使用方法更改jlabel

Question

我正在写一个转换文件的小程序，我想有一个框弹出，要求用户在程序循环和转换所有相关文件时请等待，但我遇到了一个小问题。弹出的框应该有一个JLabel和一个JButton，当用户“等待”时，我想要显示一条消息，说请等待，并禁用“确定”JButton，然后当它完成时，我想设置JLabel的文本，让他们知道它成功地转换了他们的文件，并给他们一个有多少文件被转换的计数。(我编写了一个名为alert的方法，用于设置标签的文本并启用按钮。)问题是，当程序运行时，框是空的，标签和按钮不可见，当它完成时，标签与我想要的最终文本一起出现，按钮显示为启用。我不确定到底发生了什么，我尝试了几次更改JLabel和JButton的修饰符，但似乎无法使其正常工作。这是弹出框的代码，任何帮助都是非常有用的。

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;


public class PleaseWait extends javax.swing.JFrame{

    private static final int height = 125;
    private static final int width = 350;
    final static JLabel converting = new JLabel("Please Wait while I convert your files");
    private static JButton OK = new JButton("OK");



    public PleaseWait(){
        // creates the main window //
        JFrame mainWindow = new JFrame();
        mainWindow.setTitle("Chill For A Sec");
        mainWindow.setSize(width, height);
        mainWindow.setDefaultCloseOperation(DISPOSE_ON_CLOSE);

        // creates the layouts//
        JPanel mainLayout = new JPanel(new BorderLayout());
        JPanel textLayout = new JPanel(new FlowLayout());
        JPanel buttonLayout = new JPanel(new FlowLayout());

        // Sets Text //
        converting.setText("Please wait while I convert your files");

        // disables button //
        OK.setEnabled(false);

        // adds to the layouts //
        textLayout.add(converting);
        buttonLayout.add(OK);
        mainLayout.add(textLayout, BorderLayout.CENTER);
        mainLayout.add(buttonLayout, BorderLayout.SOUTH);

        // adds to the frame //
        mainWindow.add(mainLayout);

        // sets everything visible //
        mainWindow.setVisible(true);

    }

    public static void alert(){
        OK.setEnabled(true);
        String total = String.valueOf(Convert.result());
        converting.setText("Sucsess! " + total + " files Converted");
    }

}

Answer 1

好了，问题是这样的。您正在扩展JFrame。这意味着你的类是一个JFrame。

当您创建PleaseWait框架时，您不会对它做任何操作。这就是您看到的空盒子。相反，您将在构造函数中创建一个不同的JFrame。删除你的mainWindow，改用this。现在，所有组件都将添加到PleaseWait对象中。这应该可以解决您的空白框问题。

Answer 2

你首先需要一个应用程序来创建你的框架。这是这类应用程序的一个简单示例。

import javax.swing.UIManager;
import java.awt.*;

public class Application {
  boolean packFrame = false;

  //Construct the application
  public Application() {
    PleaseWait frame = new PleaseWait();
    //Validate frames that have preset sizes
    //Pack frames that have useful preferred size info, e.g. from their layout
    if (packFrame) {
      frame.pack();
    }
    else {
      frame.validate();
    }
    //Center the window
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension frameSize = frame.getSize();
    if (frameSize.height > screenSize.height) {
      frameSize.height = screenSize.height;
    }
    if (frameSize.width > screenSize.width) {
      frameSize.width = screenSize.width;
    }
    frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
    frame.setVisible(true);

    frame.convert();

  }

  //Main method
  public static void main(String[] args) {
    try {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
    }
    catch(Exception e) {
      e.printStackTrace();
    }
    new Application();
  }
}

您必须稍微修改框架才能将控件添加到内容窗格中。你可以在创建frame之后做一些工作，然后调用alert。

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class PleaseWait extends JFrame {

  private static final int height = 125;
  private static final int width = 350;
  final static JLabel converting = new JLabel();
  private static JButton OK = new JButton("OK");
  BorderLayout borderLayout1 = new BorderLayout();
  JPanel contentPane;
  int count;

  public PleaseWait(){
    contentPane = (JPanel)this.getContentPane();
    contentPane.setLayout(borderLayout1);
    this.setSize(new Dimension(width, height));
    this.setTitle("Chill For A Sec");
    this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);

    // creates the layouts//
    JPanel mainLayout = new JPanel(new BorderLayout());
    JPanel textLayout = new JPanel(new FlowLayout());
    JPanel buttonLayout = new JPanel(new FlowLayout());

    // Sets Text //
    converting.setText("Please wait while I convert your files");

    // disables button //
    OK.setEnabled(false);
    OK.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent e) {
        System.exit(0);
      }
    });

    // adds to the layouts //
    textLayout.add(converting);
    buttonLayout.add(OK);
    mainLayout.add(textLayout, BorderLayout.CENTER);
    mainLayout.add(buttonLayout, BorderLayout.SOUTH);

    // adds to the frame //
    contentPane.add(mainLayout);
  }

  public void convert(){
    count = 0;
    for (int i = 0; i <10; i++){
      System.out.println("Copy "+i);
      try {
        Thread.sleep(1000);
      } catch (InterruptedException e) {
      }
      count++;
    }
    alert();

  }
  public void alert(){
    OK.setEnabled(true);
//        String total = String.valueOf(Convert.result());
    converting.setText("Sucsess! " + count + " files Converted");
  }

}