JTextFieldの角を丸める

概要

JTextFieldの角を丸めて表示するようBorderを設定しています。

Screenshot

Download

• Runnable JAR example.jar
• Source code src.zip
• Repository GitHub

サンプルコード

JTextField textField01 = new JTextField(20) {
  @Override protected void paintComponent(Graphics g) {
    if (!isOpaque()) {
      int w = getWidth() - 1;
      int h = getHeight() - 1;
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                          RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setPaint(UIManager.getColor("TextField.background"));
      g2.fillRoundRect(0, 0, w, h, h, h);
      g2.setPaint(Color.GRAY);
      g2.drawRoundRect(0, 0, w, h, h, h);
      g2.dispose();
    }
    super.paintComponent(g);
  }

  @Override public void updateUI() {
    super.updateUI();
    setOpaque(false);
    setBorder(BorderFactory.createEmptyBorder(4, 8, 4, 8));
  }
};

解説

• 上: Override: JTextField#paintComponent(...)
  • JTextField#paintComponent(...)をオーバーライド
  • BorderをEmptyBorderに変更
  • JTextField#setOpaque(false)を設定
  • 参考: Unleash Your Creativity with Swing and the Java 2D API!
  • 背景が画像などの場合でも角丸が描画可能

• 下: setBorder(new RoundedCornerBorder())
  • RoundedCornerBorderを設定
  • 角を親コンポーネントの背景色で上書きしているので、背景が画像などの場合はその上に角が描画されてしまう
  • JTextFieldの縁と背景を透明化し、RoundedCornerBorderから取得した図形を描画するように修正

    JTextField textField02 = new JTextField(20) {
      @Override protected void paintComponent(Graphics g) {
        if (!isOpaque() && getBorder() instanceof RoundedCornerBorder) {
          Graphics2D g2 = (Graphics2D) g.create();
          g2.setPaint(getBackground());
          g2.fill(((RoundedCornerBorder) getBorder()).getBorderShape(
              0, 0, getWidth() - 1, getHeight() - 1));
          g2.dispose();
        }
        super.paintComponent(g);
      }
    
      @Override public void updateUI() {
        super.updateUI();
        setOpaque(false);
        setBorder(new RoundedCornerBorder());
      }
    };
    
    class RoundedCornerBorder extends AbstractBorder {
      private static final Color ALPHA_ZERO = new Color(0x0, true);
      @Override public void paintBorder(
          Component c, Graphics g, int x, int y, int width, int height) {
        Graphics2D g2 = (Graphics2D) g.create();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        Shape border = getBorderShape(x, y, width - 1, height - 1);
        g2.setPaint(ALPHA_ZERO);
        Area corner = new Area(new Rectangle2D.Double(x, y, width, height));
        corner.subtract(new Area(border));
        g2.fill(corner);
        g2.setPaint(Color.GRAY);
        g2.draw(border);
        g2.dispose();
      }
    
      public Shape getBorderShape(int x, int y, int w, int h) {
        int r = h; // h / 2;
        return new RoundRectangle2D.Double(x, y, w, h, r, r);
      }
    
      @Override public Insets getBorderInsets(Component c) {
        return new Insets(4, 8, 4, 8);
      }
    
      @Override public Insets getBorderInsets(Component c, Insets insets) {
        insets.set(4, 8, 4, 8);
        return insets;
      }
    }
    

参考リンク

• Unleash Your Creativity with Swing and the Java 2D API!
• Border on an rounded JTextField? (Swing / AWT / SWT / JFace forum at JavaRanch)
• java - how i remove unneeded background under roundedborder? - Stack Overflow

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