我們經(jīng)常需要執(zhí)行耗時較長的代碼。為了良好的用戶體驗，我們在異步處理耗時代碼時，采用Loading加載動畫的形式來等待處理。

這里參考了《React native Model組件的使用》。

1.在components下新建loading.js文件，如下

/**
?*?調(diào)用說明：
?*{this.Loading?=?r}}?hide?=?{true}?/>?//放在布局的最后即可
?*?在需要顯示的地方調(diào)用this.Loading.show();
?*?在需要隱藏的地方調(diào)用this.Loading.close();
?*/

import?React,?{?Component?}?from?'react';
import?{
????Platform,
????View,
????ActivityIndicator,
????Modal,
}?from?'react-native';

import?PropTypes?from?'prop-types';

export?default?class?Loading?extends?Component?{
????constructor(props)?{
????????super(props);
????????this.state?=?{
????????????modalVisible:?!this.props.hide,
????????}
????}

????close()?{
????????if?(Platform.OS?===?'android')?{
????????????setTimeout(()=>{
????????????????this.setState({modalVisible:?false});
????????????},1000)
????????}else?{
????????????this.setState({modalVisible:?false});
????????}
????}

????show()?{
????????this.setState({modalVisible:?true});
????}

????render()?{
????????if?(!this.state.modalVisible)?{
????????????return?null
????????}
????????return?({}}
????????????>);
????}
}

Loading.PropTypes?=?{
????hide:?PropTypes.bool.isRequired,
};

2.在App.js中引入loading.js

import?Loading?from?'./components/loading';

在最外層的View中底部渲染Loading

????????????{/*{/*......*/}
????????????????{/**/}
????????????????{/**/}{this.Loading?=?r}}?hide?=?{true}?/>

定義全局的方法

let?self;?//將App組件中的this賦給全局的self
global.showLoading?=?false;?//所有子頁面均可直接調(diào)用global.showLoading()來展示Loading
global.closeLoading?=?false;?//所有子頁面均可直接調(diào)用global.closeLoading()來關(guān)閉Loading

給全局方法賦值，使其可以在任何頁面調(diào)用

????componentDidMount()?{
????????self?=?this;
????????global.showLoading?=?function()?{
????????????self.Loading.show();
????????};
????????global.closeLoading?=?function()?{
????????????self.Loading.close();
????????};
????}

調(diào)用Loading

????_showLoading()?{
????????global.showLoading();
????????setTimeout(()=>{
????????????global.closeLoading();
????????},500)
????}

this._showLoading();