android - 从sqlite数据库获取数据作为livedata android
问题描述
我有应用程序,现在我想使用新的 android 功能更新它的某些部分。我的数据库是 SQLite,由于某种原因我不能使用 Room 数据库。所以我想在我的应用程序中使用视图模型和实时数据。问题是我无法从我的数据库中获取数据作为 Livedata。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,我将数据作为 itema 列表获取。现在我怎样才能将数据作为 Livedata<List> 获取。任何帮助将不胜感激。
解决方案
我认为你可以做这样的事情。只需LiveData<<ArrayList<itema>>
从函数返回并稍后在后台对其进行变异以反映结果。
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者。
getDataContact2().observe(this, Observer<List<itema>>{ it->
//some action on change of data
})
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