MouseDragged 作品或 mouseMoved 作品，但不是两者兼而有之

Question

我目前正在执行一项任务。我必须在框架上显示一组与鼠标相关的坐标。我不允许使用 Swing 组件。当使用鼠标而不点击时，文本应该是红色的。单击并拖动鼠标后，文本应为黑色。在这两种情况下，文本都应该跟随鼠标。我可以让文本改变颜色，我可以让它显示适当的信息。当我尝试在 MouseMoved 和 MousedDragged 中设置标签的位置时，当我拖动时它无法识别。如果我为标签取出一个或另一个设置位置，另一个就可以了。我究竟做错了什么？我正在研究一个跑步者课程，我会包括它。主类只是实例化我的跑步者类的一个对象。

import java.awt.Button;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Panel;
import java.awt.TextField;
import java.awt.event.*;
import java.awt.Rectangle ; 
import java.awt.Label;
import java.awt.Color;
import java.awt.Toolkit;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;


class Proj06Runner extends Frame
{

  //Proj06Runner Constructor
  public Proj06Runner() {

System.out.println("Proj06");
System.out.println("I certify that this program is my own work and is not the work of others. ");
System.out.println("I agree not to share my solution with others.");
System.out.println("Eric Jackson.");

GUI gui = new GUI();//instantiate a GUI
  }}
//End Proj06Runner Class
//________________________________________________________________________


class GUI extends Frame {

  public GUI()//constructor
  {


Rectangle bounds = this.getBounds();

   //Create Frame 
    Frame displayWindow = new Frame("Eric Jackson");
//Set size of Frame
displayWindow.setSize(300,200);
displayWindow.setLayout(null); 
displayWindow.setLocation(30 + bounds.x, 30 + bounds.y);



//Create Top button
Button TopButton = new Button("This Button does nothing");
TopButton.setBounds(7+bounds.x,30+bounds.y,285,25);
displayWindow.add(TopButton);

//Create Left button
Button LeftButton = new Button("Button");
LeftButton.setBounds(7+bounds.x,54+bounds.y,50,122);
displayWindow.add(LeftButton);

//Create Textfield      
TextField myTextField=new TextField("This TextField does nothing");  
myTextField.setBounds(7+bounds.x,175+bounds.y,285,22);
displayWindow.add(myTextField);

//Create Label to display coord text
Label myLabel=new Label();
myLabel.setBounds(50,50,100,20);
myLabel.setForeground(Color.red);
myLabel.setText(" ");
displayWindow.add(myLabel);


displayWindow.addWindowListener( new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) 
{
  System.exit(0);
}
} );


displayWindow.addMouseMotionListener(new MyMouseMotionProcessor(myLabel));
displayWindow.addMouseListener(new MyMouseProcessor(myLabel));

displayWindow.setVisible(true);    
  }
    }
//End GUI Definition
    //=========================================================

//=========================================================
//This class recognizes mousePressed(). This method is
// used to determine the starting position of the mouse
// pointer.
class MyMouseProcessor extends MouseAdapter{

Label theLabel;
int MouseX, MouseY;
//Constructor
MyMouseProcessor( Label inLabel){
 //save references to the input objects
 theLabel = inLabel;
 }//end constructor

public void mousePressed(MouseEvent e){
}//end mousePressed()
 }//end MyMouseProcessor
     //=======================================================


 class MyMouseMotionProcessor extends MouseMotionAdapter{

Label theLabel;
int MouseX, MouseY;

//Constructor
MyMouseMotionProcessor(Label inLabel){
 //save incoming object reference
 theLabel = inLabel;
}// end constructor

public void mouseDragged(MouseEvent e){
System.out.println("Drag = " + e);
  MouseX= e.getX()-2;
  if (MouseX<0)
  {
   MouseX=0; 
  }
  MouseY= e.getY()-15;
  if (MouseY <0)
  {
    MouseY=0;
  }
 //move label to the new location

 theLabel.setLocation(MouseX,MouseY);

theLabel.setForeground(Color.black);
String coordtextClick = MouseX+" , " + MouseY;
 theLabel.setText(coordtextClick);

}//end mouseDragged()

public void mouseMoved(MouseEvent e){
  System.out.println("Move = " + e);
  theLabel.setForeground(Color.red);
  MouseX= e.getX()-2;
  if (MouseX<0)
  {
   MouseX=0; 
  }
  MouseY= e.getY()-4;
  if (MouseY <0)
  {
    MouseY=0;
  }
  String coordtext = MouseX+" , " + MouseY;
 theLabel.setLocation(MouseX,MouseY);
 theLabel.setText(coordtext);

}//



}//end class MyMouseMotionProcessor

Answer 1

mouseDragged 和mouseMoved 一起使用没有问题。他们工作得很好。问题在于您设置为theLabel 的位置。

问题： 问题是当您在mouseMoved 方法中设置theLabel 的位置时，theLabel 位于鼠标指针下方。因此，您无法创建应该在 displayWindow 组件上发生的 healthy mouseDrag 手势。换句话说，您的 mouseDrag 被应用于theLabel 本身而不是displayWindow，因为theLabel 位于displayWindow 顶部的鼠标指针下方。

我是怎么知道的？我只是用了一个老把戏！我刚刚将背景颜色设置为theLabel：

myLabel.setBackground(Color.lightGray);

这帮助我查看了myLabel 的位置，从而解决了问题！

解决方案： 解决方案是为theLabel 设置一个位置，该位置不在鼠标指针下方。这将有助于从鼠标位置启动健康的 mouseDrag。像这样的：

public void mouseDragged(MouseEvent e) {
    System.out.println("Drag = " + e);
    MouseX = e.getX() + 5; // <- note here
    if (MouseX < 0) {
        MouseX = 0;
    }
    MouseY = e.getY() - 15; // <- note here
    if (MouseY < 0) {
        MouseY = 0;
    }
    // move label to the new location

    theLabel.setLocation(MouseX, MouseY);

    theLabel.setForeground(Color.black);
    String coordtextClick = MouseX + " , " + MouseY;
    theLabel.setText(coordtextClick);
}// end mouseDragged()

public void mouseMoved(MouseEvent e) {
    System.out.println("Move = " + e);
    theLabel.setForeground(Color.red);
    MouseX = e.getX() + 5; // <- note here
    if (MouseX < 0) {
        MouseX = 0;
    }
    MouseY = e.getY() - 15; // <- note here
    if (MouseY < 0) {
        MouseY = 0;
    }
    String coordtext = MouseX + " , " + MouseY;
    theLabel.setLocation(MouseX, MouseY);
    theLabel.setText(coordtext);
}//

希望这会有所帮助！