Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

Question

I am trying to check if my application is launched for the first time. If yes, the user is asked for an input. Then, check if Wi-Fi is connected. If Wi-Fi is connected, I use the input provides by the user to load a WebView.

But, the app crashes on launch with an error

Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

Code

public class MainActivity extends Activity {


ProgressBar progressbar;
WebView webView;
LayoutInflater li = LayoutInflater.from(getBaseContext());
View promptsView = li.inflate(R.layout.propmt, null);
String URL;

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    this.getWindow().requestFeature(Window.FEATURE_PROGRESS);
    setContentView(R.layout.activity_main);

    Boolean isFirstRun = getSharedPreferences("PREFERENCE", MODE_PRIVATE)
            .getBoolean("isFirstRun", true);

    if (isFirstRun) {

        otherWork(promptsView);

    }


       getSharedPreferences("PREFERENCE", MODE_PRIVATE).edit()
                .putBoolean("isFirstRun", false).commit();





    ConnectivityManager connManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
    NetworkInfo mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);

    if (mWifi.isConnected()) {


    getWindow().setFeatureInt( Window.FEATURE_PROGRESS, Window.PROGRESS_VISIBILITY_ON);

    webView = (WebView) findViewById(R.id.webView);
    webView.getSettings().setBuiltInZoomControls(true);
    webView.getSettings().setDisplayZoomControls(false);
    webView.getSettings().setRenderPriority(RenderPriority.HIGH);
    webView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE);
    if (Build.VERSION.SDK_INT >= 19) {
        webView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
    }       
    else {
        webView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }
    webView.loadUrl(URL);
    webView.setWebViewClient(new WebViewClient());
    WebSettings webSettings = webView.getSettings();
    webSettings.setJavaScriptEnabled(true);



       webView.setWebViewClient(new MyWebViewClient());

       progressbar=(ProgressBar)findViewById(R.id.progressBar); 

       webView.setWebChromeClient(new WebChromeClient() {

       // this will be called on page loading progress

       @Override

       public void onProgressChanged(WebView view, int newProgress) {

               super.onProgressChanged(view, newProgress);


               progressbar.setProgress(newProgress);
               //loadingTitle.setProgress(newProgress);
               // hide the progress bar if the loading is complete

               if (newProgress == 100) {
               progressbar.setVisibility(View.GONE);

               } else{
               progressbar.setVisibility(View.VISIBLE);

               }

               }

            });

       } else {

           AlertDialog.Builder AD = new AlertDialog.Builder(this);
            AD.setIcon(R.drawable.ic_launcher);
            AD.setTitle("Not Connected To Wi-Fi/WLAN");
            AD.setMessage("You need an Active Wi-Fi/WLAN on Alliance Broadband Network");
            AD.setPositiveButton(android.R.string.ok, new OnClickListener() {

                @Override
                public void onClick(DialogInterface arg0, int arg1) {
                    finish();

                }
            });
            AD.show();

       }


} 

public void otherWork(View promptsView) {
    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
            this);

    // set prompts.xml to alertdialog builder
    alertDialogBuilder.setView(promptsView);

    final EditText userInput = (EditText) promptsView
            .findViewById(R.id.editTextDialogUserInput);

    // set dialog message
    alertDialogBuilder
    .setCancelable(false)
    .setPositiveButton("OK",
            new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,int id) {
            // get user input and set it to result
            // edit text
            //result.setText(userInput.getText());
            SharedPreferences pos;
            String fileName = "file";

            pos = getSharedPreferences(fileName, 0);
            SharedPreferences.Editor editor = pos.edit();
            editor.putString("pwd", userInput.getText().toString());      
            editor.commit();

            pos = getSharedPreferences(fileName, 0);
            String data = pos.getString("pwd", "");


            URL = data.toString();

        }
    })
    .setNegativeButton("Cancel",
            new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,int id) {
            dialog.cancel();
        }
    });

    // create alert dialog
    AlertDialog alertDialog = alertDialogBuilder.create();

    // show it
    alertDialog.show();
}


       @Override
       public boolean onKeyDown(int keyCode, KeyEvent event) {

       if(keyCode == KeyEvent.KEYCODE_BACK){
           finish();
         }
       return super.onKeyDown(keyCode, event);
       }

       private class MyWebViewClient extends WebViewClient {


     @Override
     public boolean shouldOverrideUrlLoading(WebView view, String url) {

     view.loadUrl(url);
     return true;
     }
     }<br>

LogCat

05-24 01:11:19.279: E/AndroidRuntime(3719): FATAL EXCEPTION: main
05-24 01:11:19.279: E/AndroidRuntime(3719): Process: com.mavenmaverick.ipconnect, PID: 3719
05-24 01:11:19.279: E/AndroidRuntime(3719): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.mavenmaverick.ipconnect/com.mavenmaverick.ipconnect.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread.access$800(ActivityThread.java:144)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.os.Handler.dispatchMessage(Handler.java:102)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.os.Looper.loop(Looper.java:135)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread.main(ActivityThread.java:5221)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at java.lang.reflect.Method.invoke(Native Method)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at java.lang.reflect.Method.invoke(Method.java:372)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-24 01:11:19.279: E/AndroidRuntime(3719): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.view.LayoutInflater.from(LayoutInflater.java:219)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at com.mavenmaverick.ipconnect.MainActivity.<init>(MainActivity.java:47)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at java.lang.reflect.Constructor.newInstance(Native Method)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at java.lang.Class.newInstance(Class.java:1572)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
05-24 01:11:19.279: E/AndroidRuntime(3719):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
05-24 01:11:19.279: E/AndroidRuntime(3719):     ... 10 more

Solution 1

LayoutInflater li = LayoutInflater.from(getBaseContext());

First, you do not need getBaseContext(), nor do you need LayoutInflater.from(). Use getLayoutInflater().

Second, you cannot call methods on the Activity superclass until after super.onCreate(), except in certain situations. Please postpone your initialization of promptsView until after super.onCreate() has been called.

Solution 2

View view = inflater.inflate(R.layout.fragment_name, container, false);
view.getContext();

Use view.getContext() wherever you need Application Context in fragments.

Comments

[Admin]

Can you please elaborate a bit ? LayoutInflater li = getLayoutInflater() is not working `

[CommonsWare]

@MavenMaverick: That is because you cannot call methods on the Activity superclass until super.onCreate(), except in certain situations, as I wrote in my answer. Please postpone your initialization of li until after super.onCreate() has been called.

[Admin]

Yes! I fixed it. Now, on passing the input via AlertDialog, does not load the WebView. Any leads on that ?

[Tash Pemhiwa]

@MavenMaverick if this solved your issue you should accept the answer