我对android应用程序开发还是相当陌生，stackoverflow是一个很好的资源，所以谢谢你！问题。我遇到了SQliteDatabase / OpenHelper / AssetHelper很难解决的问题，因为我无法复制许多应用程序用户在我的设备或任何android studio模拟设备上遇到的错误，因此我将向您展示此代码为我工作，但不为其他人工作，我也不知道为什么。
当我的应用程序从数据库（资产文件夹中）填充的List中获取值时，我的用户有时会获得indexoutofboundsexception（我相信）。因此，似乎数据库未正确加载。我相信问题可能与我在Fragment生命周期的DBProgressAccess中获得DatabaseAccess类OnResume的实例时传递的上下文有关。
我没有做太多的努力来解决这个问题，仅是因为崩溃很少发生（仅在我的android 6.0手机上发生过一次），但是我从Google那里收到有关其他android设备（包括android在内）频繁崩溃的报告6.0）。我崩溃的堆栈跟踪来自Google开发人员控制台。
我有一个在应用程序启动时加载的片段。在从showSets12()调用的onResume()方法中（我看到indexoutofbounds错误），我访问了用户得分的数据库：
private void showSets12()
{
DBProgressAccess dbProgressAccess = DBProgressAccess.getInstance(getActivity());
dbProgressAccess.openUserProgressDb();
dbProgressAccess.getDayValues();
int scoreToday = dbProgressAccess.getScores().get(0); <--I think the error comes from this
...
dbProgressAccess.closeUserProgressDb();
}
在公共DBProgressAccess类中，我具有：
public class DBProgressAccess {
private SQLiteOpenHelper openHelper;
private SQLiteDatabase database;
private static DBProgressAccess instance;
private List<String> dates;
private List<Integer> scores;
private List<String> times;
public static final String TABLE_NAME = "UserProgress";
public List<Integer> getScores() {return scores;}
private DBProgressAccess(Context context) {
this.openHelper = new DBProgressHandler(context);
}
public static DBProgressAccess getInstance(Context context)
{
Log.d(TAG, "getInstance");
if(instance == null) {
instance = new DBProgressAccess(context);
}
return instance;
}
/**
* Open the database connection.
*/
public void openUserProgressDb() {
Log.d(TAG, "openUserProgress");
this.database = openHelper.getWritableDatabase();
}
/**
* Is todays date included in the database? If not, create it and search the database to populate lists for times and scores
*/
public void getDayValues()
{
if (checkIfDateExists()) {
Cursor cursor = searchDayProgress();
searchDatabase(cursor);
}
else
{
createDayEntry();
Cursor cursor = searchDayProgress();
searchDatabase(cursor);
}
}
/**
* Check to see if there is a record in the database for today
*/
public boolean checkIfDateExists()
{
Cursor cursor = searchDayProgress();
if(cursor.getCount() <= 0)
{
cursor.close();
return false;
}
cursor.close();
return true;
}
/**
* Insert todays date into the database
*/
private void createDayEntry()
{
Date today = Calendar.getInstance().getTime();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
String todayString = formatter.format(today);
int score = 0;
String time = "0:00:0";
ContentValues cv = new ContentValues();
cv.put("date", todayString);
cv.put("score", score);
cv.put("time", time);
database.insert(TABLE_NAME, null, cv);
}
/**
* Find the database record for today
*/
private Cursor searchDayProgress() {
String whereQuery = "SELECT * FROM UserProgress WHERE date = date('now')";
Log.d(TAG, "searchWeekProgress " + whereQuery);
return database.rawQuery(whereQuery, null);
}
/**
* Populate lists of time, date and progress taken from the database
*/
public void searchDatabase(Cursor cursor)
{
List<String> listDate = new ArrayList<>();
List<Integer> listUserProgress = new ArrayList<>();
List<String> listTime = new ArrayList<>();
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
listDate.add(cursor.getString(cursor.getColumnIndex("date")));
listUserProgress.add(cursor.getInt(cursor.getColumnIndex("score")));
listTime.add(cursor.getString(cursor.getColumnIndex("time")));
cursor.moveToNext();
}
cursor.close();
setDates(listDate);
setScores(listUserProgress);
setTimes(listTime);
}
private void setDates(List<String> dates) {this.dates = dates;}
private void setScores(List<Integer> scores) {this.scores = scores;}
private void setTimes(List<String> times) {this.times = times;}
}
我相信List<string>变量结果为空。
我希望我可以输入更具体的代码，但是Google开发人员控制台堆栈跟踪尚不清楚。
我收到的错误来自Google开发人员控制台，而不是android studio，因为我无法在我的设备或任何仿真设备上复制该问题。
java.lang.RuntimeException:
at android.app.ActivityThread.performResumeActivity (ActivityThread.java:3573)
at android.app.ActivityThread.handleResumeActivity (ActivityThread.java:3613)
at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2862)
at android.app.ActivityThread.-wrap12 (ActivityThread.java)
at android.app.ActivityThread$H.handleMessage (ActivityThread.java:1574)
at android.os.Handler.dispatchMessage (Handler.java:110)
at android.os.Looper.loop (Looper.java:203)
at android.app.ActivityThread.main (ActivityThread.java:6364)
at java.lang.reflect.Method.invoke (Method.java)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:1076)
at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:937)
Caused by: java.lang.IndexOutOfBoundsException:
at java.util.ArrayList.get (ArrayList.java:411)
at org.ieltstutors.academicwordlist.AcademicWordListFragment.showSets12 (AcademicWordListFragment.java)
at org.ieltstutors.academicwordlist.AcademicWordListFragment.access$000 (AcademicWordListFragment.java)
or .access$200 (AcademicWordListFragment.java)
or .drawCircularLockedProgress (AcademicWordListFragment.java)
or .onCreateView (AcademicWordListFragment.java)
or .openCloseSet (AcademicWordListFragment.java)
or .showCircularScores (AcademicWordListFragment.java)
or .showScores (AcademicWordListFragment.java)
or .updateScores (AcademicWordListFragment.java)
at org.ieltstutors.academicwordlist.AcademicWordListFragment.onResume (AcademicWordListFragment.java)
很遗憾，这是我对错误的全部信息。
因此IndexOutOfBoundsException来自showSets12。错误可能是由于为getInstance使用了错误的上下文吗？还是来自getWriteableDatabase？为什么有时可以正确访问数据库，但有时却不能正确访问？我记得当应用程序启动时当该应用程序在手机上崩溃时，我立即尝试在我的朋友手机上打开该应用程序，但它也崩溃了，之前从未发生过崩溃。巧合？
唷！任何帮助是极大的赞赏。谢谢！
仅在调用Activity onResume（）或onPause（）时才调用片段onResume（）或onPause（）。它们与活动紧密相关。如果要将片段添加到活动中时要执行某些操作，则可以使用OnAttach（）或其他片段生命周期
阅读本文以了解片段Lifecycle