Android-practice-4-InputControls

Controlling user inputs with spinner and radio button.

With Spinner we can select one item from a set easily. For example, when we need users to provide contact information, we can put spinner so users can specify whether it's contact of home, mobile or work etc.

Related methods

• Spinner needs an Adapter object to assign an array to itself. Like an adapter in the real world, it connects the desired data to the spinner. For spinner we use ArrayAdapter class.

  public class ArrayAdapter .. {
      public static ArrayAdapter createFromResource( .., int textArrayResId, .. ) { .. }
      public void setDropDownViewResource( .. ) { .. }
  }
  

  In above methods, 2 layout resources must be provided for spinner's appearance. Android provides predefined layouts in android.R.layout class for them, unless we make our own customized layout.

  After creation of an adapter with the content, set this adapter as the Adapter of spinner view throguh setAdapter(Adapter T) in AdapterView class. The Spinner class inherits from AbsSpinner class which again, inherits from AdapterView.

• To respond to user selection, use onItemSelected(..) method defined in OnItemSelectedListener interface. This interface is inside Adapterview class.

  public abstract class AdapterView .. {
      public interface OnItemSelectedListener {
          void onItemSelected(AdapterView parent, int position, ..); 
          void onNothingSelected( .. );
      }
      public void setOnItemSelectedListener(AdapterView.OnItemSelectedListener listener) { .. }
      public abstract void setAdapter(Adapter T);
      public Object getItemAtPosition(int position) { .. }
  }
  

  Implement getItemAtPosition() method inside OnItemSelected() upon system-passed AdapterView object with position to get the selected data.

  public void onItemSelected(AdapterView parent, int position, ..) {
      String spinnerMessage = parent.getItemAtPosition(position).toString();
  }
  

  Above, the system-passed AdapterView parent parameter is the AdapterView where the user selection happened, which is in this case, the spinner object.

For more detail implementation of Spinner for each step please refer to the attached example.