我的程序应该等待按下左箭头键或右箭头键,然后更改一个值,以便下次更新PaintComponent时,屏幕看起来不同。但是,运行程序时屏幕不会改变。
以下是变量声明:
static KeyListener listen;
public static int slide = 0;
这是main中的KeyListener声明:
listen = new KeyListener() {
public void keyPressed(KeyEvent arg0) {
if(arg0.getKeyCode() == KeyEvent.VK_LEFT && slide>0) {
slide--;
System.out.println("Left pressed. Slide is " + slide);
}
else if(arg0.getKeyCode() == KeyEvent.VK_RIGHT) {
slide++;
System.out.println("Right pressed. Slide is " + slide);
}
}
public void keyReleased(KeyEvent arg0) {}
public void keyTyped(KeyEvent arg0) {}
};
以下是用于绘画的方法:
public void paintComponent(Graphics g){
super.paintComponent(g);
this.setBackground(new Color(0, 0, 20));
g.drawImage(exitButton, 20, 20, null);
drawBoard(g);
}
public void drawBoard(Graphics g){
if(slide == 0) {
String[] text0 = {"This is the test",
"for the Presenter application",
"Here is a nicely framed picture of the Berlin Wall."
};
makeTextBox(text0);
g.drawImage(textBox, textX, textY,(boxW)*2,(boxH)*2, null);
g.setColor(Color.blue);
g.fillRect(wallX-10, wallY-10, wallW+20, wallH+20);
g.drawImage(wall, wallX, wallY, null);
}
else if(slide == 1) {
String[] text1 = {"Here is the second page...",
"Welcome."};
makeTextBox(text1);
g.drawImage(textBox, textX, textY,(boxW)*2,(boxH)*2, null);
}
}
当我运行程序时,程序会打印if(slide == 0)
个案,但是当我按箭头键时,屏幕上没有任何变化。
答案 0 :(得分:1)
在调用组件之前,您需要将键侦听器添加到组件中:
addKeyListener(new KeyListener() {
/* ... methods as before ... */
});
您还需要使组件具有可聚焦性并使其成为焦点:
setFocusable(true);
requestFocusInWindow();
最后,如果要在按下键时重新绘制屏幕,则必须在按键处理程序中调用组件的repaint()
方法。
答案 1 :(得分:1)
不要使用KeyListener它现在可以在组件没有焦点时工作!
Swing旨在与Key Bindings
一起使用。有关使用Key Bindings
。