I am writing code for a listview which has fixed number of rows and when the user scrolls the listview, instead of moving the list elements (views), I want to change the content of the views where as the list elements (views) stay at the there position.
For this I am returning a number Eg. 5 in getCount(), however I am no clue on how can I change contents of list items while keeping the list items in a fixed position.
Any help is welcomed.
Regards
with getItemAtPosition()
you get the item at position, there you can change its content and then call notifyDataSetChanged() to signal the adapter that the data has changed.
Related
How do you call the ListView items - objects? or elements? or items? what is the right name for it?
You can call it whatever you want. I personally call it items
When referring to the model, i.e. arrays, I say objects.
From ListView
ListView is a view group that displays a list of scrollable items. The list items are automatically inserted to the list using an Adapter that pulls content from a source such as an array or database query and converts each item result into a view that's placed into the list.
So, I guess there's no mistake to talk about list items as simply items that are converted to views when the Adapter comes in.
I have a list view that fetch data from server when it scroll to bottom. once the data received it pass to the adapter via an array list.
But when i set the array list values to adapter, it appends the data and automatically the position moves to top.
Could some one tell me what is the problem occured here?
I guess that you recreated new Adapter and set it to your listview.
If you do like that, your listview will scroll to top.
To keep your listview item position, just call mAdapter.notifyDataSetChanged(); after update your array list.
Hope it can help you!
I want to make a list of SMSs in my own application..
my question is about the steps makes by the adapter (automatic)
-when new message arrived I adds it to list object (not the ListView).
-then I passes the list to the adapter of the listView.
the adapter GetView() method run for every Item in the list
-I notify the listview about the change.
- the listview re-draws all its existing rows and then draw the new row.
My question: this behavior (re-draw and redraw, it mean every row will be drown times equal to the total rows) affect the performance?
*if the question is not clear I say: does the ListView Draw all the Raws just to add new row? *
The ListView doesn't redraw every single item in order to add one. It will only be drawn when you scroll to it. And yes you have to notify ListView that the change had happened.
I guess you want to add the item at the top position. So all other item's position and index will change . Adapter will redraw the whole list(only elements which are visible on the screen) .
For performance you can use viewHolder pattern.
see this link
[Making ListView Scrolling Smooth][1]http://developer.android.com/training/improving-layouts/smooth-scrolling.html
In my project i have a ListView for handling the list of a product. In that i have a list of 100 Items in that List view. Each and Every time i have been seeing the first row of the ListView..
If i need to see the data in the ListView Means, i need to scroll down, Can i focus directly to a particular item by any function by passing the position(ID) of the ListView..
For Example this is my ListView that contains 11 items in it..
I'm seeing every time the ListView as the following,..
And my try is, If i give the ListView position as ID=5 means, can i get the Focus of the ListView as follow, in the opening itself...
Can we get this by ListFragment method or anything else?
Suggest me for the Best..
try this, use setselection
listview.setSelection(position);
Don't know about ListFragment but in listview, you can use listview.setSelection(position);
This method will help you to achieve this
for example: listview.setSelection(5);
I have a ListView with custom_row , every row has a textView1 and a textView2 , the list has now 2 records , and i have a button that is not on the list.
When i click the button i want to get the text from textView2 of the 2 records.
Is it possible?
I would take a shortcut, you ListView is being populated by an Adapter that uses a dataset. This dataset can be almost any datastructure such as Array, ArrayList, etc.
The layout you define, such as custom_row in you case only defines the structure of your view i.e. "where" items will show within on item on the list.
On the other hand, it is still your responsibility to tell the ListView "what" to show within the textView1 and textView2. You do this using the Adapter which connects the ListView to the dataset. More often than not, the ListView is a one-to-one mapping of the dataset i.e. the first item on the list is the first item in you dataset (I don't know what you are using for only two items, might be an array).
The ListView calls getCount() on the Adapter to find out how many total views there will be. It then call getView() for each view to be shown on the screen. It is in this method that you define what will actually show in a single view on the list (your custom_row).
Now you would know which entry of the dataset is supposed to populate which view in the ListView so you can just read it off there. For example, if your getView() does:
textView2.setText(getItem(position).getSomeTextField());
And the original dataset is an ArrayList named listDataSet
You could just do listDataSet.get(2).getSomeTextField()
NOTE: You will have to manage the scope of the dataset so that it's visible from wherever you are calling.
Get back your ListView (maybe already stored in an object thanks to findViewById, or by calling getListView() on your ListActivity).
Then call getItemAtPosition() on your list view, with the position you want.