I have a ListView where the view for each item is a string (the name of the item). But I have to associate a lot of other data with that item: price, size, weight, tax, etc. So, I'm of creating a new Java class called Item, and then an object for each item in the list.
I don't know which is the bext way to implement this. There's two obvious choices:
1) I can simply create the data structure outside of any Android Views, and then write a method called UpdateList() which takes the name of each item in this data structure and puts it in the ListView. The problem with this is that some of the data is duplicated twice (the original data structure, and the adapter for the ListView) and when you duplicate data, bug potential arises.
2) Or, I can somehow associate the data structure directly with the adapter for the ListView and have it figure out how to display the name for each ListView entry that is displayed. The advantage here is that you only have a single data structure. But I don't know if this is possible in Android, or very complex.
Which is the preferred way to do this with Android apps?
You would be better with the ListView and the Adapter option, You would need to create a custom ArrayAdapter to populate a ListView from this objects the way you want.
The advantage of this technic is that you gain a Views recycle mechanism that will recycle the Views inside you ListView in order to spend less memory.
In Short you would have to:
1. Create an object that represents your data for a single row.
2. Create an ArrayList of those objects.
3. Create a layout that contains a ListView or add a ListView to you main layout using code.
4. Create a layout of a single row.
5. Create a ViewHolder that will represent the visual aspect of you data row from the stand point of Views.
6. Create a custom ArrayAdapter that will populate the rows according to you needs.
7. Finally assign this ArrayAdapter to your ListView in onCreate.
You can get an Idea of how to implement this by reading this blog post I wrote:
Create a Custom ArrayAdapter
Just use the adapter. It's much cleaner. Then you can retrieve the info you need when you display the list item with getView(). See this example.
Related
I'm pretty new to Android and I have a question about an application that I'm trying to develop.
My problem is about listview and adapter: I have a list of objects that contain information about a user's favorite routes (i created an object FavouriteRoute and i pass an ArrayList to the BaseAdapter). However, each object can contain a variable number of cities, of stops and days of the week ... how do I handle this dynamic content and show it inside of each row of listview? What's the best approach? I have to manage these elements within the getView () of the adapter and insert them dynamically within the layout of each row?
You can take the reference of these tutorials to learn creating your adapter which will server your purpose.
http://androidexample.com/How_To_Create_A_Custom_Listview_-_Android_Example/index.php?view=article_discription&aid=67&aaid=92
https://www.caveofprogramming.com/guest-posts/custom-listview-with-imageview-and-textview-in-android.html
http://www.androidhive.info/2014/07/android-custom-listview-with-image-and-text-using-volley/
If you want that some of your views are visible and some are not then in getView() do this:
if(your condition)
textView.setVisibility(View.GONE);
after inflating the views.
I am doing android application. In That I want to display a List of podcast urls like shown in the Image. In this I also share this url into FB, twitter and etc and also the user clicks the arrow symbol I want to forward to that podcast url.
I am having those values in separate arraylist (i.e. "4353,3424" as a arraylist and "567567, 234234" as a another arraylist likewise). So how can I display these values like shown in the attached image. Can anyone help me how to proceed to display like this?
I'd recommend you had a look at some of the tutorials on how to implement your own custom ListView.
An example can be found here: http://www.thepcwizard.in/2012/09/android-creating-custom-listview-for.html
Also I'd recommend you create a custom class for holding the different informations in every row of the ListView. When doing it like this you can have one single List<MyCustomObject> holding all informations and then when a row is clicked, you simple get the item from the List<MyCustomObject> and get the specific property of the custom object and act accordingly.
EDIT: Small example of how to add onClickListener to a sub-view of the row:
Inside the getView method of the custom Adapter you can use setOnClickListener to the views, you'd like to respond to clicks. For instance:
myImageView.setOnClickListener(this);
Then let your custom Adapter implement the interface OnClickListener and act accordingly to the clicks.
Another way would also be to add a Share Intent to the different images, like in this example:
http://sudarmuthu.com/blog/sharing-content-in-android-using-action_send-intent
You would need to create a custom ArrayAdapter to populate a ListView from this objects the way you want.
The advantage of this technic is that you gain a Views recycle mechanism that will recycle the Views inside you ListView in order to spend less memory.
In Short you would have to:
1. Create an object that represents your data for a single row.
2. Create an ArrayList of those objects.
3. Create a layout that contains a ListView or add a ListView to you main layout using code.
4. Create a layout of a single row.
5. Create a ViewHolder that will represent the visual aspect of you data row from the stand point of Views.
6. Create a custom ArrayAdapter that will populate the rows according to you needs.
7. Finally assign this ArrayAdapter to your ListView in onCreate.
You can get an Idea of how to implement this by reading this blog post I wrote:
Create a Custom ArrayAdapter
I have an object submission which contains some informations which I would like to show in a list view.
For example, in my object I can do this:
submission.firstElement().getDate()
and
submission.firstElement().getTitle()
which returns me a date and a title.
My problem is: how to show those two elements (not only the first's) in a listview (two elements per list item).
I have thinked on a for loop with the submission.size() but I have no idea how to get forward with.
Thank you for your help.
You'll want to look at using a ListView and a ArrayAdapter. You could use a BaseAdapter but I have found a ArrayAdapter more than adequate for displaying a list of custom objects in a ListView.
First create a layout that will be used to show the desired data per row in the ListView. In your case I assume that it will be two TextViews, one showing the title and date.
Once done, create a ListAdapter and in it's constructor give it the layout for the row created above. Once done, use the getView() function to access the layout and populate the TextView's with the object's date and title.
Have a look at the following links:
http://developer.android.com/reference/android/widget/ArrayAdapter.html
http://developer.android.com/reference/android/widget/BaseAdapter.html
http://www.vogella.de/articles/AndroidListView/article.html
EDIT:
Ana, to aid you a bit further use a ListActivity as shown in this Google documentation: http://developer.android.com/reference/android/app/ListActivity.html. In the example given they use a SimpleListAdapter. However, for an ArrayAdapter the constructor is a little simpler:
new ArrayListAdapter(this, R.layout.row_layout, listOfObjects);
When using a ListActivity a layout does not need to be created as by default it includes one.
I've been trying to fix this problem for a while and have exhausted all the different Google searches that I could think of. I'm a beginner with Android, but understand most of the fundamentals (I think). Anyways, I'm trying to display a list of data in a multi-column layout spreadsheet style. I'm using a ListView for that because I need users to be able to click on a row to get a more detailed look at the data since only so much can fit in a row. I have it working perfectly using a SimpleAdapter, but since the amount of data can sometimes be large, up to 500 entries, I wanted to change over to a Lazy Loader system so users don't have to stare at a black screen for 20 seconds while everything loads. I think I can manage with the Lazy Loader part, but I can't figure out how to switch over from my multi-columned format SimpleAdapter to an ArrayAdapter that all the Lazy Loader examples use.
Here's an example of my SimpleAdapter code:
SimpleAdapter adapter = new SimpleAdapter(this, fillMaps, R.layout.grid_item, from, to);
fillMaps is the List of HashMaps that are to be inserted. 'grid_item' is the layout that the entries are inserted into. 'from' is an array of column names (alternatively the keys in the HashMap) to be used. 'to' is an array of TextView items that will be filled in 'grid_item'. Any idea how to convert this to an ArrayAdapter? Or how to Lazy Load with a SimpleAdapter?
Thanks in advance!
To solve this issue for others, here is what I did to get it working perfectly:
Created my own class called Entry which simply contains the strings for the rows
Created a custom adapter that extends ArrayAdapter. For the constructor I pass into it an ArrayList of type Entry.
Create a ViewHolder for better UI efficiency
Inflate the row layout xml which is then added to my listview
To get the lazy loading working:
Added a method in my custom adapter that will append a new ArrayList of Entry objects to the ArrayList that I already have in my adapter
Created an onScrollListener and from some debugging test found that if the top visible item plus the remaining entries equalled the total entries, then I was scrolled all the way to the bottom
Once the bottom was detected, I would call my fetch method to retrieve another 30 entries, add these entries using the add method I created, and then use the notifyDataSetChanged() method for the ArrayAdapter to display the newly loaded items
Just write your own adapter. Create a private a class in your Activity that houses your ListView that extends BaseAdapter. Fill out the abstract methods and display your data however you want to. As useful as SimpleAdapter obviously is, you'll get a lot more traction out of your own adapter, and they're really not difficult to write.
Can I use my existing ListView as a sub-view in another view.
eg. I have a custom view, players list, I have implemented with a ListActivity and ArrayAdapter and is working fine.
Now I want a way to get this listview as View object so that I can add this view object as a child to another view.
I am thinking like, to build entire listview: my ListActivity is calling the ArrayAdapter iteratively by passing ArrayList item each time to build a list item view.
If I am correct, I need a way to call the same ArrayAdapter and need to prepare a ListView Object, right?
Can anybody plz help me.
Thanks in advance.
vpapana
The ListView and the Adapter are two different things:
The data is somewhere (in an array or if you need to be able to add/remove items, in an ArrayList)
The Adapter contains the data
The ListView displays it.
So:
Construct your empty ArrayList
Construct your adapter based on your ArrayList
Construct your ListView based on the Adapter
Then:
Each time you need to change the data, update the ArrayList
Call Adapter.notifyDataSetChanged()
Watch your list being automatically updated :)
To add your list to a tablelayout, see the API documentation, SDK tutorial and this tutorial which has a specific section on how to add rows programmatically.