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。