_id列被称为不存在，即使在我将其包含在createtable语句中之后也是如此

Question

我正在尝试从数据库中填充列表视图。当我尝试使用光标时，我会得到一个错误：

android.database.sqlite.SQLiteException：编译时没有这样的列：_id（代码1）：，SELECT _id FROM contacts WHERE _id ORDER BY name DESC

这是我的代码：

MainActivity.java

package com.boggs.barr.barrboggscontactlist;
import android.content.ContentValues;
import android.content.Loader;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.provider.ContactsContract;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        populateListView();
    }
    public static final String KEY_ID = "_id";

    private void populateListView() {
        String[] projection = {
                KEY_ID
        };
        FeedReaderDbHelper mDbHelper = new FeedReaderDbHelper(getApplicationContext());
        SQLiteDatabase db = mDbHelper.getWritableDatabase();
        String sortOrder =
                FeedReaderContract.FeedEntry.COLUMN_NAME_NAME + " DESC";
        Cursor cursor = db.query(
                FeedReaderContract.FeedEntry.TABLE_NAME,  // The table to query
                projection,                               // The columns to return
                KEY_ID,                                // The columns for the WHERE clause
                null,                            // The values for the WHERE clause
                null,                                     // don't group the rows
                null,                                     // don't filter by row groups
                sortOrder                                 // The sort order
        );
        String[] fromColumns = new String[] {FeedReaderContract.FeedEntry.COLUMN_NAME_NAME, FeedReaderContract.FeedEntry.COLUMN_NAME_PHONE};
        int[] toViews = {R.id.name, R.id.phone};
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
                R.layout.name_and_number, cursor, fromColumns, toViews, 0);
        ListView listView = (ListView) findViewById(R.id.listView);
        listView.setAdapter(adapter);

}
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

FeedReaderDbHelper.java

    package com.boggs.barr.barrboggscontactlist;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.sql.RowId;
/**
 * Created by adnroid developer site
 */
public class FeedReaderDbHelper extends SQLiteOpenHelper {
    // If you change the database schema, you must increment the database version.
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "FeedReader.db";
    public static final String LONG_TYPE = " Long";
    public static final String STRING_TYPE = " STRING";
    public static final String BYTE_TYPE = " BYTE";
    private static final String COMMA_SEP = ",";
    private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + FeedReaderContract.FeedEntry.TABLE_NAME + " (" +
                    FeedReaderContract.FeedEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    FeedReaderContract.FeedEntry.COLUMN_NAME_PICTURE + STRING_TYPE + COMMA_SEP +
                    FeedReaderContract.FeedEntry.COLUMN_NAME_NAME + STRING_TYPE + COMMA_SEP +
                    FeedReaderContract.FeedEntry.COLUMN_NAME_EMAIL + STRING_TYPE + COMMA_SEP +
                    FeedReaderContract.FeedEntry.COLUMN_NAME_PHONE + STRING_TYPE +
                    ")";

    private static final String SQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + FeedReaderContract.FeedEntry.TABLE_NAME;
    public FeedReaderDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);
    }
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

FeedReaderContract.java

    package com.boggs.barr.barrboggscontactlist;
import android.provider.BaseColumns;
import android.support.annotation.Nullable;
/**
 * Created by android developer site.
 * attempted to do database ran out of time
 */
public final class FeedReaderContract {
    // To prevent someone from accidentally instantiating the contract class,
    // give it an empty constructor.
    public FeedReaderContract() {}
    /* Inner class that defines the table contents */
    public static abstract class FeedEntry implements BaseColumns {
        public static final String TABLE_NAME = "contacts";
        public static final String _ID = "_id";
        public static final String COLUMN_NAME_PICTURE = "picture";
        public static final String COLUMN_NAME_NAME = "name";
        public static final String COLUMN_NAME_EMAIL = "email";
        public static final String COLUMN_NAME_PHONE = "phone";
        public static  final Nullable COLUMN_NAME_NULLABLE = null;
    }
}

我读到我需要将ID传递给光标？但我不确定这意味着什么。对我来说，它应该起作用，因为我将ID包含在要包含在光标中的列的列表中。感谢您的帮助！

编辑：我之所以问这个问题，是因为有同样问题的人提出的解决方案对我不起作用。他们一直建议尝试使用RowId或.moveToFirst来包含ID。Laalto被提出了一个对我有效的解决方案。

Answer 1

正如用户laalto所指出的，我需要从模拟器中卸载该应用程序，因为我更改了模式。一旦我这么做了，应用程序就开始工作了。