QML -->按键元素

import QtQuick 2.0

Rectangle{
   width: 400;
   height: 200;
   GreenRect{  // 封装的绿色方框组件  
       id:square;
       x:8;y:8;
   }
   focus:true;
   Keys.onLeftPressed: square.x -= 8;    // 左
   Keys.onRightPressed: square.x += 8;    // 右
   Keys.onUpPressed: square.y -= 8;    // 上
   Keys.onDownPressed: square.y += 8;    // 下
   Keys.onPressed: {
       switch(event.key){
       case Qt.Key_Plus:    // +
           square.scale += 0.2;
           break;
       case Qt.Key_Minus:  // -
           square.scale -= 0.2;
           break;
       }
   }
}