Question

我需要在android上使用SQLite。我可以添加数据和查看数据。但是现在我需要在这种情况下添加更多列我设置“COL_TIME”。首先我尝试更改列以将数据从“COL_LASTNAME”记录到“COL_TIME”，但是日志cat显示列“COL_TIME”不存在。尽管我在Databasestudent.Java中声明了public static final String COL_TIME = "date"; 或者我做错了，请提供一些建议。这是添加数据和数据库类的类。

DatabaseStudent.Java

class DatabaseStudent extends SQLiteOpenHelper {
private static final String DB_NAME = "MyStudent";
private static final int DB_VERSION = 1;

public static final String TABLE_NAME = "Student";

public static final String COL_NAME = "name";
public static final String COL_LASTNAME = "last_name";
public static final String COL_SCHOOL = "school";
public static final String COL_TIME = "date";



public DatabaseStudent(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
}

public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + TABLE_NAME 
            + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, " 
            + COL_NAME + " TEXT, " + COL_LASTNAME 
            + " TEXT, " + COL_SCHOOL + " TEXT);");
    db.execSQL("INSERT INTO " + TABLE_NAME + " (" 
            + COL_NAME + ", " + COL_LASTNAME  
            + ", " + COL_SCHOOL + ") VALUES ('Sleeping'"
            + ", 'For Less', 'Android School');"); 
    //db.execSQL("INSERT INTO " + TABLE_NAME + " (" 
    //        + COL_DATE + ") VALUES ('Android School');"); 
}

public void onUpgrade(SQLiteDatabase db, int oldVersion
        , int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

}

AddStudent.Java

public class AddStudent extends Activity {
DatabaseStudent mHelper;
SQLiteDatabase mDb;


public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add);

    mHelper = new DatabaseStudent(this);
    mDb = mHelper.getWritableDatabase();

    final EditText editName = (EditText)findViewById(R.id.editName);
    final EditText editLastName = (EditText)findViewById(R.id.editLastName);
    final EditText editSchool = (EditText)findViewById(R.id.editSchool);

    Button buttonAdd = (Button)findViewById(R.id.buttonAdd);

    buttonAdd.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            String name = editName.getText().toString();
            String lastname = editLastName.getText().toString();
            double school = getIntent().getDoubleExtra("Intent", 5.322);

            //Date&Time
            java.util.Date dt = new java.util.Date();
            java.text.SimpleDateFormat sdf = 
                 new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String currentTime = sdf.format(dt);

            if(name.length() != 0 && lastname.length() != 0 
                     ) {//&& school.length() != 0

                Cursor mCursor = mDb.rawQuery("SELECT * FROM " 
                        + DatabaseStudent.TABLE_NAME + " WHERE " 
                        + DatabaseStudent.COL_NAME + "='" + name + "'" 
                        + " AND " + DatabaseStudent.COL_LASTNAME + "='" 
                        + currentTime + "'" + " AND " 
                        + DatabaseStudent.COL_SCHOOL + "='" + school //add COL_SCHOOL = currentTime
                        + "'", null);

                if(mCursor.getCount() == 0) {
                    mDb.execSQL("INSERT INTO " + DatabaseStudent.TABLE_NAME 
                            + " (" + DatabaseStudent.COL_NAME 
                            + ", " + DatabaseStudent.COL_LASTNAME  
                            + ", " + DatabaseStudent.COL_SCHOOL 
                            + ") VALUES ('" + name + "', '" + currentTime //result ไม่มา
                            + "', '" + school + "');");



                    editName.setText("");
                    editLastName.setText("");
                    editSchool.setText("");


        }
    });

}

public void onStop() {
    super.onStop();
    mHelper.close();
    mDb.close();
}
}

Answer 1

如果要在创建后修改数据库。您可以通过更改其版本代码将旧版本的数据库升级到新版本。

您需要从设备中卸载旧版本的数据库，然后才会显示已更改的数据库版本的反映。

因此，在从设备安装新的应用程序之前，请确保更改数据库版本并卸载旧的应用程序数据。

private static final int DB_VERSION = 1;

到

private static final int DB_VERSION = 2;

Answer 2

如果要升级数据库，即更改表结构，则必须增加数据库版本，以便android知道必须升级它。为此，您需要增加此值。

 private static final int DB_VERSION = 1;

到

private static final int DB_VERSION = 2;

如何在SQLite中添加更多列与android

2 个答案: