Question

我有一个奇怪的问题需要解决。系统正确调用SQLiteOpenHelper onCreate（）方法，似乎 db.execSQL（sql）成功，但从未创建表。

我使用＆＃34; adb设备＆＃34;访问虚拟机＆GT;＆GT; cd到/ data / data / package / databases＆gt;＆gt; sqlite3运行.tables。如果我执行＆＃34;从帖子中选择*＆＃34;结果是＆＃34;没有这样的表格。＆＃34;感谢您提供任何指导。

EDITED

我添加了MainActivity类，以显示我调用了.getWritableDatabase（）。当我这样做时，我可以看到onCreate方法被调用，并且没有任何错误，但当我检查表是否存在时......它不是。

DatabaseHelper.java

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

import java.util.ArrayList;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String TAG = "DnDa";

    public static final String DATABASE_NAME = "db-rss.db";
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_TABLE = "posts";
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_TITLE = "title";
    public static final String COLUMN_LINK = "link";
    public static final String COLUMN_DESCRIPTION = "description";
    public static final String COLUMN_PUBDATE = "pubdate";
    public static final String COLUMN_CATEGORY = "category";
    public static final String COLUMN_GUID = "guid";

    private Post post;
    private ArrayList<Post> posts;
    private Cursor cursor;

    /**
     * constructor
     * @param context
     */
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) throws SQLiteException {
        String sql = String.format("CREATE TABLE %s ( %s INTEGER PRIMARY KEY AUTOINCREMENT, %s TEXT, %s TEXT, %s TEXT, %s TEXT, %s TEXT, %s TEXT )",
                DATABASE_TABLE, COLUMN_ID, COLUMN_TITLE, COLUMN_LINK, COLUMN_DESCRIPTION, COLUMN_PUBDATE, COLUMN_CATEGORY, COLUMN_GUID);

        try {
            db.execSQL(sql);
            Log.d(TAG, "Successfully created table: " + sql);
        } catch (SQLiteException e) {
            e.printStackTrace();
        }

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String sql = "DROP TABLE IF EXISTS" + DATABASE_TABLE;
        db.execSQL(sql);

        this.onCreate(db);
    }

    @Override
    public void onOpen(SQLiteDatabase db) {
        super.onOpen(db);
        Log.d(TAG, "Opening database");
    }

    /**
     * Retrieve all records
     */
    public Cursor getAllRecords(SQLiteDatabase db) {
        db = this.getReadableDatabase();
        cursor = db.query(DATABASE_TABLE, new String[] {COLUMN_TITLE, COLUMN_PUBDATE, COLUMN_DESCRIPTION}, null, null, null, null, null);
        return cursor;
    }

}

MainActivity.java

public class MainActivity extends ActionBarActivity {
    private static final String TAG = "DnDa";

    private String finalUri = "http://wordpress.com/feed/";
    private DatabaseHelper databaseHelper;
    private SQLiteDatabase database;
    private Post post;
    private ArrayList posts;
    private ScrollView scrollView;
    private ListView listView;
    private SimpleCursorAdapter dataAdapter;

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

        databaseHelper = new DatabaseHelper(this);
        database = databaseHelper.getWritableDatabase();
    }


}

Answer 1

不幸的是，您的表未创建。此SQL Create Table命令

 String sql = "CREATE TABLE "+DATABASE_TABLE+" ( "+
   COLUMN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+
   COLUMN_TITLE+" TEXT,"+
   COLUMN_LINK+" TEXT,"+
   COLUMN_DESCRIPTION+" TEXT,"+
   COLUMN_PUBDATE+" TEXT,"+
   COLUMNCOLUMN_CATEGORY+" TEXT,"+
   COLUMN_GUID+" TEXT)"

 db.execSQL(sql);

Answer 2

您是否在getWritableDatabase()对象上致电DatabaseHelper？可能你有这样的problem吗？

==编辑==

我已使用DatabaseHelper和Activity中的此代码创建了一个项目：

DatabaseHelper mOpenHelper = new DatabaseHelper(this);
SQLiteDatabase db = mOpenHelper.getWritableDatabase();

Cursor с = mOpenHelper.getAllRecords(db);

效果很好，游标包含三列，没有例外。

Answer 3

确定;我觉得自己像个傻瓜。每次执行代码时都会成功创建表。问题是我在没有指定数据库的情况下运行了“sqlite3”。现在我实际上正在管理正确的数据库，我可以看到该表就在那里。

http://developer.android.com/tools/help/sqlite3.html

sqlite3 /data/data/<package>/databases/<database-name>.db

再次感谢您的贡献和测试我的代码。

即使db.execSQL（sql）执行没有错误，也没有这样的表

3 个答案: