# Loading Web Pages
Page loading is a basic capability of the **Web** component. Depending on the data source, page loading falls into three types: loading of network pages, loading of local pages, and loading of HTML rich text data.
If you need to obtain online resources when loading a page, declare the network access permission in the **module.json5** file. For details, see [Declaring Permissions](../security/AccessToken/declare-permissions.md).
```
"requestPermissions":[
{
"name" : "ohos.permission.INTERNET"
}
]
```
## Loading Network Pages
You can specify the default network page to be loaded when creating a **Web** component. After the default network page is loaded, call [loadUrl()](../reference/apis-arkweb/js-apis-webview.md#loadurl) if you want to change the network page displayed by the **Web** component. The value of the first parameter **src** of the **Web** component cannot be dynamically changed through a state variable (for example, @State). To change the value, call [loadUrl()](../reference/apis-arkweb/js-apis-webview.md#loadurl).
In the following example, after the **www.\example.com** page is loaded by the **Web** component, **loadUrl** is called to change the displayed page to **www\.example1.com**.
```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';
@Entry
@Component
struct WebComponent {
controller: webview.WebviewController = new webview.WebviewController();
build() {
Column() {
Button('loadUrl')
.onClick(() => {
try {
// Upon button clicking, call loadUrl to redirect to www.example1.com.
this.controller.loadUrl('www.example1.com');
} catch (error) {
console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`);
}
})
// When creating a Web component, set the default network page to be loaded to www.example.com.
Web({ src: 'www.example.com', controller: this.controller })
}
}
}
```
## Loading Local Pages
The following example shows how to load a local page file.
Local page files are stored in the application's **rawfile** directory. You can specify the local page to be loaded by default when creating a **Web** component. After page loading is complete, you can call [loadUrl()](../reference/apis-arkweb/js-apis-webview.md#loadurl) to change the displayed page of the **Web** component.
To reference a local CSS file when loading a local HTML file, perform the following steps:
```html
// Load the local CSS file in the sandbox path.
```
- Local page file in the application's resources/rawfile directory:
**Figure 1** Path of local page files
- Application code:
```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';
@Entry
@Component
struct WebComponent {
controller: webview.WebviewController = new webview.WebviewController();
build() {
Column() {
Button('loadUrl')
.onClick(() => {
try {
// Upon button clicking, call loadUrl to redirect to local1.html.
this.controller.loadUrl($rawfile("local1.html"));
} catch (error) {
console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`);
}
})
// When creating a Web component, load the local.html file through $rawfile.
Web({ src: $rawfile("local.html"), controller: this.controller })
}
}
}
```
- Code of the **local.html** page:
```html
Hello World
```
- Code of the **local1.html** page:
```html
This is local1 page
```
Example of loading local page files in the sandbox:
1. Obtain the sandbox path through the constructed singleton object **GlobalContext**.
```ts
// GlobalContext.ets
export class GlobalContext {
private constructor() {}
private static instance: GlobalContext;
private _objects = new Map();
public static getContext(): GlobalContext {
if (!GlobalContext.instance) {
GlobalContext.instance = new GlobalContext();
}
return GlobalContext.instance;
}
getObject(value: string): Object | undefined {
return this._objects.get(value);
}
setObject(key: string, objectClass: Object): void {
this._objects.set(key, objectClass);
}
}
```
```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { GlobalContext } from '../GlobalContext';
let url = 'file://' + GlobalContext.getContext().getObject("filesDir") + '/index.html';
@Entry
@Component
struct WebComponent {
controller: webview.WebviewController = new webview.WebviewController();
build() {
Column() {
// Load the files in the sandbox.
Web({ src: url, controller: this.controller })
}
}
}
```
2. Modify the **EntryAbility.ets** file.
The following uses **filesDir** as an example to describe how to obtain the path of the sandbox. For details about how to obtain other paths, see [Obtaining Application File Paths](../application-models/application-context-stage.md#obtaining-application-file-paths).
```ts
// xxx.ets
import { AbilityConstant, UIAbility, Want } from '@kit.AbilityKit';
import { webview } from '@kit.ArkWeb';
import { GlobalContext } from '../GlobalContext';
export default class EntryAbility extends UIAbility {
onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
// Data synchronization between the UIAbility component and UI can be implemented by binding filesDir to the GlobalContext object.
GlobalContext.getContext().setObject("filesDir", this.context.filesDir);
console.log("Sandbox path is " + GlobalContext.getContext().getObject("filesDir"));
}
}
```
HTML file to be loaded:
```html
Hello World
```
## Loading HTML Rich Text Data
The **Web** component provides the [loadData()](../reference/apis-arkweb/js-apis-webview.md#loaddata) API for you to load HTML rich text data. This API is applicable if you want to display some page sections instead of the entire page. To load a large number of HTML files, set **baseUrl** to data.
```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';
@Entry
@Component
struct WebComponent {
controller: webview.WebviewController = new webview.WebviewController();
build() {
Column() {
Button('loadData')
.onClick(() => {
try {
// Upon button clicking, call loadData to load HTML rich text data.
this.controller.loadData(
"Source:
source
",
"text/html",
"UTF-8"
);
} catch (error) {
console.error(`ErrorCode: ${(error as BusinessError).code}, Message: ${(error as BusinessError).message}`);
}
})
// When creating a Web component, set the default network page to be loaded to www.example.com.
Web({ src: 'www.example.com', controller: this.controller })
}
}
}
```
The **Web** component can load HTML strings using data urls.
```ts
// xxx.ets
import { webview } from '@kit.ArkWeb';
import { BusinessError } from '@kit.BasicServicesKit';
@Entry
@Component
struct WebComponent {
controller: webview.WebviewController = new webview.WebviewController();
htmlStr: string = "data:text/html, Source:
source
";
build() {
Column() {
// When creating a Web component, set the default network page to be loaded to htmlStr.
Web({ src: this.htmlStr, controller: this.controller })
}
}
}
```
## Dynamically Creating a Web Component
**Web** components can be created with commands. Components created in this mode are not immediately mounted to the component tree, that is, they are not presented to users (their state is **Hidden** or **InActive**). You can dynamically mount the components as required in subsequent use. It is recommended that the number of **Web** instances started in the background be less than or equal to 200.
```ts
// Carrier ability
// EntryAbility.ets
import { createNWeb } from "../pages/common"
onWindowStageCreate(windowStage: window.WindowStage): void {
windowStage.loadContent('pages/Index', (err, data) => {
// Dynamically create a Web component (UIContext needs to be passed in). The component can be created at any time after loadContent() is called.
createNWeb("https://www.example.com", windowStage.getMainWindowSync().getUIContext());
if (err.code) {
return;
}
});
}
```
```ts
// Create a NodeController instance.
// common.ets
import { UIContext, NodeController, BuilderNode, Size, FrameNode } from '@kit.ArkUI';
import { webview } from '@kit.ArkWeb';
// @Builder contains the specific content of the dynamically created component.
// Data is an input parameter of encapsulation class.
class Data{
url: string = "https://www.example.com";
controller: WebviewController = new webview.WebviewController();
}
@Builder
function WebBuilder(data:Data) {
Column() {
Web({ src: data.url, controller: data.controller })
.width("100%")
.height("100%")
}
}
let wrap = wrapBuilder(WebBuilder);
// NodeController is used to control and report the behavior of the node on the NodeContainer. This function must be used together with NodeContainer.
export class myNodeController extends NodeController {
private rootnode: BuilderNode | null = null;
// This function must be overridden. It is used to build the number of nodes and return the number of nodes mounted to the corresponding NodeContainer.
// Call it when the NodeContainer is created or call rebuild() to refresh.
makeNode(uiContext: UIContext): FrameNode | null {
console.log(" uicontext is undefined : "+ (uiContext === undefined));
if (this.rootnode != null) {
// Return the FrameNode.
return this.rootnode.getFrameNode();
}
// Return null to detach the dynamic component from the bound node.
return null;
}
// Called when the layout size changes.
aboutToResize(size: Size) {
console.log("aboutToResize width : " + size.width + " height : " + size.height );
}
// Called when the NodeContainer bound to the controller is about to appear.
aboutToAppear() {
console.log("aboutToAppear");
}
// Called when the NodeContainer bound to the controller is about to disappear.
aboutToDisappear() {
console.log("aboutToDisappear");
}
// This function is a custom function and can be used as an initialization function.
// Initialize BuilderNode through UIContext, and then initialize the content in @Builder through the build API in BuilderNode.
initWeb(url:string, uiContext:UIContext, control:WebviewController) {
if(this.rootnode != null)
{
return;
}
// Create a node. UIContext is required.
this.rootnode = new BuilderNode(uiContext);
// Create a dynamic Web component.
this.rootnode.build(wrap, { url:url, controller:control });
}
}
// Create a map to save the required NodeController.
let NodeMap:Map = new Map();
// Create a map to save the required WebViewController.
let controllerMap:Map = new Map();
// UIContext is required for initialization and needs to be obtained from the ability.
export const createNWeb = (url: string, uiContext: UIContext) => {
// Create a NodeController instance.
let baseNode = new myNodeController();
let controller = new webview.WebviewController() ;
// Initialize the custom Web component.
baseNode.initWeb(url, uiContext, controller);
controllerMap.set(url, controller)
NodeMap.set(url, baseNode);
}
// Customize the API for obtaining the NodeController.
export const getNWeb = (url : string) : myNodeController | undefined => {
return NodeMap.get(url);
}
```
```ts
// Use the Page page of the NodeController.
// Index.ets
import { getNWeb } from "./common"
@Entry
@Component
struct Index {
build() {
Row() {
Column() {
// NodeContainer is used to bind to the NodeController. A rebuild call triggers makeNode.
// The Page page is bound to the NodeController through the NodeContainer API to display the dynamic component.
NodeContainer(getNWeb("https://www.example.com"))
.height("90%")
.width("100%")
}
.width('100%')
}
.height('100%')
}
}
```
**Common troubleshooting procedure**
1. Check the network permission configuration of the application.
Check whether the network permission has been added to the **module.json5** file. For details, see [Declaring Permissions in the Configuration File](../security/AccessToken/declare-permissions.md).
```ts
"requestPermissions":[
{
"name" : "ohos.permission.INTERNET"
}
]
```
2. Check the logic for binding **NodeContainer** to nodes.
Check whether the node is added to the component tree. You are advised to add **Text** above the existing **Web** component (see the following example). If **Text** is not displayed when a white screen is displayed, check the binding between **NodeContainer** and the node.
```ts
@Builder
function WebBuilder(data:Data) {
Column() {
Text('test')
Web({ src: data.url, controller: data.controller })
.width("100%")
.height("100%")
}
}
```
3. Check the visibility of the **Web** component.
If the entire node has been added to the tree, you can view the [WebPattern::OnVisibleAreaChange](../reference/apis-arkui/arkui-ts/ts-universal-component-visible-area-change-event.md#onvisibleareachange) log to check whether the **Web** component is visible. Invisible **Web** components may cause a white screen.
## Samples
The following samples are provided to help you better understand how to develop the **Web** component:
- [Browser (ArkTS) (Full SDK) (API9)](https://gitee.com/openharmony/applications_app_samples/tree/OpenHarmony-5.0.1-Release/code/BasicFeature/Web/Browser)