react-native/RNTester/js/AppStateExample.js

96 lines
2.5 KiB
JavaScript

/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
'use strict';
const React = require('react');
const ReactNative = require('react-native');
const {
AppState,
Text,
View
} = ReactNative;
class AppStateSubscription extends React.Component<$FlowFixMeProps, $FlowFixMeState> {
state = {
appState: AppState.currentState,
previousAppStates: [],
memoryWarnings: 0,
};
componentDidMount() {
AppState.addEventListener('change', this._handleAppStateChange);
AppState.addEventListener('memoryWarning', this._handleMemoryWarning);
}
componentWillUnmount() {
AppState.removeEventListener('change', this._handleAppStateChange);
AppState.removeEventListener('memoryWarning', this._handleMemoryWarning);
}
_handleMemoryWarning = () => {
this.setState({memoryWarnings: this.state.memoryWarnings + 1});
};
_handleAppStateChange = (appState) => {
var previousAppStates = this.state.previousAppStates.slice();
previousAppStates.push(this.state.appState);
this.setState({
appState,
previousAppStates,
});
};
render() {
if (this.props.showMemoryWarnings) {
return (
<View>
<Text>{this.state.memoryWarnings}</Text>
</View>
);
}
if (this.props.showCurrentOnly) {
return (
<View>
<Text>{this.state.appState}</Text>
</View>
);
}
return (
<View>
<Text>{JSON.stringify(this.state.previousAppStates)}</Text>
</View>
);
}
}
exports.title = 'AppState';
exports.description = 'app background status';
exports.examples = [
{
title: 'AppState.currentState',
description: 'Can be null on app initialization',
render() { return <Text>{AppState.currentState}</Text>; }
},
{
title: 'Subscribed AppState:',
description: 'This changes according to the current state, so you can only ever see it rendered as "active"',
render(): React.Element<any> { return <AppStateSubscription showCurrentOnly={true} />; }
},
{
title: 'Previous states:',
render(): React.Element<any> { return <AppStateSubscription showCurrentOnly={false} />; }
},
{
platform: 'ios',
title: 'Memory Warnings',
description: 'In the IOS simulator, hit Shift+Command+M to simulate a memory warning.',
render(): React.Element<any> { return <AppStateSubscription showMemoryWarnings={true} />; }
},
];