Android上的SQLite数据库错误

Question

我的应用程序未在该应用程序上运行，并且显示错误。 我已经阅读了所有与此相关的答案和文章，并进行了相应的更改，我从模拟器中卸载了该应用程序，清除了模拟器，却一无所获。

DatabaseHelper类：

package com.example.projectthree;



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

public class DatabaseHelper extends SQLiteOpenHelper {

private SQLiteDatabase db;
private static final String DATABASE_NAME="countries_db";
static final int DATABASE_VERSION = 1;

private static final String SQLITE_TABLE = "countries";
private static final String KEY_ID = "_id";
static final String COUNTRY="country";
static final String CAPITAL="capital";
static final String CURRENCY="currency";
static final String POPULATION="population";


public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);

}

//this created a table called "countries" that has primary key which auto-increments
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + SQLITE_TABLE + "(" + KEY_ID + "
 INTEGER PRIMARY KEY," + COUNTRY + " TEXT," + CAPITAL + " TEXT," + CURRENCY + " TEXT,"
 + POPULATION + " INTEGER" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);



//this is populating the database
ContentValues cv=new ContentValues();
cv.put(COUNTRY, "EGYPT");
cv.put(CAPITAL, "CAIRO");
cv.put(CURRENCY, "EGP");
cv.put(POPULATION, "90");
db.insert("SQLITE_TABLE", null, cv);

cv.put(COUNTRY, "Jordan");
cv.put(CAPITAL, "Amman");
cv.put(CURRENCY, "Jordanian Dinar");
cv.put(POPULATION, "6.3");
db.insert("SQLITE_TABLE", null, cv);

cv.put(COUNTRY, "Kuwait");
cv.put(CAPITAL, "Kuwait City");
cv.put(CURRENCY, "Kuwait Dinar");
cv.put(POPULATION, "3.25");
db.insert("SQLITE_TABLE", null, cv);

cv.put(COUNTRY, "Saudi Arabia");
cv.put(CAPITAL, "Riyadh");
cv.put(CURRENCY, "Riyal");
cv.put(POPULATION, "29");
db.insert("SQLITE_TABLE", null, cv);

}


// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + SQLITE_TABLE);

// Create tables again
onCreate(db);
}

public void open() {
// TODO Auto-generated method stub

}
public Cursor fetchAllCountries() {
SQLiteDatabase db = this.getWritableDatabase();

  Cursor cursor = db.query(true, SQLITE_TABLE, new String[] 
          {COUNTRY, CAPITAL, CURRENCY, POPULATION}, 
    null, null, null, null, null, null);

  if (cursor != null) {
   cursor.moveToFirst();
  }

  return cursor;

 }


public SQLiteDatabase getMydb() {
return db;
}

public void setMydb(SQLiteDatabase mydb) {
this.db = mydb;
}
}

我在logcat上收到此错误

07-08 03:29:28.207: E/AndroidRuntime(998): FATAL EXCEPTION: main
07-08 03:29:28.207: E/AndroidRuntime(998): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.projectthree/com.example.projectthree.MainActivity}:     java.lang.IllegalArgumentException: column '_id' does not exist
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.os.Looper.loop(Looper.java:137)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread.main(ActivityThread.java:4340)
07-08 03:29:28.207: E/AndroidRuntime(998):  at java.lang.reflect.Method.invokeNative(Native Method)
07-08 03:29:28.207: E/AndroidRuntime(998):  at java.lang.reflect.Method.invoke(Method.java:511)
07-08 03:29:28.207: E/AndroidRuntime(998):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-08 03:29:28.207: E/AndroidRuntime(998):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-08 03:29:28.207: E/AndroidRuntime(998):  at dalvik.system.NativeStart.main(Native Method)
07-08 03:29:28.207: E/AndroidRuntime(998): Caused by: java.lang.IllegalArgumentException: column '_id' does not exist
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:301)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.support.v4.widget.CursorAdapter.init(CursorAdapter.java:174)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.support.v4.widget.CursorAdapter.<init>(CursorAdapter.java:151)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.support.v4.widget.ResourceCursorAdapter.<init>(ResourceCursorAdapter.java:93)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.support.v4.widget.SimpleCursorAdapter.<init>(SimpleCursorAdapter.java:89)
07-08 03:29:28.207: E/AndroidRuntime(998):  at com.example.projectthree.MainActivity.displayListView(MainActivity.java:67)
07-08 03:29:28.207: E/AndroidRuntime(998):  at com.example.projectthree.MainActivity.onCreate(MainActivity.java:33)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.Activity.performCreate(Activity.java:4465)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
07-08 03:29:28.207: E/AndroidRuntime(998):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
07-08 03:29:28.207: E/AndroidRuntime(998):  ... 11 more

为什么我仍然得到“ _id”列不存在错误？

先感谢您

Answer 1

您已将列“ _id”创建为整数主键。 但您没有提到它自动递增或未指定任何默认值。 因此，在插入任何记录时，缺少“ _id”列的值，因此显示此错误。

解决方案：1.将“ _id”作为自动增量值。 2.添加第一个记录，并将_id值提及为1。由于要进行自动递增，它需要第一个值才能对下一个记录进行自动递增。