[英]How to drag and draw line between 2 points in Java Swing
I would like to draw a line between two xy coordinate with mouse drag, but cannot get anything to draw 我想用鼠标拖动在两个xy坐标之间绘制一条线,但无法绘制任何内容
its a gui application using swing and awt, I currently have the mouse log the initial and final xy positions using mouse events which are stored in an array as [x1,y1,x2,y2]
, however, cannot get a line to draw between them. 它是一个使用swing和awt的gui应用程序,目前我使用鼠标事件将鼠标事件的初始和最终xy位置记录为[x1,y1,x2,y2]
,但是无法在两者之间绘制线条他们。
The drawline is its own function called into the main 画线是自己的函数,称为主函数
edit: say I have 2 classes; 编辑:说我有2节课;
public class mainApp extends JFrame implements ActionListener, Runnable {
private JPanel jpanel = new JPanel();
private mainApp(String title) throws HeadlessException {
super(title);
}
private void createGUI() {
// TODO
// ...
// cannot call unless is static
drawStraightLine.drawLine(jpanel);
this.pack();
setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e) {}
@Override
public void run() {createGUI();}
public static void main(String[] args) {
JFrame.setDefaultLookAndFeelDecorated(true);
SwingUtilities.invokeLater(new mainApp("drawline"));
}
}
public class drawStraightLine extends JPanel {
public static void drawLine(JPanel jpanel) {
// content which conceivably works
// mouselisteners and repaint()
public void paintComponent (Graphics g){
super.paintComponent(g);
if (check != null) {
Color purple = new Color(128, 0, 128);
g.setColor(purple);
g.drawLine(x1, y1, x2, y2);
}
}
}
i cannot call drawline(jpanel) unless it is a static function, but making it static causes the mouselisteners and repaint to become invalid. 我不能调用drawline(jpanel),除非它是一个静态函数,但是将其设为静态会导致mouselisteners和repaint变得无效。
while as long as Graphics g is inside a function and not directly in the class it will become an invalid symbol (ignoring check and xy values as placeholders) 只要Graphics g在函数内部而不是直接在类中,它将变为无效符号(忽略check和xy值作为占位符)
you don't need to have arrays or even X & Y.you can use the getPoint() method of mouseEvent. 您不需要数组甚至X&Y。您可以使用mouseEvent的getPoint()方法。 try this: 尝试这个:
public static void main(String args[]) throws Exception {
JFrame f = new JFrame("Draw a Line");
f.setSize(300, 300);
f.setLocation(300, 300);
f.setResizable(false);
JPanel p = new JPanel() {
Point pointStart = null;
Point pointEnd = null;
{
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
pointStart = e.getPoint();
}
public void mouseReleased(MouseEvent e) {
pointStart = null;
}
});
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseMoved(MouseEvent e) {
pointEnd = e.getPoint();
}
public void mouseDragged(MouseEvent e) {
pointEnd = e.getPoint();
repaint();
}
});
}
public void paint(Graphics g) {
super.paint(g);
if (pointStart != null) {
g.setColor("put your color here");
g.drawLine(pointStart.x, pointStart.y, pointEnd.x, pointEnd.y);
}
}
};
f.add(p);
f.setVisible(true);
}
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