Android AppState

Summary: Closes https://github.com/facebook/react-native/pull/5152

Reviewed By: svcscm

Differential Revision: D2850250

Pulled By: mkonicek

fb-gh-sync-id: 0b5063fa7121d4e304a70da8573c9ba1d05a757c

Examples/UIExplorer/AppStateExample.js

@@ -0,0 +1,80 @@
+/**
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @providesModule AppStateExample
+ * @flow
+ */
+'use strict';
+
+var React = require('react-native');
+var {
+  AppState,
+  Text,
+  View
+} = React;
+
+var AppStateSubscription = React.createClass({
+  getInitialState() {
+    return {
+      appState: AppState.currentState,
+      previousAppStates: [],
+    };
+  },
+  componentDidMount: function() {
+    AppState.addEventListener('change', this._handleAppStateChange);
+  },
+  componentWillUnmount: function() {
+    AppState.removeEventListener('change', this._handleAppStateChange);
+  },
+  _handleAppStateChange: function(appState) {
+    var previousAppStates = this.state.previousAppStates.slice();
+    previousAppStates.push(this.state.appState);
+    this.setState({
+      appState,
+      previousAppStates,
+    });
+  },
+  render() {
+    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(): ReactElement { return <AppStateSubscription showCurrentOnly={true} />; }
+  },
+  {
+    title: 'Previous states:',
+    render(): ReactElement { return <AppStateSubscription showCurrentOnly={false} />; }
+  },
+];