Hey there! Let's work through your two Android WebView issues step by step.

If your WebView isn't showing preview content, it's usually down to missing settings, permissions, or unhandled page behaviors. Here are the most common fixes:

• Check for internet permission: Make sure you've added the internet permission in your AndroidManifest.xml—without it, WebView can't load any online content:

  <uses-permission android:name="android.permission.INTERNET" />
  

• Enable essential WebSettings: Your WebView needs certain settings enabled to render content properly. Add these lines before loading your URL:

  WebSettings settings = wvPDF.getSettings();
  settings.setJavaScriptEnabled(true); // Critical for dynamic content
  settings.setDomStorageEnabled(true); // Needed for pages that use local storage
  settings.setLoadsImagesAutomatically(true); // Ensure images load
  settings.setSupportZoom(true); // Optional but helpful for previewing
  

• Fix WebViewClient configuration: If you're using a custom WebViewClient, make sure you're not blocking page loads. Override shouldOverrideUrlLoading to let WebView handle URLs internally:

  wvPDF.setWebViewClient(new WebViewClient() {
      @Override
      public boolean shouldOverrideUrlLoading(WebView view, String url) {
          view.loadUrl(url);
          return true;
      }
  
      @Override
      public void onPageFinished(WebView view, String url) {
          // Optional: Add logic here once the page loads, like hiding a progress bar
      }
  
      @Override
      public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
          // Handle errors here, e.g., show an error message to the user
          Toast.makeText(getApplicationContext(), "Failed to load content: " + description, Toast.LENGTH_SHORT).show();
      }
  });
  

• Handle mixed content (Android 9+): If your page uses HTTPS but loads HTTP resources (or vice versa), Android 9+ blocks this by default. Enable mixed content support:

  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
      settings.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
  }
  

• Check for SSL certificate issues: If your target URL uses HTTPS with a self-signed certificate, WebView will block it. To handle this (only for testing/trustworthy sources), override onReceivedSslError in your WebViewClient:

  @Override
  public void onReceivedSslError(WebView view, SslErrorHandler handler, SslError error) {
      // Only use this for trusted servers—don't enable this for production apps!
      handler.proceed();
  }
  

Your current approach using Google Docs' viewer is valid, but there's a small issue in your code that might be causing problems, plus some tweaks to improve reliability:

First, fix your PDF URL #

Notice your pdf string has a leading space: " http://192.168.1.181:8081/reports/RepoActivityLog181.pdf "—this will break the URL. Remove the leading space:

String pdf = "http://192.168.1.181:8081/reports/RepoActivityLog181.pdf";

Optimized code for loading the PDF #

Here's the improved version of your code with extra settings to ensure the PDF loads smoothly:

// Initialize WebView settings
WebSettings pdfSettings = wvPDF.getSettings();
pdfSettings.setJavaScriptEnabled(true);
pdfSettings.setDomStorageEnabled(true);
pdfSettings.setSupportZoom(true);
pdfSettings.setBuiltInZoomControls(true);
pdfSettings.setDisplayZoomControls(false); // Optional: Hide default zoom controls

// Load the PDF using Google Docs viewer
String googleDocsUrl = "https://docs.google.com/gview?embedded=true&url=" + pdf;
wvPDF.loadUrl(googleDocsUrl);

// Configure WebViewClient with error handling
wvPDF.setWebViewClient(new WebViewClient() {
    @Override
    public void onPageFinished(WebView view, String url) {
        // Optional: Add post-load logic here
        super.onPageFinished(view, url);
    }

    @Override
    public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error) {
        // Show error message if PDF fails to load
        Toast.makeText(getApplicationContext(), "Failed to load PDF: " + error.getDescription(), Toast.LENGTH_SHORT).show();
        super.onReceivedError(view, request, error);
    }
});

Alternative: Use a local PDF renderer (if Google Docs viewer isn't ideal) #

If you don't want to rely on Google's service, you can use Android's built-in PdfRenderer class to render the PDF locally. This requires downloading the PDF first, then rendering it to an ImageView or custom view. However, this is more complex than using the viewer approach.

内容的提问来源于stack exchange，提问作者Shaikh Danish