onLoad(){

var that=this;

wx.getSystemInfo({

success: function (res) {

console.log(res)

that.setData({

width: res.windowWidth ,

height: res.windowHeight

})

var ctx = wx.createCanvasContext(‘canvas’);

ctx.drawImage(‘https://xxxxx.jpg’, -200, -200, res.windowWidth*2, res.windowHeight*2);

ctx.draw();

}

})

},这样设置一张图片能不能让他在canvas容器内上下左右移动（类似于腾讯地图那样  可以随意拖动）

跪求大神解答