在微调器选择中使用加载器重新加载光标

Question

我知道在使用LoaderCallbacks时如何使用notifyChange方法。但是我有一种情况，我需要通过URI从任何ContentProvider方法外部通知游标，该游标已更改。实际上，我正在使用微调器根据微调器选择（selectionArgs）的更改来查询数据库。选择微调器后，我单击搜索按钮。在按钮单击侦听器上，我使用getLoaderManager().initLoader()启动加载程序。我试图在getContext().getContentResolver().notifyChange(URI, null)方法之前添加initLoader方法。但这给了我getContext()方法一个错误。那么，在这种情况下我该怎么办？

这是我的Main_Activity.java代码

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

//Spinner for selecting blood group on search
private Spinner mBloodTypeSpinner;

private int mBloodType;

private Button searchBtn;

private static final int DONOR_LOADER = 0;

DonorCursorAdapter mCursorAdapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    searchBtn = (Button) findViewById(R.id.search_btn);

    // Setup FAB to open EditorActivity
    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(MainActivity.this, EditorActivity.class);
            startActivity(intent);
        }
    });

    mBloodTypeSpinner = (Spinner) findViewById(R.id.spinner_bloodType_search);

    //Set the blood picker spinner
    setupBloodTypeSpinner();

    // Find the ListView which will be populated with the pet data
    ListView donorListView = (ListView) findViewById(R.id.list);

    // Setup an Adapter to create a list item for each row of donor data in the Cursor.
    // There is no donor data yet (until the loader finishes) so pass in null for the Cursor.
    mCursorAdapter = new DonorCursorAdapter(this, null);
    donorListView.setAdapter(mCursorAdapter);

    searchBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Kick off the loader in Main_Activity
            getLoaderManager().initLoader(DONOR_LOADER, null,MainActivity.this);
        }
    });
}


/**Setup spinner for blood type pickup*/

private void setupBloodTypeSpinner() {
    // Create adapter for spinner. The list options are from the String array it will use
    // the spinner will use the default layout
    ArrayAdapter bloodTypeSpinnerAdapter = ArrayAdapter.createFromResource(this,
            R.array.array_bloodType_options, android.R.layout.simple_spinner_item);

    // Specify dropdown layout style - simple list view with 1 item per line
    bloodTypeSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    // Apply the adapter to the spinner
    mBloodTypeSpinner.setAdapter(bloodTypeSpinnerAdapter);

    // Set the integer mSelected to the constant values
    mBloodTypeSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            String selection = (String) parent.getItemAtPosition(position);
            if (!TextUtils.isEmpty(selection)) {
                if (selection.equals(getString(R.string.a_positive))) {
                    mBloodType = BloodContract.DonorEntry.A_Positive;
                } else if (selection.equals(getString(R.string.a_negative))) {
                    mBloodType = BloodContract.DonorEntry.A_Negative;
                } else if (selection.equals(getString(R.string.b_positive))) {
                    mBloodType = BloodContract.DonorEntry.B_Positive;
                }else if (selection.equals(getString(R.string.b_negative))) {
                    mBloodType = BloodContract.DonorEntry.B_Negative;
                }else if (selection.equals(getString(R.string.o_positive))) {
                    mBloodType = BloodContract.DonorEntry.O_Positive;
                }else if (selection.equals(getString(R.string.o_negative))) {
                    mBloodType = BloodContract.DonorEntry.O_Negative;
                }else if (selection.equals(getString(R.string.ab_positive))) {
                    mBloodType = BloodContract.DonorEntry.AB_Positive;
                }else if (selection.equals(getString(R.string.ab_negative))) {
                    mBloodType = BloodContract.DonorEntry.AB_Negative;
                } else{
                    mBloodType = BloodContract.DonorEntry.TYPE_UNKNOWN;
                }
            }
        }

        // Because AdapterView is an abstract class, onNothingSelected must be defined
        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            mBloodType = BloodContract.DonorEntry.TYPE_UNKNOWN;
        }
    });
}

// Get value of readable blood type
public String getBloodTypeString(int bloodType) {
    switch (bloodType) {
        case DonorEntry.A_Positive:
            return getResources().getString(R.string.a_positive);
        case DonorEntry.A_Negative:
            return getResources().getString(R.string.a_negative);
        case DonorEntry.B_Positive:
            return getResources().getString(R.string.b_positive);
        case DonorEntry.B_Negative:
            return getResources().getString(R.string.b_negative);
        case DonorEntry.O_Positive:
            return getResources().getString(R.string.o_positive);
        case DonorEntry.O_Negative:
            return getResources().getString(R.string.o_negative);
        case DonorEntry.AB_Positive:
            return getResources().getString(R.string.ab_positive);
        case DonorEntry.AB_Negative:
            return getResources().getString(R.string.ab_negative);
        default:
            return "UNKNOWN";
    }
}

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    //Projection for query method
    String[] projection = {
            DonorEntry._ID,
            DonorEntry.COLUMN_DONOR_NAME,
            DonorEntry.COLUMN_DONOR_MOBILE,
            DonorEntry.COLUMN_DONATE_DATE,
            DonorEntry.COLUMN_BLOOD_GROUP};

    String selection = DonorEntry.COLUMN_BLOOD_GROUP + "=?";

    String[] selectionArgs = new String[]{String.valueOf(mBloodType)};

    // This loader will execute the ContentProvider's query method on a background thread
    return new CursorLoader(this,
            DonorEntry.CONTENT_URI,
            projection,
            selection,
            selectionArgs,
            null);
}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    mCursorAdapter.swapCursor(data);
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {
    mCursorAdapter.swapCursor(null);
}

}