未创建SQLite数据库

Question

这段代码并没有创建我的数据库。我想创建一个预填充表，在创建表时使用一些默认值。虽然在执行时没有错误。有什么帮助吗？

DatabaseHelper代码：

public class DatabaseHelper extends SQLiteOpenHelper {

public static String dbName = "whatever.db";
public static int dbVersion = 2; 

public DatabaseHelper(Context context) {
    super(context, dbName, null, dbVersion);
    // TODO Auto-generated constructor stub
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    String createTable = "CREATE TABLE smart (UID INTEGER PRIMARY KEY, NAME TEXT);";
    db.execSQL(createTable);
    ContentValues cv = new ContentValues();
    cv.put("UID", 9);
    cv.put("NAME", "clear");
    db.insert("smart", null, cv);
    db.close();

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS smart");

}


}

MainActivity代码：

public class MainActivity extends Activity {

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

    DatabaseHelper dbHelper = new DatabaseHelper(this);
    dbHelper.close();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

Answer 1

试试这段代码

在您的DatabaseHelper中：

public static String dbName = "whatever.db";
public static int dbVersion = 2;

public DatabaseHelper(Context context) {
    super(context, dbName, null, dbVersion);
}

@Override
public void onCreate(SQLiteDatabase db) 
{
    String createTable = "CREATE TABLE smart (UID INTEGER PRIMARY KEY, NAME TEXT);";
    db.execSQL(createTable);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
{
    db.execSQL("DROP TABLE IF EXISTS smart");

}

在你的活动中：

    DatabaseHelper helper = new DatabaseHelper(MainActivity.this);
    SQLiteDatabase myDB = helper.getWritableDatabase();

    ContentValues cv = new ContentValues();
    cv.put("UID", 9);
    cv.put("NAME", "clear");
    myDB.insert("smart", null, cv);
    myDB.close();

或者在Database helper中添加此方法：

    public void save(int yourUID, String yourText)
{
    SQLiteDatabase myDB = this.getWritableDatabase();
    ContentValues cv = new ContentValues();

    cv.put("UID", yourUID);
    cv.put("NAME", yourText);
    myDB.insert("smart", null, cv);
    myDB.close();
}

然后在你的活动中编写代码：

            DatabaseHelper helper = new DatabaseHelper(MainActivity.this);
    helper.save(12, "Clear");

我希望我能帮到你。

Answer 2

不使用sqliteopenhelper尝试此操作

在你的活动课上

private SqliteDatabase Dbname;
Dbname =  this.openOrCreateDatabase(YourDbname, MODE_PRIVATE, null);//inside oncreate()

String createTable = "CREATE TABLE smart (UID INTEGER PRIMARY KEY, NAME TEXT);";
db.execSQL(createTable); 

ContentValues cv = new ContentValues();
cv.put("UID", 9);
cv.put("NAME", "clear");

db.insert("smart", null, cv);
db.close();