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我知道有很多關於componentdidmount和setState insde的問題。但我不明白爲什麼我的console.log它時,我的this.state.context爲空?componentDidMount中的setState不會改變狀態
這是我的組件的一個片段。我用畫布畫出一些數字。
var App = React.createClass({
getInitialState(){
var board = [];
for(var i=0; i<30; i++){
var temp=[];
for(var j=0; j<50; j++){
temp.push(0);
}
board.push(temp);
}
//glider pattern
board[0][2]=1;
board[1][0]=1;
board[1][1]=1;
board[2][1]=1;
board[2][2]=1;
return {
width: 550,
height: 350,
step: 0,
board: board,
isOn: true,
isPaused: false,
context: null
}
},
componentDidMount(){
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
//drawing text
ctx.fillStyle = "#777";
ctx.font = "16px arial";
ctx.fillText("Yonger", 25, 343);
ctx.fillText("Older", 120, 343);
ctx.fillText("Generation:", 25, 18);
ctx.fillStyle = "rgb(140, 198, 101)";
ctx.fillRect (85, 333, 10, 10);
ctx.fillStyle = "rgb(30, 104, 35)";
ctx.fillRect (100, 333, 10, 10);
this.setState({context:ctx});
console.log(this.state.context);
this.draw();
},
這時奇怪的事情:
console.log(this.state.context);
的console.log將打印空!但ctx實際上不是空!
我在這裏回答了http://stackoverflow.com/questions/39531547/issue-with-setstate-in-if-statement/39531639 #39531639 – StateLess