Question

所以我有一个由二维数组内容填充的JPanel。我有一个鼠标监听器，可以在按下时更改单元格的颜色。我的问题是，是否有可能让用户将鼠标拖过一行单元格并连续着色它们？我已经研究过鼠标运动监听器，但这似乎没什么帮助。

有什么想法吗？

Answer 1

您可以将mouseDragged()的{{1}}方法与MouseMotionListener的{{1}}方法结合使用。

mousePressed()方法将处理一个没有移动的简单点击，MouseListener将处理任何拖动。我将我为原始问题here的答案编写的代码结合起来，以便更好地阐明所有内容的作用，并且非常感谢您对其他问题的回复。

mousePressed()

Answer 2

如果扩展JPanel，则不需要鼠标侦听器。只需启用鼠标事件，然后覆盖组件的鼠标事件处理程序。一般逻辑是：

if mouse pressed {
    dragging = true 
    begin drag
}

if mouse dragged and dragging == true {
    process drag
}

if mouse released and dragging == true {
    dragging = false
    finalize drag
}

以下是一个例子：

import java.awt.AWTEvent;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class DragTest {

    // example JPanel. click and drag on it to create lines.
    static class DragPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        static class Line {
            int x1, y1, x2, y2;
        }

        private final List<Line> lines = new ArrayList<Line>();
        private Line draggedLine; // null if not dragging

        public DragPanel() {

            // enable mouse event processing even if no listeners are registered
            enableEvents(AWTEvent.MOUSE_EVENT_MASK | AWTEvent.MOUSE_MOTION_EVENT_MASK);

        }

        @Override
        public void paintComponent(Graphics g) {

            super.paintComponent(g);
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, getWidth(), getHeight());
            // draw saved lines
            g.setColor(Color.WHITE);
            for (Line line : lines)
                g.drawLine(line.x1, line.y1, line.x2, line.y2);
            // draw currently active line if there is one
            if (draggedLine != null) {
                g.setColor(Color.RED);
                g.drawLine(draggedLine.x1, draggedLine.y1, draggedLine.x2, draggedLine.y2);
            }

        }

        // does the work; since motion and press/release are all MouseEvent,
        // we can just direct MouseEvents here from the event handler overrides
        // and handle based on event ID.
        private void handleMouseEvent(MouseEvent e) {

            if (e.getID() == MouseEvent.MOUSE_PRESSED && e.getButton() == MouseEvent.BUTTON1) {
                // begin drag by initializing a new Line at mouse position
                if (draggedLine == null) {
                    draggedLine = new Line();
                    draggedLine.x1 = draggedLine.x2 = e.getX();
                    draggedLine.y1 = draggedLine.y2 = e.getY();
                    e.consume();
                }
            } else if (e.getID() == MouseEvent.MOUSE_DRAGGED) {
                // if drag in progress, update line endpoint
                if (draggedLine != null) {
                    draggedLine.x2 = e.getX();
                    draggedLine.y2 = e.getY();
                    e.consume();
                }
            } else if (e.getID() == MouseEvent.MOUSE_RELEASED && e.getButton() == MouseEvent.BUTTON1) {
                // if drag in progress, accept new line and end drag
                if (draggedLine != null) {
                    draggedLine.x2 = e.getX();
                    draggedLine.y2 = e.getY();
                    lines.add(draggedLine);
                    draggedLine = null;
                    e.consume();
                }
            }

            if (e.isConsumed())
                repaint();

        }

        @Override
        public void processMouseMotionEvent(MouseEvent e) {
            handleMouseEvent(e); // pass to our handler, may consume event
            super.processMouseMotionEvent(e); // in case there are registered listeners
        }

        @Override
        public void processMouseEvent(MouseEvent e) {
            handleMouseEvent(e); // pass to our handler, may consume event
            super.processMouseEvent(e); // in case there are registered listeners
        }

    }

    public static final void main(String[] args) {

        JFrame frame = new JFrame("Panel Drag Example");
        frame.getContentPane().add(new DragPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(640, 480);
        frame.setVisible(true);

    }

}

扩展JPanel通常比添加内联类的侦听器更好，因为它为您提供了一个完全独立的可重用组件。

Java：在按住鼠标时填充基于2D数组的图形

2 个答案: