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Swinghacks——动感JList

ok,我承认动感这个词用的有点过,还是先上图看效果
解释一下,图片中是没有什么动感的,其实效果是这样
当选中item时,蓝色的选中背景会从白色渐变到蓝色,给人动感~
虽然这种动感没有特别实际的用处,不过实现原理还是有点意思,来看看
1、先通过lookandfeel获取选中和未选中的背景颜色,在转换成rgb浮点数组float[3]
[java]   www.zzzyk.com
UIDefaults uid = UIManager.getLookAndFeel().getDefaults();  
Color listForeground =  uid.getColor ("List.foreground");  
float[] foregroundComps = listForeground.getRGBColorComponents(null);  
2、在valueChanged方法中,启动thread做背景渐变效果;通过计时,每50ms进行一次repaint,总共执行500ms
[java]  
public void run() {  
    startTime = System.currentTimeMillis();  
    stopTime = startTime + ANIMATION_DURATION;  
    while (System.currentTimeMillis() < stopTime) {  
        colorizeSelections();  
        repaint();  
        //每间隔ANIMATION_REFRESH时间就repaint一次  
        try { Thread.sleep (ANIMATION_REFRESH); }   
        catch (InterruptedException ie) {}  
    }  
    // one more, at 100% selected color  
    colorizeSelections();  
    repaint();  
}  
 
3、repaint之前调用colorizeSelections方法设置背景前景颜色,而colorizeSelections方法是根据时间来计算背景显示的百分比
这个计算其实就是把背景的rgb值取百分比
[java]  
public void colorizeSelections() {  
    // calculate % completion relative to start/stop times  
    float elapsed = (float) (System.currentTimeMillis() - startTime);  
    float completeness = Math.min ((elapsed/ANIMATION_DURATION), 1.0f);  
    // System.out.println ("completeness = " + completeness);  
    // calculate scaled color  
    float colorizedForeComps[] = new float[3];  
    float colorizedBackComps[] = new float[3];  
    for (int i=0; i<3; i++) {  
        colorizedForeComps[i] =  
            foregroundComps[i] +  
            (completeness *   
             (foregroundSelectionComps[i] - foregroundComps[i]));  
        colorizedBackComps[i] =  
            backgroundComps[i] +  
            (completeness *   
             (backgroundSelectionComps[i] - backgroundComps[i]));  
    }  
 
这样repaint之前就设置好了背景色,不断repaint的话就产生动感渐变的效果了
上代码:
[java]  
import java.awt.*;  
import javax.swing.*;  
import javax.swing.event.*;  
import java.util.*;  
  
public class AnimatedJList extends JList   
    implements ListSelectionListener {  
  
    static java.util.Random rand = new java.util.Random();  
  
    static Color listForeground, listBackground,  
        listSelectionForeground, listSelectionBackground;  
    static float[] foregroundComps, backgroundComps,  
        foregroundSelectionComps, backgroundSelectionComps;  
  
    static {  
        UIDefaults uid = UIManager.getLookAndFeel().getDefaults();  
        listForeground =  uid.getColor ("List.foreground");  
        listBackground =  uid.getColor ("List.background");  
        listSelectionForeground =  uid.getColor ("List.selectionForeground");  
        listSelectionBackground =  uid.getColor ("List.selectionBackground");  
        foregroundComps =  
            listForeground.getRGBColorComponents(null);  
        foregroundSelectionComps =   
            listSelectionForeground.getRGBColorComponents(null);  
        backgroundComps =  
            listBackground.getRGBColorComponents(null);  
        backgroundSelectionComps =  
            listSelectionBackground.getRGBColorComponents(null);  
    }  
    public Color colorizedSelectionForeground,  
        colorizedSelectionBackground;  
  
    public static final int ANIMATION_DURATION = 500;  
    public static final int ANIMATION_REFRESH = 50;  
  
    public AnimatedJList() {  
        super();  
        addListSelectionListener (this);  
        setCellRenderer (new AnimatedCellRenderer());  
    }  
  
    public void valueChanged (ListSelectionEvent lse) {  
        if (! lse.getValueIsAdjusting()) {  
            HashSet selections = new HashSet();  
            // System.out.println ("got last lse");  
            for (int i=0; i < getModel().getSize(); i++) {  
                if (getSelectionModel().isSelectedIndex(i))  
                    selections.add (new Integer(i));  
            }  
            CellAnimator animator = new CellAnimator (selections.toArray());  
            animator.start();  
        }  
    }  
  
    public static void main (String[] args) {  
        JList list = new AnimatedJList ();  
        DefaultListModel defModel = new DefaultListModel();  
        list.setModel (defModel);  
        String[] listItems = {  
            "Chris", "Joshua&
补充:软件开发 , Java ,
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