package com.timehop.stickyheadersrecyclerview;
import android.graphics.Rect;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import com.timehop.stickyheadersrecyclerview.caching.HeaderProvider;
import com.timehop.stickyheadersrecyclerview.calculation.DimensionCalculator;
import com.timehop.stickyheadersrecyclerview.util.OrientationProvider;
/**
* Calculates the position and location of header views
*/
public class HeaderPositionCalculator {
private final StickyRecyclerHeadersAdapter mAdapter;
private final OrientationProvider mOrientationProvider;
private final HeaderProvider mHeaderProvider;
private final DimensionCalculator mDimensionCalculator;
/**
* The following fields are used as buffers for internal calculations. Their sole purpose is to avoid
* allocating new Rect every time we need one.
*/
private final Rect mTempRect1 = new Rect();
private final Rect mTempRect2 = new Rect();
public HeaderPositionCalculator(StickyRecyclerHeadersAdapter adapter, HeaderProvider headerProvider,
OrientationProvider orientationProvider, DimensionCalculator dimensionCalculator) {
mAdapter = adapter;
mHeaderProvider = headerProvider;
mOrientationProvider = orientationProvider;
mDimensionCalculator = dimensionCalculator;
}
/**
* Determines if a view should have a sticky header.
* The view has a sticky header if:
* 1. It is the first element in the recycler view
* 2. It has a valid ID associated to its position
*
* @param itemView given by the RecyclerView
* @param orientation of the Recyclerview
* @param position of the list item in question
* @return True if the view should have a sticky header
*/
public boolean hasStickyHeader(View itemView, int orientation, int position) {
int offset, margin;
mDimensionCalculator.initMargins(mTempRect1, itemView);
if (orientation == LinearLayout.VERTICAL) {
offset = itemView.getTop();
margin = mTempRect1.top;
} else {
offset = itemView.getLeft();
margin = mTempRect1.left;
}
return offset <= margin && mAdapter.getHeaderId(position) >= 0;
}
/**
* Determines if an item in the list should have a header that is different than the item in the
* list that immediately precedes it. Items with no headers will always return false.
*
* @param position of the list item in questions
* @param isReverseLayout TRUE if layout manager has flag isReverseLayout
* @return true if this item has a different header than the previous item in the list
*/
public boolean hasNewHeader(int position, boolean isReverseLayout) {
if (indexOutOfBounds(position)) {
return false;
}
long headerId = mAdapter.getHeaderId(position);
if (headerId < 0) {
return false;
}
long nextItemHeaderId = -1;
int nextItemPosition = position + (isReverseLayout? 1: -1);
if (!indexOutOfBounds(nextItemPosition)){
nextItemHeaderId = mAdapter.getHeaderId(nextItemPosition);
}
int firstItemPosition = isReverseLayout? mAdapter.getItemCount()-1 : 0;
return position == firstItemPosition || headerId != nextItemHeaderId;
}
private boolean indexOutOfBounds(int position) {
return position < 0 || position >= mAdapter.getItemCount();
}
public void initHeaderBounds(Rect bounds, RecyclerView recyclerView, View header, View firstView, boolean firstHeader) {
int orientation = mOrientationProvider.getOrientation(recyclerView);
initDefaultHeaderOffset(bounds, recyclerView, header, firstView, orientation);
if (firstHeader && isStickyHeaderBeingPushedOffscreen(recyclerView, header)) {
View viewAfterNextHeader = getFirstViewUnobscuredByHeader(recyclerView, header);
int firstViewUnderHeaderPosition = recyclerView.getChildAdapterPosition(viewAfterNextHeader);
View secondHeader = mHeaderProvider.getHeader(recyclerView, firstViewUnderHeaderPosition);
translateHeaderWithNextHeader(recyclerView, mOrientationProvider.getOrientation(recyclerView), bounds,
header, viewAfterNextHeader, secondHeader);
}
}
private void initDefaultHeaderOffset(Rect headerMargins, RecyclerView recyclerView, View header, View firstView, int orientation) {
int translationX, translationY;
mDimensionCalculator.initMargins(mTempRect1, header);
ViewGroup.LayoutParams layoutParams = firstView.getLayoutParams();
int leftMargin = 0;
int topMargin = 0;
if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
ViewGroup.MarginLayoutParams marginLayoutParams = (ViewGroup.MarginLayoutParams) layoutParams;
leftMargin = marginLayoutParams.leftMargin;
topMargin = marginLayoutParams.topMargin;
}
if (orientation == LinearLayoutManager.VERTICAL) {
translationX = firstView.getLeft() - leftMargin + mTempRect1.left;
translationY = Math.max(
firstView.getTop() - topMargin - header.getHeight() - mTempRect1.bottom,
getListTop(recyclerView) + mTempRect1.top);
} else {
translationY = firstView.getTop() - topMargin + mTempRect1.top;
translationX = Math.max(
firstView.getLeft() - leftMargin - header.getWidth() - mTempRect1.right,
getListLeft(recyclerView) + mTempRect1.left);
}
headerMargins.set(translationX, translationY, translationX + header.getWidth(),
translationY + header.getHeight());
}
private boolean isStickyHeaderBeingPushedOffscreen(RecyclerView recyclerView, View stickyHeader) {
View viewAfterHeader = getFirstViewUnobscuredByHeader(recyclerView, stickyHeader);
int firstViewUnderHeaderPosition = recyclerView.getChildAdapterPosition(viewAfterHeader);
if (firstViewUnderHeaderPosition == RecyclerView.NO_POSITION) {
return false;
}
boolean isReverseLayout = mOrientationProvider.isReverseLayout(recyclerView);
if (firstViewUnderHeaderPosition > 0 && hasNewHeader(firstViewUnderHeaderPosition, isReverseLayout)) {
View nextHeader = mHeaderProvider.getHeader(recyclerView, firstViewUnderHeaderPosition);
mDimensionCalculator.initMargins(mTempRect1, nextHeader);
mDimensionCalculator.initMargins(mTempRect2, stickyHeader);
if (mOrientationProvider.getOrientation(recyclerView) == LinearLayoutManager.VERTICAL) {
int topOfNextHeader = viewAfterHeader.getTop() - mTempRect1.bottom - nextHeader.getHeight() - mTempRect1.top;
int bottomOfThisHeader = recyclerView.getPaddingTop() + stickyHeader.getBottom() + mTempRect2.top + mTempRect2.bottom;
if (topOfNextHeader < bottomOfThisHeader) {
return true;
}
} else {
int leftOfNextHeader = viewAfterHeader.getLeft() - mTempRect1.right - nextHeader.getWidth() - mTempRect1.left;
int rightOfThisHeader = recyclerView.getPaddingLeft() + stickyHeader.getRight() + mTempRect2.left + mTempRect2.right;
if (leftOfNextHeader < rightOfThisHeader) {
return true;
}
}
}
return false;
}
private void translateHeaderWithNextHeader(RecyclerView recyclerView, int orientation, Rect translation,
View currentHeader, View viewAfterNextHeader, View nextHeader) {
mDimensionCalculator.initMargins(mTempRect1, nextHeader);
mDimensionCalculator.initMargins(mTempRect2, currentHeader);
if (orientation == LinearLayoutManager.VERTICAL) {
int topOfStickyHeader = getListTop(recyclerView) + mTempRect2.top + mTempRect2.bottom;
int shiftFromNextHeader = viewAfterNextHeader.getTop() - nextHeader.getHeight() - mTempRect1.bottom - mTempRect1.top - currentHeader.getHeight() - topOfStickyHeader;
if (shiftFromNextHeader < topOfStickyHeader) {
translation.top += shiftFromNextHeader;
}
} else {
int leftOfStickyHeader = getListLeft(recyclerView) + mTempRect2.left + mTempRect2.right;
int shiftFromNextHeader = viewAfterNextHeader.getLeft() - nextHeader.getWidth() - mTempRect1.right - mTempRect1.left - currentHeader.getWidth() - leftOfStickyHeader;
if (shiftFromNextHeader < leftOfStickyHeader) {
translation.left += shiftFromNextHeader;
}
}
}
/**
* Returns the first item currently in the RecyclerView that is not obscured by a header.
*
* @param parent Recyclerview containing all the list items
* @return first item that is fully beneath a header
*/
private View getFirstViewUnobscuredByHeader(RecyclerView parent, View firstHeader) {
boolean isReverseLayout = mOrientationProvider.isReverseLayout(parent);
int step = isReverseLayout? -1 : 1;
int from = isReverseLayout? parent.getChildCount()-1 : 0;
for (int i = from; i >= 0 && i <= parent.getChildCount() - 1; i += step) {
View child = parent.getChildAt(i);
if (!itemIsObscuredByHeader(parent, child, firstHeader, mOrientationProvider.getOrientation(parent))) {
return child;
}
}
return null;
}
/**
* Determines if an item is obscured by a header
*
*
* @param parent
* @param item to determine if obscured by header
* @param header that might be obscuring the item
* @param orientation of the {@link RecyclerView}
* @return true if the item view is obscured by the header view
*/
private boolean itemIsObscuredByHeader(RecyclerView parent, View item, View header, int orientation) {
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) item.getLayoutParams();
mDimensionCalculator.initMargins(mTempRect1, header);
int adapterPosition = parent.getChildAdapterPosition(item);
if (adapterPosition == RecyclerView.NO_POSITION || mHeaderProvider.getHeader(parent, adapterPosition) != header) {
// Resolves https://github.com/timehop/sticky-headers-recyclerview/issues/36
// Handles an edge case where a trailing header is smaller than the current sticky header.
return false;
}
if (orientation == LinearLayoutManager.VERTICAL) {
int itemTop = item.getTop() - layoutParams.topMargin;
int headerBottom = getListTop(parent) + header.getBottom() + mTempRect1.bottom + mTempRect1.top;
if (itemTop >= headerBottom) {
return false;
}
} else {
int itemLeft = item.getLeft() - layoutParams.leftMargin;
int headerRight = getListLeft(parent) + header.getRight() + mTempRect1.right + mTempRect1.left;
if (itemLeft >= headerRight) {
return false;
}
}
return true;
}
private int getListTop(RecyclerView view) {
if (view.getLayoutManager().getClipToPadding()) {
return view.getPaddingTop();
} else {
return 0;
}
}
private int getListLeft(RecyclerView view) {
if (view.getLayoutManager().getClipToPadding()) {
return view.getPaddingLeft();
} else {
return 0;
}
}
}
