WebViewAssetLoader

class WebViewAssetLoader

Helper class to load local files including application's static assets and resources using http(s):// URLs inside a android.webkit.WebView class. Loading local files using web-like URLs instead of "file://" is desirable as it is compatible with the Same-Origin policy.

For more context about application's assets and resources and how to normally access them please refer to Android Developer Docs: App resources overview.

This class is expected to be used within android.webkit.WebViewClient#shouldInterceptRequest, which is invoked on a different thread than application's main thread. Although instances are themselves thread-safe (and may be safely constructed on the application's main thread), exercise caution when accessing private data or the view system.

Using http(s):// URLs to access local resources may conflict with a real website. This means that local files should only be hosted on domains your organization owns (at paths reserved for this purpose) or the default domain reserved for this: appassets.androidplatform.net.

A typical usage would be like:

final WebViewAssetLoader assetLoader = new WebViewAssetLoader.Builder()
           .addPathHandler("/assets/", new AssetsPathHandler(this))
           .addPathHandler("/res/", new ResourcesPathHandler(this))
           .build();
 
  webView.setWebViewClient(new WebViewClient() {
      @Override
      public WebResourceResponse shouldInterceptRequest(WebView view,
                                       WebResourceRequest request) {
          return assetLoader.shouldInterceptRequest(request.getUrl());
      }
  });
  // Assets are hosted under http(s)://appassets.androidplatform.net/assets/... .
  // If the application's assets are in the "main/assets" folder this will read the file
  // from "main/assets/www/index.html" and load it as if it were hosted on:
  // https://appassets.androidplatform.net/assets/www/index.html
  webview.loadUrl("https://appassets.androidplatform.net/assets/www/index.html");
  

Summary

Constants

static val DEFAULT_DOMAIN: String

Value: "appassets.androidplatform.net"

Public methods

@WorkerThread @Nullable fun shouldInterceptRequest(@NonNull url: Uri): WebResourceResponse?