Navigating asset based html files in webview on Nougat

Question

I am loading a HTML file from assets into a webview.

The html has links to other html asset files. Clicking the links works correctly on SDK < 24 but produces a FileUriExposedException error when clicking a link to a second html page on Nougat (SDK 24) devices.

Code to load the html from assets into a webview:

wbHelp.loadDataWithBaseURL("file:///android_asset/", readAssetFileAsString("Index.html"), "text/html", "UTF-8", null);

and readAssetFileAsString is:

private String readAssetFileAsString(String sourceHtmlLocation)
{
    InputStream is;
    try
    {
        is = getContext().getAssets().open(sourceHtmlLocation);
        int size = is.available();

        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();

        return new String(buffer, "UTF-8");
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }

    return "";
}

The html can be very basic. Index.html

<html><a href="Page2.html">Page 2</a></html>

Page2.html

<html><h1>Page 2</h1>

The full error log is:

11-12 17:58:03.694 5831-5831/appname W/System.err: android.os.FileUriExposedException: file:///android_asset/Page2.html exposed beyond app through Intent.getData()
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.os.StrictMode.onFileUriExposed(StrictMode.java:1799)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.net.Uri.checkFileUriExposed(Uri.java:2346)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.content.Intent.prepareToLeaveProcess(Intent.java:8933)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.content.Intent.prepareToLeaveProcess(Intent.java:8894)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.app.Instrumentation.execStartActivity(Instrumentation.java:1517)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.app.Activity.startActivityForResult(Activity.java:4224)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:48)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:77)
11-12 17:58:03.694 5831-5831/appname W/System.err:     at android.app.Activity.startActivityForResult(Activity.java:4183)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:859)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.app.Activity.startActivity(Activity.java:4507)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.app.Activity.startActivity(Activity.java:4475)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.content.ContextWrapper.startActivity(ContextWrapper.java:356)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.android_webview.ResourcesContextWrapperFactory$WebViewContextWrapper.startActivity(ResourcesContextWrapperFactory.java:121)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.android_webview.AwContentsClient.sendBrowsingIntent(AwContentsClient.java:203)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.android_webview.AwContentsClient.shouldIgnoreNavigation(AwContentsClient.java:170)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.android_webview.AwContentsClientBridge.shouldOverrideUrlLoading(AwContentsClientBridge.java:256)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:39)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.os.Looper.loop(Looper.java:154)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:6077)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
11-12 17:58:03.695 5831-5831/appname W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
11-12 17:58:03.699 5831-5831/appname A/chromium: [FATAL:jni_android.cc(236)] Please include Java exception stack in crash report
                                                    
                                                    
                                                    --------- beginning of crash
11-12 17:58:03.856 5831-5831/appname W/google-breakpad: ### ### ### ### ### ### ### ### ### ### ### ### ###
11-12 17:58:03.856 5831-5831/appname W/google-breakpad: Chrome build fingerprint:
11-12 17:58:03.856 5831-5831/appname W/google-breakpad: 1.0
11-12 17:58:03.856 5831-5831/appname W/google-breakpad: 72
11-12 17:58:03.856 5831-5831/appname W/google-breakpad: ### ### ### ### ### ### ### ### ### ### ### ### ###
11-12 17:58:03.857 5831-5831/appname A/libc: Fatal signal 6 (SIGABRT), code -6 in tid 5831 (appname)
                                                
                                                [ 11-12 17:58:03.857   270:  270 W/         ]
                                                debuggerd: handling request: pid=5831 uid=10379 gid=10379 tid=5831

I've tried using some form of provider (such as in this answer: android.os.FileUriExposedException: file:///storage/emulated/0/test.txt exposed beyond app through Intent.getData()) but it doesn't have any effect.

Why dont you use `"file:///android_asset/Index.html"` to let the file be loaded by the WebView? — greenapps, Nov 12 '16 at 15:27
I thought it was required to be able to auto load the images from assets but it looks like it works without it, however it still exhibits the same exception — behelit, Nov 13 '16 at 23:22

score 13 · Accepted Answer · edited May 23 '17 at 12:02

13

I was able to overcome the exception by using the shouldOverrideUrlLoading, as suggested by @CommonsWare here:

Tested on an emulator running Nougat:

    web.setWebViewClient(new WebViewClient()
    {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url)
        {
            Log.i("WebView", "Attempting to load URL: " + url);

            view.loadUrl(url);
            return true;
        }
    });

edited May 23 '17 at 12:02

Community

1
1

answered Nov 22 '16 at 23:30

behelit

1,765
2
20
34

I do see this crash in my Dashboard, but I cannot reproduce this problem on the emulator (maybe depends on the browser associated with the Intent to trigger HTML links?) However, with the proposed solution the links mailto: and tel: do not work. I can think of excluding this type of links from being loaded in the WebView (and also, to only use the shouldOverrideUrlLoading for APIs over 7.0). – kikoso Aug 28 '17 at 02:59

Sebastian Corradi · Answer 2 · 2017-03-10T20:15:41.303

Also you can add this code in the onCreate method of you application or activity:

   StrictMode.VmPolicy.Builder builder = new StrictMode.VmPolicy.Builder();
   StrictMode.setVmPolicy(builder.build());

this lines makes your app ignore that exception.

And reading the documentation you will find that just using this code:

    WebViewClient client = new WebViewClient() {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            return false;
        }
    };

    webView.setWebViewClient(client);

Will also work, because returning false you are asking for your webView to handle that operation. https://developer.android.com/reference/android/webkit/WebViewClient.html#shouldOverrideUrlLoading(android.webkit.WebView, java.lang.String)

Navigating asset based html files in webview on Nougat

2 Answers2

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