出于某种原因，我似乎无法弄清楚为什么一旦用户释放鼠标就无法绘制矩形。应该激活draw()方法并创建一个矩形对象以将对象绘制到drawPanel上。
ShapeGui.java类：
public class ShapeGui extends JFrame{
private JButton[] buttons;
private final String[] butLabel = {"Red","Green","Blue","Rectangle","Circle","Exit"};
private Container pane;
private JLabel dateLabel;
private int x1,x2,y1,y2;
private String color;
JTextArea textArea;
ButtonHandler butHandle = new ButtonHandler();
private boolean isRect=true; //set default draw shape when program run to rectangel
JPanel drawPanel= new JPanel();
public ShapeGui(){
super("Draw Shape GUI");
pane = getContentPane();
pane.setLayout(new BorderLayout());
pane.add(createButton(), BorderLayout.CENTER);
pane.add(textArea(), BorderLayout.EAST);
pane.add(drawSpace(), BorderLayout.WEST);
}
public JPanel createButton(){
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(2,3));
buttons = new JButton[butLabel.length];
for(int i=0; i<butLabel.length; i++){
buttons[i]= new JButton(butLabel[i]);
buttons[i].addActionListener(butHandle);
buttonPanel.add(buttons[i]);
}
return buttonPanel;
}
public JPanel drawSpace(){
JPanel leftPanel = new JPanel();
leftPanel.setLayout(new BorderLayout());
leftPanel.setPreferredSize(new Dimension(200,450));
//create panel for mouse click event
drawPanel= new JPanel();
leftPanel.add(drawPanel, BorderLayout.CENTER);
MouseHandler mouseHandle = new MouseHandler();
drawPanel.addMouseListener(mouseHandle);
drawPanel.addMouseMotionListener(mouseHandle);
//create date label and format to show only date
LocalDate today = LocalDate.now(ZoneId.of("America/Montreal"));
dateLabel= new JLabel(today.toString());
leftPanel.add(dateLabel,BorderLayout.SOUTH); //add date to panel
return leftPanel;
}
public JPanel textArea(){
JPanel textPanel= new JPanel();
textArea= new JTextArea(15,15);
//add textarea inside scroll pane
JScrollPane scroll = new JScrollPane(textArea,JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
textPanel.add(scroll);
return textPanel;
}
//method to draw shape after button is pressed
public void drawShape(){
if(isRect){
Rectangle rect = new Rectangle(x1,y1,x2,y2,color);
drawPanel.add(rect);
rect.draw();
}
}
private class ButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
Object obj = e.getSource();
if(obj == buttons[0]){
color="RED";
System.out.println("Color: "+color);
}
if(obj == buttons[1]){
color="GREEN";
System.out.println("Color: "+color);
}
if(obj == buttons[2]){
color="BLUE";
System.out.println("Color: "+color);
}
if(obj == buttons[3]){
isRect=true;
System.out.println("Boolean Rectangle: "+isRect);
}
if(obj == buttons[4]){ //change to false once button circle is clicked
isRect=false;
System.out.println("Boolean Rectangle: "+isRect);
}
if(obj == buttons[5]){
//serialization
System.exit(0);
}
}
} //end of buttonHandler
private class MouseHandler extends MouseAdapter{
@Override
public void mousePressed(MouseEvent e){
textArea.append(String.format("Pressed at [%d, %d]\n", e.getX(),e.getY()));
x1=e.getX();
y1=e.getY();
}
@Override
public void mouseReleased(MouseEvent e){
textArea.append(String.format("Released at [%d, %d]\n", e.getX(),e.getY()));
x2=e.getX();
y2=e.getY();
drawShape();
}
}
}
矩形类：
public class Rectangle extends JPanel{
private int x1,x2,y1,y2;
String color;
public Rectangle(int x1, int y1, int x2, int y2,String color) {
this.x1=x1;
this.y1=y1;
this.x2=x2;
this.y2=y2;
this.color=color;
}
public void paintComponent(Graphics g){
super.paintComponent(g);
//change color
if(color.equalsIgnoreCase("Red"))
g.setColor(Color.RED);
else if(color.equalsIgnoreCase("Green")){
g.setColor(Color.GREEN);
}
else
g.setColor(Color.BLUE);
g.fillRect(x1, y1, (x2-x1), (y2-y1));
}
public void draw(){
repaint();
}
}
答案 0 :(得分：0)
我建议采用以下解决方案 - 重新绘制和绘画的过程很复杂，特别是如果你在面板上添加面板并依赖于系统 - 它并不意味着因为你说“绘制”它会立即绘制它：
class ShapeGui extends JFrame{
private JButton[] buttons;
private final String[] butLabel = {"Red","Green","Blue","Rectangle","Circle","Exit"};
private Container pane;
private JLabel dateLabel;
private int x1,x2,y1,y2;
private Color color;
JTextArea textArea;
ButtonHandler butHandle = new ButtonHandler();
private boolean isRect=true; //set default draw shape when program run to rectangel
DrawPanel drawPanel= new DrawPanel();
public JPanel drawSpace(){
JPanel leftPanel = new JPanel();
leftPanel.setLayout(new BorderLayout());
leftPanel.setPreferredSize(new Dimension(200,450));
//create panel for mouse click event
leftPanel.add(drawPanel, BorderLayout.CENTER);
MouseHandler mouseHandle = new MouseHandler();
drawPanel.addMouseListener(mouseHandle);
drawPanel.addMouseMotionListener(mouseHandle);
//create date label and format to show only date
Date today = new Date();
dateLabel= new JLabel(today.toString());
leftPanel.add(dateLabel,BorderLayout.SOUTH); //add date to panel
return leftPanel;
}
public void drawShape(){
if(isRect){
Rectangle rect = new Rectangle(x1,y1,x2,y2,color);
drawPanel.add(rect);
drawPanel.repaint();
}
}
private class ButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e){
Object obj = e.getSource();
if(obj == buttons[0]){
color=Color.red;
System.out.println("Color: "+color);
}
if(obj == buttons[1]){
color=Color.green;
System.out.println("Color: "+color);
}
if(obj == buttons[2]){
color=Color.blue;
System.out.println("Color: "+color);
}
if(obj == buttons[3]){
isRect=true;
System.out.println("Boolean Rectangle: "+isRect);
}
if(obj == buttons[4]){ //change to false once button circle is clicked
isRect=false;
System.out.println("Boolean Rectangle: "+isRect);
}
if(obj == buttons[5]){
//serialization
System.exit(0);
}
}
} //end of buttonHandler
class DrawPanel extends JPanel {
Rectangle rect;
private int x1,x2,y1,y2;
Color color;
public DrawPanel() {
}
public void add(Rectangle rect) {
this.rect=rect;
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g.setColor(rect.color);
g.fillRect(rect.x1, rect.y1, rect.x2-rect.x1, rect.y2-rect.y1);
}
}
class Rectangle {
int x1,x2,y1,y2;
Color color;
public Rectangle(int x1, int y1, int x2, int y2, Color color) {
this.x1=x1;
this.y1=y1;
this.x2=x2;
this.y2=y2;
this.color=color;
}
}
其余的保持不变。