微信小程序图片缩放、移动

一波干货

.wxml

  
    scroll-view子元素缩放
    说明：双指缩放开发工具上并不支持，需要在真机上进行。 
  

  
      
  

  
    x: {{stv.offsetX}}, 
    y: {{stv.offsetY}}, 
    d: {{stv.distance}}, 
    s: {{stv.scale}}, 
  

 

.wxss

/**scale.wxss**/
.img {
  width: 100%;
  height: 500rpx;
  background: #AAA;
  text-align: center;
}
.img image {
  /* height: 800rpx;
  width: 600rpx; */
}

 

.js

//scale.js
//获取应用实例
var app = getApp()
Page({
  data: {
    stv: {
      offsetX: 0,
      offsetY: 0,
      zoom: false, //是否缩放状态
      distance: 0,  //两指距离
      scale: 1,  //缩放倍数
    }
  },
  //事件处理函数
  touchstartCallback: function (e) {
    //触摸开始
    console.log('touchstartCallback');
    console.log(e);

    if (e.touches.length === 1) {
      let { clientX, clientY } = e.touches[0];
      this.startX = clientX;
      this.startY = clientY;
      this.touchStartEvent = e.touches;
    } else {
      let xMove = e.touches[1].clientX - e.touches[0].clientX;
      let yMove = e.touches[1].clientY - e.touches[0].clientY;
      let distance = Math.sqrt(xMove * xMove + yMove * yMove);
      this.setData({
        'stv.distance': distance,
        'stv.zoom': true, //缩放状态
      })
    }

  },
  touchmoveCallback: function (e) {
    //触摸移动中
    console.log('touchmoveCallback');
    console.log(e);

    if (e.touches.length === 1) {
      //单指移动
      if (this.data.stv.zoom) {
        //缩放状态，不处理单指
        return;
      }
      let { clientX, clientY } = e.touches[0];
      let offsetX = clientX - this.startX;
      let offsetY = clientY - this.startY;
      this.startX = clientX;
      this.startY = clientY;
      let { stv } = this.data;
      stv.offsetX += offsetX;
      stv.offsetY += offsetY;
      stv.offsetLeftX = -stv.offsetX;
      stv.offsetLeftY = -stv.offsetLeftY;
      this.setData({
        stv: stv
      });

    } else {
      //双指缩放
      let xMove = e.touches[1].clientX - e.touches[0].clientX;
      let yMove = e.touches[1].clientY - e.touches[0].clientY;
      let distance = Math.sqrt(xMove * xMove + yMove * yMove);

      let distanceDiff = distance - this.data.stv.distance;
      let newScale = this.data.stv.scale + 0.005 * distanceDiff;
      // 为了防止缩放得太大，所以scale需要限制，同理最小值也是 
      if (newScale >= 2) {
        newScale = 2
      }
      if (newScale <= 0.6) {
        newScale = 0.6
      }
      this.setData({
        'stv.distance': distance,
        'stv.scale': newScale,
      })
    }

  },
  touchendCallback: function (e) {
    //触摸结束
    console.log('touchendCallback');
    console.log(e);

    if (e.touches.length === 0) {
      this.setData({
        'stv.zoom': false, //重置缩放状态
      })
    }
  },
  onLoad: function () {
    console.log('onLoad');
  }
})