CODEWITHSUNDEEP
javamultithreadingcallback
Sunny
Sunny

Reputation: 7604

Callback from new thread to class from which thread was initiated

I have a class from which I am calling a new thread. 

public class MainClass{

 private void cleardata() {
                // do something on a separate thread
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        //Do Something
        //After this I would like to notify my MainClass that some thing has been done and pass a value. 
        }
      }
     }
   private void callbackFunc(int a){

    // Do something based on value of a 
  }
}

I have a function in my MainClass. But how do i call this function from my new thread, so as to receive a callback. Thanks.

Upvotes: 2

Views: 159

Answers (4)

Ian Roberts
Ian Roberts

Reputation: 122364

You should just be able to call the method in MainClass by its name just as if you were calling from directly inside MainClass itself (as opposed to from the inner class).

If a method name you want to call happens to conflict with one that your inner class has inherited from Object then you can prefix the call with MainClass.this, e.g. MainClass.this.toString() calls toString on MainClass, whereas just toString() calls it on the inner class instance.

Upvotes: 1

kan
kan

Reputation: 28951

Just do it:

public class MainClass{

  private void cleardata() {
            // do something on a separate thread
            new Thread(new Runnable() {
                @Override
                public void run() {
                    //Do Something
                    notifyTheClass("a parameter");
     }
  }

  private void notifyTheClass(String aParam) {
  //..do something else
  }  
 }
}

But it is not related to threads, this is about inner classes. If you want the main thread to wait until the new thread is finishes, use Futures for a result. Or use some other multithreading primitives.

Upvotes: 0

shazin
shazin

Reputation: 21883

public class MainClass{

private void cleardata() {
        // do something on a separate thread
        new Thread(new Runnable() {
            @Override
            public void run() {
                callBackFunc(result); 
            }
        }
}

private void callBackFunc(int a) {

}
}

Upvotes: 0

Sudhanshu Umalkar
Sudhanshu Umalkar

Reputation: 4202

In such a case pass the instance of MainClass to the thread class ((during creation)) so that it can call method on it. Having inner class as suggested by others is also a good option.

Something similar-

class MainClass {

private void cleardata() {
    new Thread(new MyThread(this)).start();
}

}

class MyThread implements Runnable {

private MainClass mc;

MyThread(MainClass mc) {
    this.mc = mc;
}

public void run() {
    // do something
    // mc.someMethod();
}

}

Upvotes: 0

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