Simple way to add back button in webview in android by Adding this override method into your project

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (event.getAction() == event.ACTION_DOWN) {
            switch (keyCode) {
                case KeyEvent.KEYCODE_BACK:
                    if (webView.canGoBack()) {
                        webView.goBack();
                    }
                    return true;
            }
        }
        return super.onKeyDown(keyCode, event);
    }