Android webview get closed when press back button

Question

This is the code of my WebView. The WebView run correctly but the issue occurs when I press the back button: the app get closed.

   @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        //enable layout
        setContentView(R.layout.activity_main);

        //create istance webview
        WebView myWebView = (WebView) findViewById(R.id.webview);

        //initialize webview's settings
        WebSettings webSettings = myWebView.getSettings();

        //enable javascript
        webSettings.setJavaScriptEnabled(true);

        //load image
        webSettings.setLoadsImagesAutomatically(true);

        //inizialize client
        MyWebViewClient myWebViewClient = new MyWebViewClient();

        //set webview to client
        myWebView.setWebViewClient(myWebViewClient);

        //load website by URL
        myWebView.loadUrl(website_url);

        this.onStart();
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        // Check if the key event was the Back button and if there's history
        if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack()) {
            myWebView.goBack();
            return true;
        }
        // If it wasn't the Back key or there's no web page history, bubble up to the default
        // system behavior (probably exit the activity)
        return super.onKeyDown(keyCode, event);
    }
}

CrashLog:

03-23 14:43:18.530 14051-14051/com.quogito.quogito W/UnimplementedWebViewApi: Unimplemented WebView method onKeyDown called from: android.webkit.WebView.onKeyDown(WebView.java:2319)
03-23 14:43:18.620 14051-14051/com.quogito.quogito E/InputEventSender: Exception dispatching finished signal.
03-23 14:43:18.620 14051-14051/com.quogito.quogito E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
03-23 14:43:18.620 14051-14051/com.quogito.quogito E/MessageQueue-JNI: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.webkit.WebView.canGoBack()' on a null object reference
at com.quogito.quogito.MainActivity.onBackPressed(MainActivity.java:113)
at android.app.Activity.onKeyUp(Activity.java:2497)

Answer 1

You're shadowing your myWebView object inside the onCreate method at this line:

WebView myWebView = (WebView) findViewById(R.id.webview);

which means that your global variable called myWebView is never set.

Change the line inside the onCreate to this instead:

myWebView = (WebView) findViewById(R.id.webview);

then it should work fine.