Question

我正在做一个程序，它创建一个包含50个数字的数组，然后在面板中将它们绘制为矩形，大小基于数字。单击面板时，将对数组进行排序，并重新绘制面板以显示正在排序的数字的动画类型。这是在点击面板之前和之后应该看起来的样子： picture http://oi47.tinypic.com/o57scm.jpg

以下是我的代码：

public class AnimatedSelectionSortPanel extends javax.swing.JPanel {

int[] numbers = new int[50];
int min = 20;
int max = 100;

private void loadArray() {
    int num;
    for (int i = 0; i < numbers.length; i++) {
        numbers[i] = min + (int) Math.random() * ((max - min) + 1);
    }
}

public static void selectionSort(int[] x) {
    for (int i = 0; i < x.length - 1; i++) {
        int minIndex = i;      // Index of smallest remaining value.
        for (int j = i + 1; j < x.length; j++) {
            if (x[minIndex] > x[j]) {
                minIndex = j;  // Remember index of new minimum
            }
        }
        if (minIndex != i) {
            //...  Exchange current element with smallest remaining.
            int temp = x[i];
            x[i] = x[minIndex];
            x[minIndex] = temp;
        }
    }
}

private void drawPass(Graphics g) {
    int xPos = 10;
    int yPos = 120;
    int rectWidth = 1;

    for (int num : numbers) {
        g.setColor(Color.black);
        g.drawRect(xPos, yPos, rectWidth, num);
        xPos += 11;
    }
}

@Override
public void paintComponent (Graphics g) {
    while (numbers.length == 0) {
        loadArray();
    }
    drawPass(g);
}

private void sortPanelMouseClicked(java.awt.event.MouseEvent evt) {
    selectionSort(numbers);
    sortPanel.repaint();
}

我遇到的问题是当我点击面板时框架中没有任何东西被涂上。有人能告诉我我正在做的事情有什么问题吗？

以下是GUI构建器中自动生成的代码，如果有帮助的话：

    private void initComponents() {

    sortPanel = new javax.swing.JPanel();

    sortPanel.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));
    sortPanel.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseClicked(java.awt.event.MouseEvent evt) {
            sortPanelMouseClicked(evt);
        }
    });

    javax.swing.GroupLayout sortPanelLayout = new javax.swing.GroupLayout(sortPanel);
    sortPanel.setLayout(sortPanelLayout);
    sortPanelLayout.setHorizontalGroup(
        sortPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 398, Short.MAX_VALUE)
    );
    sortPanelLayout.setVerticalGroup(
        sortPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 165, Short.MAX_VALUE)
    );

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(sortPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addComponent(sortPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
}// </editor-fold>

Answer 1

以下是一些建议：

请发布可编辑的示例 - SSCCE
不要在paintComponent中加入太多逻辑，也不要在此方法中分配数据。它的目的是绘画。提前准备好一系列数字。
min + (int) Math.random() * ((max - min) + 1);始终为20，因为(int) Math.random()始终为零。您应该投射结果，即：min + (int) (Math.random() * ((max - min) + 1));
将排序过程包装到线程或计时器中。在迭代之间等待并调用repaint()来绘制中间结果。包装到Swing计时器更清晰，更可取，但在发布的代码中，将selectionSort的整个逻辑转储到线程中可能更容易/更快。有关示例，请参阅Performing Custom Painting教程。另请参阅How to Use Swing Timers。
看起来drawPass上下颠倒了矩形。

以下是使用现有代码进行最小更改的示例：

enter image description here

import java.awt.*;
import java.awt.event.*;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class AnimatedSelectionSortPanel extends javax.swing.JPanel {

    public static void main(String[] args){
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new AnimatedSelectionSortPanel());
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationByPlatform(true);
                frame.setVisible(true);
            }
        });
    }


    private int[] numbers = new int[50];
    private int min = 20;
    private int max = 100;
    private boolean shuffle = false;
    public static final int ITERATION_SLEEP = 100;

    public AnimatedSelectionSortPanel() {
        loadArray();
        addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent e) {
                if (shuffle)
                    loadArray();
                selectionSort(numbers);
                shuffle = true;
            }
        });
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(300, 100);
    }

    private void loadArray() {
        for (int i = 0; i < numbers.length; i++) {
            numbers[i] = min + (int) (Math.random() * ((max - min) + 1));
        }
    }

    public void selectionSort(final int[] x) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                    for (int i = 0; i < x.length - 1; i++) {
                    int minIndex = i; // Index of smallest remaining value.
                    for (int j = i + 1; j < x.length; j++) {
                        if (x[minIndex] > x[j]) {
                            minIndex = j; // Remember index of new minimum
                        }
                    }
                    if (minIndex != i) {
                        // ... Exchange current element with smallest remaining.
                        int temp = x[i];
                        x[i] = x[minIndex];
                        x[minIndex] = temp;
                    }
                    repaint();
                    try {
                        Thread.sleep(ITERATION_SLEEP);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }               
            }
        }).start();
    }

    private void drawPass(Graphics g) {
        int rectWidth = 1;

        int width = getWidth() - 1;
        int height = getHeight() - 1;
        int colSpan = Math.round((float)width / (float)numbers.length);
        int x = 0;

        for (int num : numbers) {
            int colHeight = (int) ((float) height * ((float) num / (float) 100));
            g.fillRect(x, height - colHeight, rectWidth, colHeight);
             x += colSpan;
        }
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        drawPass(g);
    }
}

绘制选择排序的视觉效果

1 个答案: