我需要为JPanel创建一个自定义边框，其边框的左上角包含JButton（如标题边框中的标题）。有没有办法在Java中这样做？
答案 0 :(得分：3)
ComponentBorder可能适合该法案。我在过去成功地使用它，经过一些小小的调整，用CheckBox制作一个TitledBorder。
（从网站复制）：
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
/**
* The ComponentBorder class allows you to place a real component in
* the space reserved for painting the Border of a component.
*
* This class takes advantage of the knowledge that all Swing components are
* also Containers. By default the layout manager is null, so we should be
* able to place a child component anywhere in the parent component. In order
* to prevent the child component from painting over top of the parent
* component a Border is added to the parent componet such that the insets of
* the Border will reserve space for the child component to be painted without
* affecting the parent component.
*/
public class ComponentBorder implements Border
{
public enum Edge
{
TOP,
LEFT,
BOTTOM,
RIGHT;
}
public static final float LEADING = 0.0f;
public static final float CENTER = 0.5f;
public static final float TRAILING = 1.0f;
private JComponent parent;
private JComponent component;
private Edge edge;
private float alignment;
private int gap = 5;
private boolean adjustInsets = true;
private Insets borderInsets = new Insets(0, 0, 0, 0);
/**
* Convenience constructor that uses the default edge (Edge.RIGHT) and
* alignment (CENTER).
*
* @param component the component to be added in the Border area
*/
public ComponentBorder(JComponent component)
{
this(component, Edge.RIGHT);
}
/**
* Convenience constructor that uses the default alignment (CENTER).
*
* @param component the component to be added in the Border area
* @param edge a valid Edge enum of TOP, LEFT, BOTTOM, RIGHT
*/
public ComponentBorder(JComponent component, Edge edge)
{
this(component, edge, CENTER);
}
/**
* Main constructor to create a ComponentBorder.
*
* @param component the component to be added in the Border area
* @param edge a valid Edge enum of TOP, LEFT, BOTTOM, RIGHT
* @param alignment the alignment of the component along the
* specified Edge. Must be in the range 0 - 1.0.
*/
public ComponentBorder(JComponent component, Edge edge, float alignment )
{
this.component = component;
component.setSize( component.getPreferredSize() );
component.setCursor(Cursor.getDefaultCursor());
setEdge( edge );
setAlignment( alignment );
}
public boolean isAdjustInsets()
{
return adjustInsets;
}
public void setAdjustInsets(boolean adjustInsets)
{
this.adjustInsets = adjustInsets;
}
/**
* Get the component alignment along the Border Edge
*
* @return the alignment
*/
public float getAlignment()
{
return alignment;
}
/**
* Set the component alignment along the Border Edge
*
* @param alignment a value in the range 0 - 1.0. Standard values would be
* CENTER (default), LEFT and RIGHT.
*/
public void setAlignment(float alignment)
{
this.alignment = alignment > 1.0f ? 1.0f : alignment < 0.0f ? 0.0f : alignment;
}
/**
* Get the Edge the component is positioned along
*
* @return the Edge
*/
public Edge getEdge()
{
return edge;
}
/**
* Set the Edge the component is positioned along
*
* @param edge the Edge the component is position on.
*/
public void setEdge(Edge edge)
{
this.edge = edge;
}
/**
* Get the gap between the border component and the parent component
*
* @return the gap in pixels.
*/
public int getGap()
{
return gap;
}
/**
* Set the gap between the border component and the parent component
*
* @param gap the gap in pixels (default is 5)
*/
public void setGap(int gap)
{
this.gap = gap;
}
//
// Implement the Border interface
//
public Insets getBorderInsets(Component c)
{
return borderInsets;
}
public boolean isBorderOpaque()
{
return false;
}
/**
* In this case a real component is to be painted. Setting the location
* of the component will cause it to be painted at that location.
*/
public void paintBorder(Component c, Graphics g, int x, int y, int width, int height)
{
float x2 = (width - component.getWidth()) * component.getAlignmentX() + x;
float y2 = (height - component.getHeight()) * component.getAlignmentY() + y;
component.setLocation((int)x2, (int)y2);
}
/*
* Install this Border on the specified component by replacing the
* existing Border with a CompoundBorder containing the original Border
* and our ComponentBorder
*
* This method should only be invoked once all the properties of this
* class have been set. Installing the Border more than once will cause
* unpredictable results.
*/
public void install(JComponent parent)
{
this.parent = parent;
determineInsetsAndAlignment();
// Add this Border to the parent
Border current = parent.getBorder();
if (current == null)
{
parent.setBorder(this);
}
else
{
CompoundBorder compound = new CompoundBorder(current, this);
parent.setBorder(compound);
}
// Add component to the parent
parent.add(component);
}
/**
* The insets need to be determined so they are included in the preferred
* size of the component the Border is attached to.
*
* The alignment of the component is determined here so it doesn't need
* to be recalculated every time the Border is painted.
*/
private void determineInsetsAndAlignment()
{
borderInsets = new Insets(0, 0, 0, 0);
// The insets will only be updated for the edge the component will be
// diplayed on.
//
// The X, Y alignment of the component is controlled by both the edge
// and alignment parameters
if (edge == Edge.TOP)
{
borderInsets.top = component.getPreferredSize().height + gap;
component.setAlignmentX(alignment);
component.setAlignmentY(0.0f);
}
else if (edge == Edge.BOTTOM)
{
borderInsets.bottom = component.getPreferredSize().height + gap;
component.setAlignmentX(alignment);
component.setAlignmentY(1.0f);
}
else if (edge == Edge.LEFT)
{
borderInsets.left = component.getPreferredSize().width + gap;
component.setAlignmentX(0.0f);
component.setAlignmentY(alignment);
}
else if (edge == Edge.RIGHT)
{
borderInsets.right = component.getPreferredSize().width + gap;
component.setAlignmentX(1.0f);
component.setAlignmentY(alignment);
}
if (adjustInsets)
adjustBorderInsets();
}
/*
* The complimentary edges of the Border may need to be adjusted to allow
* the component to fit completely in the bounds of the parent component.
*/
private void adjustBorderInsets()
{
Insets parentInsets = parent.getInsets();
// May need to adust the height of the parent component to fit
// the component in the Border
if (edge == Edge.RIGHT || edge == Edge.LEFT)
{
int parentHeight = parent.getPreferredSize().height - parentInsets.top - parentInsets.bottom;
int diff = component.getHeight() - parentHeight;
if (diff > 0)
{
int topDiff = (int)(diff * alignment);
int bottomDiff = diff - topDiff;
borderInsets.top += topDiff;
borderInsets.bottom += bottomDiff;
}
}
// May need to adust the width of the parent component to fit
// the component in the Border
if (edge == Edge.TOP || edge == Edge.BOTTOM)
{
int parentWidth = parent.getPreferredSize().width - parentInsets.left - parentInsets.right;
int diff = component.getWidth() - parentWidth;
if (diff > 0)
{
int leftDiff = (int)(diff * alignment);
int rightDiff = diff - leftDiff;
borderInsets.left += leftDiff;
borderInsets.right += rightDiff;
}
}
}
}