本文介绍如何在Java中实现多个监听接口间的变量共享问题，通过创建静态变量实现在不同接口方法间的数据传递，实现拖动组件的功能。
都知道java中类只能单继承，但可以实现多个接口，但我发现实现多个接口之后，多个接口却不能共享同一个数据，应用开发中想实现：当用户按着ctrl键时，可以用鼠标点击拖动组件，比如说文本框。
编写一个监听实现KeyListener,NouseListener,MouseMotionListener三个接口，重写方法。定义一个全局变量boolean ctrlPressed;
@Override
public void keyPressed(KeyEvent e) {
if(e.getModifiers()==InputEvent.CTRL_MASK)
{
ctrlPressed=true;
System.out.println("ctrl is pressed");
}
}@Override
public void keyReleased(KeyEvent e) {
ctrlPressed=false;
System.out.println("ctrl release");
}
用户在按下ctrl的时候为true,在MouseMotionListener接口的方法中判断ctrlPressed是否为真。
public void mouseDragged(MouseEvent e) {
if(ctrlPressed)
{
...........//实现拖动
}
}
这么写也不会报错，结果呢，mouseDragged方法中ctrlPressed却一直是false,按照逻辑来说用户按着ctrl,在keyPressed已经更改了ctrlPressed=true了呀！所以咯，不同的接口的方法是不能共用同一个变量的，全局变量，ctrlPressed,在不同的监听域中创建了不同的存储单元，也可以说是私有化了!我的解决办法是，创建一个类SharedData,创建静态变量ctrlPressed,而在keyPressed,和MouseDagged方法中都是用这个静态变量就能共用了！下面是我的具体实现代码，这个监听类，这个类可以实现选中组件中间移动组件，四周放大缩小组件，用的时候只需要添加监听即可，三个都要加哦
diamend.addMouseMotionListener(new PainRectListener(mJFrame,diamend));
diamend.addMouseListener(new PainRectListener(mJFrame,diamend));
diamend.addKeyListener(new PainRectListener(mJFrame,diamend));
package com.msi.frame;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextPane;
import javax.swing.KeyStroke;
/**
* 組件拖動事件的監聽，任意組件都可以使用這個方法
* @author sharkliu
*
*/
public class PainRectListener implements KeyListener,MouseListener,MouseMotionListener{
private JFrame mJFrame;
private JTextPane panel;
//private boolean ctrlPressed=false;
public PainRectListener(JFrame mJFrame,JTextPane panel)
{
this.mJFrame=mJFrame;
this.panel=panel;
}
/**当前是否操作图片**/
private boolean isContains(Point point){
Rectangle rectangle = new Rectangle();
rectangle.x=0;
rectangle.y = 0;
rectangle.width = ShareData.componentSize[0];
rectangle.height = ShareData.componentSize[1];
return rectangle.contains(point);
}
/**得到是否是点击的4个边中的1个(0,1,2,3,4)**/
private int getPressSide(Point point){
int side = 0;
Rectangle rectTop = new Rectangle(0,0,ShareData.componentSize[0],8);
Rectangle rectBottom = new Rectangle(0,ShareData.componentSize[1]-8,ShareData.componentSize[0],8);
Rectangle rectLeft = new Rectangle(0,8,8,ShareData.componentSize[1]-8);
Rectangle rectRight = new Rectangle(ShareData.componentSize[0]-8,8,8,ShareData.componentSize[1]-8);
if(rectTop.contains(point)){
return 1; //上
}else if(rectBottom.contains(point)){
System.out.println("下");
return 2; //下
}else if(rectLeft.contains(point)){
System.out.println("左");
return 3; //左
}else if(rectRight.contains(point)){
System.out.println("右");
return 4; //右
}
return side; //中间
}
public void mouseDragged(MouseEvent e) {
System.out.println(ctrlPressed);
if(ShareData.isPressComponent&&ShareData.ctrlPressed){
System.out.println("mouseDragged ininin");
Point nowPoint = e.getPoint(); //当前鼠标拖拽到的鼠标位置
int diffX = nowPoint.x - ShareData.pressPoint.x;
int diffY = nowPoint.y - ShareData.pressPoint.y;
/**移动**/
if(ShareData.moveSide == 0){
ShareData.componentPoint.x += diffX;
ShareData.componentPoint.y += diffY;
}
/**收缩**/
else{
//收缩 下和右时
if(ShareData.moveSide == 2 || ShareData.moveSide == 4){
if(ShareData.moveSide == 2) //拉下（只能拉长拉短）
ShareData.componentSize[1] += diffY;
else //拉右（只能拉宽拉窄）
ShareData.componentSize[0] += diffX;
}
//收缩 上和左时
else if(ShareData.moveSide == 1 || ShareData.moveSide == 3){
if(ShareData.moveSide == 1){ //拉上边（只能拉长拉短）
ShareData.componentPoint.y += diffY;
ShareData.componentSize[1] -= diffY;
}else{ //拉左边（只能拉宽拉窄）
ShareData.componentPoint.x += diffX;
ShareData.componentSize[0] -= diffX;
}
}
ShareData.pressPoint = nowPoint;
}
//拖動組件改變組件的的寬不能超出黑框區域，以及防止拖動時把組件給拖沒了當size小於0組件無法匯出，便消失了
if( (ShareData.componentSize[0]>=20)&&(ShareData.componentSize[1]>=20))
{
System.out.println("e"+e.getComponent());
panel.setBounds(ShareData.componentPoint.x, ShareData.componentPoint.y, ShareData.componentSize[0], ShareData.componentSize[1]);
panel.setPreferredSize(new Dimension(ShareData.componentSize[0],ShareData.componentSize[1]));
panel.setSize(ShareData.componentSize[0], ShareData.componentSize[1]);
mJFrame.validate();// 重构内容面板
mJFrame.repaint();// 重绘内容面板
}
}
}
private void paintRect(Graphics graphics) {
graphics.drawLine(1, ShareData.componentSize[1]/2-1, ShareData.componentSize[0]/2-1, 1);
graphics.drawLine(ShareData.componentSize[0]/2-1,2, ShareData.componentSize[0]-1, ShareData.componentSize[1]/2-1);
graphics.drawLine(ShareData.componentSize[0]-1, ShareData.componentSize[1]/2-1, ShareData.componentSize[0]/2-1, ShareData.componentSize[1]-1);
graphics.drawLine(ShareData.componentSize[0]/2-1, ShareData.componentSize[1]-1, 1, ShareData.componentSize[1]/2-1);
}
public void mouseMoved(MouseEvent e) {
Rectangle rectTop = new Rectangle(0,0,ShareData.componentSize[0],8);
Rectangle rectBottom = new Rectangle(0,ShareData.componentSize[1]-8,ShareData.componentSize[0],8);
Rectangle rectLeft = new Rectangle(0,8,8,ShareData.componentSize[1]-8);
Rectangle rectRight = new Rectangle(ShareData.componentSize[0]-8,8,8,ShareData.componentSize[1]-8);
if(rectTop.contains(e.getPoint())){
e.getComponent().setCursor(new Cursor(Cursor.N_RESIZE_CURSOR));
}else if(rectBottom.contains(e.getPoint())){
System.out.println("下");
e.getComponent().setCursor(new Cursor(Cursor.S_RESIZE_CURSOR));
}else if(rectLeft.contains(e.getPoint())){
e.getComponent().setCursor(new Cursor(Cursor.W_RESIZE_CURSOR));
}else if(rectRight.contains(e.getPoint())){
e.getComponent().setCursor(new Cursor(Cursor.E_RESIZE_CURSOR));
}
else{
e.getComponent().setCursor(new Cursor(Cursor.MOVE_CURSOR));
}
}
public void mouseClicked(MouseEvent e) {
}
/**把組件所占的矩阵用变量表示出来(便于判断是否操作图片)**/
/**
*
* 跟新初始化數
* */
public void mousePressed(MouseEvent e) {
ShareData.componentPoint=e.getComponent().getLocation();
ShareData.componentSize[0]=e.getComponent().getSize().width;
ShareData.componentSize[1]=e.getComponent().getSize().height;
//這是爲了區分對待圖片和文本，圖片隨時可以拖動，不受管控
if(isContains(new Point(e.getPoint().x, e.getPoint().y))){
ShareData.moveSide = getPressSide(new Point(e.getPoint().x, e.getPoint().y)); //记录操作图片的边
ShareData.isPressComponent = true;
ShareData.pressPoint = e.getPoint();
}else{
ShareData.isPressComponent = false;
}
}
public void mouseReleased(MouseEvent e) {
ShareData.isPressComponent = false;
ShareData.pressPoint = null;
}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
@Override
public void keyTyped(KeyEvent e) {}
@Override
public void keyPressed(KeyEvent e) {
if(e.getModifiers()==InputEvent.CTRL_MASK)
{
ShareData.ctrlPressed=true;
System.out.println("ctrl is pressed");
}
}
@Override
public void keyReleased(KeyEvent e) {
ShareData.ctrlPressed=false;
System.out.println("ctrl release");
}
}
package com.msi.frame;
import java.awt.Component;
import java.awt.Point;
import javax.swing.JComponent;
/**
* 名字為共享數據，專門記錄工具欄點擊了那些屬性，
* 在版面繪製的時候，可先查看這個類中有哪些動作
* @author sharkliu
*
*/
public class ShareData {
public static int textFont=12;
public static int textStyle;
public static boolean dragable=false;//可拖動
public static boolean editable=true;//可編輯
public static Component selectCompoment=null;
public static int layer=1000;//
/*
* 控制組件移動、變形等需要共用到的數據
*/
public static int[]componentSize=new int[]{1,1};//組件大小
public static boolean isPressComponent=false; //是否操作組件、圖片或者文本框
public static int moveSide=0; //拉升的边(0:移动 1:上 2：下 3：左 4：右)
public static Point componentPoint; //組件（圖片或者文本框）位置
public static Point pressPoint; //press組件时的鼠标位置
//控制文字樣式的按鈕背景變換
public static boolean isBorder=false;
public static boolean isItalic=false;
public static boolean isUnderline=false;
public static String CMD="";
public static boolean ctrlPressed=false;
}
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