WebView - only show back button if back history exists

Question

I developed a simple webview app. I added a button which should act as the back button, so users can navigate back one page.

The button is initially hidden and should only show if a back history exists. How can I realise this?

The code is simple:

backButton = findViewById(R.id.backButton);
backButton.setEnabled(blizzView.canGoBack());

but where do I have to call this? How is the "some site loaded" event called?

Update:

I tried to apply @Murats answer, but nothing happens:

private WebView blizzView;  // my webview
private Button backButton;

public void onPageFinished(WebView view, String url)
{
    backButton = findViewById(R.id.backButton);
    backButton.setEnabled(blizzView.canGoBack());

    if (blizzView.canGoBack()) {
        backButton.setVisibility(View.VISIBLE);
    } else {
        backButton.setVisibility(View.INVISIBLE);
    }

}

To clarify: you have a WebView, and you have a Button. You want the button click event to navigate the WebView back one page but only if there is navigation history in the WebView, right? — pappbence96, Jul 19 '19 at 10:53
Yes, thats right. If there is no back history, then the button should be invisible and disabled. — Black, Jul 19 '19 at 10:54
Because it leaded me to the solution and I can accept mine only in 2 days. — Black, Jul 19 '19 at 11:33

score 2 · Answer 1 · answered Jul 19 '19 at 10:55

2

You can use WebView#canGoBack to find out if there is a backstack. You can check for that after the page is loaded e.g. in WebViewClient#onPageFinished

answered Jul 19 '19 at 10:55

Murat Karagöz

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Ah, you beat me to it! Yes, this would a correct solution. – pappbence96 Jul 19 '19 at 10:56
@Murat, I tried it and updated my question with my attempt. Does not work. – Black Jul 19 '19 at 11:14
@Black That is not how you use the method.. See https://stackoverflow.com/questions/6719814/onpagefinished-never-called-webview – Murat Karagöz Jul 19 '19 at 11:15
@Black You have to override the `onPageFinished` in the `WebViewClient`. – Murat Karagöz Jul 19 '19 at 11:24
Ok, I see. Thx :) – Black Jul 19 '19 at 11:27

Black · Accepted Answer · 2019-07-23T09:07:11.437

It works like this:

blizzView.setWebViewClient(new WebViewClient() {      //
    @Override
    public void onPageFinished(WebView view, String url) {
        super.onPageFinished(view, url);

        backButton = findViewById(R.id.backButton);
        backButton.setEnabled(blizzView.canGoBack());

        if (blizzView.canGoBack()) {
            backButton.setVisibility(View.VISIBLE);
        } else {
            backButton.setVisibility(View.INVISIBLE);
        }

    }
});

WebView - only show back button if back history exists

2 Answers2