java - 如何在Activity和其他Activity创建的线程之间进行通信

Question

当您有 2 个 Activity ( A 和 B )并且 A 是 MainActivity 时，现在您启动您的应用程序，A 启动 B。B 是一个带有与用户交互的对话框的 Activity ，创建蓝牙连接和 2 个线程，1 个接收线程和 1 个发送线程。现在，将信息从 A 发送到 B 的线程以及反之亦然的最佳方式是什么？

首先我使用了静态WeakReference，但我听说这会导致很多问题，所以我想寻求一个更通用的解决方案。

请记住，当从另一个 Activity 启动一个 Activity 时，只能传递可序列化的 Objs 和简单数据。因此不可能以这种方式使用处理程序。

这是我使用的静态 WeakReference:

public class T1 extends Thread{
private static WeakReference<T1> weak_T1;


public void T1 (){
weak_T1 = new WeakReference<T1> (This);
}

public static WeakReference getWeakReverence() {
    return weak_T1;
}

}

以下是在堆栈中查找正在运行的线程的方法:

for (Thread thread : Thread.getAllStackTraces().keySet()) { 
    if (thread.getName().equalsIgnoreCase("T1")){ 
    T1A =thread; 
     }else if (thread.getName().equalsIgnoreCase("T2")){ 
     T2A =thread; 
     } 
}

还有可能的解决方案:

public class example extends Thread {
    private static example instance;

  private example() {
  }

  public static example getIsntance(){
    if(instance == null){
      instance = new example();
    }

    return instance;
  }
}

Answer 1

WeakReference 可能不是您想要的。也就是说，假设您的 Thread 对象要么不会终止，要么在 Activity B 停止后以某种方式维护一些对 Activity A 有用的信息。如果您使用WeakReference，一旦 Activity B 结束并且线程终止，它可能会变为“null”。只需使用常规的旧强引用即可。它将确保 T1 及其包含的信息继续存在，直到您用完为止。

public class ActivityB extends Activity
{
    private T1 t1;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        t1 = startMyThread();
    }

    @Override
    public void onBackPressed()
    {
        ActivityA.tempT1 = t1;

        //This technique presumes that Activity A is guaranteed to resume after a 
        //back button press, based on the arrangement of your backstack, etc. If
        //Activity A is started via some other means (e.g., an explicit startActivity(),
        //finish(), etc.), then this reference will have to be set prior to
        //that call, as well, in order to establish the appropriate "happens before" relationship.
        //If you fail to ensure that Activity A resumes after this point, you will
        //risk a memory leak.

        super.onBackPressed();
    }
}

public class ActivityA extends Activity
{
    public static T1 tempT1 = null;
    private T1 t1;

    @Override
    public void onResume()
    {
        super.onResume();
        if(tempT1 == null)
        {
            //Apparently, Activity B hasn't executed yet. Provide the user with a button to start it.
        }
        else
        {
            t1 = tempT1;
            tempT1 = null;     //To avoid a memory leak

            //We just retrieved the reference that Activity B left for us.
            //Now, change UI states so that the user can see information about t1.
        }
    }
}