反应详细信息列表始终为空

我正在尝试使用以下 React Office ui 组件：https : //developer.microsoft.com/en-us/fabric#/components/detailslist

所以我有一个带有组件的 webpart，但我有两个问题：

1. webpart第一次加载时，列表没有被选中，所以它应该打开属性页但它没有打开，这就是为什么我不得不做一个小技巧：我根本不喜欢

 public render(): void {
    const element: React.ReactElement<IFactoryMethodProps > = React.createElement(
      FactoryMethod,
      {
        spHttpClient: this.context.spHttpClient,
        siteUrl: this.context.pageContext.web.absoluteUrl,
        listName: this._dataProvider.selectedList === undefined ? "GenericList" : this._dataProvider.selectedList.Title,
        dataProvider: this._dataProvider,
        configureStartCallback: this.openPropertyPane
      }
    );

    //ReactDom.render(element, this.domElement);
    this._factorymethodContainerComponent = <FactoryMethod>ReactDom.render(element, this.domElement);

  }

第二个问题是当用户选择另一个 List 来呈现项目时， readItemsAndSetStatus 没有被调用，因此状态没有得到更新。

webpart代码如下：

import * as React from "react";
import * as ReactDom from "react-dom";
import { Version } from "@microsoft/sp-core-library";
import {
  BaseClientSideWebPart,
  IPropertyPaneConfiguration,
  PropertyPaneTextField,
  PropertyPaneDropdown,
  IPropertyPaneDropdownOption,
  IPropertyPaneField,
  PropertyPaneLabel
} from "@microsoft/sp-webpart-base";

import * as strings from "FactoryMethodWebPartStrings";
import FactoryMethod from "./components/FactoryMethod";
import { IFactoryMethodProps } from "./components/IFactoryMethodProps";
import { IFactoryMethodWebPartProps } from "./IFactoryMethodWebPartProps";
import * as lodash from "@microsoft/sp-lodash-subset";
import List from "./components/models/List";
import { Environment, EnvironmentType } from "@microsoft/sp-core-library";
import IDataProvider from "./components/dataproviders/IDataProvider";
import MockDataProvider from "./test/MockDataProvider";
import SharePointDataProvider from "./components/dataproviders/SharepointDataProvider";

export default class FactoryMethodWebPart extends BaseClientSideWebPart<IFactoryMethodWebPartProps> {
  private _dropdownOptions: IPropertyPaneDropdownOption[];
  private _selectedList: List;
  private _disableDropdown: boolean;
  private _dataProvider: IDataProvider;
  private _factorymethodContainerComponent: FactoryMethod;

  protected onInit(): Promise<void> {
    this.context.statusRenderer.displayLoadingIndicator(this.domElement, "Todo");

    /*
    Create the appropriate data provider depending on where the web part is running.
    The DEBUG flag will ensure the mock data provider is not bundled with the web part when you package the
     solution for distribution, that is, using the --ship flag with the package-solution gulp command.
    */
    if (DEBUG && Environment.type === EnvironmentType.Local) {
      this._dataProvider = new MockDataProvider();
    } else {
      this._dataProvider = new SharePointDataProvider();
      this._dataProvider.webPartContext = this.context;
    }

    this.openPropertyPane = this.openPropertyPane.bind(this);

    /*
    Get the list of tasks lists from the current site and populate the property pane dropdown field with the values.
    */
    this.loadLists()
      .then(() => {
        /*
         If a list is already selected, then we would have stored the list Id in the associated web part property.
         So, check to see if we do have a selected list for the web part. If we do, then we set that as the selected list
         in the property pane dropdown field.
        */
        if (this.properties.spListIndex) {
          this.setSelectedList(this.properties.spListIndex.toString());
          this.context.statusRenderer.clearLoadingIndicator(this.domElement);
        }
      });

    return super.onInit();
  }

  // render method of the webpart, actually calls Component
  public render(): void {
    const element: React.ReactElement<IFactoryMethodProps > = React.createElement(
      FactoryMethod,
      {
        spHttpClient: this.context.spHttpClient,
        siteUrl: this.context.pageContext.web.absoluteUrl,
        listName: this._dataProvider.selectedList === undefined ? "GenericList" : this._dataProvider.selectedList.Title,
        dataProvider: this._dataProvider,
        configureStartCallback: this.openPropertyPane
      }
    );

    //ReactDom.render(element, this.domElement);
    this._factorymethodContainerComponent = <FactoryMethod>ReactDom.render(element, this.domElement);

  }

  // loads lists from the site and filld the dropdown.
  private loadLists(): Promise<any> {
    return this._dataProvider.getLists()
      .then((lists: List[]) => {
        // disable dropdown field if there are no results from the server.
        this._disableDropdown = lists.length === 0;
        if (lists.length !== 0) {
          this._dropdownOptions = lists.map((list: List) => {
            return {
              key: list.Id,
              text: list.Title
            };
          });
        }
      });
  }

  protected get dataVersion(): Version {
    return Version.parse("1.0");
  }

  protected onPropertyPaneFieldChanged(propertyPath: string, oldValue: any, newValue: any): void {
    /*
    Check the property path to see which property pane feld changed. If the property path matches the dropdown, then we set that list
    as the selected list for the web part.
    */
    if (propertyPath === "spListIndex") {
      this.setSelectedList(newValue);
    }

    /*
    Finally, tell property pane to re-render the web part.
    This is valid for reactive property pane.
    */
    super.onPropertyPaneFieldChanged(propertyPath, oldValue, newValue);
  }

  // sets the selected list based on the selection from the dropdownlist
  private setSelectedList(value: string): void {
    const selectedIndex: number = lodash.findIndex(this._dropdownOptions,
      (item: IPropertyPaneDropdownOption) => item.key === value
    );

    const selectedDropDownOption: IPropertyPaneDropdownOption = this._dropdownOptions[selectedIndex];

    if (selectedDropDownOption) {
      this._selectedList = {
        Title: selectedDropDownOption.text,
        Id: selectedDropDownOption.key.toString()
      };

      this._dataProvider.selectedList = this._selectedList;
    }
  }


  // we add fields dynamically to the property pane, in this case its only the list field which we will render
  private getGroupFields(): IPropertyPaneField<any>[] {
    const fields: IPropertyPaneField<any>[] = [];

    // we add the options from the dropdownoptions variable that was populated during init to the dropdown here.
    fields.push(PropertyPaneDropdown("spListIndex", {
      label: "Select a list",
      disabled: this._disableDropdown,
      options: this._dropdownOptions
    }));

    /*
    When we do not have any lists returned from the server, we disable the dropdown. If that is the case,
    we also add a label field displaying the appropriate message.
    */
    if (this._disableDropdown) {
      fields.push(PropertyPaneLabel(null, {
        text: "Could not find tasks lists in your site. Create one or more tasks list and then try using the web part."
      }));
    }

    return fields;
  }

  private openPropertyPane(): void {
    this.context.propertyPane.open();
  }

  protected getPropertyPaneConfiguration(): IPropertyPaneConfiguration {
    return {
      pages: [
        {
          header: {
            description: strings.PropertyPaneDescription
          },
          groups: [
            {
              groupName: strings.BasicGroupName,
              /*
              Instead of creating the fields here, we call a method that will return the set of property fields to render.
              */
              groupFields: this.getGroupFields()
            }
          ]
        }
      ]
    };
  }
}

组件webpart代码，为简洁起见省略代码

//#region Imports
import * as React from "react";
import styles from "./FactoryMethod.module.scss";
import { IFactoryMethodProps } from "./IFactoryMethodProps";
import {
  IDetailsListItemState,
  IDetailsNewsListItemState,
  IDetailsDirectoryListItemState,
  IDetailsAnnouncementListItemState,
  IFactoryMethodState
} from "./IFactoryMethodState";
import { IListItem } from "./models/IListItem";
import { IAnnouncementListItem } from "./models/IAnnouncementListItem";
import { INewsListItem } from "./models/INewsListItem";
import { IDirectoryListItem } from "./models/IDirectoryListItem";
import { escape } from "@microsoft/sp-lodash-subset";
import { SPHttpClient, SPHttpClientResponse } from "@microsoft/sp-http";
import { ListItemFactory} from "./ListItemFactory";
import { TextField } from "office-ui-fabric-react/lib/TextField";
import {
  DetailsList,
  DetailsListLayoutMode,
  Selection,
  IColumn
} from "office-ui-fabric-react/lib/DetailsList";
import { MarqueeSelection } from "office-ui-fabric-react/lib/MarqueeSelection";
import { autobind } from "office-ui-fabric-react/lib/Utilities";
//#endregion

export default class FactoryMethod extends React.Component<IFactoryMethodProps, IFactoryMethodState> {
  private listItemEntityTypeName: string = undefined;
  private _selection: Selection;

  constructor(props: IFactoryMethodProps, state: any) {
    super(props);
    this.setInitialState();
    this._configureWebPart = this._configureWebPart.bind(this);
  }

  public componentWillReceiveProps(nextProps: IFactoryMethodProps): void {
    this.listItemEntityTypeName = undefined;
    this.setInitialState();
  }

  public componentDidMount(): void {
    this.readItemsAndSetStatus();
  }

  public setInitialState(): void {
    this.state = {
      type: "ListItem",
      status: this.listNotConfigured(this.props)
        ? "Please configure list in Web Part properties"
        : "Ready",
      DetailsListItemState:{
        columns:[],
        items:[]
      },
      DetailsNewsListItemState:{
        columns:[],
        items:[]
      },
      DetailsDirectoryListItemState:{
        columns:[],
        items:[]
      },
      DetailsAnnouncementListItemState:{
        columns:[],
        items:[]
      },
    };
  }

  private _configureWebPart(): void {
    this.props.configureStartCallback();
  }

  // reusable inline component
  public ListMarqueeSelection = (itemState: {columns: IColumn[], items: IListItem[] }) => (
      <div>
        <MarqueeSelection selection={ this._selection }>
          <DetailsList
            items={ itemState.items }
            columns={ itemState.columns }
            setKey="set"
            layoutMode={ DetailsListLayoutMode.fixedColumns }
            selection={ this._selection }
            selectionPreservedOnEmptyClick={ true }
            compact={ true }>
          </DetailsList>
        </MarqueeSelection>
      </div>
  )

  public render(): React.ReactElement<IFactoryMethodProps> {
      switch(this.props.listName)      {
          case "GenericList":
            // tslint:disable-next-line:max-line-length
            return <this.ListMarqueeSelection items={this.state.DetailsListItemState.items} columns={this.state.DetailsListItemState.columns} />;
          case "News":
            // tslint:disable-next-line:max-line-length
            return <this.ListMarqueeSelection items={this.state.DetailsNewsListItemState.items} columns={this.state.DetailsNewsListItemState.columns}/>;
          case "Announcements":
            // tslint:disable-next-line:max-line-length
            return <this.ListMarqueeSelection items={this.state.DetailsAnnouncementListItemState.items} columns={this.state.DetailsAnnouncementListItemState.columns}/>;
          case "Directory":
            // tslint:disable-next-line:max-line-length
            return <this.ListMarqueeSelection items={this.state.DetailsDirectoryListItemState.items} columns={this.state.DetailsDirectoryListItemState.columns}/>;
          default:
            return null;
      }
  }

  // read items using factory method pattern and sets state accordingly
  private readItemsAndSetStatus(): void {

    this.setState({
      status: "Loading all items..."
    });

    const factory: ListItemFactory = new ListItemFactory();
    const items: IListItem[] = factory.getItems(this.props.spHttpClient, this.props.siteUrl, this.props.listName);
    const keyPart: string = this.props.listName === "GenericList" ? "" : this.props.listName;
    if(items != null  )
    {
      // the explicit specification of the type argument `keyof {}` is bad and
      // it should not be required.
      this.setState<keyof {}>({
        status: `Successfully loaded ${items.length} items`,
        ["Details" + keyPart + "ListItemState"] : {
          items,
          columns: [
          ]
        }
      });
    }

  }

  private listNotConfigured(props: IFactoryMethodProps): boolean {
    return props.listName === undefined ||
      props.listName === null ||
      props.listName.length === 0;
  }
}

readitemsandsetstatus 显然只在开始时执行一次，而不是在源更改时执行

更新 1：

感谢首先回答的人，根据他的回答，我去研究了生命周期事件，发现了这篇不错的帖子：

https://staminaloops.github.io/undefinedisnotafunction/understanding-react/

基于这一点和你的回答，我更新了我的代码：

//#region Imports
import * as React from "react";
import styles from "./FactoryMethod.module.scss";
import  { IFactoryMethodProps } from "./IFactoryMethodProps";
import {
  IDetailsListItemState,
  IDetailsNewsListItemState,
  IDetailsDirectoryListItemState,
  IDetailsAnnouncementListItemState,
  IFactoryMethodState
} from "./IFactoryMethodState";
import { IListItem } from "./models/IListItem";
import { IAnnouncementListItem } from "./models/IAnnouncementListItem";
import { INewsListItem } from "./models/INewsListItem";
import { IDirectoryListItem } from "./models/IDirectoryListItem";
import { escape } from "@microsoft/sp-lodash-subset";
import { SPHttpClient, SPHttpClientResponse } from "@microsoft/sp-http";
import { ListItemFactory} from "./ListItemFactory";
import { TextField } from "office-ui-fabric-react/lib/TextField";
import {
  DetailsList,
  DetailsListLayoutMode,
  Selection,
  buildColumns,
  IColumn
} from "office-ui-fabric-react/lib/DetailsList";
import { MarqueeSelection } from "office-ui-fabric-react/lib/MarqueeSelection";
import { autobind } from "office-ui-fabric-react/lib/Utilities";
import PropTypes from "prop-types";
//#endregion


export default class FactoryMethod extends React.Component<IFactoryMethodProps, IFactoryMethodState> {
  private _selection: Selection;

  constructor(props: IFactoryMethodProps, state: any) {
    super(props);
  }

  // lifecycle help here: https://staminaloops.github.io/undefinedisnotafunction/understanding-react/

  //#region Mouting events lifecycle
  // the object returned by this method sets the initial value of this.state
  getInitialState(): {}   {
    return {
        type: "GenericList",
        status: this.listNotConfigured(this.props)
          ? "Please configure list in Web Part properties"
          : "Ready",
        columns: [],
        DetailsListItemState:{
          items:[]
        },
        DetailsNewsListItemState:{
          items:[]
        },
        DetailsDirectoryListItemState:{
          items:[]
        },
        DetailsAnnouncementListItemState:{
          items:[]
        },
      };
  }

  // the object returned by this method sets the initial value of this.props
  // if a complex object is returned, it is shared among all component instances
  getDefaultProps(): {}  {
    return {

    };
  }

  // invoked once BEFORE first render
  componentWillMount(nextProps: IFactoryMethodProps): void {
    // calling setState here does not cause a re-render

    this.readItemsAndSetStatus(nextProps);
  }

  // the data returned from render is neither a string nor a DOM node.
  // it's a lightweight description of what the DOM should look like.
  // inspects this.state and this.props and create the markup.
  // when your data changes, the render method is called again.
  // react diff the return value from the previous call to render with
  // the new one, and generate a minimal set of changes to be applied to the DOM.
  public render(nextProps: IFactoryMethodProps): React.ReactElement<IFactoryMethodProps> {
    this.readItemsAndSetStatus(nextProps);
    switch(this.props.listName) {
        case "GenericList":
          // tslint:disable-next-line:max-line-length
          return <this.ListMarqueeSelection items={this.state.DetailsListItemState.items} columns={this.state.columns} />;
        case "News":
          // tslint:disable-next-line:max-line-length
          return <this.ListMarqueeSelection items={this.state.DetailsNewsListItemState.items} columns={this.state.columns}/>;
        case "Announcements":
          // tslint:disable-next-line:max-line-length
          return <this.ListMarqueeSelection items={this.state.DetailsAnnouncementListItemState.items} columns={this.state.columns}/>;
        case "Directory":
          // tslint:disable-next-line:max-line-length
          return <this.ListMarqueeSelection items={this.state.DetailsDirectoryListItemState.items} columns={this.state.columns}/>;
        default:
          return null;
    }
  }

   // invoked once, only on the client (not on the server), immediately AFTER the initial rendering occurs.
   public componentDidMount(nextProps: IFactoryMethodProps): void {
    // you can access any refs to your children
    // (e.g., to access the underlying DOM representation - ReactDOM.findDOMNode). 
    // the componentDidMount() method of child components is invoked before that of parent components.
    // if you want to integrate with other JavaScript frameworks,
    // set timers using setTimeout or setInterval, 
    // or send AJAX requests, perform those operations in this method.
    this._configureWebPart = this._configureWebPart.bind(this);

    // calling read items does not make any sense here, so I called in the will Mount, is that correct?
    // this.readItemsAndSetStatus(nextProps);
  }

  //#endregion

  //#region Props changes lifecycle events (after a property changes from parent component)
  public componentWillReceiveProps(nextProps: IFactoryMethodProps): void {
    this.readItemsAndSetStatus(nextProps);
  }

  // determines if the render method should run in the subsequent step
  // dalled BEFORE a second render
  // not called for the initial render
  shouldComponentUpdate(nextProps: IFactoryMethodProps, nextState: IFactoryMethodProps): boolean {
    // if you want the render method to execute in the next step
    // return true, else return false
      return true;
  }

  // called IMMEDIATELY BEFORE a second render
  componentWillUpdate(nextProps: IFactoryMethodProps, nextState: IFactoryMethodProps): void {
    // you cannot use this.setState() in this method
  }

  // called IMMEDIATELY AFTER a second render
  componentDidUpdate(prevProps: IFactoryMethodProps, prevState: IFactoryMethodProps): void {
    // nothing here yet
  }

  //#endregion

  // called IMMEDIATELY before a component is unmounted from the DOM, No region here, its only one method for that lifecycle
  componentWillUnmount(): void {
    // nothing here yet
  }

  //#region private methods
  private _configureWebPart(): void {
    this.props.configureStartCallback();
  }

  // reusable inline component
  private ListMarqueeSelection = (itemState: {columns: IColumn[], items: IListItem[] }) => (
      <div>
        <MarqueeSelection selection={ this._selection }>
          <DetailsList
            items={ itemState.items }
            columns={ itemState.columns }
            setKey="set"
            layoutMode={ DetailsListLayoutMode.fixedColumns }
            selection={ this._selection }
            selectionPreservedOnEmptyClick={ true }
            compact={ true }>
          </DetailsList>
        </MarqueeSelection>
      </div>
  )

  // read items using factory method pattern and sets state accordingly
  private readItemsAndSetStatus(props: IFactoryMethodProps): void {

    this.setState({
      status: "Loading all items..."
    });

    const factory: ListItemFactory = new ListItemFactory();
    factory.getItems(props.spHttpClient, props.siteUrl, props.listName)
    .then((items: IListItem[]) => {
      const keyPart: string = props.listName === "GenericList" ? "" : props.listName;
        // the explicit specification of the type argument `keyof {}` is bad and
        // it should not be required.
        this.setState<keyof {}>({
          status: `Successfully loaded ${items.length} items`,
          ["Details" + keyPart + "ListItemState"] : {
            items
          },
          columns: buildColumns(items)
        });
    });
  }

  private listNotConfigured(props: IFactoryMethodProps): boolean {
    return props.listName === undefined ||
      props.listName === null ||
      props.listName.length === 0;
  }

  //#endregion
}

那么，现在，它更有意义吗？