如何从 MainActivity 获取价值？

Question

So I have this main activity:

import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
private volatile boolean stopTask = false;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.layout);
   }
   
   public boolean getStopTask() {
      return stopTask;
   }
   
   public void startMyTask(View view) {
      stopTask = false;
      TextView textView = findViewById(R.id.text_view);
      MyTask myTask = new MyTask(10, textView);

      new Thread(myTask).start();
   }
   
   public void stopMyTask(View view) {
      stopTask = true;
   }
}

I was told that I could access getStopTask() from MyTask by getting an instance of MainActivity and accessing that function directly.

I tried that, but I get an error: "Can't create handler inside thread Thread[Thread-6,5,main] that has not called Looper.prepare()" .

Here's MyTask:

import android.widget.TextView;

public class MyTask implements Runnable {
    int seconds;
    TextView textView;

    MyTask(int seconds, TextView textView) {
        this.seconds = seconds;
        this.textView = textView;
    }

    @Override
    public void run() {

    MainActivity mainActivity = new MainActivity();

    for (int x = 0; x < seconds; x++) {
        boolean stopTask = mainActivity.getStopTask();

        if (stopTask)
           break;

        textView.setText(String.format("x: %s", x));

        try {
           Thread.sleep(1000);
        } catch (InterruptedException e) {
           e.printStackTrace();
        }    
      }
    }
}

The error happens right after the app hits:

MainActivity mainActivity = new MainActivity();

How can I get the value of stopTask from MyTask?

Answer 1

I would turn boolean stopTask to static and use it instead of getStopTask() this way:

MainActivity.java:

public class MainActivity extends AppCompatActivity {
public static boolean stopTask = false;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.layout);
   }
   
   /*
   
   public boolean getStopTask() {
      return stopTask;
   }*/
   
   public void startMyTask(View view) {
      stopTask = false;
      TextView textView = findViewById(R.id.text_view);
      MyTask myTask = new MyTask(10, textView);

      new Thread(myTask).start();
   }
   
   public void stopMyTask(View view) {
      stopTask = true;
   }
}

MyTask.java:

public class MyTask implements Runnable {
    int seconds;
    TextView textView;

    MyTask(int seconds, TextView textView) {
        this.seconds = seconds;
        this.textView = textView;
    }

    @Override
    public void run() {

    //MainActivity mainActivity = new MainActivity();

    for (int x = 0; x < seconds; x++) {
        boolean stopTask = MainActivity.stopTask;

        if (stopTask)
           break;

        textView.setText(String.format("x: %s", x));

        try {
           Thread.sleep(1000);
        } catch (InterruptedException e) {
           e.printStackTrace();
        }    
      }
    }
}