10. Load Existing Pet in EditorActivity

Solution code

Start by implementing the loader callbacks and using the Ctrl + I hotkey to get all of the loader callback methods:

public class EditorActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor> {

Next, initialize the loader, using this code:

       getLoaderManager().initLoader(EXISTING_PET_LOADER, null, this);

In onCreateLoader(), I’ll make a new CursorLoader, passing in the uri and the projection. I need the uri from onCreate() so I’ll need to put it in an instance variable called mCurrentPetUri:

/** Content URI for the existing pet (null if it's a new pet) */
private Uri mCurrentPetUri;

...
    @Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
    // Since the editor shows all pet attributes, define a projection that contains
    // all columns from the pet table
    String[] projection = {
            PetEntry._ID,
            PetEntry.COLUMN_PET_NAME,
            PetEntry.COLUMN_PET_BREED,
            PetEntry.COLUMN_PET_GENDER,
            PetEntry.COLUMN_PET_WEIGHT };

    // This loader will execute the ContentProvider's query method on a background thread
    return new CursorLoader(this,   // Parent activity context
            mCurrentPetUri,         // Query the content URI for the current pet
            projection,             // Columns to include in the resulting Cursor
            null,                   // No selection clause
            null,                   // No selection arguments
            null);                  // Default sort order
}

When the data from the pet is loaded into a cursor, onLoadFinished() is called. Here, I’ll first most the cursor to it’s first item position. Even though it only has one item, it starts at position -1.

    // Proceed with moving to the first row of the cursor and reading data from it
    // (This should be the only row in the cursor)
    if (cursor.moveToFirst()) {

Then I’ll get the data out of the cursor by getting the index of each data item, and then using the indicees and the get methods to grab the actual integers and strings.

    if (cursor.moveToFirst()) {
        // Find the columns of pet attributes that we're interested in
        int nameColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_NAME);
        int breedColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_BREED);
        int genderColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_GENDER);
        int weightColumnIndex = cursor.getColumnIndex(PetEntry.COLUMN_PET_WEIGHT);

        // Extract out the value from the Cursor for the given column index
        String name = cursor.getString(nameColumnIndex);
        String breed = cursor.getString(breedColumnIndex);
        int gender = cursor.getInt(genderColumnIndex);
        int weight = cursor.getInt(weightColumnIndex);

For each of the textViews I’ll set the proper text.

        // Update the views on the screen with the values from the database
        mNameEditText.setText(name);
        mBreedEditText.setText(breed);
        mWeightEditText.setText(Integer.toString(weight));

For the spinner, I’ll use a switch statement to set its state correctly using the setSelection method.

        // Gender is a dropdown spinner, so map the constant value from the database
        // into one of the dropdown options (0 is Unknown, 1 is Male, 2 is Female).
        // Then call setSelection() so that option is displayed on screen as the current selection.
        switch (gender) {
            case PetEntry.GENDER_MALE:
                mGenderSpinner.setSelection(1);
                break;
            case PetEntry.GENDER_FEMALE:
                mGenderSpinner.setSelection(2);
                break;
            default:
                mGenderSpinner.setSelection(0);
                break;
        }