WebView加载本地HTML后点击链接崩溃，报FileUriExposedException错误

Got it, let's resolve this crash you're facing. The root cause here is Android's security restriction introduced in API level 24 (Android 7.0): apps are blocked from exposing file:// URIs to other components (even within your own app) via Intents. When your WebView tries to navigate to a local asset link like file:///android_asset/page2.html, it triggers this FileUriExposedException and crashes the app.

Here are two reliable solutions, with the first being the official recommended approach:

1. Use WebViewAssetLoader (AndroidX, Recommended) #

Google provides the WebViewAssetLoader as part of the AndroidX WebKit library to safely load local assets/files in WebView without exposing risky file:// URIs. It uses a secure fake HTTPS domain to serve your assets.

Step 1: Add the dependency #

Add this to your module-level build.gradle file (use the latest available version):

dependencies {
    implementation 'androidx.webkit:webkit:1.5.0'
}

Step 2: Configure WebView with the asset loader #

In your Activity/Fragment where you initialize the WebView:

WebView webView = findViewById(R.id.your_webview_id);
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true); // Enable if your HTML uses JS

// Initialize the asset loader to serve files from the assets folder
final WebViewAssetLoader assetLoader = new WebViewAssetLoader.Builder()
        .addPathHandler("/assets/", new WebViewAssetLoader.AssetsPathHandler(this))
        .build();

// Set a custom WebViewClient to intercept requests and use the asset loader
webView.setWebViewClient(new WebViewClient() {
    @Override
    public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
        // Let the asset loader handle requests to local assets
        return assetLoader.shouldInterceptRequest(request.getUrl());
    }

    // Optional: Ensure links open within the WebView instead of triggering an Intent
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
        view.loadUrl(request.getUrl().toString());
        return true;
    }
});

// Load your initial HTML using the secure asset loader URL
webView.loadUrl("https://appassets.androidplatform.net/assets/index.html");

How it works #

All links in your HTML (like <a href="page2.html">) will automatically resolve to the secure HTTPS-like URI, avoiding any file:// exposure. This is the cleanest, most future-proof solution.

2. Custom ContentProvider (For non-AndroidX projects) #

If you can't use AndroidX, create a custom ContentProvider to serve your assets via safe content:// URIs.

Step 1: Create the ContentProvider class #

public class AssetContentProvider extends ContentProvider {
    private static final String AUTHORITY = "com.your.package.name.assetprovider"; // Replace with your app's package
    private static final Uri BASE_URI = Uri.parse("content://" + AUTHORITY);

    // Helper method to convert asset paths to content URIs
    public static Uri getAssetUri(String assetPath) {
        return BASE_URI.buildUpon().appendEncodedPath(assetPath).build();
    }

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
        String assetPath = uri.getEncodedPath().substring(1); // Remove leading '/'
        return getContext().getAssets().openFd(assetPath).getParcelFileDescriptor();
    }

    @Override
    public String getType(Uri uri) {
        String assetPath = uri.getEncodedPath().substring(1);
        return MimeTypeMap.getSingleton().getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(assetPath));
    }
}

Step 2: Register the provider in AndroidManifest.xml #

Add this inside the <application> tag:

<provider
    android:name=".AssetContentProvider"
    android:authorities="com.your.package.name.assetprovider" // Match the AUTHORITY above
    android:exported="false" />

Step 3: Update WebView setup #

WebView webView = findViewById(R.id.your_webview_id);
webView.setWebViewClient(new WebViewClient() {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        // Convert any file:///android_asset/ links to content URIs
        if (url.startsWith("file:///android_asset/")) {
            String assetPath = url.substring("file:///android_asset/".length());
            Uri contentUri = AssetContentProvider.getAssetUri(assetPath);
            view.loadUrl(contentUri.toString());
            return true;
        }
        return super.shouldOverrideUrlLoading(view, url);
    }
});

// Load initial HTML using the content URI
webView.loadUrl(AssetContentProvider.getAssetUri("index.html").toString());

This approach wraps your assets in content:// URIs, which are allowed to be used within your app without triggering the exception.

Whichever method you choose, make sure to test on devices running Android 7.0+ to confirm the crash is resolved.

内容的提问来源于stack exchange，提问作者Ashonko