Develop Reference

Android how to get an ancestor view from a child view?

I have a list of type Foo with a custom array Adapter. I want to be able to click on a child element in one of the views in the array adapter and get back the view I clicked on of type Foo.
This is how I am clicking on a child element:
// fill array with a test set of objects
final ArrayList<Foo> locations = Foo.getTestingList();
final myCustomArrayAdapter adapter = new myCustomArrayAdapter(rootView.getContext(), myarrayList);
adapter.setDefaultRequestBtnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v){
//if child element is clicked
if(v.getId() == R.id.deleteBTN){
//tag is set to the position in my custom adapter
int pos = (Integer)v.getTag();
//Get this child's parent view (type foo)
}
}
});
I want to be able to use certain Foo methods on the Fooparent of the child View I just clicked on.

If you wanna get the direct parent of a view, you can call the method getParent() and it will return immediate parent of the target view. Note, this method doesn't directly return a view but instead a ViewParent. ViewParent does not technically need to be a View but all views capable of holding child views i.e. a "view parent" in the Android SDK are of type ViewGroup which itself implements the ViewParent. So in reality virtually all ViewParents are a ViewGroup, which in itself is a View.
Furthermore, if you wanna access an ancestor view that's beyond the direct parent, you can recursively call getParent() and perform checks on the return parent view to determine if they are the desired view.

Re-arrange the view order on Framelayout android

I've add five views on frameLayout.
how to re arrange the childIndex of framelayout.
i use below code:
fromindex = 3;
toindex = 4;
View tempFrom = frameLayout.getChildAt(fromindex);
View tempTo = frameLayout.getChildAt(toindex);
frameLayout.removeViewAt(fromindex)
frameLayout.removeViewAt(toindex)
frameLayout.addView(tempFrom, toindex)
frameLayout.addView(tempTo,fromindex)
But its throws the below error.
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
How to re arrange the childindex of framelayout ?

how to re arrange the childIndex of framelayout.
The FrameLayout doesn't have the ability to re arrange its children directly but you can do it by removing those children and re adding them in the right positions. Your code doesn't work because you remove the views in an incorrect order resulting in views still being attached to the parent:
fromindex = 3;
toindex = 4;
View tempFrom = frameLayout.getChildAt(fromindex);
View tempTo = frameLayout.getChildAt(toindex);
// first remove the view which is above in the parent's stack
// otherwise, if you remove the other child you'll call the `removeViewAt`
// method with the wrong index and the view which was supposed to be detached
// from the parent is still attached to it
frameLayout.removeViewAt(toindex);
frameLayout.removeViewAt(fromindex);
// first add the child which is lower in the hierarchy so you add the views
// in the correct order
frameLayout.addView(tempTo,fromindex)
frameLayout.addView(tempFrom, toindex)

Try this code
frameLayout.removeView(tempFrom) //to remove views
frameLayout.removeView(tempTo)

You can't swap views I think. You need to define new view group and inflate to his parent and remove old one.
View C = findViewById(R.id.C);
ViewGroup parent = (ViewGroup) C.getParent();
int index = parent.indexOfChild(C);
parent.removeView(C);
C = getLayoutInflater().inflate(optionId, parent, false);
parent.addView(C, index);

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);

How to find element inside a gridview in Android?

I have a grid view which I populate using a custom adapter.
While populating the gridview I give each element inside a unique tag.
Once this gridview is populated, I wish to find a specific element inside the gridview with its tag. How do I find this?
Currently I'm doing this:
gridviewobject.findViewById(thetag);
// gridview object is the object of the gridview that i have populated.

What you have written above will work, except be aware that a) searching for a view by its tag is probably the slowest method you could use to find a view and b) if you try requesting a view with a tag and that view is not currently visible, then you will get null.
This is because GridView recycles its views, so essentially it only ever makes enough views to fit on screen, and then just changes the positions and content of these as you scroll about.
Possibly a better way might be to do
final int numVisibleChildren = gridView.getChildCount();
final int firstVisiblePosition = gridView.getFirstVisiblePosition();
for ( int i = 0; i < numVisibleChildren; i++ ) {
int positionOfView = firstVisiblePosition + i;
if (positionOfView == positionIamLookingFor) {
View view = gridView.getChildAt(i);
}
}
Essentially findViewWithTag does something similar, but rather than comparing integers it compares the tags (which is slower since they're objects and not ints)

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.