Action Bar Back Button Crashes on WebView - android-studio

I am currently implementing a back button action for navigating webview history. My webview has been working(including handling opening links within the webview). However, after adding the back button action it crashes whenever I try to use the back button. This is my Main Activity Code:
public class MainActivity extends Activity {
WebView mWebView;
//Back Button Code
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(event.getAction() == KeyEvent.ACTION_DOWN){
switch(keyCode)
{
case KeyEvent.KEYCODE_BACK:
if(mWebView.canGoBack() == true){
mWebView.goBack();
}else{
finish();
}
return true;
}
}
return super.onKeyDown(keyCode, event);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(amapps.com.uhss.R.layout.activity_main);
WebView mWebView = (WebView) findViewById(R.id.activity_main_webview);
mWebView.setWebViewClient(new WebViewClient());
WebSettings webSettings = mWebView.getSettings();
webSettings.setJavaScriptEnabled(false);
mWebView = (WebView) findViewById(R.id.activity_main_webview);
mWebView.loadUrl("http://uhsswordandshield.com/");
mWebView.getSettings().setSupportMultipleWindows(true);
}
Could someone please tell me what is wrong with the code. I believe it has to do with my
WebView mWebView;
declaration before I initialize the webview. But I am not sure of any way to handle webview history navigation. Also, I am unsure of how to post my log cat and what to post so if someone could please tell me which part of the logcat I need to post that would be great. Thanks!

try this code:
if((keyCode==KeyEvent.ACTION_DOWN)){
if(mWebView.canGoBack() == true){
mWebView.goBack();
}else{
finish();
}
return true;
}
return super.onKeyDown(keyCode, event);

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Thanks
thanks for the help... and the negative.
I have solved it anyway, I leave my solution below:
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Any help shall be appreciated?
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That's because in the adapter android passes the same view over and over again (recycling), try to set the visibility of the button to visible every time.
I checked the code and it works fine for me.!
Hey quick question though, have you declared your btnUninstall anywhere?
I cannot see it anywhere in the code you have provided, thats all.
Button btnUninstall;

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