App crashes after ok button click on alert dialog on android

Question

please help me with this as I have searched for solutions online without getting one.

What I am trying to do is get data from an alert dialog onclick the OK button. The alert dialog pops up after clicking an item on TypeActivity. The result of this click is passed to HomeActivity from where the alert dialog pops up with a text field. But each time I type in the text field and press the "OK" button, the app crashes. The logcat shows A null pointer Exception. I will display the logcat content too. Thanks for your help.

My codes are as follows

TypeActivity:

    String[] typeTag = {"TypeA","TypeB","TypeC","TypeD"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setListAdapter(new MyAdapter(TypeActivity.this,R.layout.spinnerrow, typeTag));
    getListView().setAdapter(new MyAdapter(TypeActivity.this,R.layout.spinnerrow, typeTag));


    getListView().setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            Intent returnIntent = new Intent();
            returnIntent.putExtra("selectedType", typeTag[position]);
            setResult(RESULT_OK, returnIntent);
            finish();
        }
    });

HomeActivity:

@Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == 1 && resultCode == RESULT_OK){
            String temp = data.getStringExtra("selectedType");

            AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this); 
            LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
            ViewGroup parent = null;
            builder2.setView(inflater.inflate(R.layout.inputtype, parent, false));

            final EditText tagname = (EditText)findViewById(R.id.uname);                        

            builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
            {                   

            @Override
            public void onClick(DialogInterface dialog, int id) {
                String tag = tagname.getText().toString();
                Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
                }
            })
            .setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {

                    }
            })
            .show();  
        }
    }

The Logcat:

1-11 05:22:45.427: E/AndroidRuntime(2298): FATAL EXCEPTION: main
11-11 05:22:45.427: E/AndroidRuntime(2298): Process: com.example.myapp, PID: 2298
11-11 05:22:45.427: E/AndroidRuntime(2298): java.lang.NullPointerException
11-11 05:22:45.427: E/AndroidRuntime(2298):     at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:278)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at android.os.Handler.dispatchMessage(Handler.java:102)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at android.os.Looper.loop(Looper.java:136)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at android.app.ActivityThread.main(ActivityThread.java:5017)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at java.lang.reflect.Method.invokeNative(Native Method)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at java.lang.reflect.Method.invoke(Method.java:515)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
11-11 05:22:45.427: E/AndroidRuntime(2298):     at dalvik.system.NativeStart.main(Native Method)

the new logcat

 11-11 06:06:35.917: E/AndroidRuntime(4530): FATAL EXCEPTION: main
 11-11 06:06:35.917: E/AndroidRuntime(4530): Process: com.example.myapp, PID: 4530
 11-11 06:06:35.917: E/AndroidRuntime(4530): java.lang.NullPointerException
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:282)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at android.os.Handler.dispatchMessage(Handler.java:102)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at android.os.Looper.loop(Looper.java:136)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at android.app.ActivityThread.main(ActivityThread.java:5017)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at java.lang.reflect.Method.invokeNative(Native Method)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at java.lang.reflect.Method.invoke(Method.java:515)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
 11-11 06:06:35.917: E/AndroidRuntime(4530):    at dalvik.system.NativeStart.main(Native Method)

The layout:

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical" >

  <ImageView
   android:id="@+id/dispimg"        
   android:layout_width="match_parent"        
   android:layout_height="64dp"        
   android:background="#d1d1d1"        
   android:contentDescription="@string/app_name"        
   android:scaleType="center"        
   android:src="@drawable/addme" /> 

    <EditText        
     android:id="@+id/uname"        
     android:layout_width="match_parent"        
     android:layout_height="wrap_content"        
     android:layout_marginBottom="10dp"        
     android:layout_marginLeft="10dp"        
     android:layout_marginRight="10dp"        
     android:layout_marginTop="16dp"                
     android:inputType="text"
     android:background="@drawable/textfield" />   

     </LinearLayout>

the new code:

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == 1 && resultCode == RESULT_OK){
            String temp = data.getStringExtra("selectedType");            

            AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this);              
            LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
            ViewGroup parent = null;
             View view = inflater.inflate(R.layout.inputtype, parent, true);
             final EditText tagname = (EditText)findViewById(R.id.uname);   
             builder2.setView(view);

            builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
            {                   

            @Override
            public void onClick(DialogInterface dialog, int id) {
                String tag = tagname.getText().toString();
                Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
                    }
                })
                 .setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {

                        }
                 })
                .show();  
            }
        }

new logcat:

    11-11 06:58:49.804: E/AndroidRuntime(7148): FATAL EXCEPTION: main
    11-11 06:58:49.804: E/AndroidRuntime(7148): Process: com.example.myapp, PID: 7148
    11-11 06:58:49.804: E/AndroidRuntime(7148): java.lang.NullPointerException
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at com.example.myapp.HomeActivity$3.onClick(HomeActivity.java:288)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at android.os.Handler.dispatchMessage(Handler.java:102)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at android.os.Looper.loop(Looper.java:136)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at android.app.ActivityThread.main(ActivityThread.java:5017)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at java.lang.reflect.Method.invokeNative(Native Method)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at java.lang.reflect.Method.invoke(Method.java:515)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
    11-11 06:58:49.804: E/AndroidRuntime(7148):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

your editText is belong to AlertDialog, so following line is null in your code:

 final EditText tagname = (EditText)findViewById(R.id.uname);  

so you get NPE on

String tag = tagname.getText().toString();

you need following code:

 View view = inflater.inflate(R.layout.inputtype, parent, false)
 builder2.setView(view);

and

 final EditText tagname = (EditText)view.findViewById(R.id.uname); 

so your code must be as following:

  AlertDialog.Builder builder2 = new AlertDialog.Builder(HomeActivity.this); 
            LayoutInflater inflater = HomeActivity.this.getLayoutInflater();
            ViewGroup parent = null;
             View view = inflater.inflate(R.layout.inputtype, parent, false);
             final EditText tagname = (EditText)view.findViewById(R.id.uname); 
             builder2.setView(view);




            builder2.setPositiveButton("OK", new DialogInterface.OnClickListener()
            {                   

            @Override
            public void onClick(DialogInterface dialog, int id) {
                String tag = tagname.getText().toString();
                Toast.makeText(getApplicationContext(), "U entered "+tag, Toast.LENGTH_LONG).show();
                }
            })
            .setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {

                    }
            })
            .show();