webview（Android）加载h5实体按键（虚拟按键）返回处理

添加onNavigationStateChange方法并判断

/*** 是否可以返回* &＃64;param navState*/
onNavigationStateChange&＃61;(navState)&＃61;>{this.setState({backButtonEnabled: navState.canGoBack});
}


添加监听处理

if(Platform.OS&＃61;&＃61;&＃61;&＃39;android&＃39;){this.backHandler&＃61;BackHandler.addEventListener("hardwareBackPress",()&＃61;>{if (this.state.backButtonEnabled) {this.webview.goBack();return true;} else {this.onBack();}});
}


移除监听

if(Platform.OS&＃61;&＃61;&＃61;&＃39;android&＃39;) {this.backHandler.remove();
}