请完成下列Java程序:生成一个窗口,包含一个长度为100的横向滚动条,实现对这个滚动条状态的监视,
注意:请勿改动main()主方法和其他已有语句内容,仅在下划线处填入适当的语句。
程序运行结果如下:
import java.awt.*;
import java.awt.event.*;
public class ex19_2 extends Frame. implements AdjustmentListener {
private Scrollbar sb;
private msgWnd mw;
private int val;
public static void main(String[] arg) {
ex19_2 obj19_2=new ex19_2();
}
public ex19_2() {
setTitle("ex19_2");
addWindowListener((WindowListener)new winListener());
mw = new msgWnd();
add("Center",mw);
sb = new Scrollbar(Scrollbar. HORIZONTAL);
sb.setVisibleAmount(10);
sb.setBlockIncrement(6);
sb.setUnitIncrement(5);
sb.addAdjustmentListener(this);
add("South",sb);
pack();
show();
}
public void adjustmentValueChanged(AdjustmentEvent ae) {
val = ae.getValue();
_______________;
}
class msgWnd extends Canvas {
msgWnd() {
setSize(450,20);
}
public void paint(Graphics g) (
g.drawString(" val=" +____________________+"%",10,15);
}
}
class winListener extends WindowAdapter {
public void windowClosing(WindowEvent we) {
System.exit(0);
}
}
}