Develop Reference

Children not clickable outside parent view

I have a created a mapview with markers on it.
Looking at this picture below:
Grandparent is a filling View
Parent is my MarkerView
Child is a marker which is clickable
Parent has clipChildren(false) and thus the children are visible.
My problem is that the children are clickable, except for the part where Child 2 is outside the Parent.
Parent also has the appropriate TouchDelegate (and I also tried this for the children).
How can I make the complete child clickable?

I couldn't make it work without changing the elements.
I ended up enlarging the parent and using setTranslationY for the markers to keep them in place like this:

I had a similar issue and fixed it by setting app:elevation="XXdp" to the child.

The reason why you can't do this is that the default implementation of ViewGroup#dispatchTouchEvent(MotionEvent ev) iterates over the children (not the grandchildren) to look for a child that are a target (is on bottom of the click event point) and can receive touch events. It will find nothing if you touched the part that it is outside the bounds of Parent, which is the only child of Grandparent. If it does not find Parent, Parent will never be able to make a look up on its children (Children 1 and Children 2) and eventually dispatch the event to Child 2.
So you either increase the size of Parent (as the acceptable answer), which is the most easy way, or you will have to override the method ViewGroup#dispatchTouchEvent(MotionEvent ev) of your Grandparent to make a more complex lookup, like looking up grandchildren too. The method is already fairly complex, if anyone finds a implementation, please share because I don't have one.

android - what is view hierarchy?

I'm studying android, of course I'm novice, I always read something like view hierarchy, so what exactly does this mean? what is view hierarchy? e.g.
// fragment's containing frame doesn't exist. The fragment
// may still be created from its saved state, but there is
// no reason to try to create its view hierarchy because it
// won't be displayed. Note this is not needed -- we could
// just run the code below, where we would create and return
// the view hierarchy; it would just never be used.
http://developer.android.com/reference/android/app/Fragment.html

A View inside another View creates an hierarchy, the outer view becomes the parent of the inner view and the inner view is its child. It's just nested views.
Here's an example:

You'll want to read the docs on the View class, but essentially views can be children of certain other views. You can nest views in complicated ways. This whole structure of views is referred to as the view hierarchy.

http://i.stack.imgur.com/gN6AO.png
Each view in a user interface represents a rectangular area of the display. A view is responsible for what is drawn in that rectangle and for responding to events that occur within that part of the screen (such as a touch event).
A user interface screen is comprised of a view hierarchy with a root view positioned at the top of the tree and child views positioned on branches below. The child of a container view appears on top of its parent view and is constrained to appear within the bounds of the parent view’s display area.
you can refer to this link : [
http://www.techotopia.com/index.php/Understanding_Android_Views,_View_Groups_and_Layouts_in_Android_Studio][1]

Parent view draw child view efficient

For example, top level LinearLayout view has 300 child view. But device screen dimension only show 11 child view once. How android compute how many child views can show once? How a view know that it will be draw?
Edited
In my work, one case like this:
An parent LinearLayout view may be has hundreds child view. In order to better performance , my solution like this:like lazy load.
List list = new ArrayList();//contain entity object that use construct View object
Default load 5 child view.
Parent LinearLayout view last child view is custom Loading View, I have override it`s onDraw() method. If loading View is draw, that means i need get next 5 child view(get next 5 object from list,and create correspond view).
I want to know how android framework handle this case?

Have u used scroll bar inside the top level LinearLayout view and add child view on that layout that's simple...

An parent LinearLayout view may be has hundreds child view. In order
to better performance , my solution like this:like lazy load.
LinearLayout with(possible) hundreds of child views kind of contradicts better performance. I think what you're looking for is a ListView with an endless adapter(a simple google search will show how to implement it, not something that difficult). This adapter will start loading views(with a loading view showing while the new content loads) as soon as you get to the last loaded element.
If you still want to use a LinearLayout:
If you just want to make the LinearLayout fill the content of the screen when it's first laid out you could post a Runnable on one of your views in the onCreate method (if this is where you'll first populate the LinearLayout). In that Runnable find the height of the LinearLayout and compare it with the combined height of its currently present children. If the combined child height is smaller then the LinearLayout height then add more views to compensate.
If the LinearLayout is in a ScrollView and you want to add additional children when the loading view becomes visible then monitor the scrolling of the ScrollView and when the loading view becomes visible add new children. Seeing when the loading view becomes visible would be done by checking how much the user has scrolled compared with the combined height of the currently present children of the LinearLayout.
Initial response:
Your question is a bit ambiguous regarding what you want to know. If you have a specific problem you should start with that.
For example, top level LinearLayout view has 300 child view. But
device screen dimension only show 11 child view once.
Please don't get yourself in a scenario like this. That number of views is to big an will result in poor performance or even the app crashing if you run out of memory(as all those views will be kept in memory).
How android compute how many child views can show once?
Each View and ViewGroup has the onMeasure method to measure itself and its children if available. The LinearLayout will have its onMeasure method called and in this method it will measure its children(with the measure method) giving them some suggestions on how big should they be(the LinearLayout receives some suggestions on how big it should be from its parent). If you want to see how this is done have a look at the source code of the LinearLayout.
How a view know that it will be draw?
I don't understand what you want to know. To draw the view on the screen its onDraw method will be called.

How to restrict bounds for Translate Animation for a view in Android?

Let me explain the scenario that I want to achieve:-
Consider the below as the Layout I have inside a Parent_Linearlayout:
[Linear Layout] (Fill_Parent, Wrap_Content)
[ScrollView]
Activity's setContentView is set to the Parent_Linearlayout
In the application, when a condition is met, I want the Scrollview to be removed from the screen and instead put another View in its place.
I've been able to do this, & when I remove the ScrollView, I'm applying translate Animation to it so that it seems as if the View has gone to the top -before removing it.
But when the animation occurs, the ScrollView translates OVER the Linear layout present above it.
How do I restrict it, so that the scrollview does not go over the linear layout, but disappears at the base of the Linearlayout. I want the linearlayout to always stay visible..
I've been trying to do this from quite some time, but I've not been able to get desired results..
Could someone kindly help me out here??

I don't quite understand your description of your layout, but the Android view system is drawn based on the ordering of the views in the hierarchy. Views added later to a parent are drawn after those added earlier. So if you always want the LinearLayout to be drawn on top of the ScrollView if/when they overlap, then declare or add the ScrollView object to its parent before the LinearLayout object.
In thinking more about this, I suppose the ordering here is important because you want the ScrollView to be placed below the LinearLayout in the parent of both of these views. Putting the ScrollView first (and thus having it painted first) would then put it above the other LinearLayout, which isn't what you want.
There are various ways to achieve what you want. For example, you could use a RelativeLayout as the parent of the views, then the ordering is not important.
Alternatively, you could place the ScrollView inside another LinearLayout (and that LinearLayout would be the second child of the overall parent layout). Then when you animate the ScrollView, it would be clipped by its immediate parent, which I believe would give you the effect you're looking for (make sure that setClipChildren() is set to true on this new intermediate LinearLayout, which it is by default, otherwise it won't clip the ScrollView as it animates out of it). Note that this approach would necessitate different animation values, since you are now animating the view outside of its parent (the new LinearLayout).

How to synchronize content of one view depending on scroll position in sibling ScrollView?

I have extended LinearLayout (vertical) to create a custom compound component. This in turn contains two children:
one custom view that is drawn directly onto the view canvas.
one HorizontalScrollView->LinearView(Horizontal)->Multiple custom views.
I would now like to redraw the custom view to match the visible contents of the scroll view. The reason for this is that the long array of custom components in the scroll view are mainly static and suitable to be drawn ahead of time, while the top view is supposed to be highly dynamic and relate to whatever things are visible in the scroll view.
I hope I made the problem/idea somewhat clear. I am not att all confident this is the best approach, and I'd enjoy hearing any suggestions on alternative solutions or perhaps some idea on how to trigger a redraw-event everytime the scroll position changes in the HorizontalScrollView.
Thank!

You can have your activity listen to the scroll view adapter. in the adapter when ever the scroll position changes you execute the delegate in the Activity.
That way the activity can update the rest of the views upon scroll view change.