[英]Getting the bounds of the text inside a jlabel
我想從 JLabel 中的文本繪制一個箭頭到 JLabel 之外的點。 要在適當的位置開始箭頭,我需要 JLabel 中實際文本的邊界。 我在下面的回答將展示如何獲得這些界限。
Swing API 已經提供了 API 來執行這個操作 - SwingUtilities#layoutCompoundLabel
protected TextBounds calculateTextBounds(JLabel label) {
Rectangle paintIconR = new Rectangle();
Rectangle paintTextR = new Rectangle();
Dimension size = label.getSize();
Insets insets = label.getInsets(null);
String text = label.getText();
Icon icon = (label.isEnabled()) ? label.getIcon()
: label.getDisabledIcon();
Rectangle paintViewR = new Rectangle();
paintViewR.x = insets.left;
paintViewR.y = insets.top;
paintViewR.width = size.width - (insets.left + insets.right);
paintViewR.height = size.height - (insets.top + insets.bottom);
paintIconR.x = paintIconR.y = paintIconR.width = paintIconR.height = 0;
paintTextR.x = paintTextR.y = paintTextR.width = paintTextR.height = 0;
String result = SwingUtilities.layoutCompoundLabel(
(JComponent) label,
label.getFontMetrics(label.getFont()),
text,
icon,
label.getVerticalAlignment(),
label.getHorizontalAlignment(),
label.getVerticalTextPosition(),
label.getHorizontalTextPosition(),
paintViewR,
paintIconR,
paintTextR,
label.getIconTextGap());
TextBounds bounds = new TextBounds(paintViewR, paintTextR, paintIconR);
return bounds;
}
基本上這將提供“視圖”邊界(基本上是可以繪制 label 的區域)、“文本”邊界和“圖標”邊界,我只是將它們包裝在一個易於使用的 class 中
那么為什么要使用這種方法呢?
JLabel
的任何實例import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.Rectangle;
import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TextBounds {
private Rectangle paintBounds;
private Rectangle textBounds;
private Rectangle iconBounds;
public TextBounds(Rectangle paintBounds, Rectangle textBounds, Rectangle iconBounds) {
this.paintBounds = paintBounds;
this.textBounds = textBounds;
this.iconBounds = iconBounds;
}
public Rectangle getPaintBounds() {
return paintBounds;
}
public Rectangle getTextBounds() {
return textBounds;
}
public Rectangle getIconBounds() {
return iconBounds;
}
}
public class TestPane extends JPanel {
private JLabel label = new JLabel("Hello");
public TestPane() {
setLayout(new BorderLayout());
label.setHorizontalAlignment(JLabel.CENTER);
label.setVerticalAlignment(JLabel.CENTER);
add(label);
}
protected TextBounds calculateTextBounds(JLabel label) {
Rectangle paintIconR = new Rectangle();
Rectangle paintTextR = new Rectangle();
Dimension size = label.getSize();
Insets insets = label.getInsets(null);
String text = label.getText();
Icon icon = (label.isEnabled()) ? label.getIcon()
: label.getDisabledIcon();
Rectangle paintViewR = new Rectangle();
paintViewR.x = insets.left;
paintViewR.y = insets.top;
paintViewR.width = size.width - (insets.left + insets.right);
paintViewR.height = size.height - (insets.top + insets.bottom);
paintIconR.x = paintIconR.y = paintIconR.width = paintIconR.height = 0;
paintTextR.x = paintTextR.y = paintTextR.width = paintTextR.height = 0;
String result = SwingUtilities.layoutCompoundLabel(
(JComponent) label,
label.getFontMetrics(label.getFont()),
text,
icon,
label.getVerticalAlignment(),
label.getHorizontalAlignment(),
label.getVerticalTextPosition(),
label.getHorizontalTextPosition(),
paintViewR,
paintIconR,
paintTextR,
label.getIconTextGap());
TextBounds bounds = new TextBounds(paintViewR, paintTextR, paintIconR);
System.out.println(result);
System.out.println("view " + paintViewR);
System.out.println("paint " + paintIconR);
System.out.println("text " + paintTextR);
return bounds;
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
TextBounds bounds = calculateTextBounds(label);
g2d.setColor(Color.RED);
g2d.draw(bounds.getPaintBounds());
g2d.setColor(Color.GREEN);
g2d.draw(bounds.getTextBounds());
g2d.setColor(Color.BLUE);
g2d.draw(bounds.getIconBounds());
g2d.dispose();
}
}
}
其他解決方案的潛在優勢是不會在每次調用時創建三個新的 Rectangle 對象。 如果在 MouseMoved 事件偵聽器中調用 getTextBounds,這可能會成為問題。 以復雜性為代價,最終的 Rectangle 可以與 JLabel 的寬度和高度一起緩存。
Rectangle
只需要創建一次,它們被傳遞到 API 並直接應用它們的值,因此您不必每次都創建新對象。
您也不需要使用專門的組件,可以使用現有 label 上的工作流
您可以使用SwingUtilities.layoutCompoundLabel
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
public class LabelLayout extends JLabel
{
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics grid = g.create();
grid.setColor( Color.ORANGE );
Rectangle viewR = new Rectangle();
viewR.width = getSize().width;
viewR.height = getSize().height;
Rectangle iconR = new Rectangle();
Rectangle textR = new Rectangle();
String clippedText = SwingUtilities.layoutCompoundLabel
(
this,
grid.getFontMetrics(),
getText(),
getIcon(),
getVerticalAlignment(),
getHorizontalAlignment(),
getVerticalTextPosition(),
getHorizontalTextPosition(),
viewR,
iconR,
textR,
getIconTextGap()
);
int gridSize = 10;
int start = iconR.x;
int end = iconR.x + iconR.width;
System.out.println("Text bounds: " + textR );
System.out.println("Icon bounds: " + iconR );
for (int i = start; i < end; i += gridSize)
{
grid.drawLine(i, iconR.y, i, iconR.y + iconR.height);
}
grid.dispose();
}
private static void createAndShowGUI()
{
LabelLayout label = new LabelLayout();
label.setBorder( new LineBorder(Color.RED) );
label.setText( "Some Text" );
label.setIcon( new ImageIcon( "DukeWaveRed.gif" ) );
label.setVerticalAlignment( JLabel.CENTER );
label.setHorizontalAlignment( JLabel.CENTER );
// label.setVerticalTextPosition( JLabel.BOTTOM );
label.setVerticalTextPosition( JLabel.TOP );
label.setHorizontalTextPosition( JLabel.CENTER );
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( label );
frame.setLocationByPlatform( true );
frame.pack();
frame.setSize(300, 200);
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
此示例在 label 中的圖標上方繪制了額外的線條。
要獲取 JLabel 中文本的邊界,我們需要可訪問的上下文,一個受保護的字段。 所以我們擴展了 JLabel。 可訪問的上下文只知道文本是 HTML,所以我在構造函數中添加了“<html>”; 更通用的版本將首先檢查文本是否已經以該字符串開頭。
class FieldLabel extends JLabel {
FieldLabel(String text) {
super("<html>"+text);
}
Rectangle getTextBounds() {
JLabel.AccessibleJLabel acclab
= (JLabel.AccessibleJLabel) getAccessibleContext();
if (acclab.getCharCount() <= 0)
return null;
Rectangle r0 = acclab.getCharacterBounds(0);
Rectangle rn = acclab
.getCharacterBounds(acclab.getCharCount()-1);
return new Rectangle(r0.x, r0.y,
rn.x+rn.width-r0.x, Math.max(r0.height, rn.height));
}
}
其他解決方案的潛在優勢是不會在每次調用時創建三個新的 Rectangle 對象。 如果在 MouseMoved 事件偵聽器中調用 getTextBounds,這可能會成為問題。 以復雜性為代價,最終的 Rectangle 可以與 JLabel 的寬度和高度一起緩存。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.