Android programatically add layout resource to view - java

I have a scrollview in an activity that I want to populate. Each item I want to add to the list is made up of several views (text view, image view, etc). Instead of programmatically creating each view, and adding it to a linear layout, and then adding that to the containing layout, is it possible to instead create a predefined layout resource with these items and instead add it to the view and programmatically change the item contents?
Essentially, is it possible to do something like:
container.addView(R.layout.listItem);
And if so, how could I access views within the list item to change them?

It's just what inflate(int, ViewGroup, boolean) does with the third parameter attachToRoot set to true
getLayoutInflater().inflate(R.layout.listItem, container, true);
After that everything is straightforward
container.findViewById(R.id.text_view)

You have to "inflate" your view by LayoutInflater. For example like this:
View view = LayoutInflater.from(context).inflate(R.layout.listItem, container, true);
or
View view = LayoutInflater.from(context).inflate(R.layout.listItem, container, false);
container.addView(view);

Related

Make Fragment appear first in LinearLayout

I am building parts of my layout programmatically.
My process looks like this:
I inflate a layout: View view = inflater.inflate(R.layout.view_layout, viewGroup, false);
I add this view to the ViewGroup: viewGroup.addView(view);
Before adding views in this way, I first add a fragment to the root view of viewGroup:
getChildFragmentManager().beginTransaction().add(R.id.viewgroup_root, fragment, "fragment_tag").commit();
My ViewGroup is a LinearLayout and I am adding the Fragment before I add the other views. However, the Fragment is appearing last - after all the views I add using ViewGroup.addView().
How can I get the added Fragment to be displayed first in the LinearLayout, and why is the LinearLayout displaying it last if it was added first?
commit() is asynchronous - it does not run immediately. Therefore you definitely are running your addView methods before your fragment is actually added.
As Fragments automatically are re-added to their respective layout based on ID and you do not control the ordering of when the fragment is added to the layout in those cases, you can't rely on any initial ordering.
Instead, you should always add a Fragment to its own container - if using Fragment 1.2.0 or higher (the latest right now is 1.2.5), you should add a FragmentContainerView to your LinearLayout. If you're using an earlier version of Fragments, you'd want to add a FrameLayout to your LinearLayout. In either case, you'd need to make sure you use setId() with that layout and use the same ID when you use add.
You will have to leave placeholder under your LinearLayout and use placeholder's ID to do beginTransaction/add stuff. Any viewgroup would do. You are not just adding another view to your viewgroup, you are adding a fragment. It has its own lifecycle, bound to entities hosting it (activity, fragment).

Android Custom View (Table)

I have a problem figuring out how to create a custom android view that contains other views in it like a table. How can I create a method in that android custom view class for adding a view inside it, I would like to know how the parent view will resize and position the child view.
How can I create a table like view that I can use to add other views in ?
Should I extend View(since I actually want to create a view not a layout) or ViewGroup(since I want to add other views in it) ?
This is what I hope to obtain:

How Android Custom Adapter works?

I'am trying to use a custom listView in my application and i have some questions about its working principles.When i implemented a custom adapter,how its methods(especially the getView method)work without calling them from any other class ?
When you set the adapter to a view (e.g. ListView or GridView), that view at some point wants to have some items to show. So it calls getView in the adapter:
getView(int position, View convertView, ViewGroup parent).
The position is the position of the item in the list/grid/etc. The convertView is a recycled view that can be already inflated by a previous getView() call, or null when it's not inflated yet (see this answer about convertView and view recycling.
The parent is used to inflated the view, so the correct layout parameters can be computed in relation to the parent view.
Note that inflation is slow. That is why the convertView mechanism exists, to recycle views so the number of inflations is minimized. Next to that, finding views (findViewById()) is also relatively slow. To improve on that, check out the ViewHolder pattern, which keeps references to views in memory so they don't have to be searched for each time.
I think this link can help you. getview is a callback function which will be called automatically when you will display your listview on Activity. When you display your listview then you overrides getview and inflates your row from XML or dynamically creates your row. That row you return as a view which displays in your listview.
How does the getView() method work when creating your own custom adapter?
For each row getview will be called once. You create your layouts and return them as view. Those respective views displays in your lisview rows.
You are calling the custom adapter class from you activity class.Your customised adapter class extends a BaseAdapter which is an abstract class.The methods of an abstract will be used by the extended class(the methods like getView(), getItemId(), getItem(), and getCount()).These methods should not need a seperate call from your Class since you are calling the customised adapter classs .

How to Implement Custom List View for the list Items in Android Application

I had a problem with the list view having both parent list and the child list of the list activity(implemented through database query). I wish to show them differing their properties by changing the text style (parent list items are in bold, child list items are in normal style).
I wish to differ with Parentid(Null, NotNull)in their text style(bold, normal) for parent and child items respectively. Please help me with the code/links. Thanks a lot in advance.
Maybe an ExpandableListAdapter would be a way to go? (You can make the parent elements non-expandable if you want.)
If you want to stick with the simple list, you can override getView(int position, View convertView, ViewGroup parent).
And maybe also override bindView(View view, Context context, Cursor cursor).
I have used the option of overriding bindView() to add a tag to a view and examine this later on. Maybe this would also work for you...

How can I update one view at a time in an ArrayAdapter?

I want to be able to access my ArrayAdapter's view:
public View getView(int position, View convertView, ViewGroup parent)
I'm not sure how I can access this:
View myView = myArrayAdapter.getView(myPosition, myView, ?);
I am not sure how I can get a ViewGroup parent?
Well as far as I understand you don't suppose to Adapter in general serves as a source to instance of AdapterView so getView contract is follows :
in params : inPosition,convertView,viewParent
result : View witch will be shown at position inPosition , you can use convertView to bind data to if it's not null, returned view will be attached to viewParent.
So if you want to acquire view that will be shown by adapter view at specific position, why don't just call
AdapterView<?> adapterView = getAdapterView();
View myView = adapterView.getChildAt(position);
If you want to change way of showing view at specific position you should use
Adapter myAdapter = getAdapter();
//change data inside adapter
myAdapter.notifyDataSetChanged();
Update:
Try adding a field to the data in the data set that holds the background resource/color to be used when returning the view, and in the getView do
holder.background = dataSet.get(position).getBackground()
If you don't know what I'm talking about with this holder thing, check How to load the Listview "smoothly" in android
Old:
I'd say the ListView containing the adapter is the parent ViewGroup.
Anyway, why don't you use the ListView containing the ArrayAdapter? The ListView is the container of the Views, rather than the adapter, that only holds the data collection and creates and returns Views on demand when the ListView asks for them (f.e, when scrolling). Even if you were able to fetch a view for the position X, I'd say that won't work, as the convertView you pass as a parameter is not the one the ListView is holding and showing.
Take into account that in a ListView there are at most 7-8 Views inflated at any given moment (I don't know the exact number), and what the ListView does is fill them in by calling the adapter's getview.
This said, to update a single row (a single view) you'll need to update the adapter's data collection. Then, speculating, try to get that View from the ListView and invalidate it, but I doubt this'll work.
I think these concepts are right, if they are wrong I'd be grateful if anyone corrects me.
Why do you want to update only one view at a time?

Categories