var screen = wx.createCanvas();

var screencontext = screen.getContext('2d');

screencontext.fillStyle = "#ffffff";

screencontext.fillRect(0, 0, screen.width, screen.height);

screencontext.fillStyle = "#ff0000";

screencontext.font = "22px";

screencontext.fillText("sfda", screen.width / 2, screen.height / 2);

小游戏画布无法设置字体大小，上述设置方法无效