使组件对 Swing 中的拖动不那么敏感

Posted 2023-05-08

【中文标题】使组件对 Swing 中的拖动不那么敏感

【英文标题】：Making a component less sensitive to Dragging in Swing

【发布时间】：2010-10-06 01:17:32

【问题描述】：

我的一个JComponent 过于激烈地触发了一个mouseDragged 事件。当用户试图点击时，即使鼠标只移动了 1 个像素，它也会将其解释为拖动。

如何为特定组件添加一条规则，相当于：

不要将其视为拖动事件，除非 鼠标移动了 10 个像素 被按下的点。

注意：我知道这不是我操作系统中的系统设置，因为只有该组件上的事件才会受到这种过度敏感的影响。

谢谢。

【参考方案1】：

以前的答案结合在一起，并带有适当的事件类型：

public class DragInsensitiveMouseClickListener implements MouseInputListener 

    protected static final int MAX_CLICK_DISTANCE = 15;

    private final MouseInputListener target;

    public MouseEvent pressed;

    public DragInsensitiveMouseClickListener(MouseInputListener target) 
        this.target = target;
    

    @Override
    public final void mousePressed(MouseEvent e) 
        pressed = e;
        target.mousePressed(e);
    

    private int getDragDistance(MouseEvent e) 
        int distance = 0;
        distance += Math.abs(pressed.getXOnScreen() - e.getXOnScreen());
        distance += Math.abs(pressed.getYOnScreen() - e.getYOnScreen());
        return distance;
    

    @Override
    public final void mouseReleased(MouseEvent e) 
        target.mouseReleased(e);

        if (pressed != null) 
            if (getDragDistance(e) < MAX_CLICK_DISTANCE) 
                MouseEvent clickEvent = new MouseEvent((Component) pressed.getSource(),
                        MouseEvent.MOUSE_CLICKED, e.getWhen(), pressed.getModifiers(),
                        pressed.getX(), pressed.getY(), pressed.getXOnScreen(), pressed.getYOnScreen(),
                        pressed.getClickCount(), pressed.isPopupTrigger(), pressed.getButton());
                target.mouseClicked(clickEvent);
            
            pressed = null;
        
    

    @Override
    public void mouseClicked(MouseEvent e) 
        //do nothing, handled by pressed/released handlers
    

    @Override
    public void mouseEntered(MouseEvent e) 
        target.mouseEntered(e);
    

    @Override
    public void mouseExited(MouseEvent e) 
        target.mouseExited(e);
    

    @Override
    public void mouseDragged(MouseEvent e) 
        if (pressed != null) 
            if (getDragDistance(e) < MAX_CLICK_DISTANCE) return; //do not trigger drag yet (distance is in "click" perimeter
            pressed = null;
        
        target.mouseDragged(e);
    

    @Override
    public void mouseMoved(MouseEvent e) 
        target.mouseMoved(e);
    

【参考方案2】：

我以前必须这样做。这是我的鼠标事件处理代码，减少到仅与使拖动相关的位在被视为拖动之前需要几个像素。

public void mousePressed(int mod, Point loc) 
    pressLocation=copyLocation(loc,pressLocation);
    dragLocation=null;
    

public void mouseReleased(int mod, Point loc) 
    if(pressLocation!=null && dragLocation!=null) 
        // Mouse drag reverted to mouse click - not dragged far enough
        // action for click
        pressLocation=null;
        
    else if(dragLocation!=null) 
        // action for drag completed
        
    else 
        // do nothing
        

    pressLocation=null;
    dragLocation=null;
    

public void mouseDragged(int mod, Point loc) 
    if(pressLocation!=null)                                                    // initial drag actions following mouse press
        dragLocation=pressLocation;                                             // consider dragging to be from start point
        if(Math.abs(loc.x-pressLocation.x)<dragMinimum && Math.abs(loc.y-pressLocation.y)<dragMinimum) 
            return;                                                             // not dragged far enough to count as drag (yet)
            
        // action drag from press location
        pressLocation=null;
        
    else 
        // action drag from last drag location
        dragLocation=copyLocation(loc,dragLocation);
        
    

请注意，我还遇到了 Java 一些 JVM 在拖动后生成点击事件的问题，我必须检测并抑制它。

【参考方案3】：

如果我正确阅读了您的问题，那么您正在跟踪单击和鼠标拖动事件。您可以在 mousedown 时跟踪坐标，然后在 mousedrag 中进行简短计算以查看鼠标是否已移动所需的最小像素数？当然，您还想在 mouseup 或鼠标被拖动到 JComponent 边界之外时取消/重置。

警告：我自己没有这样做，但我认为如果是我，我会从这里开始。

【参考方案4】：

Software Monkey 的代码好像少了一些代码，所以我写了这个解决方案：

navigationTree.addMouseListener(new DragInsensitiveMouseClickListener(10) 
    @Override
    public void mouseClicked(MouseEvent e) 
        TreePath treePath = navigationTree.getPathForLocation(e.getX(), e.getY());

        if(treePath != null) 
            processChoice();
        
    
);

当用户产生最多 10 个像素的“拖动行程”时，这仍会触发 mouseClicked() 事件。

点击监听的代码：

import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class DragInsensitiveMouseClickListener extends MouseAdapter 

    private final int allowedTravel;

    public Point mouseDownPoint;

    public DragInsensitiveMouseClickListener(int allowedTravel) 
        this.allowedTravel = allowedTravel;
    

    @Override
    public void mousePressed(MouseEvent e) 
        mouseDownPoint = e.getPoint();
    

    @Override
    public void mouseReleased(MouseEvent e) 
        double horizontalTravel = Math.abs(mouseDownPoint.getX() - e.getX());
        double verticalTravel = Math.abs(mouseDownPoint.getY() - e.getY());

        if (horizontalTravel < allowedTravel && verticalTravel < allowedTravel) 
            mouseClicked(e);