Question

I have a AlertDialog that uses a Custom Layout. In the OnClick Event I want to read what the user has typed in so I do this:

//Login Dialog
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            // Get the layout inflater
            LayoutInflater inflater = this.getLayoutInflater();

            // Inflate and set the layout for the dialog
            // Pass null as the parent view because its going in the dialog layout
            builder.setView(inflater.inflate(R.layout.dialog_signin, null))
            .setPositiveButton(R.string.tvLoginTitle, new DialogInterface.OnClickListener() {
                   @Override
                   public void onClick(DialogInterface dialog, int id) {
                       String username = ((EditText)findViewById(R.id.loginUsername)).getText().toString();
                       String password = ((EditText)findViewById(R.id.loginPassword)).getText().toString();
                       System.out.println(username);
                       System.out.println(password);
                       ConnectionID.loginToServer(cMainActivity, username, password);
                   }
               })
               .setNegativeButton(R.string.btnExit, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       System.exit(0);

                   }
               }).show();  

But when I want to read whats inside I always get a NullPointerException the Layout from dialog_signin looks like:

<EditText
    android:id="@+id/loginUsername"
    android:inputType="textEmailAddress"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="4dp"
    android:hint="@string/tvUsername" />
<EditText
    android:id="@+id/loginPassword"
    android:inputType="textPassword"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="4dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="16dp"
    android:fontFamily="sans-serif"
    android:hint="@string/tvPassword"/>

Answer 1

If username and password are fields belong to a dialog, you should do as shown in following code:

Edited:

View v = inflater.inflate(R.layout.dialog_signin, null);
builder.setView(v); 
String username = ((EditText)v.findViewById(R.id.loginUsername)).getText().toString();       
String password = ((EditText)v.findViewById(R.id.loginPassword)).getText().toString();