package cn.sinata.xldutils.widget;
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import android.content.Context;
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import android.graphics.Canvas;
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import android.util.AttributeSet;
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import android.view.View;
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import android.widget.ListAdapter;
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import android.widget.ListView;
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public class PinnedHeaderListView extends ListView {
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/**
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* Adapter interface. The list adapter must implement this interface.
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*/
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public interface PinnedHeaderAdapter {
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/**
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* Pinned header state: don't show the header.
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*/
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public static final int PINNED_HEADER_GONE = 0;
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/**
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* Pinned header state: show the header at the top of the list.
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*/
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public static final int PINNED_HEADER_VISIBLE = 1;
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/**
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* Pinned header state: show the header. If the header extends beyond
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* the bottom of the first shown element, push it up and clip.
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*/
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public static final int PINNED_HEADER_PUSHED_UP = 2;
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/**
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* Computes the desired state of the pinned header for the given
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* position of the first visible list item. Allowed return values are
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* {@link #PINNED_HEADER_GONE}, {@link #PINNED_HEADER_VISIBLE} or
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* {@link #PINNED_HEADER_PUSHED_UP}.
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*/
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int getPinnedHeaderState(int position);
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/**
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* Configures the pinned header view to match the first visible list item.
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*
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* @param header pinned header view.
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* @param position position of the first visible list item.
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* @param alpha fading of the header view, between 0 and 255.
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*/
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void configurePinnedHeader(View header, int position, int alpha);
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}
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private static final int MAX_ALPHA = 255;
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private PinnedHeaderAdapter mAdapter;
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private View mHeaderView;
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private boolean mHeaderViewVisible;
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private int mHeaderViewWidth;
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private int mHeaderViewHeight;
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public PinnedHeaderListView(Context context) {
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super(context);
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}
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public PinnedHeaderListView(Context context, AttributeSet attrs) {
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super(context, attrs);
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}
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public PinnedHeaderListView(Context context, AttributeSet attrs, int defStyle) {
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super(context, attrs, defStyle);
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}
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public void setPinnedHeaderView(View view) {
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mHeaderView = view;
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// Disable vertical fading when the pinned header is present
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// TODO change ListView to allow separate measures for top and bottom fading edge;
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// in this particular case we would like to disable the top, but not the bottom edge.
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if (mHeaderView != null) {
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setFadingEdgeLength(0);
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}
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requestLayout();
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}
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@Override
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public void setAdapter(ListAdapter adapter) {
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super.setAdapter(adapter);
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mAdapter = (PinnedHeaderAdapter)adapter;
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}
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@Override
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protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
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super.onMeasure(widthMeasureSpec, heightMeasureSpec);
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if (mHeaderView != null) {
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measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
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mHeaderViewWidth = mHeaderView.getMeasuredWidth();
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mHeaderViewHeight = mHeaderView.getMeasuredHeight();
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}
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}
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@Override
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protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
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super.onLayout(changed, left, top, right, bottom);
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if (mHeaderView != null) {
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mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
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configureHeaderView(getFirstVisiblePosition());
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}
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}
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public void configureHeaderView(int position) {
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if (mHeaderView == null) {
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return;
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}
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int state = mAdapter.getPinnedHeaderState(position);
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switch (state) {
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case PinnedHeaderAdapter.PINNED_HEADER_GONE: {
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mHeaderViewVisible = false;
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break;
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}
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case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE: {
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mAdapter.configurePinnedHeader(mHeaderView, position, MAX_ALPHA);
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if (mHeaderView.getTop() != 0) {
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mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
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}
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mHeaderViewVisible = true;
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break;
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}
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case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP: {
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View firstView = getChildAt(0);
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int bottom = firstView.getBottom();
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int itemHeight = firstView.getHeight();
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int headerHeight = mHeaderView.getHeight();
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int y;
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int alpha;
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if (bottom < headerHeight) {
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y = (bottom - headerHeight);
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alpha = MAX_ALPHA * (headerHeight + y) / headerHeight;
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} else {
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y = 0;
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alpha = MAX_ALPHA;
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}
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mAdapter.configurePinnedHeader(mHeaderView, position, alpha);
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if (mHeaderView.getTop() != y) {
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mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight + y);
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}
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mHeaderViewVisible = true;
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break;
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}
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}
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}
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@Override
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protected void dispatchDraw(Canvas canvas) {
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super.dispatchDraw(canvas);
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if (mHeaderViewVisible) {
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drawChild(canvas, mHeaderView, getDrawingTime());
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}
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}
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}
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