getCount（）NullPointerException Fragment

Question

我是android编程的新手，所以请帮助我： 我需要获取特定记录的计数，这是我的代码：

public int countFiltered(String selection){
    Cursor cursor = database.query(DenverDBOpenHelper.TABLE_DENVERS, denverAllColumns, selection, null, null, null, null);
    Log.i(LOGTAG, "Get " + cursor.getCount() + " rows");

    int countItem = cursor.getCount();
    if(cursor==null) {
        return 0;
    }else
        return countItem;
}

我将其称为另一项活动：

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.fragment_baby, container, false);

    txtPass = (TextView)rootView.findViewById(R.id.txtPass);
    int countPass = dataSource.countFiltered("score == 1");
    txtPass.setText(countPass);}

countPass显示NullPinterException

我的得分列类型是INTEGER，这是我的DBOpenHelper：

public class DenverDBOpenHelper extends SQLiteOpenHelper {

private static final String LOGTAG = "LitleDenver";

private static final String DATABASE_NAME = "db_denver";
private static final int DATABASE_VERSION = 1;

public static final String TABLE_DENVERS = "denvers";
public static final String COLUMN_ID = "itemId";
public static final String COLUMN_CATEGORY = "category";
public static final String COLUMN_TITLE = "title";
public static final String COLUMN_DESC = "description";
public static final String COLUMN_DETAIL = "detail";
public static final String COLUMN_IMAGE = "image";
public static final String COLUMN_MIN = "min";
public static final String COLUMN_MAX = "max";
public static final String COLUMN_SCORE = "score";
public static final String COLUMN_STATUS = "status";

private static final String TABLE_CREATE =
        "CREATE TABLE " + TABLE_DENVERS + " (" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_CATEGORY + " TEXT, " +
                COLUMN_TITLE + " TEXT, " +
                COLUMN_DESC + " TEXT, " +
                COLUMN_DETAIL + " TEXT, " +
                COLUMN_IMAGE + " TEXT, " +
                COLUMN_MIN + " INTEGER, " +
                COLUMN_MAX + " INTEGER, " +
                COLUMN_SCORE + " INTEGER, " +
                COLUMN_STATUS + " INTEGER " +
                ")";

Answer 1

您将希望使用query，其中selectionArgs（您有null）作为您要查找的值的String数组（想想where子句）。此外，我通过在空游标上调用getCount()来清除代码，以便在游标为空的情况下不会导致NPE

public int countFiltered(String selection, String argValue){
    String selectionArg = new String[] {  argValue };                                     
    Cursor cursor = database.query(DenverDBOpenHelper.TABLE_DENVERS,   
                                   denverAllColumns, 
                                   selection, 
                                   selectionArg, 
                                   null, null, null);
    if(cursor==null) {
        return 0;
    } else {
        return cursor.getCount();
    }
}

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.fragment_baby, container, false);

    txtPass = (TextView)rootView.findViewById(R.id.txtPass);
    int countPass = dataSource.countFiltered("score = ?", "1");
    Log.i(LOGTAG, "Get countPass = " + countPass);
    txtPass.setText(countPass);
}

Answer 2

尝试修改第二行到最后一行，如下所示：

int countPass = dataSource.countFiltered("['score'] = 1");

我有一个非常类似的问题，这是我的修复。

Answer 3

您需要发布更多信息，作为字段的名称，类的可见性，这将返回您的logcat。