为什么我的方法不清除的ArrayList？ [英] Why is my method not clearing the ArrayList?
问题描述
的注：我的code中的问题只是我创建清除rects和一切，但我做错了唯一的方法，实例化去内DrawPanel类的myDraw对象（）方法。所以，我必须与再次停止实例DrawPanel并创造了一个全新的对象。所以，我最终调用比分别被添加到一个rects不同DrawPanel对象的clearRects方法。反正，我决定用MadProgrammer code建议去，因为他的code是究竟是如何的Java：初学者指南教了，就干净多了的
好吧，我一直在跑来跑去的计算器，因为今天上午已经能够解决了很多问题，我的code，但我还是坚持了这个问题的ArrayList
Well, I have been running around StackOverflow since this morning and have been able to fix a lot of problems with my code but I am still stuck with this problem with ArrayLists.
我有下面这段code的似乎并不做什么，我打算为它做。现在我知道我是一个犯了一个错误的地方，但真的不知道如何纠正它。
I have the following piece of code that does not seem to do what I intend for it to do. Now I am aware that I am the one making a mistake somewhere but not really sure how to correct it.
这是设置方式是，当我打的停止按钮，ArrayList中应明确，所以我有一个空白的JPanel可以这么说，这里的code片段。我可以张贴整个程序，如果你要我，虽然，但我只是在这里粘贴代码片段，因为我假设我在我的部分制作pretty简单而愚蠢的错误：
The way it is set up is that when I hit the stop button, the ArrayList should clear so I have a blank JPanel so to speak, here's the code snippets. I can post the whole program if you want me to though but I am only pasting the snippet here because I'm assuming I'm making a pretty simple and dumb mistake on my part:
class DrawPanel extends JPanel {
ArrayList<MyRectangle> rects = new ArrayList<>();
Random rand = new Random();
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
addRect();
for(MyRectangle r : rects) {
g.setColor(r.getColor());
g.fillRect(r.x, r.y, r.width, r.height);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500,500);
}
public ArrayList<MyRectangle> addRect() {
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
int r = rand.nextInt(256);
int g = rand.nextInt(256);
int b = rand.nextInt(256);
rects.add(new MyRectangle(x, y, wd, ht, new Color(r, b, g)));
System.out.println(rects.size());
return rects;
}
public void clearEvent(ActionEvent e) {
System.out.println(rects.size());
rects.clear();
frame.repaint();
System.out.println("I was called");
}
}
和这里的地方的按钮调用它的actionPerformed方法的一部分：
And here's the part where the button calls it in its actionPerformed method:
class StopListener implements ActionListener {
DrawPanel draw = new DrawPanel();
public void actionPerformed(ActionEvent e) {
timer.stop();
draw.clearEvent(e);
}
}
编辑：据我所知，我的clearEvent方法是指ArrayList对象是不一样的一个的addRect（）添加的东西。什么我问，我猜，是如何使其连接这样我就可以擦干净的东西用的JButton。
I understand that the arraylist object that my clearEvent method refers to is not the same one that addRect()'s adding stuff to. What I am asking, I guess, is how to make it "connect" so I can wipe things clean using the JButton.
编辑：以下是完整的程序：
Here's the full program:
import javax.swing.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Random;
import java.awt.*;
public class TwoButtonsRandomRec {
JFrame frame;
Timer timer;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
TwoButtonsRandomRec test = new TwoButtonsRandomRec();
test.go();
}
});
}
public void go() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton startButton = new JButton("Start");
startButton.addActionListener(new StartListener());
JButton stopButton = new JButton("Stop");
stopButton.addActionListener(new StopListener());
final DrawPanel myDraw = new DrawPanel();
timer = new Timer(50, new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
myDraw.repaint();
}
});
frame.add(startButton, BorderLayout.NORTH);
frame.add(stopButton, BorderLayout.SOUTH);
frame.add(myDraw, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
class StartListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
timer.start();
}
}
class StopListener implements ActionListener {
DrawPanel draw = new DrawPanel();
public void actionPerformed(ActionEvent e) {
timer.stop();
draw.clearEvent(e);
}
}
class DrawPanel extends JPanel {
ArrayList<MyRectangle> rects = new ArrayList<>();
Random rand = new Random();
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
addRect();
for(MyRectangle r : rects) {
g.setColor(r.getColor());
g.fillRect(r.x, r.y, r.width, r.height);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500,500);
}
public ArrayList<MyRectangle> addRect() {
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
int r = rand.nextInt(256);
int g = rand.nextInt(256);
int b = rand.nextInt(256);
rects.add(new MyRectangle(x, y, wd, ht, new Color(r, b, g)));
System.out.println(rects.size());
return rects;
}
public void clearEvent(ActionEvent e) {
System.out.println(rects.size());
rects.clear();
repaint();
System.out.println("I was called");
}
}
}
class MyRectangle extends Rectangle {
Color color;
public MyRectangle(int x, int y, int w, int h, Color c) {
super(x, y, w, h);
this.color = c;
}
public Color getColor() {
return color;
}
}
这里的previous相关的问题，我在这里问的情况下，任何人的兴趣。
Here's the previous relevant question I asked here in case anyone's interested.
推荐答案
我看到了两个紧迫的问题。
I see two immediate issues.
第一个是，你打电话 addRect 的的paintComponent 方法，这意味着，即使您明确的内在列表，就下重画，一个新的矩形将被添加到它。
The first is, you're calling addRect within the paintComponent method, which means, even after you clear the List, on the next repaint, a new rectangle will be added to it.
其次，我称之为重绘中的 DrawPanel 而不是使用 frame.repaint （），因为你真的只想要更新的平局面板，而不是整个帧
Secondly, I would call repaint in the DrawPanel instead of using frame.repaint(), as you really only want to update the draw panel, not the entire frame
public class BadPaint05 {
public static void main(String[] args) {
new BadPaint05();
}
public BadPaint05() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new MasterPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MasterPane extends JPanel {
private DrawPanel drawPane;
private Timer timer;
public MasterPane() {
setLayout(new BorderLayout());
drawPane = new DrawPanel();
add(drawPane);
JButton stop = new JButton("Stop");
stop.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
drawPane.clearEvent(e);
timer.stop();
}
});
timer = new Timer(500, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
drawPane.addRect();
}
});
timer.setRepeats(true);
timer.setCoalesce(true);
timer.start();
add(stop, BorderLayout.SOUTH);
}
}
class DrawPanel extends JPanel {
ArrayList<MyRectangle> rects = new ArrayList<>();
Random rand = new Random();
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
// addRect();
for (MyRectangle r : rects) {
g.setColor(r.getColor());
g.fillRect(r.x, r.y, r.width, r.height);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
public ArrayList<MyRectangle> addRect() {
int ht = rand.nextInt(getHeight());
int wd = rand.nextInt(getWidth());
int x = rand.nextInt(getWidth() - wd);
int y = rand.nextInt(getHeight() - ht);
int r = rand.nextInt(256);
int g = rand.nextInt(256);
int b = rand.nextInt(256);
rects.add(new MyRectangle(x, y, wd, ht, new Color(r, b, g)));
System.out.println(rects.size());
repaint();
return rects;
}
public void clearEvent(ActionEvent e) {
System.out.println(rects.size());
rects.clear();
// frame.repaint();
repaint();
System.out.println("I was called");
}
}
public class MyRectangle {
private int x, y, width, height;
private Color color;
private MyRectangle(int x, int y, int wd, int ht, Color color) {
this.x = x;
this.y = y;
this.width = wd;
this.height = ht;
this.color = color;
}
public Color getColor() {
return color;
}
}
}
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