app18_5.java

JAVA 2面向对象程序设计(随书范例程序)16-19.rar

// app18_5, RGB color色阶的应用
import java.awt.*;  
import java.awt.event.*;  
class app18_5 extends Frame implements AdjustmentListener
{
   static app18_5 frm=new app18_5();
   static Scrollbar scr1=new Scrollbar(Scrollbar.VERTICAL);
   static Scrollbar scr2=new Scrollbar(Scrollbar.HORIZONTAL); 
   static Scrollbar scr3=new Scrollbar(Scrollbar.VERTICAL); 
    
   public static void main(String args[])
   {
      BorderLayout br=new BorderLayout(5,5);
      frm.setTitle("Display colors");
      frm.setSize(200,150); 
      frm.add(scr1,br.WEST);      // scr1滚动条，用来控制红色
      frm.add(scr2,br.SOUTH);     // scr2滚动条，用来控制绿色
      frm.add(scr3,br.EAST);      // scr3滚动条，用来控制蓝色
      scr1.setValues(255,45,0,300);   // 设置scr1的相关数值
      scr2.setValues(255,45,0,300);   // 设置scr2的相关数值
      scr3.setValues(140,45,0,300);   // 设置scr3的相关数值
      scr1.addAdjustmentListener(frm);
      scr2.addAdjustmentListener(frm);
      scr3.addAdjustmentListener(frm);
      frm.setVisible(true);
   }
   public void adjustmentValueChanged(AdjustmentEvent e)
   {
      Graphics g=getGraphics();
      paint(g);
   }  
   
   public void paint(Graphics g)
   {
      int red=scr1.getValue();        // 取得滚动条scr1的值
      int green=scr2.getValue();      // 取得滚动条scr2的值
      int blue=scr3.getValue();       // 取得滚动条scr3的值
      String str="Color("+red+","+green+","+blue+")";
      g.setColor(new Color(red,green,blue));  // 设置绘图颜色
      g.fillRect(0,0,getWidth(),getHeight()); 
      g.setColor(Color.black);    // 设置绘图颜色为黑色
      g.drawString(str,45,80);    //在(45,80)处写上字符串
   }
}