java - 从我的内容提供者返回一列的所有行

Question

我正在尝试访问我已经创建的 Content Provider(这是我非常严格地遵循教程创建的，我已经使用教程引导我完成的代码对其进行了测试并且它工作正常)并阅读电子邮件地址我已经添加到 SQLite 数据库中。在数据库中是 ID、COLUMN_NAME 和 COLUMN_EMAIL。我想获取电子邮件列的所有行，并将其作为返回到该 Activity 中的字符串的 ArrayList。

到目前为止，我最好的猜测是，我会在某个地方使用内容提供程序的查询方法查询数据库，将光标返回到 Activity ，然后从行中收集所有字符串，或者设法发送查询仅对该列进行投影或过滤掉所有@lorem.com 或光标的第二个索引或某种后期数据检索过滤器。

基本上我只是被困住了。

好的，这是我的代码:

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

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_email_scheduler);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        final TextView emailText = (TextView) findViewById(R.id.emailText);
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Cursor cursor = getContacts();
                Log.i("TAG", cursor.getColumnName(2));
                emailText.append(cursor.toString());
            }
        });
    }

    private static final int CONTACT_LOADER = 0;
    public Uri contactUri;
    ArrayList<String> addresses = new ArrayList<>();
    Cursor cursor;

    private Cursor getContacts() {
        // Run query
        Uri uri = Contact.CONTENT_URI;
        String[] projection = new String[] { Contact._ID,
                Contact.COLUMN_NAME };
        String selection = Contact.COLUMN_EMAIL + " = '"
                + ("1") + "'";
        String[] selectionArgs = null;
        String sortOrder = Contact.COLUMN_NAME
                + " COLLATE LOCALIZED ASC";
        return getContentResolver().query(uri, projection, selection, selectionArgs,
                sortOrder);
    }
    // called by LoaderManager to create a Loader
    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        CursorLoader cursorLoader;

        switch (id) {
            case CONTACT_LOADER:
                cursorLoader = new CursorLoader(this,
                        contactUri, // Uri of contact to display
                        null, // null projection returns all columns
                        null, // null selection returns all rows
                        null, // no selection arguments
                        null); // sort order
                break;
            default:
                cursorLoader = null;
                break;
        }

        return cursorLoader;
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {

        Log.i("TAG", "got to the beginning of onloadfinish " + data);
        if (data != null && data.moveToFirst()) {
            int nameIndex = data.getColumnIndex(Contact.COLUMN_NAME);
            int emailIndex = data.getColumnIndex(Contact.COLUMN_EMAIL);
            String address = data.getString(emailIndex);
            Log.i("TAG", address);

            while (data.getString(emailIndex) != null){
                addresses.add(cursor.getString(cursor.getColumnIndex(
                        Contact.COLUMN_EMAIL)));
                Log.i("TAG", addresses.toString());}
        }
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) { }
}

在 onCreate 方法中，当我运行它时它返回此数据:android.content.ContentResolver$CursorWrapperInner@60c9bd2

我如何从中获取我需要的信息？我尝试的一切都变成了死胡同。

Answer 1

private void getContacts() {
    List<String> addresses = new ArrayList<String>();    

    // Run query

    Uri uri = Contact.CONTENT_URI;
    String[] projection = new String[] { Contact.COLUMN_EMAIL };
    String selection = null;
    String[] selectionArgs = null;
    String sortOrder = Contact.COLUMN_EMAIL
            + " COLLATE LOCALIZED ASC";
    Cursor cursor = getContentResolver().query(uri, projection, selection, selectionArgs,
            sortOrder);
    TextView emailText = (TextView) findViewById(R.id.emailText);
    if (cursor != null) {
        cursor.moveToFirst();
        String category;
        for (int i = 0; i < cursor.getCount(); i++){
            category = cursor.getString(cursor
            .getColumnIndexOrThrow(Contact.COLUMN_EMAIL));
            addresses.add(category);
            cursor.moveToNext();
        }
        // always close the cursor
        cursor.close();
    }
}