What is the best way to utilize and modify global variables within a React Native environment?

Question

What is the best way to utilize and modify global variables within a React Native environment?

I am a beginner in the world of react-native and recently created a stop watch. However, I encountered an issue where the stop watch stops working when I navigate to another page and then return. My goal is to have the stop watch continue running until the user presses the stop button. I believe using a global variable might solve this problem, but I am unsure how to implement it. Below is my current code:

export default class Record extends Component {
 constructor(props) {
  super(props);
  this.state = {
  stopwatchStart: false,
  stopWatchTime: '00:00:00'

};
toggleStopwatch() {

if (!this.state.stopwatchStart) {
  startDate = new Date();
  startTime = startDate.getTime();
  that = this;
  setInterval(function () {
    var date = new Date();
    time = (date.getTime() - startTime) / 1000;
    hour = parseInt(time / 3600);
    timeAgo = parseInt(time % 3600);
    min = parseInt(timeAgo / 60);
    second = parseInt(timeAgo % 60);
    that.setState({
      stopWatchTime: (hour + ':' + min + ':' + second)
    })
  }, 1000);  
}
this.setState({ stopwatchStart: !this.state.stopwatchStart });}

javascript android react-native

Answer 1

Answer №1

It might be beneficial to implement redux for managing this situation. Check out more information on Redux here!

Answer 2

It might be beneficial to implement redux for managing this situation. Check out more information on Redux here!

Answer 3

Answer №2

I'm seeking clarification on your specific needs. Would you like the interval to continue running even after changing screens? It's important to note that components do not typically function in this way. To properly manage the lifecycle of components, it is recommended to refer to the documentation at https://reactjs.org/docs/react-component.html. This means that when you change screens within the "Record" component, it will be unmounted and the interval will consequently be destroyed. If you could provide more details about how you intend to use the interval, especially if you plan to utilize it across multiple components, it would greatly assist in providing a suitable solution.

Answer 4

I'm seeking clarification on your specific needs. Would you like the interval to continue running even after changing screens? It's important to note that components do not typically function in this way. To properly manage the lifecycle of components, it is recommended to refer to the documentation at https://reactjs.org/docs/react-component.html. This means that when you change screens within the "Record" component, it will be unmounted and the interval will consequently be destroyed. If you could provide more details about how you intend to use the interval, especially if you plan to utilize it across multiple components, it would greatly assist in providing a suitable solution.

Answer 5

Answer №3

It's still unclear to me what you mean by "view", but it could be related to switching to another app or putting the current app in the background. To ensure data persistence in your React Native application, consider utilizing AsyncStorage. In the future, you may explore options like Sqlite, Redux Persist, or similar solutions to maintain persistent data.

You can save data before the app is sent to the background using the following code:

try {
  await AsyncStorage.setItem('timeKey', myTimeVar.toString());
} catch (error) {
  // Handle error saving data
}

To retrieve the most recent value using the respective key, use this code snippet:

try {
  const value = await AsyncStorage.getItem('timeKey');
  if (value !== null){
    console.log(value);
  }
} catch (error) {
  // Handle error retrieving data
}

You don't necessarily need to run a timer in the background; instead, you can calculate the difference between when the app was closed and the current time plus any time wasted during the first session to achieve your desired outcome.

Answer 6

It's still unclear to me what you mean by "view", but it could be related to switching to another app or putting the current app in the background. To ensure data persistence in your React Native application, consider utilizing AsyncStorage. In the future, you may explore options like Sqlite, Redux Persist, or similar solutions to maintain persistent data.

You can save data before the app is sent to the background using the following code:

try {
  await AsyncStorage.setItem('timeKey', myTimeVar.toString());
} catch (error) {
  // Handle error saving data
}

To retrieve the most recent value using the respective key, use this code snippet:

try {
  const value = await AsyncStorage.getItem('timeKey');
  if (value !== null){
    console.log(value);
  }
} catch (error) {
  // Handle error retrieving data
}

You don't necessarily need to run a timer in the background; instead, you can calculate the difference between when the app was closed and the current time plus any time wasted during the first session to achieve your desired outcome.

What is the best way to utilize and modify global variables within a React Native environment?

Answer №1

Answer №2

Answer №3

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