[英]Getting Unexpected output with the swing code
我正在嘗試構建一個簡單的應用程序,該應用程序具有半透明的框架並在用戶想要的位置繪制線條。我還添加了偵聽器以捕獲鼠標事件並相應地顯示這些事件。一切正常,但問題是:1)窗口不透明2)它是完全黑色的,線條顯示為白色。
任何人都可以在這里的代碼:
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class MouseListen2 extends JFrame implements MouseListener {
String str = "Nothing";
int x[][] = new int[100][2];
int count = 0;
int flag = 1;
boolean draw = false;
MouseListen2() {
super("Line Draw App");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 300);
this.addMouseListener(this);
setBackground(new Color(0, 0, 0, 0));
JPanel jp = new JPanel() {
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
Paint gp = new GradientPaint(300, 700, new Color(20, 20, 210, 0), 100, 00, new Color(10, 20, 40, 255));
g2.setPaint(gp);
g2.fillRect(0, 0, getWidth(), getHeight());
}
};
setContentPane(jp);
setVisible(true);
//c.setOpaque(true);
}
public void paint(Graphics g) {
//Graphics g=this.getGraphics();
//super.paint(g);
Graphics2D g2 = (Graphics2D) g;
g2.clearRect(0, 0, getWidth(), getHeight());
g2.drawString(str, 50, 50);
//initially count=0 hence i<-1 so loop will not automatically run in the beginning
for (int i = 0; i < count - 1; i = i + 2) {
g2.drawLine(x[i][0], x[i][1], x[i + 1][0], x[i + 1][1]);
}
//repaint(); using this here creates an infinite loop as after mouse event paint is called and at the end
//this method is again called using the repaint() and so on the loop continues.
}
public static void main(String[] args) {
JFrame.setDefaultLookAndFeelDecorated(true);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new MouseListen2();
}
});
}
@Override
public void mouseClicked(MouseEvent e) {
str = "clicked";
repaint();
}
@Override
public void mousePressed(MouseEvent e) {
str = "pressed";
repaint();
x[count][0] = e.getX();
x[count][1] = e.getY();
count++;
}
@Override
public void mouseReleased(MouseEvent e) {
str = "released";
draw = true;
x[count][0] = e.getX();
x[count][1] = e.getY();
count++;
//draw();
repaint();
}
@Override
public void mouseEntered(MouseEvent e) {
str = "entered";
repaint();
}
@Override
public void mouseExited(MouseEvent e) {
str = "exited";
repaint();
}
}
必須將MouseListener
添加到JPanel
,因為您已將MouseListener
添加到JFrame
( this.addMouseListener(this);
)
此代碼行setContentPane(jp);
將JPanel
放到JFrame
的BorderLayout.CENTER
位置,在這種情況下(沒有向JFrame
添加任何其他JComponent
)將整個/所有可用空間填充到JFrame
那么對於mouse event
,只有JPanel
才可以訪問,鼠標無法訪問JFrame
的RootPane
或ContentPane
刪除/注釋public void paint(Graphics g)
,並將相關的代碼塊移至JPanel
的paintComponent
請參閱如何創建半透明和成形的Windows 。
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