Webview links do not work

Question

Something has changed in the implementation of Webview, Webviewclient for android 7?

I have some html files in a subfolder inside the Assets folder. The file html list., which contains other links that call other html files that are in the same folder, is displayed normally but when I click on the links to call the other html files are not being displayed in Webview.

I tested on android 4 and 6 and works perfectly, on android 7 does not work.

Follows ocode:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.help);

    myWebView = (WebView) findViewById(R.id.webViewHelp);
    progressBar = (ProgressBar) findViewById(R.id.progressBar);

    myWebView.setWebViewClient(new ActivityHelp.myWebClient());
    myWebView.getSettings().setJavaScriptEnabled(true);
    myWebView.getSettings().setBuiltInZoomControls(true);
    myWebView.getSettings().setDisplayZoomControls(false);
    myWebView.getSettings().setSupportZoom(true);
    myWebView.loadUrl("file:///android_asset/help/lista.html");
}

public class myWebClient extends WebViewClient
{
    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
        // TODO Auto-generated method stub
        super.onPageStarted(view, url, favicon);
        progressBar.setVisibility(View.VISIBLE);
    }

    @Override
    public boolean  shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
        super.shouldOverrideUrlLoading(view, request);
        progressBar.setVisibility(View.VISIBLE);
        return true;
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        // TODO Auto-generated method stub
        super.onPageFinished(view, url);
        progressBar.setVisibility(View.INVISIBLE);
    }
}

Answer 1

In the method shouldOverrideUrlLoading() instead of returning true return false.

true indicates that the application will handle the URL (for example, launching an Intent with the link to be viewed in the native browser) and not Webview. Thus, in order for Webview to present the page referring to the URL, the method must return false.

The Overload of the method shouldOverrideUrlLoading() with that signature, boolean shouldOverrideUrlLoading (WebView view, WebResourceRequest request), only added in API 24.
The other, boolean shouldOverrideUrlLoading (WebView view, String url), is now considered obsolete.

The reason why it works in previous versions is that the override that Overload(which only exists from 7) will not be called, being called the "base" implementation of the other method, which returns false.
That is, be there or not, return true or false is the same, it is not called.
The strange thing is Android Studio give no Warning/error how the method can only be used with minSdkVersion 24.

Anyway, the correct way to implement, since you want to support lower versions, will be to do the override of the two methods.

@TargetApi(Build.VERSION_CODES.N)
@Override
public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
    super.shouldOverrideUrlLoading(view, request);

    //fazer alguma coisa aqui

    return false;
}

@SuppressWarnings("deprecation")
@Override
public boolean  shouldOverrideUrlLoading(WebView view, String url) {
    super.shouldOverrideUrlLoading(view, url);

    //fazer alguma coisa aqui

    return false;
}

Answer 2

This answer complements the question.

Let’s create an app with webview in the Android 7 (API 24) to open files HTML of local shape.

1) First let’s create the two files of HTML as an example:

The files go this way:

MyApplication\app\src\main\assets\teste.html
MyApplication\app\src\main\assets\teste2.html

html test.

<h3>Aaaa</h3>
<a href="teste2.html">Link1</a>

test2.html

<h3>Bbbb</h3>
<a href="teste.html">Link2</a>

2) Let’s edit the layout file XML of the application (Mainactivity):

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.computador1.myapplication.MainActivity">

    <WebView
        android:id="@+id/activity_main_webview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</android.support.constraint.ConstraintLayout>

3) Now let’s set up the part of java (Mainactivity) for him to upload the webview to ID defined in the layout.

package com.example.computador1.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {

    private WebView mWebView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mWebView = (WebView) findViewById(R.id.activity_main_webview);
        WebSettings webSettings = mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true); // permite o uso de javascript
        mWebView.setWebViewClient(new WebViewClient());
        mWebView.loadUrl("file:///android_asset/teste.html");

    }
}

Understand that the line:

    mWebView.setWebViewClient(new WebViewClient());

It’s very important because it doesn’t let webview links open in the default Android browser. So they will always open in webview. Now just test your application.