Question

我有2个课程，Main和DialogOrder

主要

public class Main extends Fragment{
ImageView order;


@Override
public View onCreateView(LayoutInflater inflater, final ViewGroup container, Bundle savedInstanceState) {

     order.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

               new DialogOrder(getActivity()).show();
            }
        });

  return view;
  }
  public void init(Bundle savedInstanceState) {   
   order = (ImageView) view.findViewById(R.id.order);
   order.setImageResource(R.drawable.orderd);
   RelativeLayout.LayoutParams orderparams = new RelativeLayout.LayoutParams(Main.screenHeight / 8, Main.screenHeight / 8);
   orderparams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
   orderparams.addRule(RelativeLayout.CENTER_HORIZONTAL);
    orderparams.setMargins(Main.screenHeight / 80, Main.screenHeight / 80, Main.screenHeight / 80, Main.screenHeight / 30);

    order.setLayoutParams(orderparams);


 }

  public void update_UI(){

    order.setVisibility(View.INVISIBLE);

}

}

DialogOrder

public class DialogOrder extends Dialog {
Button button;
Main main;
Activity context;


public DialogOrder(Activity context) {
    super(context);

    this.context = context;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
 setContentView(R.layout.order_dialog);
 main = new Main();
 button = (Button)findviewbyid(R.id.bd);

 button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

           main.update_UI();
           dismiss();
        }
    });
}}

我想要的是当用户按下对话框上的按钮时将订单图像设置为INVISIBLE 现在代码给了我显示java.lang.NullPointerException

可能我尝试更新UI错误那么有人可以告诉我从子类更新父UI类的正确方法是什么？

Answer 1

您可以通过将主片段传递给Dialog构造函数来更新它，也可以使用Listener/Callback在主片段和对话框之间进行通信。

最佳做法是使用侦听器/回调，因为对话不应可以访问调用者。这也是与主片段分离的对话框。

首先，通过对话框中的界面创建侦听器：

public class DialogOrder extends Dialog {
  ...
  Activity context;
  private DialogListener listener;

  public interface DialogListener {
    void onButtonClicked();
  }

  public DialogOrder(Activity context, DialogListener listener) {
    super(context);
    this.context = context;
    this.listener = listener;
  }

  ...

}

然后，当按钮单击调用侦听器时：

public class DialogOrder extends Dialog {

  Activity context;
  private DialogListener listener;

  public interface DialogListener {
    void onButtonClicked();
  }

  public DialogOrder(Activity context, DialogListener listener) {
    super(context);
    this.context = context;
    this.listener = listener;
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    ...

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
           listener.onButtonClicked();
           dismiss();
        }
    });
  }
}

现在，您可以使用侦听器创建对话框。像这样：

DialogOrder.DialogListener listener = new DialogOrder.DialogListener() {
   @Ovveride
   public void onButtonClicked() {
     update_UI();
   }
};

DialogOrder dialogOrder = new DialogOrder(getActivity(), listener);
dialogOder.show();

主要片段将在对话框中点击按钮。

从自定义Dialog类更改主UI

1 个答案: