sampledesktopmgr.java

java swing 开发代码

// SampleDesktopMgr.java
// A DesktopManager that keeps its frames inside the desktop.
//
package	jswing.ch09;

import javax.swing.*;
import java.awt.*;

public class SampleDesktopMgr extends DefaultDesktopManager {

  // This is called anytime a frame is moved.  This 
  // implementation keeps the frame from leaving the desktop.
  public void dragFrame(JComponent f, int x, int y) {
    if (f instanceof JInternalFrame) {  // Deal only w/internal frames
      JInternalFrame frame = (JInternalFrame)f;
      JDesktopPane desk = frame.getDesktopPane();
      Dimension d = desk.getSize();
      
      // Nothing all that fancy below, just figuring out how to adjust
      // to keep the frame on the desktop.
      if (x < 0) {              // too far left?
        x = 0;                  // flush against the left side
      }
      else {
        if (x + frame.getWidth() > d.width) {     // too far right?
          x = d.width - frame.getWidth();         // flush against right side
        }
      }
      if (y < 0) {              // too high?
        y=0;                    // flush against the top
      }
      else {
        if (y + frame.getHeight() > d.height) {   // too low?
          y = d.height - frame.getHeight();       // flush against the bottom
        }
      }
    }

    // Pass along the (possibly cropped) values to the normal drag handler.
    super.dragFrame(f, x, y);
  }
}