There are a lot of ways to access views in Android. A quick overview: My advise would be: findViewById: old school. Avoid. ButterKnife: old school, but less boilerplate and some added functionality. Still lacks compile time safety. Avoid if possible. Kotlin Synthetic: really a elegant cached version of findViewbyId. Better performance and way less boilerplate … Read more
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 … Read more
Starting with API 26, findViewById uses inference for its return type, so you no longer have to cast. Old definition: View findViewById(int id) New definition: <T extends View> T findViewById(int id) So if your compileSdk is at least 26, it means that you can make use of this 🙂
Android id overview An Android id is an integer commonly used to identify views; this id can be assigned via XML (when possible) and via code (programmatically.) The id is most useful for getting references for XML-defined Views generated by an Inflater (such as by using setContentView.) Assign id via XML Add an attribute of … Read more
You have to call setContentView(…) BEFORE you attempt to find any of the UI components. You’re trying to find the TextView before you’ve called it. Change your code to this… super.onCreate(savedInstanceState); setContentView(R.layout.other_activity); TextView textView = (TextView)findViewById(R.id.txt02);
Instance member variables are initialized when the instance itself is initialized. It’s too early for findViewById() Before onCreate() your activity does not yet have a Window that findViewById() needs internally. Before setContentView() (that you should be calling in onCreate()) there are no views to be found either. Therefore init your view references in onCreate() and … Read more
An Activity is not fully initialized and ready to look up views until after setContentView(…) is called in onCreate(). Only declare the fields like the following: private EditText usernameField, passwordField; private TextView error; private ProgressBar progress; and then assign the values in onCreate: @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_login); usernameField = (EditText)findViewById(R.id.username); passwordField … Read more
findViewById in Fragment
findViewById() returns a View if it exists in the layout you provided in setContentView(), otherwise it returns null and that’s what happening to you. Note that if you don’t setContentView(), and don’t have a valid view to findViewById() on, findViewById() will always return null until you call setContentView(). This also means variables in the top-level … Read more