How to determine the size of a JTextField?

问题

I'm doing a program involving the Pythagorean theorem, and wanted to leave a triangle in the middle, with three JTextField around three sides of it. I did it, but the problem is that when I create the JTextField and add it to the desired container, it is immense. It is a very large white rectangle that when I click to enter, get a small letter. So, my question is: How can I change the size of this JTextField to decrease it and avoid unnecessary sizes? P.S:.'m Using Swing and AWT library for free! Example of code:

Container content = window.getContentPane();
Contaiiner grid = new JPanel();
grid.setLayout(new GridLayout(3,3));
grid.add(new JTextField());

Well, this simple code, gives to you one example of the JTextField, when i executes than (with main method and more...) the JTextField is very very big, so, i want to decrease it.

回答1:

Admittedly, it involves some guesses about your intention, but here is an example of what I think that you want to achieve:

It's a program that contains a panel with some points, and between each pair of points, it places a text field. The text fields are arranged so that their upper left corner remains at the center of the respective edge. When the points are dragged with the mouse, the locations of the text fields are updated accordingly. (In this example, the text fields contain the distance between the points - that is, the edge lengths - but this is just for illustration).

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class TriangleTextFieldsTest
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                new TriangleTextFieldsTest();
            }
        });
    }

    public TriangleTextFieldsTest()
    {
        JFrame frame = new JFrame();
        frame.getContentPane().add(new TriangleTextFieldsPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(800,800);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}


class TriangleTextFieldsPanel extends JPanel
    implements MouseListener, MouseMotionListener
{
    private final List<Point2D> points;
    private final List<JTextField> textFields;
    private Point2D draggedPoint = null;

    TriangleTextFieldsPanel()
    {
        super(null);

        points = new ArrayList<Point2D>();
        points.add(new Point2D.Double(250,250));
        points.add(new Point2D.Double(750,250));
        points.add(new Point2D.Double(500,500));

        textFields = new ArrayList<JTextField>();

        for (int i=0; i<points.size(); i++)
        {
            JTextField t = new JTextField(10);
            textFields.add(t);
            add(t);
        }

        updateTextFieldPositions();
        updateTextFieldContents();

        addMouseListener(this);
        addMouseMotionListener(this);
    }

    private void updateTextFieldPositions()
    {
        for (int i=0; i<points.size(); i++)
        {
            Point2D p0 = points.get(i);
            Point2D p1 = points.get((i+1)%points.size());

            JTextField textField = textFields.get(i);
            int cx = (int)(0.5 * (p1.getX() + p0.getX()));
            int cy = (int)(0.5 * (p1.getY() + p0.getY()));

            Dimension d = textField.getPreferredSize();
            textField.setBounds(cx, cy, d.width, d.height);
        }
    }

    private void updateTextFieldContents()
    {
        for (int i=0; i<points.size(); i++)
        {
            Point2D p0 = points.get(i);
            Point2D p1 = points.get((i+1)%points.size());

            JTextField textField = textFields.get(i);
            double d = p0.distance(p1);
            textField.setText(String.format("%.2f", d));
        }
    }


    @Override
    protected void paintComponent(Graphics gr)
    {
        super.paintComponent(gr);
        Graphics2D g = (Graphics2D)gr;
        g.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,  
            RenderingHints.VALUE_ANTIALIAS_ON);
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, getWidth(), getHeight());

        g.setColor(Color.BLUE);
        drawPoints(g, points);

        g.setColor(Color.BLACK);
        for (int i=0; i<points.size(); i++)
        {
            Point2D p0 = points.get(i);
            Point2D p1 = points.get((i+1)%points.size());
            g.draw(new Line2D.Double(p0,p1));
        }
    }

    static void drawPoints(Graphics2D g, List<Point2D> points)
    {
        double r = 3;
        for (Point2D point : points)
        {
            double x = point.getX();
            double y = point.getY();
            g.fill(new Ellipse2D.Double(
                x-r, y-r, r+r, r+r));
        }
    }


    @Override
    public void mouseDragged(MouseEvent e)
    {
        if (draggedPoint != null)
        {
            draggedPoint.setLocation(e.getPoint());
            updateTextFieldPositions();
            updateTextFieldContents();            
            repaint();
        }
    }

    @Override
    public void mouseMoved(MouseEvent e)
    {
    }

    @Override
    public void mouseClicked(MouseEvent e)
    {
    }

    @Override
    public void mousePressed(MouseEvent e)
    {
        draggedPoint = null;
        double thresholdSquared = 10*10;
        double minDs = Double.MAX_VALUE;
        for (Point2D point : points)
        {
            double ds = point.distanceSq(e.getPoint());
            if (ds < thresholdSquared && ds < minDs)
            {
                minDs = ds;
                draggedPoint = point;
            }
        }
    }

    @Override
    public void mouseReleased(MouseEvent e)
    {
        draggedPoint = null;
    }

    @Override
    public void mouseEntered(MouseEvent e)
    {
    }

    @Override
    public void mouseExited(MouseEvent e)
    {
    }
}

来源：https://stackoverflow.com/questions/24849691/how-to-determine-the-size-of-a-jtextfield