从SQLite数据库获取数据作为LiveData Android

Question

我在应用程序上，现在我想使用新的安卓功能更新它的某些部分。 我的数据库是SQLite 由于某种原因，我无法使用房间数据库。所以我想在我的应用程序中使用 ViewModel 和实时数据。 问题是我无法从我的数据库中获取数据作为实时数据。 这是我从数据库获取数据的代码：

public ArrayList<itema> getDataContact2 () {
SQLiteDatabase db = myhelper.getReadableDatabase();
String[] columns = {DBhelper.CONID,DBhelper.CONNAME, DBhelper.PHONE1, DBhelper.PHONE3, DBhelper.ADDRESS, DBhelper.TELEGRAM,DBhelper.INSTAGRAM,DBhelper.PHONE2,DBhelper.IMAGE,DBhelper.INFO,DBhelper.WHATSUP,DBhelper.EMAIL,DBhelper.EVENT,DBhelper.EVENTTITLE};
Cursor cursor = db.query(DBhelper.TABLE_CONTACT, columns, null, null, null, null, DBhelper.CONNAME);
ArrayList<itema> myList=new ArrayList<>();

while (cursor.moveToNext()) {
try {
int id = cursor.getInt(cursor.getColumnIndex(DBhelper.CONID));
String name = cursor.getString(cursor.getColumnIndex(DBhelper.CONNAME));
String phone1 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE1));
String phone2 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE2));
String phone3 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE3));
String add = cursor.getString(cursor.getColumnIndex(DBhelper.ADDRESS));
String date = cursor.getString(cursor.getColumnIndex(DBhelper.EVENT));
String telegram = cursor.getString(cursor.getColumnIndex(DBhelper.TELEGRAM));
String insta = cursor.getString(cursor.getColumnIndex(DBhelper.INSTAGRAM));
String whatsup = cursor.getString(cursor.getColumnIndex(DBhelper.WHATSUP));
String email = cursor.getString(cursor.getColumnIndex(DBhelper.EMAIL));
String info = cursor.getString(cursor.getColumnIndex(DBhelper.INFO));
String image = cursor.getString(cursor.getColumnIndex(DBhelper.IMAGE));
String datetitle = cursor.getString(cursor.getColumnIndex(DBhelper.EVENTTITLE));
itema item=new itema(id,name,phone1,phone2,phone3,add,email,insta,telegram,whatsup,image,info,date,datetitle);
myList.add(item);
}
catch (Exception e){
e.printStackTrace();
}
}
cursor.close();
return myList;
}

如您所见，我以意达列表的形式获取数据。 现在如何以 Livedata的形式获取数据。 任何帮助将不胜感激。

Answer 1

我认为你可以做这样的事情。只需从函数返回LiveData<<ArrayList<itema>>，稍后在后台对其进行更改即可将结果反射回来。

例如。

public LiveData<ArrayList<itema> getDataContact2 () {
LiveData<ArrayList<itema>> resultList = MutableLiveData<List<itema>>();
//use some background thread to get data from Sqlite here below......
SQLiteDatabase db = myhelper.getReadableDatabase();
String[] columns = {DBhelper.CONID,DBhelper.CONNAME, DBhelper.PHONE1, DBhelper.PHONE3, DBhelper.ADDRESS, DBhelper.TELEGRAM,DBhelper.INSTAGRAM,DBhelper.PHONE2,DBhelper.IMAGE,DBhelper.INFO,DBhelper.WHATSUP,DBhelper.EMAIL,DBhelper.EVENT,DBhelper.EVENTTITLE};
Cursor cursor = db.query(DBhelper.TABLE_CONTACT, columns, null, null, null, null, DBhelper.CONNAME);
ArrayList<itema> myList=new ArrayList<>();

while (cursor.moveToNext()) {
try {
int id = cursor.getInt(cursor.getColumnIndex(DBhelper.CONID));
String name = cursor.getString(cursor.getColumnIndex(DBhelper.CONNAME));
String phone1 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE1));
String phone2 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE2));
String phone3 = cursor.getString(cursor.getColumnIndex(DBhelper.PHONE3));
String add = cursor.getString(cursor.getColumnIndex(DBhelper.ADDRESS));
String date = cursor.getString(cursor.getColumnIndex(DBhelper.EVENT));
String telegram = cursor.getString(cursor.getColumnIndex(DBhelper.TELEGRAM));
String insta = cursor.getString(cursor.getColumnIndex(DBhelper.INSTAGRAM));
String whatsup = cursor.getString(cursor.getColumnIndex(DBhelper.WHATSUP));
String email = cursor.getString(cursor.getColumnIndex(DBhelper.EMAIL));
String info = cursor.getString(cursor.getColumnIndex(DBhelper.INFO));
String image = cursor.getString(cursor.getColumnIndex(DBhelper.IMAGE));
String datetitle = cursor.getString(cursor.getColumnIndex(DBhelper.EVENTTITLE));
itema item=new itema(id,name,phone1,phone2,phone3,add,email,insta,telegram,whatsup,image,info,date,datetitle);
myList.add(item);
}
catch (Exception e){
e.printStackTrace();
}
}
cursor.close();
resultList.postValue(myList)
//some background operation end here 
return resultList;
}

以及您使用的地方只是观察它。

getDataContact2().observe(this, Observer<List<itema>>{ it->
//some action on change of data
})

Answer 2

您应该在使用变量的视图模型中维护一个变量类型化MutuableLiveData<ArrayList<itema>>。

并通过数据库函数getDataContact2的发布值更新该实时数据。

liveData.postValue(dbData)

除此之外，您还可以从数据库函数getDataContact2中的列表中创建一个实时数据，如果您真的想要，可以返回该数据。