我一直在尝试使用Simplecursor适配器从sqlite数据库填充listview。我收到以下错误
08-09 06：52：07.875 21262-21262 / com.example.s210121629.myhealth E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.example.s210121629.myhealth，PID：21262 显示java.lang.NullPointerException at com.example.s210121629.myhealth.contacts.FragmentContact.displayContacts（FragmentContact.java:85） at com.example.s210121629.myhealth.contacts.FragmentContact.onCreateView（FragmentContact.java:47） 在android.support.v4.app.Fragment.performCreateView（Fragment.java:1789） 在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:955） 在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1138） 在android.support.v4.app.BackStackRecord.run（BackStackRecord.java:740） 在android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:1501） 在android.support.v4.app.FragmentManagerImpl $ 1.run（FragmentManager.java:458） 在android.os.Handler.handleCallback（Handler.java:733） 在android.os.Handler.dispatchMessage（Handler.java:95） 在android.os.Looper.loop（Looper.java:136）
联系人表格中有联系人。
我在下面包含了我的数据库助手类（ DBHelper ）
public class DBHelper extends SQLiteOpenHelper {
public static final String TAG = "DBHelper";
// Columns of Person Table
public static final String TABLE_PERSON = "Person";
public static final String COLUMN_PERSON_ID = "_id";
public static final String COLUMN_PERSON_USERNAME = "Username";
public static final String COLUMN_PERSON_PASSWORD = "Password";
public static final String COLUMN_PERSON_NAME = "Name";
public static final String COLUMN_PERSON_SURNAME = "Surname";
public static final String COLUMN_PERSON_GENDER = "Gender";
public static final String COLUMN_PERSON_DOB = "Dob";
public static final String COLUMN_PERSON_HEIGHT = "Height";
public static final String COLUMN_PERSON_WEIGHT = "Weight";
public static final String COLUMN_PERSON_SYSTOLICBP = "Systolicbp";
public static final String COLUMN_PERSON_DIASTOLICBP = "Diastolicbp";
public static final String COLUMN_PERSON_BPDATE = "Bpdate";
public static final String COLUMN_PERSON_MAXRATE = "Maxhrrate";
public static final String COLUMN_PERSON_MINRATE = "Minhrrate";
// Columns of Medical Profile Table
public static final String TABLE_MEDICAL_PROFILE = "MedicalProfile";
public static final String COLUMN_MEDICAL_PROFILE_ID = "_id";
public static final String COLUMN_MEDICAL_PROFILE_USERNAME = COLUMN_PERSON_USERNAME;
public static final String COLUMN_MEDICAL_PROFILE_DATE_DIAGNOSED = "DateDiagnosed";
public static final String COLUMN_MEDICAL_PROFILE_CONDITION = "Condition";
// Columns of Contact Table
public static final String TABLE_CONTACT = "Contacts";
public static final String COLUMN_CONTACT_ID = "_id";
public static final String COLUMN_CONTACT_USERNAME = COLUMN_PERSON_USERNAME;
public static final String COLUMN_CONTACT_NAME = "Kinname";
public static final String COLUMN_CONTACT_SURNAME = "Kinsurname";
public static final String COLUMN_CONTACT_CELLPHONE = "Kincellphone";
public static final String COLUMN_CONTACT_CAREGIVER_NAME = "Caregivername";
public static final String COLUMN_CONTACT_CAREGIVER_SURNAME = "Caregiversurname";
public static final String COLUMN_CONTACT_CAREGIVER_CELLPHONE = "Caregivercell";
public static final String COLUMN_CONTACT_CAREGIVER_TELEPHONE = "Caregivertel";
private static final String DATABASE_NAME = "myHealth.db";
private static final int DATABASE_VERSION = 1;
public SQLiteDatabase db;
// SQL statement of the person table creation
private static final String SQL_CREATE_TABLE_PERSON = "CREATE TABLE " + TABLE_PERSON + "("
+ COLUMN_PERSON_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COLUMN_PERSON_USERNAME + " TEXT NOT NULL, "
+ COLUMN_PERSON_PASSWORD + " TEXT NOT NULL,"
+ COLUMN_PERSON_NAME + " TEXT NOT NULL,"
+ COLUMN_PERSON_SURNAME + " TEXT NOT NULL,"
+ COLUMN_PERSON_GENDER + " TEXT NOT NULL,"
+ COLUMN_PERSON_DOB + " TEXT NOT NULL,"
+ COLUMN_PERSON_HEIGHT + " REAL NOT NULL,"
+ COLUMN_PERSON_WEIGHT + " REAL NOT NULL,"
+ COLUMN_PERSON_SYSTOLICBP + " INTEGER NOT NULL,"
+ COLUMN_PERSON_DIASTOLICBP + " INTEGER NOT NULL,"
+ COLUMN_PERSON_BPDATE + " TEXT NOT NULL,"
+ COLUMN_PERSON_MAXRATE + " INTEGER NOT NULL,"
+ COLUMN_PERSON_MINRATE + " INTEGER NOT NULL "
+ ");";
// SQL statement of the medical table creation
private static final String SQL_CREATE_TABLE_MEDICAL_PROFILE = "CREATE TABLE " + TABLE_MEDICAL_PROFILE + "("
+ COLUMN_MEDICAL_PROFILE_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COLUMN_MEDICAL_PROFILE_USERNAME + " TEXT NOT NULL, "
+ COLUMN_MEDICAL_PROFILE_DATE_DIAGNOSED + " TEXT NOT NULL, "
+ COLUMN_MEDICAL_PROFILE_CONDITION + " TEXT NOT NULL "
+ ");";
// SQL statement of the contact table creation
private static final String SQL_CREATE_TABLE_CONTACT = "CREATE TABLE " + TABLE_CONTACT + "("
+ COLUMN_CONTACT_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ COLUMN_CONTACT_USERNAME + " TEXT NOT NULL, "
+ COLUMN_CONTACT_NAME + " TEXT NOT NULL,"
+ COLUMN_CONTACT_SURNAME + " TEXT NOT NULL,"
+ COLUMN_CONTACT_CELLPHONE + " TEXT NOT NULL,"
+ COLUMN_CONTACT_CAREGIVER_NAME + " TEXT NOT NULL,"
+ COLUMN_CONTACT_CAREGIVER_SURNAME + " TEXT NOT NULL,"
+ COLUMN_CONTACT_CAREGIVER_CELLPHONE + " TEXT NOT NULL,"
+ COLUMN_CONTACT_CAREGIVER_TELEPHONE + " TEXT NOT NULL"
+ ");";
public DBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(SQL_CREATE_TABLE_PERSON);
database.execSQL(SQL_CREATE_TABLE_MEDICAL_PROFILE);
database.execSQL(SQL_CREATE_TABLE_CONTACT);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG,
"Upgrading the database from version " + oldVersion + " to " + newVersion);
// clear all data
db.execSQL("DROP TABLE IF EXISTS " + TABLE_PERSON);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_MEDICAL_PROFILE);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACT);
// recreate the tables
onCreate(db);
}
public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
/* The following Sql statements are used to manipulate the tables that have been created for the myHealth database */
public void createPerson(String username, String password, String name, String surname, String gender, String dob, double height, double weight, int systolic, int diastolic, String bpdate, int maxhr, int minhr) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_PERSON_USERNAME, username);
values.put(COLUMN_PERSON_PASSWORD, password);
values.put(COLUMN_PERSON_NAME, name);
values.put(COLUMN_PERSON_SURNAME, surname);
values.put(COLUMN_PERSON_GENDER, gender);
values.put(COLUMN_PERSON_DOB, dob);
values.put(COLUMN_PERSON_HEIGHT, height);
values.put(COLUMN_PERSON_WEIGHT, weight);
values.put(COLUMN_PERSON_SYSTOLICBP, systolic);
values.put(COLUMN_PERSON_DIASTOLICBP, diastolic);
values.put(COLUMN_PERSON_BPDATE, bpdate);
values.put(COLUMN_PERSON_MAXRATE, maxhr);
values.put(COLUMN_PERSON_MINRATE, minhr);
db.insert(TABLE_PERSON, null, values);
}
public void createMedicalProfile(String Username, String condition, String datediagnosed) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_MEDICAL_PROFILE_USERNAME, Username);
values.put(COLUMN_MEDICAL_PROFILE_CONDITION, condition);
values.put(COLUMN_MEDICAL_PROFILE_DATE_DIAGNOSED, datediagnosed);
db.insert(TABLE_MEDICAL_PROFILE, null, values);
}
public void createContact(String Username, String name, String surname, String cell, String carename, String caresurname, String carecell, String caretel) {
db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_CONTACT_USERNAME, Username);
values.put(COLUMN_CONTACT_NAME, name);
values.put(COLUMN_CONTACT_SURNAME, surname);
values.put(COLUMN_CONTACT_CELLPHONE, cell);
values.put(COLUMN_CONTACT_CAREGIVER_NAME, carename);
values.put(COLUMN_CONTACT_CAREGIVER_SURNAME, caresurname);
values.put(COLUMN_CONTACT_CAREGIVER_CELLPHONE, carecell);
values.put(COLUMN_CONTACT_CAREGIVER_TELEPHONE, caretel);
db.insert(TABLE_CONTACT, null, values);
}
public boolean checkContactTable() {
db = this.getReadableDatabase();
Cursor c = null;
boolean tableexists = true;
String selectQuery = " SELECT * FROM " + TABLE_MEDICAL_PROFILE;
Log.d("LOG", selectQuery);
try {
c = db.rawQuery(selectQuery, null);
if (c.getCount() < 1) {
c.close();
tableexists = false;
}
c.moveToFirst();
c.close();
} catch (Exception e) {
Log.d(TAG, TABLE_CONTACT + "Does not exist");
}
return tableexists;
}
public String getPassword(String Username) {
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = " SELECT " + COLUMN_PERSON_PASSWORD + " FROM " + TABLE_PERSON + " WHERE "
+ COLUMN_PERSON_USERNAME + " = '" + Username + "'";
Log.d("LOG", selectQuery);
Cursor c = db.rawQuery(selectQuery, null);
if (c != null)
c.moveToFirst();
c.moveToFirst();
String password = c.getString(c.getColumnIndex("Password"));
c.close();
return password;
}
public Person getPerson(String Username) {
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = " SELECT * FROM " + TABLE_PERSON + " WHERE "
+ COLUMN_PERSON_USERNAME + " = '" + Username + "'";
Log.d("LOG", selectQuery);
Cursor c = db.rawQuery(selectQuery, null);
if (c != null)
c.moveToFirst();
c.moveToFirst();
Person person = new Person();
person.setmHeight(c.getDouble(c.getColumnIndex("Height")));
person.setmWeight(c.getDouble(c.getColumnIndex("Weight")));
person.setmSystolic(c.getInt(c.getColumnIndex("Systolicbp")));
person.setmDiastolic(c.getInt(c.getColumnIndex("Diastolicbp")));
person.setmMaxrate(c.getInt(c.getColumnIndex("Maxhrrate")));
person.setmMinrate(c.getInt(c.getColumnIndex("Minhrrate")));
c.close();
return person;
}
public boolean getMedicalProfile(String Username) {
db = getReadableDatabase();
Cursor c = null;
boolean tableexists = true;
String selectQuery = " SELECT " + COLUMN_MEDICAL_PROFILE_USERNAME + " FROM " + TABLE_MEDICAL_PROFILE + " WHERE "
+ COLUMN_MEDICAL_PROFILE_USERNAME + " = '" + Username + "'";
Log.d("LOG", selectQuery);
try {
c = db.rawQuery(selectQuery, null);
if (c.getCount() < 1) {
c.close();
tableexists = false;
}
c.moveToFirst();
String username = c.getString(c.getInt(c.getColumnIndex("Username")));
c.close();
} catch (Exception e) {
Log.d(TAG, TABLE_MEDICAL_PROFILE + "Does not exist");
}
return tableexists;
}
public void updatePersonalInfo(String Username, Double height, Double weight, int systolic, int diastolic, int maxrate, int minrate) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues updatedvalues = new ContentValues();
updatedvalues.put(COLUMN_PERSON_HEIGHT, height);
updatedvalues.put(COLUMN_PERSON_WEIGHT, weight);
updatedvalues.put(COLUMN_PERSON_SYSTOLICBP, systolic);
updatedvalues.put(COLUMN_PERSON_DIASTOLICBP, diastolic);
updatedvalues.put(COLUMN_PERSON_MAXRATE, maxrate);
updatedvalues.put(COLUMN_PERSON_MINRATE, minrate);
db.update(TABLE_PERSON, updatedvalues, COLUMN_PERSON_USERNAME + " = '" + Username + "'", null);
}
public void insertMedicalcondition(String Username, String condition, String dateadiagnosed) {
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_MEDICAL_PROFILE_USERNAME, Username);
values.put(COLUMN_MEDICAL_PROFILE_CONDITION, condition);
values.put(COLUMN_MEDICAL_PROFILE_DATE_DIAGNOSED, dateadiagnosed);
db.insert(TABLE_MEDICAL_PROFILE, null, values);
}
public void insertContact(String Username, String name, String surname, String cell, String carename, String caresurname, String carecell, String caretel) {
{
ContentValues values = new ContentValues();
values.put(COLUMN_CONTACT_USERNAME, Username);
values.put(COLUMN_CONTACT_NAME, name);
values.put(COLUMN_CONTACT_SURNAME, surname);
values.put(COLUMN_CONTACT_CELLPHONE, cell);
values.put(COLUMN_CONTACT_CAREGIVER_NAME, carename);
values.put(COLUMN_CONTACT_CAREGIVER_SURNAME, caresurname);
values.put(COLUMN_CONTACT_CAREGIVER_CELLPHONE, carecell);
values.put(COLUMN_CONTACT_CAREGIVER_TELEPHONE, caretel);
db.insert(TABLE_CONTACT, null, values);
}
}
public Cursor readContacts() {
db = getWritableDatabase();
String[] allColumns = new String[]{COLUMN_CONTACT_ID, COLUMN_CONTACT_NAME,
COLUMN_CONTACT_SURNAME,
COLUMN_CONTACT_CELLPHONE,
COLUMN_CONTACT_CAREGIVER_NAME,
COLUMN_CONTACT_CAREGIVER_SURNAME,
COLUMN_CONTACT_CAREGIVER_CELLPHONE,
COLUMN_CONTACT_CAREGIVER_TELEPHONE,
};
Cursor c = db.query(TABLE_CONTACT, allColumns, null,
null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
}
FragmentContact 片段
public class FragmentContact extends Fragment {
@InjectView(R.id.contactslist)
ListView _contactlist;
private ContactDAO mContactDao;
String kinname, kinsurname, kincell, caregivername, caregiversurname, caregivercell, caregivertel;
private SimpleCursorAdapter dataAdapter;
DBHelper mdbHelper;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = (LinearLayout) inflater.inflate(R.layout.fragment_contacts, container, false);
ButterKnife.inject(getActivity(), view);
// this.mContactDao = new ContactDAO(getActivity());
mdbHelper = new DBHelper(getActivity());
displayContacts();
return view;
}
public void displayContacts()
{
Cursor cursor = mdbHelper.readContacts();
String[] columns = new String[]{
mdbHelper.COLUMN_CONTACT_NAME,
mdbHelper.COLUMN_CONTACT_SURNAME,
mdbHelper.COLUMN_CONTACT_CELLPHONE,
mdbHelper.COLUMN_CONTACT_CAREGIVER_NAME,
mdbHelper.COLUMN_CONTACT_CAREGIVER_SURNAME,
mdbHelper.COLUMN_CONTACT_CAREGIVER_CELLPHONE,
mdbHelper.COLUMN_CONTACT_CAREGIVER_TELEPHONE};
// the XML defined views which the data will be bound to
int[] to = new int[]{
R.id._inputname,
R.id.inputsurname,
R.id.inputcell,
R.id.inputcaregiver_name,
R.id.inputcaregiver_surname,
R.id.inputcaregiver_cell,
R.id.inputcaregiver_tel
};
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
dataAdapter = new SimpleCursorAdapter(
getActivity(), R.layout.fragment_contacts,
cursor,
columns,
to,
0);
_contactlist.setAdapter(dataAdapter);
}
}
我已经包含了填充simplecursor适配器所需的所有变量，并且应用程序仍然崩溃。我已经包含了数据库助手类和片段类的代码，我实现了simplecursor适配器
答案 0 :(得分：1)
根据堆栈跟踪，你得到一个
java.lang.IllegalArgumentException：列'_id'不存在
要避免这种情况，请将表“联系人”的列“person_id”重命名为“_id”。
除此之外，在'readContacts（）'方法集
中 String[] allColumns = new String[]{ COLUMN_CONTACT_NAME,
COLUMN_CONTACT_SURNAME,
COLUMN_CONTACT_CELLPHONE,
COLUMN_CONTACT_CAREGIVER_NAME,
COLUMN_CONTACT_CAREGIVER_SURNAME,
COLUMN_CONTACT_CAREGIVER_CELLPHONE,
COLUMN_CONTACT_CAREGIVER_TELEPHONE,
COLUMN_CONTACT_ID
};
使数据库列的顺序与TextViews的顺序匹配。出于正式原因包含'_id'列，但如果您对其值不感兴趣，则无需提供相应的TextView。
通常，如果要使用某种CursorAdapter，请确保您的表包含名为“_id”的列（如主键），并使该列成为所选列的一部分。
最后，您需要将ListView'_contactlist'绑定到'onCreateView（）'中布局文件中的相应ListView：
View view = (LinearLayout) inflater.inflate(R.layout.fragment_contacts, container, false);
...
// in the layout file 'fragment_contacts.xml'
// let the ListView have an attribute 'android:id="@+id/theListViewId" '
_contactlist = (ListView)view.findViewById(R.id.theListViewId);
答案 1 :(得分：0)
第一个问题是我的光标没有返回Contact表中的所有列。 第二个问题是我没有实例化listview。最终代码如下：
public class FragmentContact extends Fragment {
@InjectView(R.id.contactslist)
ListView _contactlist;
private ContactDAO mContactDao;
private SimpleCursorAdapter dataAdapter;
DBHelper mdbHelper;
@InjectView(R.id._inputname)
TextView _inputname;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = (LinearLayout) inflater.inflate(R.layout.fragment_contacts, container, false);
ButterKnife.inject(getActivity(), view);
// this.mContactDao = new ContactDAO(getActivity());
mdbHelper = new DBHelper(getActivity());
_contactlist = (ListView)view.findViewById(R.id.contactslist);
displayContacts();
return view;
}
public void displayContacts()
{
Cursor cursor = mdbHelper.readContacts();
String[] columns = new String[]{
mdbHelper.COLUMN_CONTACT_NAME,
mdbHelper.COLUMN_CONTACT_SURNAME,
mdbHelper.COLUMN_CONTACT_CELLPHONE,
mdbHelper.COLUMN_CONTACT_CAREGIVER_NAME,
mdbHelper.COLUMN_CONTACT_CAREGIVER_SURNAME,
mdbHelper.COLUMN_CONTACT_CAREGIVER_CELLPHONE,
mdbHelper.COLUMN_CONTACT_CAREGIVER_TELEPHONE,
mdbHelper.COLUMN_CONTACT_ID
};
// Toast.makeText(getActivity(), "" + cursor, Toast.LENGTH_SHORT).show();
// the XML defined views which the data will be bound to
int[] to = new int[]{
R.id._inputname,
R.id.inputsurname,
R.id.inputcell,
R.id.inputcaregiver_name,
R.id.inputcaregiver_surname,
R.id.inputcaregiver_cell,
R.id.inputcaregiver_tel
};
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
dataAdapter = new SimpleCursorAdapter(
getActivity(), R.layout.contacts_listitems,
cursor,
columns,
to,
0);
_contactlist.setAdapter(dataAdapter);
}
}