214 lines
7.4 KiB
Java
214 lines
7.4 KiB
Java
package org.thoughtcrime.securesms.util;
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import android.graphics.Canvas;
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import android.graphics.Rect;
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import android.os.Build.VERSION;
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import androidx.annotation.NonNull;
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import androidx.core.view.ViewCompat;
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import androidx.recyclerview.widget.LinearLayoutManager;
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import androidx.recyclerview.widget.RecyclerView;
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import androidx.recyclerview.widget.RecyclerView.ViewHolder;
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import android.view.View;
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import android.view.ViewGroup;
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import java.util.HashMap;
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import java.util.Map;
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/**
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* A sticky header decoration for android's RecyclerView.
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* Currently only supports LinearLayoutManager in VERTICAL orientation.
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*/
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public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
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private static final String TAG = StickyHeaderDecoration.class.getSimpleName();
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private static final long NO_HEADER_ID = -1L;
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private final Map<Long, ViewHolder> headerCache;
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private final StickyHeaderAdapter adapter;
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private final boolean renderInline;
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private boolean sticky;
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/**
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* @param adapter the sticky header adapter to use
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*/
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public StickyHeaderDecoration(StickyHeaderAdapter adapter, boolean renderInline, boolean sticky) {
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this.adapter = adapter;
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this.headerCache = new HashMap<>();
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this.renderInline = renderInline;
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this.sticky = sticky;
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent,
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@NonNull RecyclerView.State state)
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{
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int position = parent.getChildAdapterPosition(view);
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int headerHeight = 0;
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if (position != RecyclerView.NO_POSITION && hasHeader(parent, adapter, position)) {
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View header = getHeader(parent, adapter, position).itemView;
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headerHeight = getHeaderHeightForLayout(header);
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}
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outRect.set(0, headerHeight, 0, 0);
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}
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protected boolean hasHeader(RecyclerView parent, StickyHeaderAdapter adapter, int adapterPos) {
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boolean isReverse = isReverseLayout(parent);
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int itemCount = ((RecyclerView.Adapter)adapter).getItemCount();
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if ((isReverse && adapterPos == itemCount - 1 && adapter.getHeaderId(adapterPos) != -1) ||
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(!isReverse && adapterPos == 0))
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{
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return true;
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}
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int previous = adapterPos + (isReverse ? 1 : -1);
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long headerId = adapter.getHeaderId(adapterPos);
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long previousHeaderId = adapter.getHeaderId(previous);
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return headerId != NO_HEADER_ID && previousHeaderId != NO_HEADER_ID && headerId != previousHeaderId;
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}
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protected ViewHolder getHeader(RecyclerView parent, StickyHeaderAdapter adapter, int position) {
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final long key = adapter.getHeaderId(position);
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ViewHolder headerHolder = headerCache.get(key);
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if (headerHolder == null) {
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headerHolder = adapter.onCreateHeaderViewHolder(parent);
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//noinspection unchecked
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adapter.onBindHeaderViewHolder(headerHolder, position);
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headerCache.put(key, headerHolder);
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}
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final View header = headerHolder.itemView;
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int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
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int heightSpec = View.MeasureSpec.makeMeasureSpec(parent.getHeight(), View.MeasureSpec.UNSPECIFIED);
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int childWidth = ViewGroup.getChildMeasureSpec(widthSpec,
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parent.getPaddingLeft() + parent.getPaddingRight(), header.getLayoutParams().width);
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int childHeight = ViewGroup.getChildMeasureSpec(heightSpec,
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parent.getPaddingTop() + parent.getPaddingBottom(), header.getLayoutParams().height);
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header.measure(childWidth, childHeight);
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header.layout(0, 0, header.getMeasuredWidth(), header.getMeasuredHeight());
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return headerHolder;
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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public void onDrawOver(@NonNull Canvas c, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
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final int count = parent.getChildCount();
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for (int layoutPos = 0; layoutPos < count; layoutPos++) {
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final View child = parent.getChildAt(translatedChildPosition(parent, layoutPos));
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final int adapterPos = parent.getChildAdapterPosition(child);
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if (adapterPos != RecyclerView.NO_POSITION && ((layoutPos == 0 && sticky) || hasHeader(parent, adapter, adapterPos))) {
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View header = getHeader(parent, adapter, adapterPos).itemView;
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c.save();
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final int left = child.getLeft();
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final int top = getHeaderTop(parent, child, header, adapterPos, layoutPos);
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c.translate(left, top);
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header.draw(c);
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c.restore();
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}
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}
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}
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protected int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos,
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int layoutPos)
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{
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int headerHeight = getHeaderHeightForLayout(header);
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int top = getChildY(parent, child) - headerHeight;
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if (sticky && layoutPos == 0) {
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final int count = parent.getChildCount();
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final long currentId = adapter.getHeaderId(adapterPos);
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// find next view with header and compute the offscreen push if needed
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for (int i = 1; i < count; i++) {
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int adapterPosHere = parent.getChildAdapterPosition(parent.getChildAt(translatedChildPosition(parent, i)));
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if (adapterPosHere != RecyclerView.NO_POSITION) {
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long nextId = adapter.getHeaderId(adapterPosHere);
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if (nextId != currentId) {
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final View next = parent.getChildAt(translatedChildPosition(parent, i));
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final int offset = getChildY(parent, next) - (headerHeight + getHeader(parent, adapter, adapterPosHere).itemView.getHeight());
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if (offset < 0) {
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return offset;
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} else {
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break;
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}
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}
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}
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}
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if (sticky) top = Math.max(0, top);
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}
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return top;
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}
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private int translatedChildPosition(RecyclerView parent, int position) {
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return isReverseLayout(parent) ? parent.getChildCount() - 1 - position : position;
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}
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private int getChildY(RecyclerView parent, View child) {
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if (VERSION.SDK_INT < 11) {
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Rect rect = new Rect();
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parent.getChildVisibleRect(child, rect, null);
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return rect.top;
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} else {
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return (int)ViewCompat.getY(child);
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}
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}
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protected int getHeaderHeightForLayout(View header) {
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return renderInline ? 0 : header.getHeight();
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}
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private boolean isReverseLayout(final RecyclerView parent) {
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return (parent.getLayoutManager() instanceof LinearLayoutManager) &&
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((LinearLayoutManager)parent.getLayoutManager()).getReverseLayout();
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}
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/**
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* The adapter to assist the {@link StickyHeaderDecoration} in creating and binding the header views.
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*
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* @param <T> the header view holder
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*/
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public interface StickyHeaderAdapter<T extends ViewHolder> {
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/**
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* Returns the header id for the item at the given position.
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*
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* @param position the item position
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* @return the header id
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*/
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long getHeaderId(int position);
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/**
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* Creates a new header ViewHolder.
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*
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* @param parent the header's view parent
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* @return a view holder for the created view
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*/
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T onCreateHeaderViewHolder(ViewGroup parent);
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/**
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* Updates the header view to reflect the header data for the given position
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* @param viewHolder the header view holder
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* @param position the header's item position
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*/
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void onBindHeaderViewHolder(T viewHolder, int position);
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}
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} |