我正在嘗試為我的大學制作一個考勤應用程序。我使用 SQLite 進行數據存儲（學生名單、出勤數據等），我希望將出勤數據導出為 CSV 文件。問題是，當我導出文件時，只有 SQLite 數據庫的最后一個條目被寫入 CSV。為了更好地理解，我附上了下面的代碼。public void exportExcelSheet() {? ? ? ? DatabaseHandler mDbHandler = new DatabaseHandler(mActivity);? ? ? ? File exportDir = new File(Environment.getExternalStorageDirectory(), "");? ? ? ? if (!exportDir.exists())? ? ? ? {? ? ? ? ? ? exportDir.mkdirs();? ? ? ? }? ? ? ? File file = new File(exportDir, "Report.csv");? ? ? ? String[] ColumnNames = {"Roll No.","Name","LA","LT","% age"};? ? ? ? String studentInfoQuery = "SELECT * FROM StudentList";? ? ? ? Cursor studentsListCursor = mDbHandler.execQuery(studentInfoQuery);? ? ? ? studentsListCursor.moveToFirst();? ? ? ? while(!studentsListCursor.isAfterLast()) {? ? ? ? ? ? String AttendanceListQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentsListCursor.getPosition() + "';";? ? ? ? ? ? String AttendanceQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentsListCursor.getPosition() + "' AND isPresent = 1";? ? ? ? ? ? int attendancePercent = 0;? ? ? ? ? ? Cursor totalClasses = mDbHandler.execQuery(AttendanceListQuery);? ? ? ? ? ? Cursor attendedClasses = mDbHandler.execQuery(AttendanceQuery);? ? ? ? ? ? if (totalClasses == null) {? ? ? ? ? ? ? ? Log.d("profile", "totalClasses null");? ? ? ? ? ? }? ? ? ? ? ? if (attendedClasses == null) {? ? ? ? ? ? ? ? Log.d("profile", "attendedClasses null");? ? ? ? ? ? }? ? ? ? ? ? if (totalClasses != null && attendedClasses != null) {? ? ? ? ? ? ? ? totalClasses.moveToFirst();? ? ? ? ? ? ? ? attendedClasses.moveToFirst();? ? ? ? ? ? ? ? try {? ? ? ? ? ? ? ? ? ? attendancePercent = (int) (((float) attendedClasses.getCount() / totalClasses.getCount()) * 100);? ? ? ? ? ? ? ? } catch (Exception e) {? ? ? ? ? ? ? ? ? ? attendancePercent = -1;? ? ? ? ? ? ? ? }? ? ? ? ? ? }
2 回答
慕村9548890
TA貢獻1884條經驗 獲得超4個贊
對于其他正在尋找類似問題答案的人，根據 Dheeraj 的代碼和另一項細微更改，最終的工作代碼將是 -
public void exportExcelSheet() throws IOException {
DatabaseHandler mDbHandler = new DatabaseHandler(mActivity);
File exportDir = new File(Environment.getExternalStorageDirectory(), "");
if (!exportDir.exists()) {
exportDir.mkdirs();
}
File file = new File(exportDir, "Report.csv");
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
String[] ColumnNames = {"Roll No.", "Name", "LA", "LT", "% age"};
CSVWriter csvWrite = new CSVWriter(new FileWriter(file));
csvWrite.writeNext(ColumnNames);
String studentInfoQuery = "SELECT * FROM StudentList";
Cursor studentsListCursor = mDbHandler.execQuery(studentInfoQuery);
studentsListCursor.moveToFirst();
do {
int studentRoll = studentsListCursor.getPosition() + 1;
String AttendanceListQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentRoll + "';";
String AttendanceQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentRoll + "' AND isPresent = 1";
int attendancePercent = 0;
Cursor totalClasses = mDbHandler.execQuery(AttendanceListQuery);
Cursor attendedClasses = mDbHandler.execQuery(AttendanceQuery);
if (totalClasses == null) {
Log.d("profile", "totalClasses null");
}
if (attendedClasses == null) {
Log.d("profile", "attendedClasses null");
}
if (totalClasses != null && attendedClasses != null) {
totalClasses.moveToFirst();
attendedClasses.moveToFirst();
try {
attendancePercent = (int) (((float) attendedClasses.getCount() / totalClasses.getCount()) * 100);
} catch (Exception e) {
attendancePercent = -1;
}
}
assert attendedClasses != null;
assert totalClasses != null;
String showAttendedLectures = String.valueOf(attendedClasses.getCount());
String showTotalLectures = String.valueOf(totalClasses.getCount());
//String showMissedLectures = String.valueOf(totalClasses.getCount() - attendedClasses.getCount());
String AttendancePercentage = String.valueOf(attendancePercent);
try {
String[] arrStr = {studentsListCursor.getString(1), studentsListCursor.getString(0), showAttendedLectures, showTotalLectures, AttendancePercentage + " %"};
csvWrite.writeNext(arrStr);
} catch (Exception sqlException) {
Toast.makeText(mActivity, "FAILED", Toast.LENGTH_SHORT).show();
Log.e("MainActivity", sqlException.getMessage(), sqlException);
}
Toast.makeText(mActivity, "Saved", Toast.LENGTH_SHORT).show();
}
while (studentsListCursor.moveToNext());
csvWrite.close();
}
九州編程
TA貢獻1785條經驗 獲得超4個贊
這段代碼中有一個小錯誤，即每次執行 do-while 循環時都會創建 csvWriter 對象，因此最后一個輸出 CSV 文件僅從光標中獲取了最后一行。這應該可以解決問題：
public void exportExcelSheet() {
DatabaseHandler mDbHandler = new DatabaseHandler(mActivity);
File exportDir = new File(Environment.getExternalStorageDirectory(), "");
if (!exportDir.exists()) {
exportDir.mkdirs();
}
File file = new File(exportDir, "Report.csv");
// ============== CHANGE ==============
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
String[] ColumnNames = {"Roll No.", "Name", "LA", "LT", "% age"};
// ============== CHANGE ==============
CSVWriter csvWrite = new CSVWriter(new FileWriter(file));
csvWrite.writeNext(ColumnNames);
String studentInfoQuery = "SELECT * FROM StudentList";
Cursor studentsListCursor = mDbHandler.execQuery(studentInfoQuery);
studentsListCursor.moveToFirst();
// ============== CHANGE ==============
do {
String AttendanceListQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentsListCursor.getPosition() + "';";
String AttendanceQuery = "SELECT * FROM AttendanceSheet WHERE StudRoll = '" + studentsListCursor.getPosition() + "' AND isPresent = 1";
int attendancePercent = 0;
Cursor totalClasses = mDbHandler.execQuery(AttendanceListQuery);
Cursor attendedClasses = mDbHandler.execQuery(AttendanceQuery);
if (totalClasses == null) {
Log.d("profile", "totalClasses null");
}
if (attendedClasses == null) {
Log.d("profile", "attendedClasses null");
}
if (totalClasses != null && attendedClasses != null) {
totalClasses.moveToFirst();
attendedClasses.moveToFirst();
try {
attendancePercent = (int) (((float) attendedClasses.getCount() / totalClasses.getCount()) * 100);
} catch (Exception e) {
attendancePercent = -1;
}
}
assert attendedClasses != null;
assert totalClasses != null;
String showAttendedLectures = String.valueOf(attendedClasses.getCount());
String showTotalLectures = String.valueOf(totalClasses.getCount());
//String showMissedLectures = String.valueOf(totalClasses.getCount() - attendedClasses.getCount());
String AttendancePercentage = String.valueOf(attendancePercent);
try {
String[] arrStr = {studentsListCursor.getString(1), studentsListCursor.getString(0), showAttendedLectures, showTotalLectures, AttendancePercentage + " %"};
csvWrite.writeNext(arrStr);
// ============== CHANGE ==============
// studentsListCursor.moveToNext();
} catch (Exception sqlException) {
Toast.makeText(mActivity, "FAILED", Toast.LENGTH_SHORT).show();
Log.e("MainActivity", sqlException.getMessage(), sqlException);
}
Toast.makeText(mActivity, "Saved", Toast.LENGTH_SHORT).show();
}
// ============== CHANGE ==============
while (studentsListCursor.moveToNext());
csvWrite.close();
}
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