Android Webview cannot render the pdf sometimes and shows blank/white page instead

Question

• Open the pdf in the webview using google docs
• Open the same pdf or different pdf again and again.
• Sometimes it will show the blank/white page in the

Answer 1

I was having the exact same issue and found that there was always a chance the WebView would not load on the first load attempt, especially if the pdf was on the larger side. The code I put together below works 100% of the time. From my beginner's understanding, it safely utilizes a separate thread to loop through and test the load status of the WebView, re-attempting a load of the view until successful. As this question was posted a year ago, I have generalized my solution to best benefit new viewers.

public class WebViewActivity extends AppCompatActivity {

String PDFView;
WebView webView;
String PDFBrowserView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //Get the intended "PDFView"
    PDFView = getIntent().getExtras().get("PDFView").toString();
    //Have to manually encode (?) the url to display it
    try {
        PDFView = URLEncoder.encode(PDFView, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    //Full display url
    PDFBrowserView = "https://docs.google.com/gview?embedded=true&url=" + PDFView;

    //Initialize a new "WebView" instance
    webView = new WebView(WebViewActivity.this);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.getSettings().setAllowFileAccessFromFileURLs(true);
    webView.getSettings().setAllowUniversalAccessFromFileURLs(true);
    webView.getSettings().setBuiltInZoomControls(true);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.getSettings().setPluginState(WebSettings.PluginState.ON);
    webView.getSettings().setDomStorageEnabled(true);
    webView.getSettings().setLoadWithOverviewMode(true);
    webView.getSettings().setUseWideViewPort(true);
    //This handles callbacks (?)
    webView.setWebChromeClient(new WebChromeClient());

    //Call this to load page if page is blank with pdf url until page is not blank
    checkPageFinished();
}

public void checkPageFinished() {
    //If view is blank:
    if (webView.getContentHeight() == 0) {

        //Run off main thread to control delay
        webView.postDelayed(new Runnable() {
            @Override
            public void run() {
                //Load url into the "WebView"
                webView.loadUrl(PDFBrowserView);
            }
            //Set 1s delay to give the view a longer chance to load before 
            // setting the view (or more likely to display blank)
        }, 1000);
        //Set the view with the selected pdf
        setContentView(webView);

        webView.postDelayed(new Runnable() {
            @Override
            public void run() {
                //If view is still blank:
                if (webView.getContentHeight() == 0) {
                    //Loop until it works
                    checkPageFinished();
                }
            }
            //Safely loop this function after 1.5s delay if page is not loaded
        }, 1500);

        }
    }
}