如何從 MainActivity 獲取價值？

Question

所以我有這個主要活動：

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;
   }
}

有人告訴我，我可以通過獲取MainActivity的實例並直接訪問該函數來從MyTask訪問getStopTask() 。

我試過了，但出現錯誤： “無法在尚未調用 Looper.prepare() 的線程 Thread[Thread-6,5,main] 內創建處理程序” 。

這是我的任務：

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();
        }    
      }
    }
}

應用程序命中后立即發生錯誤：

MainActivity mainActivity = new MainActivity();

如何從 MyTask 獲取stopTask的值？

Answer 1

我會將 boolean stopTask為 static 並以這種方式使用它而不是getStopTask() ：

主活動.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;
   }
}

我的任務.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();
        }    
      }
    }
}