Question

我正试图用一个图像和一个提示创建一些看起来更好的JTextFields。为此，我制作了一个覆盖paintComponent方法的decorator。我之所以使用decorator，是因为我想将它应用于其他类型的JTextField，如JPasswordField。

以下是我迄今为止所做的工作；

从左边的表格中可以看到的问题是，即使我使用了JPasswordField，paintComponent似乎忽略了我认为的密码paintComponent，它可能会屏蔽密码符号。

因此，问题是，我如何避免重复JTextFields和JPasswordFields的代码，但仍然具有不同的功能，如密码屏蔽。

这是decorator代码；

public class JTextFieldHint extends JTextField implements FocusListener{
private JTextField jtf;
private Icon icon;
private String hint;
private Insets dummyInsets;

public JTextFieldHint(JTextField jtf, String icon, String hint){
    this.jtf = jtf;
    setIcon(createImageIcon("icons/"+icon+".png",icon));
    this.hint = hint;

    Border border = UIManager.getBorder("TextField.border");
    JTextField dummy = new JTextField();
    this.dummyInsets = border.getBorderInsets(dummy);

    addFocusListener(this);
}

public void setIcon(Icon newIcon){
    this.icon = newIcon;
}

@Override
protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        int textX = 2;

        if(this.icon!=null){
            int iconWidth = icon.getIconWidth();
            int iconHeight = icon.getIconHeight();
            int x = dummyInsets.left + 5;
            textX = x+iconWidth+2;
            int y = (this.getHeight() - iconHeight)/2;
            icon.paintIcon(this, g, x, y);
        }

        setMargin(new Insets(2, textX, 2, 2));

        if ( this.getText().equals("")) {
            int width = this.getWidth();
            int height = this.getHeight();
            Font prev = g.getFont();
            Font italic = prev.deriveFont(Font.ITALIC);
            Color prevColor = g.getColor();
            g.setFont(italic);
            g.setColor(UIManager.getColor("textInactiveText"));
            int h = g.getFontMetrics().getHeight();
            int textBottom = (height - h) / 2 + h - 4;
            int x = this.getInsets().left;
            Graphics2D g2d = (Graphics2D) g;
            RenderingHints hints = g2d.getRenderingHints();
            g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            g2d.drawString(hint, x, textBottom);
            g2d.setRenderingHints(hints);
            g.setFont(prev);
            g.setColor(prevColor);
        }

}

protected ImageIcon createImageIcon(String path, String description) {
    java.net.URL imgURL = getClass().getResource(path);
    if (imgURL != null) {
        return new ImageIcon(imgURL, description);
    } else {
        System.err.println("Couldn t find file: " + path);
        return null;
    }
}

@Override
public void focusGained(FocusEvent arg0) {
    this.repaint();
}

@Override
public void focusLost(FocusEvent arg0) {
    this.repaint();
}


}

这就是我创造领域的地方；

JTextField usernameField = new JTextFieldHint(new JTextField(),"user_green","Username");
JTextField passwordField = new JTextFieldHint(new JPasswordField(),"bullet_key","Password");

希望我在这里没有完全走错方向！

谢谢

EDIT：我看得越多，很明显调用super.paintComponent（g）将调用JTextFields paintComponent，但我不知道如何在不复制代码的情况下解决这个问题。

Answer 1

文本提示使用JPasswordField。

一个区别是，当输入文本时，显示的图标会消失。如果你希望图标是永久的，那么我建议你创建一个自定义的“IconOrder”类来绘制图标，而不是在paintComponent（）方法中进行自定义绘制。

除非您同时复制JTextField和JPasswordField的代码，否则您的方法将不起作用。

编辑：

实际上，您不需要创建自定义的IconOrder。MatteBborder支持在边框中绘制图标。

Answer 2

In order to paint an icon inside a text field you need to add some insets. You don t want to hard-code insets in your component but just add a little bit of space for the icon, letting clients and subclasses to set their own.

在上图中，我用绿色绘制了原始插入，用红色绘制了附加插入。我们跟踪两件事：原始的insets（绿色的）mBorder和图标。

public class IconTextField extends JTextField {
    private Border mBorder;
    private Icon mIcon;

    // ...
}

然后您需要覆盖setBorder（）方法。

@Override
public void setBorder(Border border) {
    mBorder = border;

    if (mIcon == null) {
        super.setBorder(border);
    } else {
        Border margin = BorderFactory.createEmptyBorder(0, mIcon.getIconWidth() + ICON_SPACING, 0, 0);
        Border compound = BorderFactory.createCompoundBorder(border, margin);
        super.setBorder(compound);
    }
}

在这里，如果我们有一个图标（字段mIcon不是null），我们使用复合边框添加额外的插入。然后，您还应该覆盖paintComponent（）方法。

@Override
protected void paintComponent(Graphics graphics) {
    super.paintComponent(graphics);

    if (mIcon != null) {
        Insets iconInsets = mBorder.getBorderInsets(this);
        mIcon.paintIcon(this, graphics, iconInsets.left, iconInsets.top);
    }
}

最后，您需要一个setIcon（）方法。

public void setIcon(Icon icon) {
    mIcon = icon;
    resetBorder();
}

private void resetBorder() {
    setBorder(mBorder);
}

我们在这里所做的是保存图标并重新计算边界。

如果您想对JPasswordField做同样的事情，最优雅的事情可能是用上面讨论的所有方法创建一个助手类。

class IconTextComponentHelper {
    private static final int ICON_SPACING = 4;

    private Border mBorder;
    private Icon mIcon;
    private Border mOrigBorder;
    private JTextComponent mTextComponent;

    IconTextComponentHelper(JTextComponent component) {
        mTextComponent = component;
        mOrigBorder = component.getBorder();
        mBorder = mOrigBorder;
    }

    Border getBorder() {
        return mBorder;
    }

    void onPaintComponent(Graphics g) {
        if (mIcon != null) {
            Insets iconInsets = mOrigBorder.getBorderInsets(mTextComponent);
            mIcon.paintIcon(mTextComponent, g, iconInsets.left, iconInsets.top);
        }
    }

    void onSetBorder(Border border) {
        mOrigBorder = border;

        if (mIcon == null) {
            mBorder = border;
        } else {
            Border margin = BorderFactory.createEmptyBorder(0, mIcon.getIconWidth() + ICON_SPACING, 0, 0);
            mBorder = BorderFactory.createCompoundBorder(border, margin);
        }
    }

    void onSetIcon(Icon icon) {
        mIcon = icon;
        resetBorder();
    }

    private void resetBorder() {
        mTextComponent.setBorder(mOrigBorder);
    }
}

并这样使用：

public class IconTextField extends JTextField {
    private IconTextComponentHelper mHelper = new IconTextComponentHelper(this);

    public IconTextField() {
        super();
    }

    public IconTextField(int cols) {
        super(cols);
    }

    private IconTextComponentHelper getHelper() {
        if (mHelper == null)
            mHelper = new IconTextComponentHelper(this);

        return mHelper;
    }

    @Override
    protected void paintComponent(Graphics graphics) {
        super.paintComponent(graphics);
        getHelper().onPaintComponent(graphics);
    }

    public void setIcon(Icon icon) {
        getHelper().onSetIcon(icon);
    }

    public void setIconSpacing(int spacing) {
        getHelper().onSetIconSpacing(spacing);
    }

    @Override
    public void setBorder(Border border) {
        getHelper().onSetBorder(border);
        super.setBorder(getHelper().getBorder());
    }
}

友情链接