Runnable的作用及使用方式

前言

Java中實現多線程主要由以下兩種方式:繼承Thread類和實現Runnable接口，本文主要說明Runnable接口實現多線程。

Runnable接口簡介

(1)定義
Runnable接口是線程輔助類，僅定義了一個方法run()方法
(2)作用
實現多線程
(3)優點
靈活：Runnable可以繼承其他類實現對Runnable實現類的增強，避免了Thread類由於繼承Thread類而無法繼承其他類的問題
共享資源:Runnable接口的run()方法可以被多個線程共享，適用於多個進程處理一種資源的問題

使用方法

(1) 實現Runnable接口
(2) 重寫run()方法
(3) 創建runnable實例
(4) 創建Thread實例
(5) 將Runnable實例放入Thread實例中
(6) 通過線程實例控制線程的行為(運行，停止)，在運行時會調用Runnable接口中的run方法。

注意:Java中真正能創建新線程的只有Thread類對象
通過實現Runnable的方式，最終還是通過Thread類對象來創建線程

Runnable方式也分為標准方式和匿名方式
(1)標准方式

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.創建MyRunnable實例 MyRunnable runnable=new MyRunnable(); //3.創建Thread對象 //4.將MyRunnable放入Thread實例中 Thread thread=new Thread(runnable); //5.通過線程對象操作線程(運行、停止) thread.start(); } //1.實現runnable接口並重寫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.匿名實現Runnable接口並重寫run方法 Runnable runnable = new Runnable() { @Override public void run() { } }; //2.創建線程對象 //3.將runnable實例放入線程對象中 Thread thread=new Thread(runnable); //4.由線程實例控制線程的行為(運行，停止) thread.start(); } } 

實際用例

現在假設有兩個窗口賣車票，每一秒賣出一張車票，每個窗口有100張票
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) { //創建runnnable實例 TicketRunnable run1=new TicketRunnable(); TicketRunnable run2=new TicketRunnable(); //創建Thread實例並將runnable實例放入 Thread th1=new Thread(run1,"th1"); Thread th2=new Thread(run2,"th2"); //通過線程實例控制線程的行為(運行、停止) th1.start(); th2.start(); } }); } //實現Runnable接口並重寫run方法 class TicketRunnable implements Runnable{ int ticket=100; @Override public void run() { //賣票 while (ticket>0){ Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket)); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } } } 

測試結果:

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 

那么如何讓兩個窗口共享“車票”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) { //創建runnnable實例 TicketRunnable run1=new TicketRunnable(); //創建Thread實例並將runnable實例放入 Thread th1=new Thread(run1,"th1"); Thread th2=new Thread(run1,"th2"); //通過線程實例控制線程的行為(運行、停止) th1.start(); th2.start(); } }); } //實現Runnable接口並重寫run方法 class TicketRunnable implements Runnable{ int ticket=100; @Override public void run() { //賣票 while (ticket>0){ Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket)); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } } } 

這里看出兩個線程公用了一個Runnable實現對象實例，這樣兩個線程就可以操作同一個共享資源--“車票”
測試結果

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--線程同步問題

Thread與Runnable方式的對比

 

對比圖.png

兩種方式推薦使用實現Runnbale接口的方法，如果只想重寫run方法也推薦使用實現Runnable接口的方式。

以上就是實現Runnbale接口實現多線程的全部內容。