Develop Reference

Add a full width header item to a Grid View in AbsListView (Xamarin)

I have a list in my app, and it's implemented as an AbsListView, so that when we are working on a smaller screen (phone) it's a List and when we are on a larger screen (tablet) it's a Grid.
All works well.
Now I want to add in a header item which is completely different from the regular items on my list - it has a completely different xml file. It's always the first item in the list.
I've added in code to my Adapter class like so:
public override View GetView(int position, View convertView, ViewGroup parent)
{
SavedInfo subViews = null;
var rowView = convertView;
var channel = items[position];
// don't want to reuse if our previous view was a header
if (rowView?.Tag != null)
{
subViews = rowView.Tag as SavedInfo;
}
// try to put in a different view if there is a header shown
// special id value for header is -1
if (position == 0)
{
subViews = null;
}
if (subViews == null)
{
if (position == 0)
{
rowView = context.Activity.LayoutInflater.Inflate(Resource.Layout.header_layout, null);
// Do setup stuff with this layout
rowView.Tag = null;
return rowView;
}
rowView = context.Activity.LayoutInflater.Inflate(cellLayout, null);
// Do stuff with regular layout, take savedInfo from Tag
rowView.Tag = subViews;
}
// other adjustments to the regular layout
return rowView;
}
So that's fine in a regular list - I have one header item and lots of regular items. However, when I switch to GridView (which uses the same adapter) my "header" item is now just the first cell in the grid.
What I want it to be is more or less the same as it is in the list view - a single column which fills the width of the screen, then followed by the regular grid. The point is I want an item which fills all the columns across, but scrolls up with the grid. Is there a way to do this? I understand I might need to replace with some sort of custom Adapter View. Does anyone have an example of code doing a grid with one item filling multiple grid columns?
Thanks

Turns out this is not possible - the recommended way to put in a header is to use a CoordinatorLayout and a CollapsingToolbarLayout while changing the ListView to a RecyclerView

Android listview getting all items

In android, is it possible to get all items inside the list view. Lets say the list view has multiple rows and only 2 rows are visible on the screen while the rest are accessible using the scroll bar. Each row has a radio button and a text view. Is there a way to get all textview of the rows whose radio button is selected and not just the ones visible on the screen.

Your answer may be:
for(int item = 0; item < m_listitem.count(); item ++){
if(m_listitem[item].isSelected){
View view = ListView.getChildAt(i);
TextView textview = view.findViewById(your textView id);
// do some thing
}
}

You can use custom list view to show your list items with checkbox & textview.

I happened to have a similar requirement where I had multiple EditText inside a ListView and only few of them were visible on the screen. I needed to get the values of all EditText and not just the ones visible on the screen.
Well if you are using a default Adapter, then the way it will work is it will recycle the old views to create new ones. So there is no way to preserve values of those Views which are not visible.
So the only workaround is to create your own Adapter, maybe something like the following, which will not recycle any views, but every time inflate new ones.
public class ListViewAdapter extends ArrayAdapter {
public ListViewAdapter(Context context, ArrayList<Object> items) {
super(context, 0, items);
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
return LayoutInflater.from(getContext()).inflate(R.layout.your_layout_for_list_view_item, parent, false);
}
}
After that, as in above answer Lãng Tử Bị Điên has mentioned, you can check in your java code, if your radio buttons are checked or not, and according to that, selected desired TextViews
for(int item = 0; item < m_listitem.count(); item ++){
if(m_listitem[item].isSelected){
View view = ListView.getChildAt(i);
TextView textview = view.findViewById(your textView id);
// do some thing
}
}
Hopefully this should do it.. It sure worked in my case!

reuse the inflated view in android

The following piece of code is inflating the same view for 20 times. Since inflating is costly. I want to inflate it only one, and use the same view for 20 items, i just want to change the visible data in the UI.
LinearLayout ll = new LinearLayout(context);
for (int i = 0; i < 20; ++i) {
View itemView = inflater.inflate(getLayoutId(), parent, false);
itemView.setText(data.getName(i);
ll.add(itemView);
}
I want something like this.
LinearLayout ll = new LinearLayout(context);
View itemView = inflater.inflate(getLayoutId(), parent, false);
for (int i = 0; i < 20; ++i) {
itemView.setText(data.getName(i);
ll.add(itemView);
}
But am not able to use the itemView obj this way.
Can anyone tell me how to use the view many times once it inflated.

You cannot do that. If you think its costly then find another way to create your layout.
But consider gridViews for example. They create a ton of views and show them and that works great.
You cannot add the same object of a view 2 times to a layout. Every object has its own state which in your case in a way says that you will share the state between all your 20 views which doesn't make sense to do, meaning changing the text on one textView will change it on all the rest...
Just inflate 20 seperate views and fill them appropriately.
Also consider using ListView or GridView if you actually have the exact same view it can offer some nice features like view recycling.

You should use ViewHolder patern:
http://developer.android.com/training/improving-layouts/smooth-scrolling.html#ViewHolder
it should do all things You want

How to get Position of an view added dynamically on LinearLayout

I need to get an dynamically added view position in LinearLayout with vertical orientation.
For example i have 4 TextViews added dynamically on LinearLayout, then i need to change position of text colour at 3rd position will be in different color.How can i achieve it by getting position of added views.

You can do it just like that
ViewGroup parent;
int position;
for(int i = 0; i < parent.getChildCount(); ++i) {
int currentViewId = parent.getChildAt(i).getId();
if(currentViewId == wantendViewId) {
position = i;
}
}
That's (in my opinion) the simplest way

If you always know the number of TextViews in your LinearLayout, you can just use the function getChildAt( int position ). This returns a View which you can then cast to a TextView to be able to perform the desired operations.
If you do not know the number of elements you could set the id of each TextView (in order to be able to identify a particular one) and then run through them like this:
for( View view : myLinearLayout )
if( view instanceof TextView && view.getId().equals( idToSearchFor ) )
//Do what needs to be done.

I see following options:
Declare some id's in resources in form of <item type="id">first</item> and assign them to
views in adding to layout, after that use normal findViewById() mechanism
Assign some tags to views you're adding to a layout via setTag method and after that use findViewWithTag mechanism
Remeber position of your views and use them vie getChildAt method

I got simple option.
suppose you add
View v;//any view
linearlayout.addview(v);//add in layout
While u want to modify view.
simpaly remove old view.
linearlayout.removeView(v);
add new update view object
v-updated new view
linearlayout.addview(v);

Android: Access child views from a ListView

I need to find out the pixel position of one element in a list that's been displayed using a ListView. It seems like I should get one of the TextView's and then use getTop(), but I can't figure out how to get a child view of a ListView.
Update: The children of the ViewGroup do not correspond 1-to-1 with the items in the list, for a ListView. Instead, the ViewGroup's children correspond to only those views that are visible right now. So getChildAt() operates on an index that's internal to the ViewGroup and doesn't necessarily have anything to do with the position in the list that the ListView uses.

See: Android ListView: get data index of visible item
and combine with part of Feet's answer above, can give you something like:
int wantedPosition = 10; // Whatever position you're looking for
int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount(); // This is the same as child #0
int wantedChild = wantedPosition - firstPosition;
// Say, first visible position is 8, you want position 10, wantedChild will now be 2
// So that means your view is child #2 in the ViewGroup:
if (wantedChild < 0 || wantedChild >= listView.getChildCount()) {
Log.w(TAG, "Unable to get view for desired position, because it's not being displayed on screen.");
return;
}
// Could also check if wantedPosition is between listView.getFirstVisiblePosition() and listView.getLastVisiblePosition() instead.
View wantedView = listView.getChildAt(wantedChild);
The benefit is that you aren't iterating over the ListView's children, which could take a performance hit.

This code is easier to use:
View rowView = listView.getChildAt(viewIndex);//The item number in the List View
if(rowView != null)
{
// Your code here
}

A quick search of the docs for the ListView class has turned up getChildCount() and getChildAt() methods inherited from ViewGroup. Can you iterate through them using these? I'm not sure but it's worth a try.
Found it here

listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, final View view, int position, long id) {
View v;
int count = parent.getChildCount();
v = parent.getChildAt(position);
parent.requestChildFocus(v, view);
v.setBackground(res.getDrawable(R.drawable.transparent_button));
for (int i = 0; i < count; i++) {
if (i != position) {
v = parent.getChildAt(i);
v.setBackground(res.getDrawable(R.drawable.not_clicked));
}
}
}
});
Basically, create two Drawables - one that is transparent, and another that is the desired color. Request focus at the clicked position (int position as defined) and change the color of the said row. Then walk through the parent ListView, and change all other rows accordingly. This accounts for when a user clicks on the listview multiple times. This is done with a custom layout for each row in the ListView. (Very simple, just create a new layout file with a TextView - do not set focusable or clickable!).
No custom adapter required - use ArrayAdapter

int position = 0;
listview.setItemChecked(position, true);
View wantedView = adapter.getView(position, null, listview);

This assumes you know the position of the element in the ListView :
View element = listView.getListAdapter().getView(position, null, null);
Then you should be able to call getLeft() and getTop() to determine the elements on screen position.