Javascript angular2在更改detetion后在画布上绘制图像
我有一个angular2组件:Javascript angular2在更改detetion后在画布上绘制图像,javascript,canvas,angular,Javascript,Canvas,Angular,我有一个angular2组件: @Component({ selector: 'my-image', template: ` <img #img src="{{src}}" style='display: none;' /> <canvas #canvas width="{{width}}" height="{{height}}"></canvas>` }) export class ImageComponent impleme
@Component({
selector: 'my-image',
template: `
<img #img src="{{src}}" style='display: none;' />
<canvas #canvas width="{{width}}" height="{{height}}"></canvas>`
})
export class ImageComponent implements AfterViewInit {
@ViewChild('canvas') canvas: ElementRef;
@ViewChild('img') img: ElementRef;
private ctx: CanvasRenderingContext2D;
private element: HTMLImageElement;
src: string;
width: number;
height: number;
constructor(canvas: ElementRef, img: ElementRef) {
this.width = window.innerWidth;
this.height = window.innerHeight;
this.src = 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png';
}
ngAfterViewInit() {
this.ctx = this.canvas.nativeElement.getContext('2d');
this.element = this.img.nativeElement;
}
@HostListener('window:resize')
resize() {
this.width = window.innerWidth;
this.height = window.innerHeight;
this.render();
}
clear() {
this.ctx.clearRect(0, 0, this.width, this.height);
}
render() {
this.clear();
this.ctx.drawImage(this.element, 0, 0, 400, 400);
}
}
@组件({
选择器:“我的图像”,
模板:`
`
})
导出类ImageComponent实现AfterViewInit{
@ViewChild(“画布”)画布:ElementRef;
@ViewChild('img')img:ElementRef;
私人ctx:CanvasRenderingContext2D;
私有元素:HTMLImageElement;
src:字符串;
宽度:数字;
高度:数字;
构造函数(canvas:ElementRef,img:ElementRef){
this.width=window.innerWidth;
this.height=window.innerHeight;
这个.src=https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png';
}
ngAfterViewInit(){
this.ctx=this.canvas.nativeElement.getContext('2d');
this.element=this.img.nativeElement;
}
@HostListener('窗口:调整大小')
调整大小(){
this.width=window.innerWidth;
this.height=window.innerHeight;
这个。render();
}
清除(){
this.ctx.clearRect(0,0,this.width,this.height);
}
render(){
这个.clear();
this.ctx.drawImage(this.element,0,040400);
}
}
所以一切都很好,但是,当我调整窗口大小时,resize回调会被点击并调用render。然后画布上的绑定会重置上下文,留下空白画布。我最初的想法是在检测到更改后再次调用render。这是正确的方法还是有更好的方法
谢谢@rinukkusu回答正确,谢谢 可能尝试在
ngAfterViewChecked
可能尝试调用
ngAfterViewChecked
中的render
方法。