Adding items to a database from a dialog

Question

I have a spinner in my activity that upon selection of one of it's options needs to handle the addition of a new object to my Sqlite database. the following solution works but everything in it looks like one big hack.
My layout:

<Spinner
 android:id="@+id/spnMachineManufacturer"
 android:layout_width="@dimen/et_params_width"
 android:layout_height="wrap_content"
 android:prompt="@string/Select"/>

My activity code:

public class ManufacturerSelectionActivity extends Activity
{
 Spinner spnMachineManufacturer;
 List<Manufacturer> allManufacturers;
 @Override
 protected void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_manufacturer_selection);
 spnMachineManufacturer = (Spinner) findViewById(R.id.spnMachineManufacturer);
 addItemsToManufacturersSpinner();
 addListenerToManufacturersSpinner();
 }
 private void addItemsToManufacturersSpinner()
 {
 final DbConnector db = new DbConnector(this);
 //populate list from db utility
 allManufacturers = db.getAllManufacturers();
 if (allManufacturers != null && allManufacturers.size() > 0)
 {
 //hack - create a manufacturer object for add new option
 Manufacturer addNewManufacturer = new Manufacturer();
 addNewManufacturer.setId(-1);
 addNewManufacturer.setName("Add new...");
 allManufacturers.add(addNewManufacturer);
 //add items to spinner
 final ArrayAdapter adapter = new ArrayAdapter<Manufacturer>(this,
 android.R.layout.simple_spinner_dropdown_item, allManufacturers);
 adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
 spnMachineManufacturer.setAdapter(adapter);
 }
 }
 private void addListenerToManufacturersSpinner()
 {
 spnMachineManufacturer.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
 {
 @Override
 public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l)
 {
 Manufacturer m = (Manufacturer) adapterView.getItemAtPosition(i);
 if (m != null)
 {
 int size = adapterView.getCount();
 //check if selected item is "add new..."
 if (size == i + 1)
 {
 //create a dialog to receive the new manufacturer name
 AlertDialog.Builder builder = new AlertDialog.Builder(
 ManufacturerSelectionActivity.this);
 builder.setTitle("Add a manufacturer");
 // Set up the input
 final EditText input = new EditText(ManufacturerSelectionActivity.this);
 input.setInputType(InputType.TYPE_CLASS_TEXT);
 builder.setView(input);
 // Set up the buttons
 builder.setPositiveButton("OK", new DialogInterface.OnClickListener()
 {
 @Override
 public void onClick(DialogInterface dialog, int which)
 {
 String name = input.getText().toString();
 final DbConnector db = new DbConnector(
 ManufacturerSelectionActivity.this);
 //Create a new manufacturer object
 Manufacturer mnf = new Manufacturer();
 mnf.setName(name);
 //add the new manufacturer to the database
 db.addManufacturer(mnf);
 //refresh spinner
 addItemsToManufacturersSpinner();
 }
 });
 builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener()
 {
 @Override
 public void onClick(DialogInterface dialog, int which)
 {
 //do nothing
 dialog.cancel();
 }
 });
 builder.show();
 }
 }
 }
 @Override
 public void onNothingSelected(AdapterView<?> adapterView)
 {
 //do nothing
 }
 });
 }
}

My concerns:

• The addition of a manufacturer object to my list of manufacturers
• The use of ManufacturerSelectionActivity.this as a context
• The creation of a new item in the database from within the dialog method (which is found inside a setOnItemSelectedListener method
• The call to addItemsToManufacturersSpinner() method from within the dialog method

Answer 1

Your method addListenerToManufacturersSpinner() is very long. You are nesting two listeners here. It would be easier to read if you defined the listener first and then set it.

For example:

DialogInterface.OnClickListener myOnClickListener = new DialogInterface.OnClickListener()
{
 @Override
 public void onClick(DialogInterface dialog, int which)
 {
 String name = input.getText().toString();
 final DbConnector db = new DbConnector(
 ManufacturerSelectionActivity.this);
 //Create a new manufacturer object
 Manufacturer mnf = new Manufacturer();
 mnf.setName(name);
 //add the new manufacturer to the database
 db.addManufacturer(mnf);
 //refresh spinner
 addItemsToManufacturersSpinner();
 }
});

And then you can set:

builder.setPositiveButton("OK", myOnClickListener);

Another point is, that you should define string resources such as "OK" in your res/values/strings.xml and reference the string there. This makes your app more configurable and separates content from code.

Variable naming:

 public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l)

What do variables i and l do? It is good practie to use more descriptive names.