canvas
Canvas.
Property | Type | Default | Description |
id | String | Unique component identifier. | |
style | String | ||
class | String | ||
width | String | canvas width attribute | |
height | String | canvas height attribute | |
disable-scroll | Boolean | false | Forbid screen scroll and pull-to-refresh. |
onTap | EventHandle | Click. | |
onTouchStart | EventHandle | Touch action start. | |
onTouchMove | EventHandle | Move after touch. | |
onTouchEnd | EventHandle | Touch action end. | |
onTouchCancel | EventHandle | Touch action interrupted, such as incoming call reminder, pop-up. | |
onLongTap | EventHandle | Trigger on long-press for 500ms, thereafter move action does not trigger screen scroll. |
Note:
- The canvas tab has default width 300px and height 225px
- On the same page, the id cannot be repeated.
- For finer displaying in higher dpr, use the attribute settings to zoom in and use the style to zoom out the canvas. for example:
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<!-- getSystemInfoSync().pixelRatio === 2 -->
<canvas width="200" height="200" style="width:100px;height:100px;"/>
Screenshot
Sample Code
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<canvas
id="canvas"
class="canvas"
onTouchStart="log"
onTouchMove="log"
onTouchEnd="log"
/>
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Page({
onReady() {
this.point = {
x: Math.random() * 295,
y: Math.random() * 295,
dx: Math.random() * 5,
dy: Math.random() * 5,
r: Math.round(Math.random() * 255 | 0),
g: Math.round(Math.random() * 255 | 0),
b: Math.round(Math.random() * 255 | 0),
};
this.interval = setInterval(this.draw.bind(this), 17);
},
draw() {
var ctx = my.createCanvasContext('canvas');
ctx.setFillStyle('#FFF');
ctx.fillRect(0, 0, 305, 305);
ctx.beginPath();
ctx.arc(this.point.x, this.point.y, 10, 0, 2 * Math.PI);
ctx.setFillStyle("rgb(" + this.point.r + ", " + this.point.g + ", " + this.point.b + ")");
ctx.fill();
ctx.draw();
this.point.x += this.point.dx;
this.point.y += this.point.dy;
if (this.point.x <= 5 || this.point.x >= 295) {
this.point.dx = -this.point.dx;
this.point.r = Math.round(Math.random() * 255 | 0);
this.point.g = Math.round(Math.random() * 255 | 0);
this.point.b = Math.round(Math.random() * 255 | 0);
}
if (this.point.y <= 5 || this.point.y >= 295) {
this.point.dy = -this.point.dy;
this.point.r = Math.round(Math.random() * 255 | 0);
this.point.g = Math.round(Math.random() * 255 | 0);
this.point.b = Math.round(Math.random() * 255 | 0);
}
},
drawBall() {
},
log(e) {
if (e.touches && e.touches[0]) {
console.log(e.type, e.touches[0].x, e.touches[0].y);
} else {
console.log(e.type);
}
},
onUnload() {
clearInterval(this.interval)
}
})