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Home  >  Article  >  Web Front-end  >  The lightweight javascript library createjs uses Easel to achieve drag and drop effects_javascript skills

The lightweight javascript library createjs uses Easel to achieve drag and drop effects_javascript skills

WBOY
WBOYOriginal
2016-05-16 15:14:401933browse

I will share with you some of my experience in learning Createjs:

1. What is CreateJS?

Createjs is a lightweight javascript library and an open source toolkit that can build HTML5 games with rich interactive experiences. Many interesting animated games can be built using createjs. For example, surround the nervous cat and see how colorful you are and other Html5 games.

2. What are the tools of CreateJS?

There are four major engines in createjs:

  • EaselJS: Mainly used for animation, vector and bitmap drawing. Provides a series of methods to support touch on mobile devices (click, mousedown, pressup, and pressmove are events for mouse click, press, release, and movement respectively, but createjs.Touch.enable(
  • TweenJS: is an engine for making tween animations that can generate a continuously changing effect. (Children who have used flash should know what tween animation is)
  • SoundJS: is an audio playback engine that can select audio formats for playback based on browser compatibility and performance, and can be loaded and unloaded at any time.
  • PreloadJS: It is a resource preloading engine. It can also specify the loading order and load resources according to priority groups.

3. How to use Easel to create a simple drag and drop?

So if you now need to use EaselJs to drag a picture arbitrarily, and click the picture to make the picture selected or unselected, the selected state means that it can be dragged, and the unselected state means that it cannot be dragged state. And at most one picture can be in the dragging state. So how to use EaselJs to achieve this requirement and support mobile devices? Without further ado, let’s get to the source code.

HTML code: 

<html>

<head>
  <meta charset="utf-8">
  <script src="https://code.createjs.com/easeljs-0.8.2.min.js"></script>
  <script type="text/javascript">
    function Init() {
      var canvas = document.getElementById("dragCanvas");
      canvas.width = 600; //定义画布大小
      canvas.height = 400;
      var stage = new createjs.Stage(canvas);
      createjs.Touch.enable(stage); //允许设备触控
      var selectBool = []; //控制状态
      drawImgs();
      stage.update();

      function drawImgs() {
        var oX = 0,
          oY = 0;
        var fzmx, fzmy, sx, sy; //辅助变量
        for (var i = 0; i < 4; i++) {
          var randomColor = Math.floor(Math.random() * 16777215).toString(16);
          var con = new createjs.Container();
          var bitmap = new createjs.Bitmap(i + '.jpg');
          selectBool[i] = false;
          con.x = oX;
          con.y = oY;
          oX += 125;
          con.addChild(bitmap);
          con.addEventListener("mousedown", function (event) {
            var Mindex = stage.getChildIndex(event.target.parent);
            sx = event.stageX;
            sy = event.stageY;
            fzmx = event.stageX - event.target.parent.x;
            fzmy = event.stageY - event.target.parent.y;
            if (selectBool[Mindex]) {
              event.target.parent.addEventListener('pressmove', pressMove, false);
            } else {
              event.target.parent.removeEventListener('pressmove', pressMove, false);
            }
            stage.update();
          });
          //        添加鼠标"松开"事件
          con.addEventListener("pressup", function (event) {
            var Pindex = stage.getChildIndex(event.target.parent);
            if (Math.abs(event.stageX - sx) < 3 && Math.abs(event.stageY - sy) < 3) {
              selectBool[Pindex] = !selectBool[Pindex];
              shadowUr(selectBool[Pindex], event.target.parent, randomColor);
            }
            stage.update();
          });

          //        切换状态方法
          function shadowUr(bool, con, randomColor) {
            if (bool) {
              con.shadow = new createjs.Shadow("#" + randomColor, 0, 0, 10);
              var fIndex = con.parent.getChildIndex(con);
              for (var i = 0; i < con.parent.numChildren; i++) {
                if (i == fIndex)
                  continue;
                con.parent.getChildAt(i).shadow = null;
                selectBool[i] = false;
              }
            } else
              con.shadow = null;
          }
          //        图片拖动
          function pressMove(event) {
            var self = event.target.parent;
            if (event.stageX - fzmx < 0)
              self.x = 0;
            else if (event.stageX - fzmx + self.getBounds().width > stage.canvas.width)
              self.x = stage.canvas.width - self.getBounds().width;
            else
              self.x = event.stageX - fzmx;
            if (event.stageY - fzmy < 0)
              self.y = 0;
            else if (event.stageY - fzmy + self.getBounds().height > stage.canvas.height)
              self.y = stage.canvas.height - self.getBounds().height;
            else
              self.y = event.stageY - fzmy;
            stage.update();
          }
          stage.addChild(con);
        }

      }
    }
  </script>
</head>

<body onload="Init();">
  <canvas id="dragCanvas" style="border:#333 1px solid"></canvas>
</body>

</html>


Due to the same-origin policy of the browser, a local server needs to be opened, otherwise it cannot be loaded normally. Okay, this is the image dragging effect required above

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