透過點擊按鈕在JPanel 中繪製線條
問題:
問題:有人想要畫畫點擊按鈕時JPanel 中的線條但由於誤解而面臨困難繪製過程。
解:釋放滑鼠標記第二個端點。
實現:
以下代碼演示了實現:
導入java.awt.BasicStroke;
導入java.awt.Color;
導入java.awt.Dimension;
導入java.awt.Graphics;
導入java.awt.Graphics2D;
導入java.awt.Point;
導入java.awt.RenderingHints;
導入java.awt.event.ActionEvent;
導入java.awt.event.KeyEvent;
導入java.awt.event.MouseAdapter;
導入java.awt.event.MouseEvent;
導入javax. swing.AbstractAction;
導入javax.swing.JFrame;
導入javax.swing.JPanel;private MouseHandler mouseHandler = new MouseHandler(); private Point p1 = new Point(100, 100); private Point p2 = new Point(540, 380); private boolean drawing; public LinePanel() { this.setPreferredSize(new Dimension(640, 480)); this.addMouseListener(mouseHandler); this.addMouseMotionListener(mouseHandler); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.setColor(Color.blue); g2d.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); g2d.setStroke(new BasicStroke(8, BasicStroke.CAP_ROUND, BasicStroke.JOIN_BEVEL)); g.drawLine(p1.x, p1.y, p2.x, p2.y); } private class MouseHandler extends MouseAdapter { @Override public void mousePressed(MouseEvent e) { drawing = true; p1 = e.getPoint(); p2 = p1; repaint(); } @Override public void mouseReleased(MouseEvent e) { drawing = false; p2 = e.getPoint(); repaint(); } @Override public void mouseDragged(MouseEvent e) { if (drawing) { p2 = e.getPoint(); repaint(); } } } private class ControlPanel extends JPanel { private static final int DELTA = 10; public ControlPanel() { this.add(new MoveButton("\u2190", KeyEvent.VK_LEFT, -DELTA, 0)); this.add(new MoveButton("\u2191", KeyEvent.VK_UP, 0, -DELTA)); this.add(new MoveButton("\u2192", KeyEvent.VK_RIGHT, DELTA, 0)); this.add(new MoveButton("\u2193", KeyEvent.VK_DOWN, 0, DELTA)); } private class MoveButton extends JButton { KeyStroke k; int dx, dy; public MoveButton(String name, int code, final int dx, final int dy) { super(name); this.k = KeyStroke.getKeyStroke(code, 0); this.dx = dx; this.dy = dy; this.setAction(new AbstractAction(this.getText()) { @Override public void actionPerformed(ActionEvent e) { LinePanel.this.p1.translate(dx, dy); LinePanel.this.p2.translate(dx, dy); LinePanel.this.repaint(); } }); ControlPanel.this.getInputMap(WHEN_IN_FOCUSED_WINDOW) .put(k, k.toString()); ControlPanel.this.getActionMap() .put(k.toString(), new AbstractAction() { @Override public void actionPerformed(ActionEvent e) { MoveButton.this.doClick(); } }); } } } private void display() { JFrame f = new JFrame("LinePanel"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.add(this); f.add(new ControlPanel(), BorderLayout.SOUTH); f.pack(); f.setLocationRelativeTo(null); f.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { new LinePanel().display(); } }); }
公共類LinePanel 擴展JPanel {
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