我有数据表单并将其数据保存在sqlite数据库中。我的数据是英文和波斯文，包括文字，时间和日期。我想在recyclerview中显示数据。但每次部署应用程序时，列表都是空的。我查看了Device file explorer并检查了数据库文件。它看起来像这样： database
ListFragment 显示的recyclerview和包含该表单的Fragment是 NewTaskFragment
数据库处理器
public class DataBaseHandler extends SQLiteOpenHelper {
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "Task Database";
// Task table name
private static final String TASK_TABLE = "tasks";
// TaskTable Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_DATE = "date";
private static final String KEY_TIME = "time";
//private static final String KEY_REPEAT = "repeat";
public DataBaseHandler(Context context) {
super(context, DATABASE_NAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(
" CREATE TABLE " + TASK_TABLE + "(" +
KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_TITLE + " TEXT, " +
KEY_DATE + " TEXT, " +
KEY_TIME + " TEXT); " ); }
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TASK_TABLE);
onCreate(db); }
public boolean insertTask(String title, String date, String time) {
SQLiteDatabase sqLiteDatabase = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(KEY_TITLE, title);
contentValues.put(KEY_DATE, date);
contentValues.put(KEY_TIME, time);
//contentValues.put(KEY_REPEAT, repeat);
long result = sqLiteDatabase.insert(TASK_TABLE, null, contentValues);
//if date as inserted incorrectly it will return -1
if (result == -1) {
return false;
} else {
return true;
} }
boolean updateTask(Integer id, String title, String date, String time) {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(KEY_TITLE, title);
contentValues.put(KEY_DATE, date);
contentValues.put(KEY_TIME, time);
sqLiteDatabase.update(TASK_TABLE, contentValues, KEY_ID + "=?",
new String[]{Integer.toString(id)});
return true;
}
public Cursor getTasks(int id) {
SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
Cursor cursor = sqLiteDatabase.rawQuery("select * from tasks where id=" + id + "", null); return cursor; }
public int numberOfRows() {
SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
int numRows = (int) DatabaseUtils.queryNumEntries(sqLiteDatabase, TASK_TABLE); return numRows; }
public Integer deleteTask(Integer id) {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
return sqLiteDatabase.delete("tasks", "id=?",
new String[]{Integer.toString(id)}); }
public Cursor getAllTasks() {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
Cursor data = sqLiteDatabase.rawQuery("SELECT * FROM "+ TASK_TABLE, null);
return data; }}
ListFragment
public class ListFragment extends Fragment {
private SQLiteDatabase sqLiteDatabase;
private DataBaseHandler dataBaseHandler;
Cursor cursor;
public List<Tasks> tasksList= new ArrayList<>();
private RecyclerView task_recycler_view;
private TaskListAdapter taskListAdapter;
String string;
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_item_list,
container, false);
task_recycler_view=(RecyclerView) view.findViewById(R.id.task_recycler_v);
taskListAdapter= new TaskListAdapter(tasksList);
RecyclerView.LayoutManager layoutManager= new LinearLayoutManager(getContext());
task_recycler_view.setLayoutManager(layoutManager);
task_recycler_view.setItemAnimator(new DefaultItemAnimator());
dataBaseHandler=new DataBaseHandler(getContext());
ArrayList<String> theList= new ArrayList<>();
Cursor data= dataBaseHandler.getAllTasks();
if (data.getCount()==0){
Toast.makeText(getContext(),"database is empty",Toast.LENGTH_SHORT).show();
}else{
while (data.moveToNext()){
theList.add(data.getString(1));
theList.add(data.getString(2));
theList.add(data.getString(3));
taskListAdapter= new TaskListAdapter( tasksList);
task_recycler_view.setAdapter(taskListAdapter);
} } return view; } }
NewTaskFragment
public class NewTaskFragment extends Fragment implements DateSetListener{
Toolbar save_toolbar;
EditText subject;
TextView startDate;
ImageButton dateImageButton;
TextView taskTime;
ImageButton timeImageButton;
ImageButton saveBtn;
private Date mEndDate;
private Date mStartDate;
private int _hour, _minute;
String subject_data ,time_data, date_data, repeat_data,getValue;
DataBaseHandler dataBaseHandler;
String subj_str;
Bundle bundle;
public NewTaskFragment(){}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
setLocale("fa");
View view = inflater.inflate(R.layout.task_top,
container, false);
save_toolbar= (Toolbar) view.findViewById(R.id.task_toolbar) ;
bundle= getArguments();
saveBtn = (ImageButton) view.findViewById(R.id.saveImgBtn);
subject = (EditText) view.findViewById(R.id.subject);
startDate = (TextView) view.findViewById(R.id.startDateTxt);
dateImageButton = (ImageButton) view.findViewById(R.id.startDateBtn);
taskTime = (TextView) view.findViewById(R.id.timeTxt);
timeImageButton = (ImageButton)
view.findViewById(R.id.timeImageButton);
mEndDate = new Date();
mStartDate = new Date();
dataBaseHandler=new DataBaseHandler(getActivity());
saveBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String title=subject.getText().toString();
String date=startDate.getText().toString();
String time=taskTime.getText().toString();
if (subject.length()!=0||startDate.length()!=0||taskTime.length()!=0){
addData(title,date,time);
subject.setText("");
startDate.setText("");
taskTime.setText("");
}else{
Toast.makeText(getContext(),"the field id empty",Toast.LENGTH_SHORT).show();
} }
private void addData(String title, String date, String time) {
boolean insertData=dataBaseHandler.insertTask(title,date,time );
if (insertData==true){
Toast.makeText(getContext(),"subject saved",Toast.LENGTH_SHORT).show();
}else{ Toast.makeText(getContext(),"something went wrong",Toast.LENGTH_SHORT).show(); } }});
timeImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final Calendar calendar = Calendar.getInstance();
_hour = calendar.get(Calendar.HOUR_OF_DAY);
_minute = calendar.get(Calendar.MINUTE);
TimePickerDialog timePickerDialog = new TimePickerDialog(
getContext(), new TimePickerDialog.OnTimeSetListener() {
@Override
public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
taskTime.setText(hourOfDay + ":" + minute);
}
}, _hour, _minute, false);
timePickerDialog.show();
} });
dateImageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = v.getId() == R.id.startDateBtn ? 1 : 2;
new DatePicker.Builder()
.id(id)
.date(mStartDate.getDay(), mStartDate.getMonth(), mStartDate.getYear())
.build(NewTaskFragment.this)
.show(getFragmentManager(), "");
}
}); return view; }
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setLocale("fa"); }
private void setLocale(String language) {
Locale locale = new Locale(language);
Locale.setDefault(locale);
Configuration config = new Configuration();
config.locale = locale;
getContext().getResources().updateConfiguration(config,
getContext().getResources().getDisplayMetrics()); }
@Override
public void onDateSet(int id, @Nullable Calendar calendar, int day, int month, int year) {
mStartDate.setDate(day, month, year);
startDate.setText(mStartDate.getDate()); }}
答案 0 :(得分：0)
在将ArrayList初始化为if (data.getCount()==0){
Toast.makeText(getContext(),"database is empty",Toast.LENGTH_SHORT).show();
}
else {
for (data.moveToFirst(); !data.isAfterLast(); data.moveToNext()) {
theList.add(data.getString(1));
theList.add(data.getString(2));
theList.add(data.getString(3));
taskListAdapter= new TaskListAdapter( tasksList);
task_recycler_view.setAdapter(taskListAdapter);
}
}
之前，您应该使用while。
for尝试此操作，您也可以将其与{{1}}一起使用，但我更喜欢{{1}}循环。