如何从另一个类更新活动的TextView [英] How to update a TextView of an Activity from another class

问题描述

我是Android/Java编程的新手.我有两个类，一个是Activity，另一个是普通的类.我的活动课包含一个TextView.我可以从普通班级更新活动班级的TextView吗?我尝试使用随机代码，但失败了.

I am new to Android/Java programming. I have two classes, one is an Activity and the other is a normal class. My activity class contains a TextView. Can I update the TextView of the activity class from a normal class? I tried with random code, but it fails.

// activity class
public class MainMenu extends Activity {
    public TextView txtView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView txtView = (TextView)findViewById(R.id.text);   
    }
}

// Other class
public class ClassB {
    public ClassB() {
        public void Update() {
            TextView txtView = (TextView)findViewById(R.id.text);
            txtView.setText("Hello");
        }
    }
}

推荐答案

您必须通过构造函数传递Context引用.

You have to pass the Context reference via constructor.

public class ClassB {
   Context context;
   public ClassB(Context context){
     this.context=context;
   }

   public void Update(){
        TextView txtView = (TextView) ((Activity)context).findViewById(R.id.text);
        txtView.setText("Hello");
   }

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