反应秒表
React stopwatch
大家好,我最近开始学习 React,但遇到了一些问题。我正在尝试制作简单的反应应用程序,我正在制作的组件之一是秒表。现在,我在使用从父组件传递到 Stopwatch 组件的道具时遇到问题。
这是我的应用组件:
import React, {Component} from 'react';
import { Form,FormControl, Button} from 'react-bootstrap';
// Compoenents
import Clock from './Clock';
import Stopwatch from './Stopwatch';
// CSS
import './css/app.css';
class App extends Component {
constructor(props) {
super(props);
this.state = {
deadline: 'December 31, 2017',
newDeadline: '',
timer: 60,
newTimer: ''
}
}
changeDeadline () {
this.setState({deadline: this.state.newDeadline});
}
checkTimer() {
this.setState({timer: this.state.newTimer});
}
render() {
return (
<div className='app'>
<div className='appTitle'>
Countdown to {this.state.deadline}
</div>
<Clock
deadline={this.state.deadline} // This is how we send props to our child component
/>
<Form inline={true} >
<FormControl
className='deadlineInput'
type="text"
placeholder='Write date to check'
onChange={event => this.setState({newDeadline: event.target.value})}
onKeyPress={event => {
if(event.key === 'Enter') {
event.preventDefault();
this.changeDeadline();;
}
}}
/>
<Button
onClick={() => this.changeDeadline()}
>
Submit
</Button>
</Form>
<div className='stopwatchTitle'>
Use stopwatch to {this.state.timer} seconds
</div>
<Stopwatch
timer={this.state.timer} // This is how we send props to our child component
/>
<Form inline={true} >
<FormControl
className='timerInput'
type="text"
placeholder='Set your timer'
onChange={event => this.setState({newTimer: event.target.value})}
onKeyPress={event => {
if(event.key === 'Enter') {
event.preventDefault();
this.checkTimer();;
}
}}
/>
<Button
onClick={() => this.checkTimer()}
>
Start
</Button>
</Form>
</div>
)
}
}
export default App;
这是我的秒表组件:
import React, {Component} from 'react';
// CSS
import './css/stopwatch.css';
class Stopwatch extends Component {
constructor(props) {
super(props);
this.state = {
stopWatch: 0,
}
this.decrementer = null;
}
// This function runs before component completely renders on the application (otherwise we might create infinite loop)
componentWillMount() {
this.startTimer(this.props.timer);
}
startTimer(timer) {
let stopWatch = timer;
console.log(stopWatch)
this.decrementer = setInterval( () =>
this.setState({
stopWatch: this.state.stopWatch - 1
})
, 1000);
}
render() {
return (
<div>
<div className='myStopwatch'> {this.state.stopWatch} seconds</div>
</div>
)
}
}
export default Stopwatch;
现在应用程序总是从 0 开始计数并进入负数。我如何使用我从父组件传递给我的子组件的计时器道具?我希望我的秒表开始时间等于我的计时器道具。还有如何让倒计时到0时停止?
How can I use my timer props that I pass down from my parent to my child component ? I want my stopwatch starting time be equal to my timer props.
在 startTimer(timer)
上,您将 timer
传递给 stopWatch
变量,但最终使用 this.state.stopWatch
来初始化间隔。
由于 this.state.stopWatch
始终为 0,您的秒表将始终从 0 开始。
实现您想要的目标的一种方法是使用您从 props 收到的值初始化 this.state.stopWatch
:
constructor(props) {
super(props);
this.state = {
stopWatch: props.timer
}
this.decrementer = null;
}
componentWillMount() {
this.startTimer(); // now you dont need to pass timer because is already in your local state
}
Also how to make countdown stop when it reaches 0 ?
为此,您需要在计时器达到 0 时清除间隔。您可能还想检查 stopWatch
是否为 0 以防止开始间隔:
startTimer() {
if(!this.state.stopWatch) return; // check if stopWatch is 0
this.decrementer = setInterval( () => {
const stopWatch = this.state.stopWatch - 1;
this.setState({ stopWatch });
if(stopWatch < 1) clearInterval(this.decrementer); // clears interval one stopWatch reaches 0
}, 1000);
}
大家好,我最近开始学习 React,但遇到了一些问题。我正在尝试制作简单的反应应用程序,我正在制作的组件之一是秒表。现在,我在使用从父组件传递到 Stopwatch 组件的道具时遇到问题。 这是我的应用组件:
import React, {Component} from 'react';
import { Form,FormControl, Button} from 'react-bootstrap';
// Compoenents
import Clock from './Clock';
import Stopwatch from './Stopwatch';
// CSS
import './css/app.css';
class App extends Component {
constructor(props) {
super(props);
this.state = {
deadline: 'December 31, 2017',
newDeadline: '',
timer: 60,
newTimer: ''
}
}
changeDeadline () {
this.setState({deadline: this.state.newDeadline});
}
checkTimer() {
this.setState({timer: this.state.newTimer});
}
render() {
return (
<div className='app'>
<div className='appTitle'>
Countdown to {this.state.deadline}
</div>
<Clock
deadline={this.state.deadline} // This is how we send props to our child component
/>
<Form inline={true} >
<FormControl
className='deadlineInput'
type="text"
placeholder='Write date to check'
onChange={event => this.setState({newDeadline: event.target.value})}
onKeyPress={event => {
if(event.key === 'Enter') {
event.preventDefault();
this.changeDeadline();;
}
}}
/>
<Button
onClick={() => this.changeDeadline()}
>
Submit
</Button>
</Form>
<div className='stopwatchTitle'>
Use stopwatch to {this.state.timer} seconds
</div>
<Stopwatch
timer={this.state.timer} // This is how we send props to our child component
/>
<Form inline={true} >
<FormControl
className='timerInput'
type="text"
placeholder='Set your timer'
onChange={event => this.setState({newTimer: event.target.value})}
onKeyPress={event => {
if(event.key === 'Enter') {
event.preventDefault();
this.checkTimer();;
}
}}
/>
<Button
onClick={() => this.checkTimer()}
>
Start
</Button>
</Form>
</div>
)
}
}
export default App;
这是我的秒表组件:
import React, {Component} from 'react';
// CSS
import './css/stopwatch.css';
class Stopwatch extends Component {
constructor(props) {
super(props);
this.state = {
stopWatch: 0,
}
this.decrementer = null;
}
// This function runs before component completely renders on the application (otherwise we might create infinite loop)
componentWillMount() {
this.startTimer(this.props.timer);
}
startTimer(timer) {
let stopWatch = timer;
console.log(stopWatch)
this.decrementer = setInterval( () =>
this.setState({
stopWatch: this.state.stopWatch - 1
})
, 1000);
}
render() {
return (
<div>
<div className='myStopwatch'> {this.state.stopWatch} seconds</div>
</div>
)
}
}
export default Stopwatch;
现在应用程序总是从 0 开始计数并进入负数。我如何使用我从父组件传递给我的子组件的计时器道具?我希望我的秒表开始时间等于我的计时器道具。还有如何让倒计时到0时停止?
How can I use my timer props that I pass down from my parent to my child component ? I want my stopwatch starting time be equal to my timer props.
在 startTimer(timer)
上,您将 timer
传递给 stopWatch
变量,但最终使用 this.state.stopWatch
来初始化间隔。
由于 this.state.stopWatch
始终为 0,您的秒表将始终从 0 开始。
实现您想要的目标的一种方法是使用您从 props 收到的值初始化 this.state.stopWatch
:
constructor(props) {
super(props);
this.state = {
stopWatch: props.timer
}
this.decrementer = null;
}
componentWillMount() {
this.startTimer(); // now you dont need to pass timer because is already in your local state
}
Also how to make countdown stop when it reaches 0 ?
为此,您需要在计时器达到 0 时清除间隔。您可能还想检查 stopWatch
是否为 0 以防止开始间隔:
startTimer() {
if(!this.state.stopWatch) return; // check if stopWatch is 0
this.decrementer = setInterval( () => {
const stopWatch = this.state.stopWatch - 1;
this.setState({ stopWatch });
if(stopWatch < 1) clearInterval(this.decrementer); // clears interval one stopWatch reaches 0
}, 1000);
}