[英]Creating “paint” application in Java
我有一个数组列表,可以跟踪“点”,并且正在使用数组来跟踪不同的大小。 通过mouseWheelListener更改大小,并将更改保存在该数组中。 但是由于某种原因,所有的点都被调整了尺寸,这不是我想要的。 经过几次运行后,一切看起来都应该正常工作,但是我必须缺少一些简单的东西。 我的代码如下。
//********************************************************************
// DotsPanel.java
// Represents the primary panel for the Dots program.
//********************************************************************
import java.util.ArrayList;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.*;
public class DotsPanel extends JPanel
{
private int SIZE = 10; // radius of each dot
private int[] dotSizes = new int[10000];
int i = 0;
private ArrayList<Point> pointList;
//-----------------------------------------------------------------
// Constructor: Sets up this panel to listen for mouse events.
//-----------------------------------------------------------------
public DotsPanel()
{
pointList = new ArrayList<Point>();
addMouseListener (new DotsListener());
addMouseMotionListener(new DotsListener());
addMouseWheelListener(new DotsListener());
setBackground(Color.red);
setPreferredSize(new Dimension(300, 200));
}
//-----------------------------------------------------------------
// Draws all of the dots stored in the list.
//-----------------------------------------------------------------
public void paintComponent(Graphics page)
{
super.paintComponent(page);
page.setColor(Color.cyan);
for (Point spot : pointList)
//change size to sizes[n]
page.fillOval(spot.x-dotSizes[pointList.size()-1], spot.y-dotSizes[pointList.size()-1], dotSizes[pointList.size()-1]*2, dotSizes[pointList.size()-1]*2);
page.drawString("Count: " + pointList.size(), 5, 15);
}
//*****************************************************************
// Represents the listener for mouse events.
//*****************************************************************
private class DotsListener implements MouseListener, MouseMotionListener, MouseWheelListener
{
//--------------------------------------------------------------
// Adds the current point to the list of points and redraws
// the panel whenever the mouse button is pressed.
//--------------------------------------------------------------
public void mousePressed(MouseEvent event)
{
pointList.add(event.getPoint());
repaint();
}
//--------------------------------------------------------------
// Provide empty definitions for unused event methods.
//--------------------------------------------------------------
public void mouseClicked(MouseEvent event) {}
public void mouseReleased(MouseEvent event) {}
public void mouseEntered(MouseEvent event) {}
public void mouseExited(MouseEvent event) {}
@Override
public void mouseDragged(MouseEvent event)
{
pointList.add(event.getPoint());
dotSizes[pointList.size()-1] = SIZE;
//store size of dot here
repaint();
}
@Override
public void mouseMoved(MouseEvent event) {}
@Override
public void mouseWheelMoved(MouseWheelEvent event)
{
SIZE -= event.getWheelRotation();
repaint();
}
}
}
在此代码中:
for (Point spot : pointList)
//change size to sizes[n]
page.fillOval(spot.x-dotSizes[pointList.size()-1], spot.y-dotSizes[pointList.size()-1], dotSizes[pointList.size()-1]*2, dotSizes[pointList.size()-1]*2);
您对所有点都使用单个点大小:最后添加的点的大小。 (甚至还有一个评论有没有解决这个问题!)你需要一个索引来迭代,所以你可以索引到dotSizes
阵列还有pointList
ArrayList
:
for (int i = 0; i < pointList.size(); ++i) {
Point spot = pointList.get(i);
int size = dotSizes[i];
page.fillOval(spot.x-size, spot.y-size, size*2, size*2);
}
定义您自己的“具有大小的点”类来封装Point
和size
会更好:
class Spot extends Point {
public int size;
public Spot(int x, int y, int size) {
super(x, y);
this.size = size;
}
}
然后将pointList
更改为ArrayList<Spot>
然后可以返回遍历单个列表:
for (Spot spot : pointList)
page.fillOval(spot.x-spot.size, spot.y-spot.size, 2*dot.size, 2*dot.size);
当然,您还必须更新将点添加到列表的代码。
mousePressed
说mousePressed
,在我看来,您的mousePressed
处理程序存在一个错误:添加点时,它不会添加大小。 切换到Spot
类也将有助于避免此类问题。
for (Point spot : pointList)
//change size to sizes[n]
page.fillOval(spot.x-dotSizes[pointList.size()-1], spot.y-dotSizes[pointList.size()-1], dotSizes[pointList.size()-1]*2, dotSizes[pointList.size()-1]*2);
这是你的问题。 您没有将大小更改为size [n],而是将每个大小更改为size [pointList.size()-1],也就是最后一个。 除非您要查找当前点的索引,否则可能必须使用常规的for循环。
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