问答题
综合应用题
下面是一个Applet程序，其功能是在绘图区域中通过鼠标的移动来绘制直线，并且有清除绘图区域按钮，用来清除已经绘制的图像。请改正程序中的错误（有下划线的语句），使程序能输出正确的结果。程序运行结果如下：
注意：不改动程序的结构，不得增行或删行。
import java.awt.*;
import java.applet.*;
/*
*/
public class ex1_3 extends Applet{
private Button btn;
private boolean bDraw, bClear;
private int upX, upY,downX, downY;
public void init(){
setLayout(null);
bClear = false;
bDraw = false;
btn = new Button("clear");
btn.reshape(250, 150, 70, 30);
add(btn);
}
public void paint(Graphics g){
if(bClear){
g.clearRect(0, 0, getSize().width, getSize().height);
bClear = false;
}if(bDraw){
g.drawLine(upY, upX, downY, downX);
bDraw = false;
}
}
public void update(Graphics g){
paint(g);
}
public boolean mouseDown(Event event, int x, int y){
downX = x;
downY = y;
return true;
}
public boolean mouseUp(Event event, int x, int y){
upX = x;
upY = y;
bDraw = false;repaint();
return true;
}
public boolean action(Event event, Object object){
if (event.target != clear){
bClear = true;
repaint();
}return true;
}
}
ex1_3.html
ex1_3
【参考答案】
g.drawLine(downX, downY, upX, upY)bDraw = trueevent.target =......
(↓↓↓ 点击下方‘点击查看答案’看完整答案、解析 ↓↓↓)
g.drawLine(downX, downY, upX, upY)bDraw = trueevent.target =......
(↓↓↓ 点击下方‘点击查看答案’看完整答案、解析 ↓↓↓)
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