我对React JS非常陌生(例如,从今天开始)。我不太了解setState的工作方式。我将React和Easel JS结合起来,根据用户输入绘制网格。这是我的JS bin:http://jsbin.com/zatula/edit? js,输出
这是代码:
var stage;
var Grid = React.createClass({
getInitialState: function() {
return {
rows: 10,
cols: 10
}
},
componentDidMount: function () {
this.drawGrid();
},
drawGrid: function() {
stage = new createjs.Stage("canvas");
var rectangles = [];
var rectangle;
//Rows
for (var x = 0; x < this.state.rows; x++)
{
// Columns
for (var y = 0; y < this.state.cols; y++)
{
var color = "Green";
rectangle = new createjs.Shape();
rectangle.graphics.beginFill(color);
rectangle.graphics.drawRect(0, 0, 32, 44);
rectangle.x = x * 33;
rectangle.y = y * 45;
stage.addChild(rectangle);
var id = rectangle.x + "_" + rectangle.y;
rectangles[id] = rectangle;
}
}
stage.update();
},
updateNumRows: function(event) {
this.setState({ rows: event.target.value });
this.drawGrid();
},
updateNumCols: function(event) {
this.setState({ cols: event.target.value });
this.drawGrid();
},
render: function() {
return (
<div>
<div className="canvas-wrapper">
<canvas id="canvas" width="400" height="500"></canvas>
<p>Rows: { this.state.rows }</p>
<p>Columns: {this.state.cols }</p>
</div>
<div className="array-form">
<form>
<label>Number of Rows</label>
<select id="numRows" value={this.state.rows} onChange={ this.updateNumRows }>
<option value="1">1</option>
<option value="2">2</option>
<option value ="5">5</option>
<option value="10">10</option>
<option value="12">12</option>
<option value="15">15</option>
<option value="20">20</option>
</select>
<label>Number of Columns</label>
<select id="numCols" value={this.state.cols} onChange={ this.updateNumCols }>
<option value="1">1</option>
<option value="2">2</option>
<option value="5">5</option>
<option value="10">10</option>
<option value="12">12</option>
<option value="15">15</option>
<option value="20">20</option>
</select>
</form>
</div>
</div>
);
}
});
ReactDOM.render(
<Grid />,
document.getElementById("container")
);
当您使用下拉菜单之一更改行数或列数时,您会在JS bin中看到,第一次不会发生任何事情。下次更改下拉值时,网格将绘制到先前状态的行和列值。我猜这是因为我的this.drawGrid()函数在setState完成之前正在执行。也许还有另一个原因?
感谢您的时间和帮助!