在创建线程之后将值从活动传递到线程

Question

在我的android程序中,Activity调用一个新的表面视图类,然后又调用一个新的线程类.我希望能够从activity的onPause和onResume方法将值传递给线程类,因此我可以暂停并恢复该线程.我知道传递这些数据的唯一方法是创建一个新实例,它只会创建一个不同的线程.如何在不创建新线程实例的情况下解决这个问题？

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(new GameSurface(this));
}

@Override
protected void onResume() {
    super.onResume();
            //Would like to pass this value
            int state = 1;
}

@Override
protected void onPause() {
    super.onPause();
            //Would like to pass this value
            int state = 2;
}

Answer 1

关于并发的一点背景

传递并发值是很容易的部分.查看AtomicInteger数据类型(此处有更多信息).原子性也意味着All or nothing.此数据类型不一定在线程或处理器之间发送数据(就像您一样mpi),但它只是在共享内存上共享数据.

但什么是原子行动？....

原子操作是作为单个工作单元执行的操作,而不会受到来自其他操作的干扰.

在Java中,语言规范保证读取或写入变量是原子的(除非变量的类型为long或double).如果它们被声明为volatile,则long和double只是原子的....

Credit(Java Concurrency/Multithreading - Lars Vogel 教程)

我强烈建议你阅读这一点,它涵盖了从atomicity,thread pools,deadlocks和the "volatile" and "synchronized" keyword.

Start Class 这将执行一个新线程(它也可以称为我们的Main Thread).

import java.util.concurrent.atomic.AtomicInteger;
/**
 * @author Michael Jones
 * @description Main Thread
 */
public class start {
    private AtomicInteger state;
    private Thread p;
    private Thread r;
    /**
     * constructor
     * initialize the declared threads
     */
    public start(){
        //initialize the state
        this.state = new AtomicInteger(0);
        //initialize the threads r and p
        this.r = new Thread(new action("resume", state));
        this.p = new Thread(new action("pause", state));
    } //close constructor

    /**
     * Start the threads
     * @throws InterruptedException 
     */
    public void startThreads() throws InterruptedException{
        if(!this.r.isAlive()){
            r.start(); //start r
        }
        if(!this.p.isAlive()){
            Thread.sleep(1000); //wait a little (wait for r to update)...
            p.start(); //start p
        }
    } //close startThreads

    /**
     * This method starts the main thread
     * @param args
     */
    public static void main(String[] args) {
         //call the constructor of this class
        start s = new start();
        //try the code
        try {
            s.startThreads();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } //start the threads
    } //close main

} //close class start

由于整数是原子,你还可以检索它的任何地方,但main method在开始授课用System.out.println("[run start] current state is... "+state.intValue());.(如果你想从中检索它main method,你将不得不设置一个Setter/Getter,就像我在Action类中那样)

Action Class 这是我们的操作线程(它也可以称为我们的Slave Thread).

import java.lang.Thread.State;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @author Michael Jones
 * @description Slave Thread
 */
public class action implements Runnable {

    private String event = "";
    private AtomicInteger state;

    /**
     * The constructor (this represents the current instance of a thread).
     * 
     * @param event
     * @param state
     */
    public action(String event, AtomicInteger state) {
        this.event = event; // update this instance of event
        this.state = state; // update this instance of state
    } // constructor

    /**
     * This method will be called after YourThreadName.Start();
     */
    @Override
    public void run() {
        if (this.event == "resume") {
            this.OnResume(); // call resume
        } else {
            this.OnPause(); // call pause
        }
    } // close Runnable run() method

    /**
     * The resume function Use the auto lock from synchronized
     */
    public synchronized void OnResume() {
        System.out.println("[OnResume] The state was.." + this.getAtomicState()
                + " // Thread: " + Thread.currentThread().getId());
        this.setAtomicState(2); // change the state
        System.out.println("[OnResume] The state is.." + this.getAtomicState()
                + " // Thread: " + Thread.currentThread().getId());
    } // close function

    /**
     * The pause function Use the auto lock from synchronized
     */
    public synchronized void OnPause() {
        System.out.println("[OnPause] The state was.." + this.getAtomicState()
                + " // Thread: " + Thread.currentThread().getId());
        this.setAtomicState(1); // change the state
        System.out.println("[OnPause] The state is.." + this.getAtomicState()
                + " // Thread: " + Thread.currentThread().getId());
    } // close function

    /**
     * Get the atomic integer from memory
     * 
     * @return Integer
     */
    private Integer getAtomicState() {
        return state.intValue();
    }// close function

    /**
     * Update or Create a new atomic integer
     * 
     * @param value
     */
    private void setAtomicState(Integer value) {
        if (this.state == null) {
            state = new AtomicInteger(value);
        } else
            state.set(value);
    } // close function

} // close the class

控制台输出

[OnResume] The state was..0 // Thread: 9
[OnResume] The state is..2 // Thread: 9
[OnPause] The state was..2 // Thread: 10
[OnPause] The state is..1 // Thread: 10

正如您所看到的,AtomicInteger state我们在线程r和内存之间共享p.

解决方案和需要寻找的东西......

进行并发时唯一需要注意的是Race Conditions/ Deadlocks/ Livelocks.有些RaceConditions是因为Threads以随机顺序创建的(并且大多数程序员都在顺序排列的思维集中思考).

我也行Thread.sleep(1000);,这样我Main Thread给从线程r一点时间来更新state(允许之前p运行),由于线程的随机顺序.

1)保持对线程的引用并使用方法传递值. 信用(SJuan76,2012)

在我发布的解决方案中,我将我的Main Thread(又名class start)作为我的主要沟通者来跟踪Atomic Integer我的奴隶使用(又名class action).我的主线程也updating该memory buffer为Atomic Integer我的奴隶(的内存缓冲区更新发生在应用程序的背景,并通过处理AtomicInteger类).