尝试使用多个表时出现 SQLite 数据库错误

Question

我在尝试为 Android 应用程序使用多表 SQL 适配器时遇到错误。我已经搜索了网站和互联网，但尚未找到解决方案。

这是我收到错误时得到的 LogCat 堆栈：

    12-07 00:02:56.696: E/AndroidRuntime(31297): FATAL EXCEPTION: main
    12-07 00:02:56.696: E/AndroidRuntime(31297): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tma.android.recipebox/com.tma.android.recipebox.MealHomeActivity}: java.lang.IllegalArgumentException: column '_id' does not exist
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1815)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1831)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread.access$500(ActivityThread.java:122)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1024)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at   android.os.Handler.dispatchMessage(Handler.java:99)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.os.Looper.loop(Looper.java:132)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread.main(ActivityThread.java:4123)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at java.lang.reflect.Method.invokeNative(Native Method)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at java.lang.reflect.Method.invoke(Method.java:491)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at dalvik.system.NativeStart.main(Native Method)
    12-07 00:02:56.696: E/AndroidRuntime(31297): Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at  android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:299)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.widget.CursorAdapter.init(CursorAdapter.java:169)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.widget.CursorAdapter.<init>(CursorAdapter.java:117)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:52)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:78)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at com.tma.android.recipebox.MealHomeActivity.fillData(MealHomeActivity.java:38)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at com.tma.android.recipebox.MealHomeActivity.onCreate(MealHomeActivity.java:28)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.Activity.performCreate(Activity.java:4397)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at  android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1779)
    12-07 00:02:56.696: E/AndroidRuntime(31297):    ... 11 more

LogCat 似乎没有在导致错误的活动中给我一个特定的行号，所以我将发布我认为的全部内容：

package com.tma.android.recipebox;

import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.widget.Button;
import android.widget.SimpleCursorAdapter;

public class MealHomeActivity extends ListActivity {

private Button mAddButton;
private MyDbAdapter mDbHelper;

private static final int ACTIVITY_EDIT = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.meal_home);
    mDbHelper = new MyDbAdapter(this);
    mDbHelper.open();

    setButtonClickListeners();
    fillData();
}

private void fillData() {
    Cursor mealCursor = mDbHelper.fetchAllMeals();
    startManagingCursor(mealCursor);

    String[] from = new String[]{MyDbAdapter.KEY_TITLE, MyDbAdapter.KEY_MEALDATE};
    int[] to = new int[]{R.id.text1, R.id.text2};

    SimpleCursorAdapter meals = new SimpleCursorAdapter(this, R.layout.meal_row, mealCursor, from, to);
    setListAdapter(meals);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);
    MenuInflater mi = getMenuInflater();
    mi.inflate(R.menu.meal_list_menu, menu);
    return true;
}

private void createMeal() {
    Intent i = new Intent(this, MealEditActivity.class);
    startActivityForResult(i, ACTIVITY_EDIT);
}

private void setButtonClickListeners() {
    mAddButton = (Button) findViewById(R.id.add_button);
    mAddButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            createMeal();
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
    super.onActivityResult(requestCode, resultCode, intent);
    fillData();
}

}

我还将在我的 DbAdapter 中发布创建语句：

package com.tma.android.recipebox;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MyDbAdapter {

private static final String TAG = "MyDbAdapter";
private static final String DATABASE_NAME = "recipe_box";
private static final int DATABASE_VERSION = 4;

private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;

/**
 * Recipe Table Constants
 */

private static final String DATABASE_TABLE = "recipes";
public static final String KEY_NAME = "name";
public static final String KEY_ING = "ingredients";
public static final String KEY_PREP = "preparation";
public static final String KEY_DATE = "date";
public static final String KEY_ROWID = "_id";

/**
 * Meal table constants
 */

private static final String DATABASE2_TABLE = "meals";
public static final String KEY_TITLE = "title";
public static final String KEY_RECIPES = "recipes";
public static final String KEY_MEALDATE = "date";
public static final String KEY_MEALID = "mealId";

/**
 * creation statement for the Recipe table
 */

private static final String CREATE_RECIPE_TABLE = "create table " + DATABASE_TABLE + "(_id integer primary key autoincrement," 
    + KEY_NAME + " text not null, " + KEY_ING + " text not null, " + KEY_PREP + 
    " text not null, " + KEY_DATE + " text not null);";

/**
 * creation statement for the Meal table
 */

private static final String CREATE_MEAL_TABLE = "create table " + DATABASE2_TABLE + "( " + KEY_MEALID 
    + " integer primary key autoincrement," + KEY_TITLE + " text not null, " + KEY_RECIPES + " text not null, " +
    KEY_MEALDATE + " text not null);";

如果我需要发布任何其他内容可以帮助您回答我的问题，请告诉我。

Answer 1

CursorAdapters 需要有一个具有_id 列的游标。如果您的数据库中没有_id 列，只需选择您的主键（在您的情况下我猜它的mealId）mealId as _id。你应该很高兴。