我自己學習Java.嘗試建立一個包含線條的架構.它看起來很基本,但我看不出這條線.代碼編譯,我似乎無法了解為什麼我看不到這條線.我在架構中看到了其他元件.
我正在使用2個java檔案.一個檔案是容器檔案,另一個檔案是繪制線代碼.它們是包a1的一部分.
這是我的代碼(請幫助)：
容器檔案：
package a1;
import javax.swing.*;
import java.awt.*;
public class gameContainer {
public static void addComponentsToPane(Container pane) {
pane.setLayout(null);
//add button to the pane
JButton b3 = new JButton("B1");
pane.add(b3);
//add line to the pane
drawingLine line1 = new drawingLine();
pane.add(line1);
//size and position all relatively
Insets insets = pane.getInsets();
Dimension size;
size = b3.getPreferredSize();
b3.setBounds(350+insets.left,15+insets.top,size.width+50,size.height+20);
size = line1.getPreferredSize();
line1.setBounds(350+insets.left,75+insets.top,size.width+50,size.height+20);
}
private static void createAndShowGUI() {
int l = 200, w = 80;
//Create and set up the window.
JFrame frame = new JFrame("Frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up content pane
addComponentsToPane(frame.getContentPane());
//add menu bar
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("Menu");
menu.add(new JMenuItem("Do nothing"));
menuBar.add(menu);
frame.setJMenuBar(menuBar);
// size and display root pane/window
Insets insets = frame.getInsets();
frame.setSize(500+insets.left+insets.right,300+insets.top+insets.bottom);
frame.setLocation(w,l);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
畫線檔案：
package a1;
import javax.swing.*;
import java.awt.geom.Line2D;
import java.awt.Graphics2D;
import java.awt.Graphics;
public class drawingLine extends JPanel{
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
Line2D line = new Line2D.Double(200, 300, 1000, 1000);
//g2d.setColor(Color.black);
g2d.draw(line);
//g.drawLine(200, 300, 1000, 1000);
//g.setColor(color.BLACK);
}
}
為什麼我看不到這條線？
解決方法:
您的主要問題是您使用null / Absolute布局.
你應該在這裡閱讀：
1)您應該使用适當的LayoutManager(或嵌套多個LayoutManagers)和/或覆寫JComponent的getPreferredSize()以傳回适合圖紙的正确尺寸.
2)在設定JFrame可見之前不要在JFrame上調用setSize而是調用pack()(以上記住)
3)不需要通過getContentPane()添加到contentPane.添加(..)作為add(..)setLayout(..)和remove(..)已被轉發到contentPane.
4)觀看類名,堅持java約定一個類名以大寫字母開頭,之後每個新單詞的第一個字母應該是capitilized,即gameContainer應該是GameContainer,drawingLine應該是DrawingLine
這是你的代碼實作了上面的修複(不是最好的布局,但它隻是一個例子)：
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
public class GameContainer {
public static void addComponentsToPane(JFrame frame) {
JPanel buttonPanel=new JPanel();//create panel to hold button
//add button to the pane
JButton b3 = new JButton("B1");
buttonPanel.add(b3);
frame.add(buttonPanel, BorderLayout.EAST);//use contentPane default BorderLayout
//add line to the pane
DrawingLine line1 = new DrawingLine();
frame.add(line1);
}
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("Frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up content pane
addComponentsToPane(frame);
//add menu bar
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("Menu");
menu.add(new JMenuItem("Do nothing"));
menuBar.add(menu);
frame.setJMenuBar(menuBar);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
class DrawingLine extends JPanel {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
Line2D line = new Line2D.Double(10, 10, 100, 100);
g2d.draw(line);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
}
标簽：paintcomponent,java,swing,css-position,jpanel
來源： https://codeday.me/bug/20190723/1510727.html