Question

编辑：我发现我在下面描述的内容只出现在我的模拟设备上（Nexus 5，目标api 19,4.4.2带有Intel Atom（x86）cpu），但不在我的物理设备上（HTC）一）....

EDIT2：Edit1是由于我没有抓到的IllegalStateException。在尝试启动之前添加了一些代码来检查线程是否已经运行。结合已接受的答案解决了我的问题。

我已经实现了一个在activity的onCreate方法中启动一个新线程的激活，如下所示：

...

private boolean running;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    running = true;
    new Thread(null, work, "myThread").start();
}

Runnable work = new Runnable() {

    @Override
    public void run() { 
        while (running) {
            //Doing work
        }
    }
};

我正在用我的活动的onPause方法“暂停”我的帖子，如下所示：

@Override
protected void onPause() {
    running = false;
    super.onPause();
}

所以我认为恢复它会同样容易......¨

@Override
protected void onResume(){
    running = true;
    super.onResume();
}

但我的线程没有恢复。有什么想法吗？感谢任何帮助。

马库斯

Answer 1

我认为所有答案都有关于运行变量的一些问题，因为无法在没有Threads <的情况下从两个不同的synchronized block写入和读取变量/ strong>所以我发表自己的答案：

package com.example.threadandtoast; import android.os.Bundle; import android.support.v7.app.ActionBarActivity; import android.widget.Toast; public class MainActivity extends ActionBarActivity { public class MonitorObject{ public boolean running = true; public String message = ""; public boolean mustBePost = true; } Thread t; int threadNameCounter = 0; // i use this variable to make sure that old thread is deleted // when i pause, you can see it and track it in DDMS Runnable work = new Runnable() { boolean myRunning; @Override public void run() { synchronized(mSync) { myRunning = mSync.running; } while (myRunning) { runOnUiThread(new Runnable() { // in order to update the UI (create Toast) @Override // we must switch to main thread public void run() { // i want to read the message so i must use synchronized block synchronized(mSync) { // i use this variable to post a message just for one time because i am in an infinite loop // if i do not set a limit on the toast i create it infinite times if(mSync.mustBePost){ Toast.makeText(MainActivity.this, mSync.message, Toast.LENGTH_SHORT).show(); // the message post so i must set it to false mSync.mustBePost = false; // if i am going to pause set mSync.running to false so at the end of infinite loop //of thread he reads it and leaves the loop if(mSync.message.equals("Main Activity is going to pause")){ mSync.running=false; } } } } }); synchronized(mSync) { myRunning = mSync.running; } } } }; final MonitorObject mSync = new MonitorObject(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override protected void onPause() { super.onPause(); synchronized(mSync) { // mSync.running = false; you can not set it here because // it is possible for the thread to read it and exit the loop before he posts your message mSync.mustBePost=true; mSync.message = "Main Activity is going to pause"; } } @Override protected void onResume(){ super.onResume(); threadNameCounter++; synchronized(mSync) { mSync.running = true; mSync.mustBePost=true; mSync.message = "Main Activity is going to resume"; } t = new Thread(work,"My Name is " + String.valueOf(threadNameCounter)); t.start(); } }

或者您可以使用此代码：

public class MainActivity extends ActionBarActivity { Thread t; int threadNameCounter = 0; // i use this variable to make sure that old thread is deleted // when i pause, you can see it in DDMS String message = ""; boolean isPost = false; Runnable work = new Runnable() { @Override public void run() { while (true) { runOnUiThread(new Runnable() { @Override public void run() { if(!isPost){ Toast.makeText(MainActivity.this, message, Toast.LENGTH_SHORT).show(); isPost = true; if( message.equals("Main Activity is going to pause")){ t.interrupt(); } } } }); if(Thread.currentThread().isInterrupted()){ break; } } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override protected void onPause() { super.onPause(); message = "Main Activity is going to pause"; isPost = false; } @Override protected void onResume(){ super.onResume(); message = "Main Activity is going to resume"; isPost = false; threadNameCounter++; t = new Thread(work,"My Name is " + String.valueOf(threadNameCounter)); t.start(); } }

您也可以使用信号量或等待通知方法。

我将public String message = "";和public boolean mustBePost = true;放入mSync对象，但确实如此没有必要，因为只有main thread才能访问它们。

如果您有任何问题，请询问。

Answer 2

语句running = false;将停止执行Thread，而不是暂停它。使用两个变量：一个用于停止当前Thread，另一个用于暂停和恢复Thread，如下所示：

boolean isThreadPause=false;
Runnable work = new Runnable() {    
    @Override
    public void run() { 
        while (running) {
            if (!isThreadPause) {
               // Doing work
            }
        }
    }
};

在活动的onPause事件中，将isThreadPause设置为true，并在onResume事件中将isThreadPause设置为false

Answer 3

这是因为Runnable循环在while循环停止时停止。你可以试试这个：

Runnable work = new Runnable() {

    @Override
    public void run() { 
        while () {
          if(running){
            //Doing work
          }
        }
    }
};

Android：暂停并恢复活动中的某个主题

3 个答案: