findViewById() returns null for Views in a Dialog

Solution 1:

Calling findViewById() will search for views within your Activity's layout and not your dialog's view. You need to call findViewById() on the specific View that you set as your dialog's layout.

Try this

private void initSearch() {
    AlertDialog.Builder searchDialog = new AlertDialog.Builder(this);
    LayoutInflater inflater = this.getLayoutInflater();
    searchDialog.setTitle("Search Photos");
    searchDialog.setMessage("Specify tag and value...");
    // R.layout.search_dialog is my custom layour, it displays fine, it works. 
    View dialogView = inflater.inflate(R.layout.search_dialog, null);
    searchDialog.setView(dialogView);
    EditText tagText = (EdiText) dialogView.findViewById(R.id.tagField); 
    searchDialog.setPositiveButton( ... ) ...
    AlertDialog myAlert = searchDialog.create(); //returns an AlertDialog from a Builder.
    myAlert.show();
}

Notice how I'm inflating the view and storing it in a View named dialogView. Then, to find your EditText named tagField, I'm using dialogView.findViewById(R.id.tagField);

Solution 2:

The TextView with id text123 has to be declared inside the Layout you set with setContentView