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Luna Wei
bd3023abea
Summary:
[Android][Fix] - Fix how we normalize indices
Before, we were incorrectly normalizing indices given pending view deletion in the view hierarchy (namely, using LayoutAnimations)
What we had before (that was wrong):
* Maintained a pendingIndices sparse array for each tag
* For each pendingIndices sparse array we'd keep track of how many views we deleted at each abstract index
* Given an abstract index to delete a view at, we'd consult `pendingIndices` array to sum how many pending deletes we had for indices equal or smaller than and add to abstract index
^ Above algorithm is wrong and you can follow along with the following example to see how.
## The correct approach
Given these operations in this order:
1. {tagsToDelete: [123], indicesToDelete [2]}
2. {tagsToDelete: [124], indicesToDelete [1]}
3. {tagsToDelete: [125], indicesToDelete [2]}
4. {tagsToDelete: [126], indicesToDelete [1]}
The approach we want to be using to calculate normalized indices:
### Step 1: Delete tag 124 at index 2
|Views:|122|123|124|125|126|127|
|Actual Indices:|0|1|2|3|4|5|
|Abstract Indices:|0|1|2|3|4|5|
=> simple, we just mark the view at 2
### Step 2: Delete tag 123 at index 1
View tags and indices:
|Views|122|123|~~124~~|125|126|127|
|Actual indices|0|1|~~2~~|3|4|5|
|Abstract Indices|0|1||2|3|4|
=> again, simple, we can just use the normalized index 1 because no pending deletes affect this operation
### Step 3: Delete tag 126 at index 2
View tags and indices:
|Views|122|~~123~~|~~124~~|125|126|127|
|Actual Indices|0|~~1~~|~~2~~|3|4|5|
|Abstract Indices|0|||1|2|3|
=> Here we want to normalize this index to 4 because we need to account the 2 views that should be skipped
### Step 4: Delete tag 125 at index 1
View tags and indices:
|Views|122|~~123~~|~~124~~|125|~~126~~|127|
|Actual Indices|0|~~1~~|~~2~~|3|~~4~~|5|
|Abstract Indices|0|||1||2|
=> The normalized index should be 3.
This diff updates the function `normalizeIndex` to do the above algorithm by repurposing `pendingIndicesToDelete` to instead be a sparse int array that holds [normalizedIndex]=[tag] pairs
It's required that `pendingIndicesToDelete` is ordered by the normalizedIndex.
Reviewed By: mdvacca
Differential Revision: D15485132
fbshipit-source-id: 43e57dffa807e8ea50fa1650c5dec13a6fded624
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