (ticket>0){
                Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket));
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}

这里看出两个线程公用了一个Runnable实现对象实例，这样两个线程就可以操作同一个共享资源--“车票”
测试结果

08-26 10:58:10.681 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:98
08-26 10:58:10.681 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:99
08-26 10:58:11.681 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:97
08-26 10:58:11.682 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:96
08-26 10:58:12.682 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:95
08-26 10:58:12.683 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:94
08-26 10:58:13.683 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:93
08-26 10:58:13.684 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:92
08-26 10:58:14.683 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:91
08-26 10:58:14.684 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:90
08-26 10:58:15.684 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:89
08-26 10:58:15.685 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:88
08-26 10:58:16.685 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:87
08-26 10:58:16.685 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:86
08-26 10:58:17.686 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:85
08-26 10:58:17.686 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:84

需要注意的是--线程同步问题

Thread与Runnable方式的对比

 

对比图.png

两种方式推荐使用实现Runnbale接口的方法，如果只想重写run方法也推荐使用实现Runnable接口的方式。

以上就是实现Runnbale接口实现多线程的全部内容。