上面的代码有很多错误...
- 不要使用
null/ Absolute LayoutManager。看看在容器内布局组件。
- 不要调用
setSize组件并且JFrame（如果实现了正确的布局管理器，您可以简单地添加组件并调用pack().JFrame
- 在 EDT 上创建和操作 Swing 组件。阅读更多关于Swing 中的并发性。
- 在从可见容器中添加/删除组件后，您应该在容器上调用
revalidate()和。repaint()
我一直在开发自己的小ComponentDragAPI，它允许我们将 Swing 组件拖到一个JComponent或多个JComponents 上。虽然它绝不是没有错误的（尤其是今天刚刚完成的多个组件部分，所以你永远不会知道）
您将创建JButton并添加到JPanel：
JButton button = new JButton("Text");
JPanel panel1 = new JPanel() {
@Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
};
panel1.add(button);
通过传递容器的参数来创建ComponentDrag类的实例，即JFrame/JDialog或JWindow注册可拖动组件并调用setName("Droppable")您JPanel以允许拖放正确发生，尤其是跨多个 JComponents 等，您只会为您的JPanels 等执行此操作也希望能够删除 Swing 组件：
JFrame frame=..;//has access to setGlassPane same applies for JDialog and JWindow
frame.add(panel1);
ComponentDrag cd=new ComponentDrag(frame);
cd.registerComponent(button);
panel1.setName("Droppable");//needed for the dragging and dropping to work correctly especailly over multiple components
和你的好去:)。
以下是用于分析目的的 2 个完整示例：
1) 显示移动s 并相应地使用并覆盖其方法JButton重新定位的逻辑：ComponentDragcomponentDropped
拖动前：
4拖到1位置后：
import java.awt.Component;
import java.awt.Container;
import java.awt.Cursor;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class DragButtonsTest {
ArrayList<JButton> buttons = new ArrayList<>();
public DragButtonsTest() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JPanel panel = new JPanel(new GridLayout(2, 2));
ComponentDrag cd = new ComponentDrag(frame) {
@Override
protected void componentDropped(MouseEvent me) {
HashMap<Integer, JButton> collisions = new HashMap<>();
JButton draggedButton = (JButton) me.getSource();
for (JButton btn : buttons) {//iterate through all buttons and get the number of collsions of each
if (btn != draggedButton) {//dont chck button we were dragging
int col = checkPerPixelCollision(draggedButton, btn);
System.out.println("Button " + btn.getText());
System.out.println(col);
collisions.put(col, btn);
}
}
//lets get the button which had most collisions
int maxCollisions = 0;
JButton intersectingButton = null;
for (Map.Entry<Integer, JButton> entry : collisions.entrySet()) {
Integer collisionCount = entry.getKey();
JButton button = entry.getValue();
if (collisionCount > maxCollisions) {
maxCollisions = collisionCount;
intersectingButton = button;
}
}
boolean reLayout = false;
if (maxCollisions > 0) {//check if there was any
System.out.println("Button " + draggedButton.getText() + " is intersecting more of Button " + intersectingButton.getText());
System.out.println("Collisions: " + maxCollisions);
reLayout = true;
} else {
System.out.println("No change made");
reLayout = false;
}
ArrayList<JButton> tmpButtons = (ArrayList<JButton>) buttons.clone();//create clone of buttons
if (reLayout) {//a button as moved and panel needs to be layed out
buttons.clear();//clear old buttons
for (JButton b : tmpButtons) {//re-order jbuttons
if (b == intersectingButton) {
buttons.add(draggedButton);
} else if (b == draggedButton) {
buttons.add(intersectingButton);
} else {
buttons.add(b);
}
}
panel.removeAll();//remove all buttons
for (JButton btn : buttons) {//iterate through all buttons and get the number of collsions of each
panel.add(btn);//re-add buttons according to arraylist
}
panel.revalidate();
panel.repaint();
}
super.componentDropped(me);
}
};
for (int i = 0; i < 4; i++) {
JButton b = new JButton(String.valueOf(i + 1));
panel.add(b);
buttons.add(b);
cd.registerComponent(b);
}
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new DragButtonsTest();
}
});
}
public HashSet<String> getMask(JButton e) {
HashSet<String> mask = new HashSet<>();
int pixel, a;
BufferedImage bi = componentToImage(e); //gets the current image being shown
for (int i = 0; i < bi.getWidth(); i++) { // for every (x,y) component in the given box,
for (int j = 0; j < bi.getHeight(); j++) {
pixel = bi.getRGB(i, j); // get the RGB value of the pixel
a = (pixel >> 24) & 0xff;
if (a != 0) { // if the alpha is not 0, it must be something other than transparent
mask.add((e.getX() + i) + "," + (e.getY() - j)); // add the absolute x and absolute y coordinates to our set
}
}
}
return mask; //return our set
}
public static BufferedImage componentToImage(Component component) {
BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TRANSLUCENT);
Graphics g = img.getGraphics();
component.paintAll(g);
return img;
}
// Returns true if there is a collision between object a and object b
public int checkPerPixelCollision(JButton b, JButton b2) {
// This method detects to see if the images overlap at all. If they do, collision is possible
int ax1 = (int) b2.getX();
int ay1 = (int) b2.getY();
int ax2 = ax1 + (int) b2.getWidth();
int ay2 = ay1 + (int) b2.getHeight();
int bx1 = (int) b.getX();
int by1 = (int) b.getY();
int bx2 = bx1 + (int) b.getWidth();
int by2 = by1 + (int) b.getHeight();
if (by2 < ay1 || ay2 < by1 || bx2 < ax1 || ax2 < bx1) {
return 0; // Collision is impossible.
} else { // Collision is possible.
// get the masks for both images
HashSet<String> maskPlayer1 = getMask(b2);
HashSet<String> maskPlayer2 = getMask(b);
maskPlayer1.retainAll(maskPlayer2); // Check to see if any pixels in maskPlayer2 are the same as those in maskPlayer1
if (maskPlayer1.size() > 0) { // if so, than there exists at least one pixel that is the same in both images, thus
return maskPlayer1.size();
}
}
return 0;
}
}
class ComponentDrag {
private MouseAdapter ma;
private ArrayList<JComponent> components = new ArrayList<>();
private int startingX, startingY;
private boolean autoLayout = true;
private final JFrame container;
private JPanel glassPane;
boolean firstTime = true;
private JComponent lastClickedContainer;
public ComponentDrag(final JFrame container) {
this.container = container;
glassPane = new JPanel();
glassPane.setOpaque(false);
glassPane.setLayout(null);
this.container.setGlassPane(glassPane);
new Timer(10, new AbstractAction() {
@Override
public void actionPerformed(ActionEvent ae) {
if (container.isVisible()) {
glassPane.setVisible(true);
((Timer) ae.getSource()).stop();
}
}
}).start();
ma = new MouseAdapter() {
@Override
public void mousePressed(MouseEvent me) {
super.mousePressed(me);
componentPressed(me);
}
@Override
public void mouseReleased(MouseEvent me) {
super.mouseReleased(me);
componentDropped(me);
}
@Override
public void mouseDragged(MouseEvent me) {
super.mouseDragged(me);
componentDragged(me);
}
};
}
public JComponent findDroppableUnderGlassPane(Point p, Container container, Component source) {
JComponent c = null;
Component[] comps = container.getComponents();
for (Component com : comps) {
if (com.getName() != null) {
if (com.getName().equals("Droppable") && com instanceof JComponent) {
if (com.contains(SwingUtilities.convertPoint(source, p, com))) {
return (JComponent) com;
}
} else if (com instanceof Container) {
findDroppableUnderGlassPane(p, (Container) com, source);
}
}
}
return c;
}
public boolean isAutoLayout() {
return autoLayout;
}
public void setAutoLayout(boolean autoLayout) {
this.autoLayout = autoLayout;
}
protected void componentDropped(MouseEvent me) {
firstTime = true;
Component droppedComponent = (Component) me.getSource();
droppedComponent.setCursor(null);
JComponent jc = findDroppableUnderGlassPane(me.getPoint(), container.getContentPane(), (Component) me.getSource());
if (jc != null) {
glassPane.removeAll();
glassPane.revalidate();
glassPane.repaint();
jc.add(droppedComponent);
System.out.println("Removed from glasspane and added to: " + jc);
if (autoLayout) {
if (lastClickedContainer != null) {
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
}
droppedComponent.revalidate();
droppedComponent.repaint();
jc.revalidate();
jc.repaint();
}
} else {
glassPane.removeAll();
glassPane.revalidate();
glassPane.repaint();
if (lastClickedContainer != null) {
lastClickedContainer.add(droppedComponent);
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
}
}
}
protected void componentPressed(MouseEvent me) {
JComponent jc = findDroppableUnderGlassPane(me.getPoint(), container.getContentPane(), (Component) me.getSource());
if (jc != null && jc.getName().equals("Droppable")) {
lastClickedContainer = jc;
System.out.println("Pressed: " + lastClickedContainer);
}
boolean clickedRegisteredComponent = false;
Component clickedComponent = (Component) me.getSource();
for (Component component : ComponentDrag.this.components) {
if (component.equals(clickedComponent)) {
clickedRegisteredComponent = true;
break;
}
}
if (clickedRegisteredComponent) {
startingX = me.getX();
startingY = me.getY();
clickedComponent.setCursor(new Cursor(Cursor.MOVE_CURSOR));
}
}
protected void componentDragged(MouseEvent me) {
Component draggedComponent = (Component) me.getSource();
if (firstTime && lastClickedContainer != null) {
firstTime = false;
lastClickedContainer.remove(draggedComponent);
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
glassPane.add(draggedComponent);
glassPane.revalidate();
glassPane.repaint();
System.out.println("Removed from: " + lastClickedContainer + " \nAnd added to glasspane for dragging");
}
//MouseEvent will refire on each drag with the position being relative to the firing Component
draggedComponent.setLocation((me.getX() - startingX) + draggedComponent.getLocation().x, (me.getY() - startingY) + draggedComponent.getLocation().y);
}
void registerComponent(JComponent draggableComp) {
draggableComp.addMouseListener(ma);
draggableComp.addMouseMotionListener(ma);
components.add(draggableComp);
}
void deregisterComponent(JComponent draggableComp) {
draggableComp.removeMouseListener(ma);
draggableComp.removeMouseMotionListener(ma);
components.remove(draggableComp);
}
}
2) 简单展示如何JLabel在s 上拖动 2 JPanels
在拖动我之前拖动标签：
标签拖动后：
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSeparator;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
/**
*
* @author David
*/
public class DragOverMultipleComponentsTest {
public DragOverMultipleComponentsTest() {
createAndShowUI();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new DragOverMultipleComponentsTest();
}
});
}
private void createAndShowUI() {
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel draggableLabel = new JLabel("<- Drag me");
JLabel draggableLabel2 = new JLabel("<- Drag me too");
JLabel labelPanel1 = new JLabel("Drag 'em here");
JPanel panel1 = new JPanel() {
@Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
};
panel1.add(labelPanel1);
panel1.setName("Droppable");
JLabel labelPanel2 = new JLabel("Drag 'em here");
JPanel panel2 = new JPanel();
panel2.add(labelPanel2);
panel2.add(draggableLabel);
panel2.add(draggableLabel2);
panel2.setName("Droppable");
JSeparator js = new JSeparator(JSeparator.VERTICAL);
ComponentDrag cd = new ComponentDrag(frame);
cd.registerComponent(draggableLabel);
cd.registerComponent(draggableLabel2);
frame.add(panel1, BorderLayout.WEST);
frame.add(js);
frame.add(panel2, BorderLayout.EAST);
frame.pack();
frame.setVisible(true);
}
}
class ComponentDrag {
private MouseAdapter ma;
private ArrayList<JComponent> components = new ArrayList<>();
private int startingX, startingY;
private boolean autoLayout = true;
private final JFrame container;
private JPanel glassPane;
boolean firstTime = true;
private JComponent lastClickedContainer;
public ComponentDrag(final JFrame container) {
this.container = container;
glassPane = new JPanel();
glassPane.setOpaque(false);
glassPane.setLayout(null);
this.container.setGlassPane(glassPane);
new Timer(10, new AbstractAction() {
@Override
public void actionPerformed(ActionEvent ae) {
if (container.isVisible()) {
glassPane.setVisible(true);
((Timer) ae.getSource()).stop();
}
}
}).start();
ma = new MouseAdapter() {
@Override
public void mousePressed(MouseEvent me) {
super.mousePressed(me);
componentPressed(me);
}
@Override
public void mouseReleased(MouseEvent me) {
super.mouseReleased(me);
componentDropped(me);
}
@Override
public void mouseDragged(MouseEvent me) {
super.mouseDragged(me);
componentDragged(me);
}
};
}
public JComponent findDroppableUnderGlassPane(Point p, Container container, Component source) {
JComponent c = null;
Component[] comps = container.getComponents();
for (Component com : comps) {
if (com.getName() != null) {
if (com.getName().equals("Droppable") && com instanceof JComponent) {
if (com.contains(SwingUtilities.convertPoint(source, p, com))) {
return (JComponent) com;
}
} else if (com instanceof Container) {
findDroppableUnderGlassPane(p, (Container) com, source);
}
}
}
return c;
}
public boolean isAutoLayout() {
return autoLayout;
}
public void setAutoLayout(boolean autoLayout) {
this.autoLayout = autoLayout;
}
protected void componentDropped(MouseEvent me) {
firstTime = true;
Component droppedComponent = (Component) me.getSource();
droppedComponent.setCursor(null);
JComponent jc = findDroppableUnderGlassPane(me.getPoint(), container.getContentPane(), (Component) me.getSource());
if (jc != null) {
glassPane.removeAll();
glassPane.revalidate();
glassPane.repaint();
jc.add(droppedComponent);
System.out.println("Removed from glasspane and added to: " + jc);
if (autoLayout) {
if (lastClickedContainer != null) {
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
}
droppedComponent.revalidate();
droppedComponent.repaint();
jc.revalidate();
jc.repaint();
}
} else {
glassPane.removeAll();
glassPane.revalidate();
glassPane.repaint();
if (lastClickedContainer != null) {
lastClickedContainer.add(droppedComponent);
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
}
}
}
protected void componentPressed(MouseEvent me) {
JComponent jc = findDroppableUnderGlassPane(me.getPoint(), container.getContentPane(), (Component) me.getSource());
if (jc != null && jc.getName().equals("Droppable")) {
lastClickedContainer = jc;
System.out.println("Pressed: " + lastClickedContainer);
}
boolean clickedRegisteredComponent = false;
Component clickedComponent = (Component) me.getSource();
for (Component component : ComponentDrag.this.components) {
if (component.equals(clickedComponent)) {
clickedRegisteredComponent = true;
break;
}
}
if (clickedRegisteredComponent) {
startingX = me.getX();
startingY = me.getY();
clickedComponent.setCursor(new Cursor(Cursor.MOVE_CURSOR));
}
}
protected void componentDragged(MouseEvent me) {
Component draggedComponent = (Component) me.getSource();
if (firstTime && lastClickedContainer != null) {
firstTime = false;
lastClickedContainer.remove(draggedComponent);
lastClickedContainer.revalidate();
lastClickedContainer.repaint();
glassPane.add(draggedComponent);
glassPane.revalidate();
glassPane.repaint();
System.out.println("Removed from: " + lastClickedContainer + " \nAnd added to glasspane for dragging");
}
//MouseEvent will refire on each drag with the position being relative to the firing Component
draggedComponent.setLocation((me.getX() - startingX) + draggedComponent.getLocation().x, (me.getY() - startingY) + draggedComponent.getLocation().y);
}
void registerComponent(JComponent draggableComp) {
draggableComp.addMouseListener(ma);
draggableComp.addMouseMotionListener(ma);
components.add(draggableComp);
}
void deregisterComponent(JComponent draggableComp) {
draggableComp.removeMouseListener(ma);
draggableComp.removeMouseMotionListener(ma);
components.remove(draggableComp);
}
}