标签：swing mouseevent java
我希望程序能够正常工作,以便在面板上拖动鼠标时,形状应该显示出来.每次拖动鼠标时,形状都应该改变大小,最后应该显示的形状就是所显示的形状此刻释放了鼠标.
当前发生的情况是,用鼠标拖动绘制时该线不可见,仅在释放鼠标时才会显示
//DrawPanel
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JFrame;
public class DrawLine extends JPanel
{
private LineClass lines[];
private int lineCount;
private LineClass currentLine;
public JLabel statusLabel;
private int currShapeX1,currShapeY1;
public DrawLine()
{
statusLabel = new JLabel("(0,0)");
lines = new LineClass[100];
lineCount = 0;
currentLine = null;
MouseHandler handler = new MouseHandler();
addMouseListener(handler);
addMouseMotionListener(handler);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
for(int count = 0; count < lineCount; ++count)
{
lines[count].draw(g);
}
}
public static void main(String args[])
{
JFrame frame = new JFrame();
DrawLine panel = new DrawLine();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
frame.setSize(400,400);
frame.setVisible(true);
}
private class MouseHandler extends MouseAdapter implements MouseMotionListener
{
public void mousePressed(MouseEvent event)
{
//it assigns currentShape a new shape and initializes both points to the mouse position.
currShapeX1 = event.getX();
currShapeY1 = event.getY();
}
public void mouseReleased(MouseEvent event)
{
//finish drawing the current shape and place it in the array
//Set the second point of currentShape to the current mouse position
currentLine = new LineClass(currShapeX1,currShapeY1,event.getX(),event.getY());
// and add currentShape to the array.
//Instance variable shapeCount determines the insertion index. Set currentShape to null and call method repaint to update the drawing with the new shape.
lines[lineCount] = currentLine;
lineCount++;
currentLine = null;
repaint();
}
public void mouseDragged(MouseEvent event)
{
//currently not working
/*What is desired:
* As you drag the mouse across the panel, the shape should be showing
* The shape should change in size each time you drag the mouse
* Only one shape should be shown as the mouse is being dragged
* The shape that should be displayed finally is that which was being displayed at the moment the mouse was released
* */
//it sets the second point of the currentShape to the current mouse position and calls method repaint
//finish drawing the current shape and place it in the array
//Set the second point of currentShape to the current mouse position
currentLine = new LineClass(currShapeX1,currShapeY1,event.getX(),event.getY());
// and add currentShape to the array.
//Instance variable shapeCount determines the insertion index. Set currentShape to null and call method repaint to update the drawing with the new shape.
lines[lineCount] = currentLine;
currentLine = null;
repaint();
statusLabel.setText(String.format("(%d,%d)",event.getX(),event.getY()));
}
public void mouseMoved(MouseEvent event)
{
//to set the text of the statusLabel so that it displays the mouse coordinates—this will update the label with the coordinates every time the user moves
//(but does not drag) the mouse within the DrawPanel
statusLabel.setText(String.format("(%d,%d)",event.getX(),event.getY()));
}
}
}
//LineClass
class LineClass
{
private int x1;
private int y1;
private int x2;
private int y2;
public LineClass(int x1, int y1, int x2, int y2)
{
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
}
public void draw(Graphics g)
{
g.drawLine(x1,y1,x2,y2);
}
}
解决方法:
您的问题似乎是您没有绘制要拖动的最后一行.
在mouseDragged()中,您可以这样：
currentLine = new LineClass(currShapeX1,currShapeY1,event.getX(),event.getY());
lines[lineCount] = currentLine;
currentLine = null;
这会将索引为lineCount的行设置为新行.
然后在渲染时执行以下操作：
for(int count = 0; count < lineCount; ++count)
{
lines[count].draw(g);
}
您正在绘制除索引lineCount中的那条线以外的所有线.
在mouseReleased()中,您可以得到lineCount；这就是释放鼠标后该行显示的原因.
为了解决这个问题,我不会在拖动时将当前拖动的线添加到行中.而是只需在mouseDragged中对其进行更新.然后在mouseReleased中将其添加到数组,并将currentLine设置为null.
因此绘画将如下所示：
for(int count = 0; count < lineCount; ++count) {
lines[count].draw(g);
}
if( currentLine != null ) {
//you could set different rendering options here, e.g. a different color
currentLine.draw(g);
}
最后,代替使用数组,最好使用List< LineClass>.这样,您不必跟踪当前的行数,不必限于100行,也不必自己调整数组的大小.
由于列表将仅包含非空行,因此渲染可能如下所示：
lines.forEach( line -> line.draw(g) );
if( currentLine != null ) {
currentLine.draw(g);
}
标签：swing,mouseevent,java 来源： https://codeday.me/bug/20191211/2105505.html
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