From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001 From: Peter Bengtsson Date: Tue, 8 Dec 2020 14:40:17 -0500 Subject: initial commit --- .../drawfocusifneeded/index.html | 133 +++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 files/zh-cn/web/api/canvasrenderingcontext2d/drawfocusifneeded/index.html (limited to 'files/zh-cn/web/api/canvasrenderingcontext2d/drawfocusifneeded') diff --git a/files/zh-cn/web/api/canvasrenderingcontext2d/drawfocusifneeded/index.html b/files/zh-cn/web/api/canvasrenderingcontext2d/drawfocusifneeded/index.html new file mode 100644 index 0000000000..1dc87fb0b2 --- /dev/null +++ b/files/zh-cn/web/api/canvasrenderingcontext2d/drawfocusifneeded/index.html @@ -0,0 +1,133 @@ +--- +title: CanvasRenderingContext2D.drawFocusIfNeeded() +slug: Web/API/CanvasRenderingContext2D/drawFocusIfNeeded +translation_of: Web/API/CanvasRenderingContext2D/drawFocusIfNeeded +--- +
{{APIRef}}
+ +

CanvasRenderingContext2D.drawFocusIfNeeded() 是 Canvas 2D API 用来给当前路径或特定路径绘制焦点的方法，如果给定的元素获取了焦点。

+ +

语法

+ +
void ctx.drawFocusIfNeeded(element);
+void ctx.drawFocusIfNeeded(path, element);
+
+ +

参数

+ +
+
element
+
是否需要设置焦点的元素。
+
path
+
{{domxref("Path2D")}} 路径。
+
+ +

示例

+ +

使用 drawFocusIfNeeded 方法

+ +

这是一段使用 drawFocusIfNeeded 方法的简单的代码片段。

+ +

HTML

+ +
<canvas id="canvas">
+  <input id="button" type="range" min="1" max="12">
+</canvas>
+
+ +

JavaScript

+ +
var canvas = document.getElementById("canvas");
+var ctx = canvas.getContext("2d");
+var button = document.getElementById("button");
+
+button.focus();
+
+ctx.beginPath();
+ctx.rect(10, 10, 30, 30);
+ctx.drawFocusIfNeeded(button);
+
+ +

修改下面的代码并在线查看 canvas的变化：

+ +
+
Playable code
+ +
<canvas id="canvas" width="400" height="200" class="playable-canvas">
+<input id="button" type="range" min="1" max="12">
+</canvas>
+<div class="playable-buttons">
+  <input id="edit" type="button" value="Edit" />
+  <input id="reset" type="button" value="Reset" />
+</div>
+<textarea id="code" class="playable-code">
+ctx.beginPath();
+ctx.rect(10, 10, 30, 30);
+ctx.drawFocusIfNeeded(button);</textarea>
+
+ +
var canvas = document.getElementById("canvas");
+var ctx = canvas.getContext("2d");
+var textarea = document.getElementById("code");
+var button = document.getElementById("button");
+var reset = document.getElementById("reset");
+var edit = document.getElementById("edit");
+var code = textarea.value;
+button.focus();
+
+function drawCanvas() {
+  ctx.clearRect(0, 0, canvas.width, canvas.height);
+  eval(textarea.value);
+}
+
+reset.addEventListener("click", function() {
+  textarea.value = code;
+  drawCanvas();
+});
+
+edit.addEventListener("click", function() {
+  textarea.focus();
+})
+
+textarea.addEventListener("input", drawCanvas);
+window.addEventListener("load", drawCanvas);
+
+
+ +

{{EmbedLiveSample('Playable_code', 700, 360)}}

+ +

规范描述

+ + + + + + + + + + + + + + +
SpecificationStatusComment
{{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-drawfocusifneeded", "CanvasRenderingContext2D.drawFocusIfNeeded")}}{{Spec2('HTML WHATWG')}}Initial definition
+ +

浏览器兼容性

+ + + +

{{Compat("api.CanvasRenderingContext2D.drawFocusIfNeeded")}}

+ +

兼容性注解

+ + + +

参见

+ + -- cgit v1.2.3-54-g00ecf