如何在java swing中设置特定的窗口(框架)大小？

Question

我的代码不起作用:

JFrame frame = new JFrame("mull");

mull panel = new mull();

// add panel to the center of window
frame.getContentPane().add("Center", panel);
frame.setSize(500, 300); // << not working!!!
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack(); // give a suitable size to window automatically
frame.setVisible(true); // make window visible

我的窗户越来越小了.怎么解决？

Answer 1

好吧,你正在使用frame.setSize()和frame.pack().

你应该一次使用其中一个.

使用setSize()您可以给出您想要的框架大小,但如果您使用pack(),它将根据其中组件的大小自动更改框架的大小.它不会考虑您之前提到的尺寸.

尝试frame.pack()从代码中删除或在设置大小之前放置它然后运行它.

Answer 2

大多数布局管理器最适合使用组件的preferredSize,并且大多数GUI最好允许它们包含的组件根据其内容或属性设置自己的preferredSize.要最大限度地利用这些布局管理器,pack()请先调用顶级容器(如JFrame),然后再将其显示,因为这会告诉这些管理员执行操作 - 布局其组件.

通常当我需要在设置我的一个组件的大小时扮演更直接的角色时,我将覆盖getPreferredSize并让它返回一个大于super.preferredSize的Dimension(如果不是,则返回super的值).

例如,这是我为此站点上的另一个问题创建的一个小型拖动矩形应用程序:

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

public class MoveRect extends JPanel {
   private static final int RECT_W = 90;
   private static final int RECT_H = 70;
   private static final int PREF_W = 600;
   private static final int PREF_H = 300;
   private static final Color DRAW_RECT_COLOR = Color.black;
   private static final Color DRAG_RECT_COLOR = new Color(180, 200, 255);
   private Rectangle rect = new Rectangle(25, 25, RECT_W, RECT_H);
   private boolean dragging = false;
   private int deltaX = 0;
   private int deltaY = 0;

   public MoveRect() {
      MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
      addMouseListener(myMouseAdapter);
      addMouseMotionListener(myMouseAdapter);
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      if (rect != null) {
         Color c = dragging ? DRAG_RECT_COLOR : DRAW_RECT_COLOR;
         g.setColor(c);
         Graphics2D g2 = (Graphics2D) g;
         g2.draw(rect);
      }
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   private class MyMouseAdapter extends MouseAdapter {

      @Override
      public void mousePressed(MouseEvent e) {
         Point mousePoint = e.getPoint();
         if (rect.contains(mousePoint)) {
            dragging = true;
            deltaX = rect.x - mousePoint.x;
            deltaY = rect.y - mousePoint.y;
         }
      }

      @Override
      public void mouseReleased(MouseEvent e) {
         dragging = false;
         repaint();
      }

      @Override
      public void mouseDragged(MouseEvent e) {
         Point p2 = e.getPoint();
         if (dragging) {
            int x = p2.x + deltaX;
            int y = p2.y + deltaY;
            rect = new Rectangle(x, y, RECT_W, RECT_H);
            MoveRect.this.repaint();
         }
      }
   }

   private static void createAndShowGui() {
      MoveRect mainPanel = new MoveRect();

      JFrame frame = new JFrame("MoveRect");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

请注意,我的主类是JPanel,我覆盖了JPanel的getPreferredSize:

public class MoveRect extends JPanel {
   //.... deleted constants

   private static final int PREF_W = 600;
   private static final int PREF_H = 300;

   //.... deleted fields and constants

   //... deleted methods and constructors

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

另请注意,当我显示GUI时,我将其放入JFrame,调用pack(); JFrame,设置其位置,然后调用setVisible(true);我的JFrame:

   private static void createAndShowGui() {
      MoveRect mainPanel = new MoveRect();

      JFrame frame = new JFrame("MoveRect");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}