Question

我刚刚开始研究一个项目，但我的程序反复崩溃。我认为这是由于getWritableDatabase。我正在按照教程，我做了他们告诉我的所有事情，我甚至多次检查了我的代码。如果您对教程的链接感兴趣，那就是https://www.youtube.com/watch?v=38DOncHIazs

public class AddExpense extends Activity {

EditText inputDate , inputDescription, inputCategory, inputAmount;
Context context;
UserDbHelper userDbHelper;
SQLiteDatabase sqLiteDatabase;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_add_expense);
    inputDate = (EditText) findViewById(R.id.inputDate);
    inputDescription = (EditText) findViewById(R.id.inputDescription);
    inputCategory = (EditText) findViewById(R.id.inputCategory);
    inputAmount = (EditText) findViewById(R.id.inputAmount);

}

public void AddExpense(View view){
    String date = inputDate.getText().toString();
    String description = inputDescription.getText().toString();
    String category = inputCategory.getText().toString();
    String amount = inputAmount.getText().toString();
    userDbHelper = new UserDbHelper(context);
    sqLiteDatabase = userDbHelper.getWritableDatabase();
    userDbHelper.addInformations(date, description, category, amount, sqLiteDatabase);
    Toast.makeText(getBaseContext(),"Data Saved", Toast.LENGTH_LONG).show();
    userDbHelper.close();
}

}

这是我的数据库助手类

public class UserDbHelper extends SQLiteOpenHelper {

private static final String DATABASE_NAME = "EXPENSE.DB";
private static final int DATABASE_VERSION = 1;
private static final String CREATE_QUERY =
        "CREATE TABLE " + ExpenseDatabase.NewExpenseItem.TABLE_NAME + " ("+ ExpenseDatabase.NewExpenseItem.DATE+" TEXT,"+ ExpenseDatabase.NewExpenseItem.DESCRIPTION+ " TEXT,"+
        ExpenseDatabase.NewExpenseItem.CATEGORY+" TEXT," + ExpenseDatabase.NewExpenseItem.AMOUNT+ " TEXT);";

public UserDbHelper(Context context){


    super(context,DATABASE_NAME,null,DATABASE_VERSION);
    Log.e("DATABASE OPERATIONS", "Database created / opened");
}
@Override
public void onCreate(SQLiteDatabase db) {

    db.execSQL(CREATE_QUERY);
    Log.e("DATABASE OPERATIONS", "Table created");

}

public void addInformations(String date, String description, String category, String amount,SQLiteDatabase db ){
    ContentValues contentValues = new ContentValues();
    contentValues.put(ExpenseDatabase.NewExpenseItem.DATE,date);
    contentValues.put(ExpenseDatabase.NewExpenseItem.DESCRIPTION, description);
    contentValues.put(ExpenseDatabase.NewExpenseItem.CATEGORY, category);
    contentValues.put(ExpenseDatabase.NewExpenseItem.AMOUNT, amount);
    db.insert(ExpenseDatabase.NewExpenseItem.TABLE_NAME, null, contentValues);
    Log.e("DATABASE OPERATIONS", "One row inserted in DB");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

Answer 1

根据我的经验，最好只在UserDbHelper类中创建一个方法并将相关值传递给该方法。尝试在该类本身中执行与数据库相关的所有操作。我认为它会奏效。

编辑：

    public void addInformation(your values){    
        ContentValues values = new ContentValues();
        values.put();            
        SQLiteDatabase db = getWritableDatabase();
        db.insert(TABLE,null,values);
        db.close();
    }

Answer 2

尝试使用此userDbHelper = new UserDbHelper（this）;某些您的上下文未初始化。这可能是问题

getWritableDatabase关闭我的程序

2 个答案: