I am developing an eCommerce where I am fetching the Products and sub-products from database at run time.
Here the depth of the sub-products is not fix, means that I don't know at build time that a sub-product of clothes e.g. jeans, again have a sub-product or not.
I think to create Activities dynamically but as per Android Documentation we can not done it.
We have to specify Activities in Android Manifest.xml at build time.
As per your Question you want to display Products and sub-producs dynamically in your application. for that you should have to use Listview to display your UI part and use AsyncTask to Load data from your database/server.
ListView Tutorial :: http://www.vogella.com/tutorials/AndroidListView/article.html
AsyncTask Tutorial :: http://developer.android.com/reference/android/os/AsyncTask.html
First of all you need to clarify the data structure of the product defined in your application. There should be relationship such as foreign key or other constraints defined on your eCommence backend database.
So, there is no need to create activities at runtime. Instead, try to define a base activity to handle the common product operation and other special activities that extend the base activity to handle the differents between the product and the sub-products.
The logic may like this:
Load product data in common activity. then the app decide whether to load the sub-porduct via creating special activities according to the data flag/key defined in product data retrived from database, and so on.
I think expandable list view is best option for that.Because it clearly shows your main product and sub-products to the user.To create and understand expandable list view please see below link :
http://theopentutorials.com/tutorials/android/listview/android-expandable-list-view-example/
Related
Now I am working on Android application which has one main Activity that is displaying some data via GLSurface. This data can be changed in many ways. For this I have several fragments with some lists of variants with extra logic. Problem is that I need somehow transfer data from one place to another.
For example:
I have fragment with list of elements. I used RecyclerView with custom adapter. I am filling list with data from DB. SomeThingDBEntity for example. When I am getting it from Room DB (using Room entities), but it has some extra fields that only required for showing elements in RecyclerView. I need to send user's choice from adapter to fragment, then from fragment to activity, than activity sends it to some class that incapsulates logic of work with GLSurface. SomeThingGLentity for example. Now I am passing only fields, that requered by SomeThingGLentity for showing data (int, String etc.), but in future this list can grow. I can also send directly SomeThingDBEntity and get required fields only in the end when apply changes to SomeThingGLentity. But is it OK to use Room DB entity this way?
Is there any better way of doing this? I can also create third class which will only contain required fields. But where to place and how to call it? Maybe there are some patterns or guidelines of best way of doing it...
It looks like you need a data mapper. Something similar to this - https://github.com/android10/Android-CleanArchitecture/blob/master/data/src/main/java/com/fernandocejas/android10/sample/data/entity/mapper/UserEntityDataMapper.java.
If you use this approach, you will be able to encapsulate the transformation logic from your DBEntity to your BusinessEntity, and if you will change the data format in one of them, only your mapper will need to be edited.
I want to build an android app for a restaurant. I want it to display the menu in several activities using listviews. One for drinks, one for meals, one for deserts, etc. The menu comes from a json file which is being parsed in a splashscreen on app start.
Now i'm wondering what's the best way to populate the listviews and activities after parsing the json:
Populating the listviews from the splashscreen activity?
Storing the menu data in files and access them on the depending activity's oncreate()…?
Parsing a separate json file for each activity?
What is the best way in terms of performance, simplicity and effectiveness?
That would imply you have all you Acticities with their ListViews up & running when the splashscreen is starting. Probably not what you want.
You already said the JSON is stored in a file. You can parse that JSON in your splashscreen Activity, keep a global reference to it and let you Activities pick the part they need from that global class / JSONObject.
Tradeoff: Parse the complete JSON once and let all Activities retrieve the parts they need from it (this is basically 2.) at the 'risk' of parts of it never being used or split the JSON into several parts that are being loaded/parsed on demand by every Activity seperately, but having the overhead of doing file transactions in every Activity.
Either way, if the menu you're storing isn't immensely huge, the difference in performance will be minimal.
I'd go 2., load the whole file at startup, store the data globally and let every Activity make use of it.
I am new to Android App development, working on an android app which populate a list of numbers, in a listview dynamically, depending on the choice of the user, but, the moment user closes the App, the items in the listview are lost. How can I maintain the state of the listview?
Examples with code would be highly appreciated.
When I open Activity A, it allows users to add friends, and this friend list is shown in the form of items of listview in the same Activity, however, when I move to Activity B, and then come back to Activity A, this friend list disappears. I need to make sure that this friend list should not be lost while moving between activities. Please help.
I think that for your purpose there are 3 main methods, i'll explain them from the easier to the most difficult (in my opinion).
Text File
A way to do this is to create two methods in a class:
one has to create the text file in the storage if it isn't created before and read that, the other has to append a String to a StringBuilder and write it on the previous text file.
For this method you need the uses-permission of reading and writing to storage.
This link can help you: http://developer.android.com/training/basics/data-storage/files.html
JSON (also XML)
With JSON file you can create a list of objects with your data that you can serialize when you update the list and deserialize when you want to read it. For this purpose you have to study JavaScript syntax or, at least, JSON one.
SQLite Database
Android SDK incorporate a class named SQLiteOpenHelper that you can extend to create a database inside your app.
This link can help you: http://developer.android.com/training/basics/data-storage/databases.html
There are also references saving methods but i think that aren't right for your purpose, they work betters to save something like preferences or single data like last login informations.
I went through your comment. I would personally suggest using SQLiteOpenHelper
You might need to understand the use of SQLite, hence the tutorial
Simple Flow. On your Activity 1 where person Add Friends save it to DB
Then refresh the List from the DB. So when you move to Activity 2 and come back again to Activity 1 your List will refresh from DB. Hence no loss of data as you want.
EDIT
As user wanted to know how to use the ListView with DB.
Following are my suggestion
Sai Geetha
Youtube
I want to develop an e buy application. I have categories and sub-products and data is kept in external server. If I add a new category on the server I want to add category and product activity automatically. Is it possible? How can I create a new activity automatically and how can I add the activity automatically in the android manifest?
No, you cannot do this. Activity objects must be declared at compile-time and cannot be changed later. You must adapt your code to work in the different situations.
For example, let's say you are fetching a name, birthdate, and description for a human resources entry. You would create one Activity that contained your layout and text fields, then have that Activity fetch the name, birthdate, and description from your server. It would then populate the text fields with the data, or show/hide the fields if there is no data for them.
This is a design issue, the activity should not be binded with your data. You should design an activity for categories data and an activity for products data. If they have different look, just build different sub class of your root activities.
Good afternoon,
I have a simplistic app (just learning) that reads some xml data from a mocked up file. The XML data is well formed into 6 categories and I use the SAX parser to read it. My app basically has two buttons prev & next. So when the app loads I'd like to see the first category of xml data. When the user presses next button...well then I'd like to see the next category of data etc. to the end. My question is how do I go back and forth through the data? Do I load it all into a data object with some form of sorting and iterate back and forth throught the object or do I add an atty field to a parent element and just search the xml for the requested atty and child data? I don't forsee the xml ever getting very large. Just trying to get more experienced input into how to go about synchronizing the data with the gui.
TIA
JB
There are many ways you could go about it. One that is generally a decent path is parse the XML into a data structure that can be used by an Adapter to create the view structures and return them so be shown. That will give you a good level of control over how your data looks and allow you to tie in to many different complex View structures pretty easily.
The data structure that you store it in also has many possibilities. Which ones work best would depend on your particular dataset generally.
Given what I know about your data an ArrayList seems like a straightforward approach. Create yourself a class that will hold all of the data about one category. Create objects of that class in your parser as you are pulling the data out of the XML file, each time you get to a new category add your object to an ArrayList. When your done you should have an List structure that has 1 category object(with all of its data) at each index.
Once you've got that set up make yourself an ArrayAdapter with your List. Override the getView() method to inflate your View objects and populate them with the data from your List.
This Adapter can then feed a parent View (ViewPager, ViewSwitcher, ListView etc...) These parent views will make it easy to iterate over your data structures (i.e. switching from one category to the next and back.)