canvas

画布。

canvas组件的默认宽度为 300px，高度为 225px.

示例

<canvas canvas-id="canvas" class="canvas"></canvas>

Page({
  onShow: function(res) {
    this.position = {
      x: 150,
      y: 150,
      vx: 2,
      vy: 2
    };
    this.interval = setInterval(this.drawBall, 17);
  },
  drawBall: function() {
    var p = this.position;
    p.x += p.vx;
    p.y += p.vy;
    if (p.x >= 300) {
      p.vx = -2;
    }
    if (p.x <= 7) {
      p.vx = 2;
    }
    if (p.y >= 300) {
      p.vy = -2;
    }
    if (p.y <= 7) {
      p.vy = 2;
    }

    var context = tt.createCanvasContext("canvas");

    function ball(x, y) {
      context.beginPath(0);
      context.arc(x, y, 5, 0, Math.PI * 2);
      context.setFillStyle("#1aad19");
      context.fill();
      context.stroke();
    }

    ball(p.x, 150);
    ball(150, p.y);
    ball(300 - p.x, 150);
    ball(150, 300 - p.y);
    ball(p.x, p.y);
    ball(300 - p.x, 300 - p.y);
    ball(p.x, 300 - p.y);
    ball(300 - p.x, p.y);

    console.log("will call context.draw");
    context.draw();
  },
  onUnload: function() {
    clearInterval(this.interval);
  }
});

相关 api: tt.createCanvasContext