我正在为我正在制作的游戏制作地图编辑器。JScroll窗格中有一个 JPanel，用于显示要编辑的地图。我想做的是，当用户按住空格键并在 JPanel 中拖动鼠标时，JScrollPanel 将随着拖动一起滚动。这是我到目前为止所拥有的：
panelMapPanel.addMouseMotionListener(new MouseMotionListener(){
@Override
public void mouseDragged(MouseEvent e) {
//Gets difference in distance x and y from last time this listener was called
int deltaX = mouseX - e.getX();
int deltaY = mouseY - e.getY();
mouseX = e.getX();
mouseY = e.getY();
if(spacePressed){
//Scroll the scrollpane according to the distance travelled
scrollPane.getVerticalScrollBar().setValue(scrollPane.getVerticalScrollBar().getValue() + deltaY);
scrollPane.getHorizontalScrollBar().setValue(scrollPane.getHorizontalScrollBar().getValue() + deltaX);
}
}
});
目前它可以工作，但滚动根本不流畅。一次移动鼠标很多是可以的，但做小的拖动会使滚动窗格变得疯狂。
有什么想法可以改善这一点吗？
对于那些喜欢视觉帮助的人，这里是编辑器：
补充说明（编辑）：
x deltaX， scrollPane.getViewport（）.getViewPosition（）.y deltaY））;
好吧，那最终比我简单得多，尽管它会......
首先，不要弄乱 JViewport，而是直接在充当 JScrollPane 内容的组件上使用 JComponent#scrollRectToVisible，MouseListener 应该附加到该组件上。
下面的示例只是计算用户单击的点与他们拖动的量之间的差值。然后，它将此增量应用于 JViewport 的 viewRect，并使用 JComponent#scrollRectToVisible 来更新可视区域，简单:)
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 TestPane extends JPanel {
private JLabel map;
public TestPane() {
setLayout(new BorderLayout());
try {
map = new JLabel(new ImageIcon(ImageIO.read(new File("c:/treasuremap.jpg"))));
map.setAutoscrolls(true);
add(new JScrollPane(map));
MouseAdapter ma = new MouseAdapter() {
private Point origin;
@Override
public void mousePressed(MouseEvent e) {
origin = new Point(e.getPoint());
}
@Override
public void mouseReleased(MouseEvent e) {
}
@Override
public void mouseDragged(MouseEvent e) {
if (origin != null) {
JViewport viewPort = (JViewport) SwingUtilities.getAncestorOfClass(JViewport.class, map);
if (viewPort != null) {
int deltaX = origin.x - e.getX();
int deltaY = origin.y - e.getY();
Rectangle view = viewPort.getViewRect();
view.x += deltaX;
view.y += deltaY;
map.scrollRectToVisible(view);
}
}
}
};
map.addMouseListener(ma);
map.addMouseMotionListener(ma);
} catch (IOException ex) {
ex.printStackTrace();
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
}
我发现这个（非常常见的）要求出奇地难以解决。这是我们在生产中可能已经超过10年的稳定解决方案。
接受的答案似乎非常诱人，但一旦你开始使用它就会出现可用性故障（例如，尝试立即拖动到右下角然后向后拖动，你应该注意到在向后移动的过程中，长时间没有移动发生）。
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Point;
import java.awt.event.MouseEvent;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.border.MatteBorder;
import javax.swing.event.MouseInputAdapter;
public class Mover extends MouseInputAdapter {
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(200, 160);
f.setLocationRelativeTo(null);
f.setLayout(new BorderLayout());
JScrollPane scrollPane = new JScrollPane();
f.add(scrollPane, BorderLayout.CENTER);
JPanel view = new JPanel();
view.add(new JLabel("Some text"));
view.setBorder(new MatteBorder(5, 5, 5, 5, Color.BLUE));
view.setBackground(Color.WHITE);
view.setPreferredSize(new Dimension(230, 200));
new Mover(view);
scrollPane.setViewportView(view);
f.setVisible(true);
}
private JComponent m_view = null;
private Point m_holdPointOnView = null;
public Mover(JComponent view) {
m_view = view;
m_view.addMouseListener(this);
m_view.addMouseMotionListener(this);
}
@Override
public void mousePressed(MouseEvent e) {
m_view.setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR));
m_holdPointOnView = e.getPoint();
}
@Override
public void mouseReleased(MouseEvent e) {
m_view.setCursor(null);
}
@Override
public void mouseDragged(MouseEvent e) {
Point dragEventPoint = e.getPoint();
JViewport viewport = (JViewport) m_view.getParent();
Point viewPos = viewport.getViewPosition();
int maxViewPosX = m_view.getWidth() - viewport.getWidth();
int maxViewPosY = m_view.getHeight() - viewport.getHeight();
if(m_view.getWidth() > viewport.getWidth()) {
viewPos.x -= dragEventPoint.x - m_holdPointOnView.x;
if(viewPos.x < 0) {
viewPos.x = 0;
m_holdPointOnView.x = dragEventPoint.x;
}
if(viewPos.x > maxViewPosX) {
viewPos.x = maxViewPosX;
m_holdPointOnView.x = dragEventPoint.x;
}
}
if(m_view.getHeight() > viewport.getHeight()) {
viewPos.y -= dragEventPoint.y - m_holdPointOnView.y;
if(viewPos.y < 0) {
viewPos.y = 0;
m_holdPointOnView.y = dragEventPoint.y;
}
if(viewPos.y > maxViewPosY) {
viewPos.y = maxViewPosY;
m_holdPointOnView.y = dragEventPoint.y;
}
}
viewport.setViewPosition(viewPos);
}
}
我目前正在自己开发地图编辑器。我已经让鼠标滚动在我的手机上顺利工作，尽管这是一个非常冗长的解决方案。
我编写了两个自定义AWTEventListeners，一个用于鼠标事件，另一个用于鼠标移动事件。我这样做是因为我的地图是一个自定义的 JComponent，因此不会填充整个视口。这意味着，如果光标位于组件上，则不会检测到滚动窗格鼠标事件。
对我来说，这工作非常顺利，内容与鼠标光标完美地同步滚动。
（我应该提到我使用鼠标滚轮单击而不是空格键，但它很容易更改）。
Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {
public void eventDispatched(AWTEvent event) {
if(event instanceof MouseEvent){
MouseEvent e = (MouseEvent)event;
//Begin a scroll if mouse is clicked on our pane
if(isMouseInMapPane()){
if(e.getID() == MouseEvent.MOUSE_PRESSED){
if(e.getButton() == MouseEvent.BUTTON2){
mouseWheelDown = true;
currentX = MouseInfo.getPointerInfo().getLocation().x;
currentY = MouseInfo.getPointerInfo().getLocation().y;
}
}
}
//Stop the scroll if mouse is released ANYWHERE
if(e.getID() == MouseEvent.MOUSE_RELEASED){
if(e.getButton() == MouseEvent.BUTTON2){
mouseWheelDown = false;
}
}
}
}
}, AWTEvent.MOUSE_EVENT_MASK);
Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {
public void eventDispatched(AWTEvent event) {
if(event instanceof MouseEvent){
MouseEvent e = (MouseEvent)event;
//Update the scroll based on delta drag value
if(e.getID() == MouseEvent.MOUSE_DRAGGED){
if(mouseWheelDown){
int newX = MouseInfo.getPointerInfo().getLocation().x;
int newY = MouseInfo.getPointerInfo().getLocation().y;
int scrollStepX = (currentX - newX);
int scrollStepY = (currentY - newY);
currentX = newX;
currentY = newY;
//mapScroll is the reference to JScrollPane
int originalValX = mapScroll.getHorizontalScrollBar().getValue();
mapScroll.getHorizontalScrollBar().setValue(originalValX + scrollStepX);
int originalValY = mapScroll.getVerticalScrollBar().getValue();
mapScroll.getVerticalScrollBar().setValue(originalValY + scrollStepY);
}
}
}
}
}, AWTEvent.MOUSE_MOTION_EVENT_MASK);
这是 isMouseInPane 方法：
private boolean isMouseInMapPane(){
//Note: mapPane does not need to be your scroll pane.
//it can be an encapsulating container as long as it is in
//the same position and the same width/height as your scrollPane.
//For me I used the JPanel containing my scroll pane.
Rectangle paneBounds = mapPane.getBounds();
paneBounds.setLocation(mapPane.getLocationOnScreen());
boolean inside = paneBounds.contains(MouseInfo.getPointerInfo().getLocation());
return inside;
}
此代码可以放置在您有权访问滚动窗格引用的任何位置，也可以创建自定义滚动窗格类并将其添加到其中。
我希望它有所帮助！
