common/list/PinnedHeaderListView.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.contacts.common.list;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ListAdapter;
import com.android.dialer.util.ViewUtil;

/**
 * A ListView that maintains a header pinned at the top of the list. The pinned header can be pushed
 * up and dissolved as needed.
 */
public class PinnedHeaderListView extends AutoScrollListView
    implements OnScrollListener, OnItemSelectedListener {

  private static final int MAX_ALPHA = 255;
  private static final int TOP = 0;
  private static final int BOTTOM = 1;
  private static final int FADING = 2;
  private static final int DEFAULT_ANIMATION_DURATION = 20;
  private static final int DEFAULT_SMOOTH_SCROLL_DURATION = 100;
  private PinnedHeaderAdapter mAdapter;
  private int mSize;
  private PinnedHeader[] mHeaders;
  private RectF mBounds = new RectF();
  private OnScrollListener mOnScrollListener;
  private OnItemSelectedListener mOnItemSelectedListener;
  private int mScrollState;
  private boolean mScrollToSectionOnHeaderTouch = false;
  private boolean mHeaderTouched = false;
  private int mAnimationDuration = DEFAULT_ANIMATION_DURATION;
  private boolean mAnimating;
  private long mAnimationTargetTime;
  private int mHeaderPaddingStart;
  private int mHeaderWidth;

  public PinnedHeaderListView(Context context) {
    this(context, null, android.R.attr.listViewStyle);
  }

  public PinnedHeaderListView(Context context, AttributeSet attrs) {
    this(context, attrs, android.R.attr.listViewStyle);
  }

  public PinnedHeaderListView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    super.setOnScrollListener(this);
    super.setOnItemSelectedListener(this);
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    super.onLayout(changed, l, t, r, b);
    mHeaderPaddingStart = getPaddingStart();
    mHeaderWidth = r - l - mHeaderPaddingStart - getPaddingEnd();
  }

  @Override
  public void setAdapter(ListAdapter adapter) {
    mAdapter = (PinnedHeaderAdapter) adapter;
    super.setAdapter(adapter);
  }

  @Override
  public void setOnScrollListener(OnScrollListener onScrollListener) {
    mOnScrollListener = onScrollListener;
    super.setOnScrollListener(this);
  }

  @Override
  public void setOnItemSelectedListener(OnItemSelectedListener listener) {
    mOnItemSelectedListener = listener;
    super.setOnItemSelectedListener(this);
  }

  public void setScrollToSectionOnHeaderTouch(boolean value) {
    mScrollToSectionOnHeaderTouch = value;
  }

  @Override
  public void onScroll(
      AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    if (mAdapter != null) {
      int count = mAdapter.getPinnedHeaderCount();
      if (count != mSize) {
        mSize = count;
        if (mHeaders == null) {
          mHeaders = new PinnedHeader[mSize];
        } else if (mHeaders.length < mSize) {
          PinnedHeader[] headers = mHeaders;
          mHeaders = new PinnedHeader[mSize];
          System.arraycopy(headers, 0, mHeaders, 0, headers.length);
        }
      }

      for (int i = 0; i < mSize; i++) {
        if (mHeaders[i] == null) {
          mHeaders[i] = new PinnedHeader();
        }
        mHeaders[i].view = mAdapter.getPinnedHeaderView(i, mHeaders[i].view, this);
      }

      mAnimationTargetTime = System.currentTimeMillis() + mAnimationDuration;
      mAdapter.configurePinnedHeaders(this);
      invalidateIfAnimating();
    }
    if (mOnScrollListener != null) {
      mOnScrollListener.onScroll(this, firstVisibleItem, visibleItemCount, totalItemCount);
    }
  }

  @Override
  protected float getTopFadingEdgeStrength() {
    // Disable vertical fading at the top when the pinned header is present
    return mSize > 0 ? 0 : super.getTopFadingEdgeStrength();
  }

  @Override
  public void onScrollStateChanged(AbsListView view, int scrollState) {
    mScrollState = scrollState;
    if (mOnScrollListener != null) {
      mOnScrollListener.onScrollStateChanged(this, scrollState);
    }
  }

  /**
   * Ensures that the selected item is positioned below the top-pinned headers and above the
   * bottom-pinned ones.
   */
  @Override
  public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    int height = getHeight();

    int windowTop = 0;
    int windowBottom = height;

    for (int i = 0; i < mSize; i++) {
      PinnedHeader header = mHeaders[i];
      if (header.visible) {
        if (header.state == TOP) {
          windowTop = header.y + header.height;
        } else if (header.state == BOTTOM) {
          windowBottom = header.y;
          break;
        }
      }
    }

    View selectedView = getSelectedView();
    if (selectedView != null) {
      if (selectedView.getTop() < windowTop) {
        setSelectionFromTop(position, windowTop);
      } else if (selectedView.getBottom() > windowBottom) {
        setSelectionFromTop(position, windowBottom - selectedView.getHeight());
      }
    }

    if (mOnItemSelectedListener != null) {
      mOnItemSelectedListener.onItemSelected(parent, view, position, id);
    }
  }

  @Override
  public void onNothingSelected(AdapterView<?> parent) {
    if (mOnItemSelectedListener != null) {
      mOnItemSelectedListener.onNothingSelected(parent);
    }
  }

  public int getPinnedHeaderHeight(int viewIndex) {
    ensurePinnedHeaderLayout(viewIndex);
    return mHeaders[viewIndex].view.getHeight();
  }

  /**
   * Set header to be pinned at the top.
   *
   * @param viewIndex index of the header view
   * @param y is position of the header in pixels.
   * @param animate true if the transition to the new coordinate should be animated
   */
  public void setHeaderPinnedAtTop(int viewIndex, int y, boolean animate) {
    ensurePinnedHeaderLayout(viewIndex);
    PinnedHeader header = mHeaders[viewIndex];
    header.visible = true;
    header.y = y;
    header.state = TOP;

    // TODO perhaps we should animate at the top as well
    header.animating = false;
  }

  /**
   * Set header to be pinned at the bottom.
   *
   * @param viewIndex index of the header view
   * @param y is position of the header in pixels.
   * @param animate true if the transition to the new coordinate should be animated
   */
  public void setHeaderPinnedAtBottom(int viewIndex, int y, boolean animate) {
    ensurePinnedHeaderLayout(viewIndex);
    PinnedHeader header = mHeaders[viewIndex];
    header.state = BOTTOM;
    if (header.animating) {
      header.targetTime = mAnimationTargetTime;
      header.sourceY = header.y;
      header.targetY = y;
    } else if (animate && (header.y != y || !header.visible)) {
      if (header.visible) {
        header.sourceY = header.y;
      } else {
        header.visible = true;
        header.sourceY = y + header.height;
      }
      header.animating = true;
      header.targetVisible = true;
      header.targetTime = mAnimationTargetTime;
      header.targetY = y;
    } else {
      header.visible = true;
      header.y = y;
    }
  }

  /**
   * Set header to be pinned at the top of the first visible item.
   *
   * @param viewIndex index of the header view
   * @param position is position of the header in pixels.
   */
  public void setFadingHeader(int viewIndex, int position, boolean fade) {
    ensurePinnedHeaderLayout(viewIndex);

    View child = getChildAt(position - getFirstVisiblePosition());
    if (child == null) {
      return;
    }

    PinnedHeader header = mHeaders[viewIndex];
    header.visible = true;
    header.state = FADING;
    header.alpha = MAX_ALPHA;
    header.animating = false;

    int top = getTotalTopPinnedHeaderHeight();
    header.y = top;
    if (fade) {
      int bottom = child.getBottom() - top;
      int headerHeight = header.height;
      if (bottom < headerHeight) {
        int portion = bottom - headerHeight;
        header.alpha = MAX_ALPHA * (headerHeight + portion) / headerHeight;
        header.y = top + portion;
      }
    }
  }

  /**
   * Makes header invisible.
   *
   * @param viewIndex index of the header view
   * @param animate true if the transition to the new coordinate should be animated
   */
  public void setHeaderInvisible(int viewIndex, boolean animate) {
    PinnedHeader header = mHeaders[viewIndex];
    if (header.visible && (animate || header.animating) && header.state == BOTTOM) {
      header.sourceY = header.y;
      if (!header.animating) {
        header.visible = true;
        header.targetY = getBottom() + header.height;
      }
      header.animating = true;
      header.targetTime = mAnimationTargetTime;
      header.targetVisible = false;
    } else {
      header.visible = false;
    }
  }

  private void ensurePinnedHeaderLayout(int viewIndex) {
    View view = mHeaders[viewIndex].view;
    if (view.isLayoutRequested()) {
      ViewGroup.LayoutParams layoutParams = view.getLayoutParams();
      int widthSpec;
      int heightSpec;

      if (layoutParams != null && layoutParams.width > 0) {
        widthSpec = View.MeasureSpec.makeMeasureSpec(layoutParams.width, View.MeasureSpec.EXACTLY);
      } else {
        widthSpec = View.MeasureSpec.makeMeasureSpec(mHeaderWidth, View.MeasureSpec.EXACTLY);
      }

      if (layoutParams != null && layoutParams.height > 0) {
        heightSpec =
            View.MeasureSpec.makeMeasureSpec(layoutParams.height, View.MeasureSpec.EXACTLY);
      } else {
        heightSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
      }
      view.measure(widthSpec, heightSpec);
      int height = view.getMeasuredHeight();
      mHeaders[viewIndex].height = height;
      view.layout(0, 0, view.getMeasuredWidth(), height);
    }
  }

  /** Returns the sum of heights of headers pinned to the top. */
  public int getTotalTopPinnedHeaderHeight() {
    for (int i = mSize; --i >= 0; ) {
      PinnedHeader header = mHeaders[i];
      if (header.visible && header.state == TOP) {
        return header.y + header.height;
      }
    }
    return 0;
  }

  /** Returns the list item position at the specified y coordinate. */
  public int getPositionAt(int y) {
    do {
      int position = pointToPosition(getPaddingLeft() + 1, y);
      if (position != -1) {
        return position;
      }
      // If position == -1, we must have hit a separator. Let's examine
      // a nearby pixel
      y--;
    } while (y > 0);
    return 0;
  }

  @Override
  public boolean onInterceptTouchEvent(MotionEvent ev) {
    mHeaderTouched = false;
    if (super.onInterceptTouchEvent(ev)) {
      return true;
    }

    if (mScrollState == SCROLL_STATE_IDLE) {
      final int y = (int) ev.getY();
      final int x = (int) ev.getX();
      for (int i = mSize; --i >= 0; ) {
        PinnedHeader header = mHeaders[i];
        // For RTL layouts, this also takes into account that the scrollbar is on the left
        // side.
        final int padding = getPaddingLeft();
        if (header.visible
            && header.y <= y
            && header.y + header.height > y
            && x >= padding
            && padding + header.view.getWidth() >= x) {
          mHeaderTouched = true;
          if (mScrollToSectionOnHeaderTouch && ev.getAction() == MotionEvent.ACTION_DOWN) {
            return smoothScrollToPartition(i);
          } else {
            return true;
          }
        }
      }
    }

    return false;
  }

  @Override
  public boolean onTouchEvent(MotionEvent ev) {
    if (mHeaderTouched) {
      if (ev.getAction() == MotionEvent.ACTION_UP) {
        mHeaderTouched = false;
      }
      return true;
    }
    return super.onTouchEvent(ev);
  }

  private boolean smoothScrollToPartition(int partition) {
    if (mAdapter == null) {
      return false;
    }
    final int position = mAdapter.getScrollPositionForHeader(partition);
    if (position == -1) {
      return false;
    }

    int offset = 0;
    for (int i = 0; i < partition; i++) {
      PinnedHeader header = mHeaders[i];
      if (header.visible) {
        offset += header.height;
      }
    }
    smoothScrollToPositionFromTop(
        position + getHeaderViewsCount(), offset, DEFAULT_SMOOTH_SCROLL_DURATION);
    return true;
  }

  private void invalidateIfAnimating() {
    mAnimating = false;
    for (int i = 0; i < mSize; i++) {
      if (mHeaders[i].animating) {
        mAnimating = true;
        invalidate();
        return;
      }
    }
  }

  @Override
  protected void dispatchDraw(Canvas canvas) {
    long currentTime = mAnimating ? System.currentTimeMillis() : 0;

    int top = 0;
    int bottom = getBottom();
    boolean hasVisibleHeaders = false;
    for (int i = 0; i < mSize; i++) {
      PinnedHeader header = mHeaders[i];
      if (header.visible) {
        hasVisibleHeaders = true;
        if (header.state == BOTTOM && header.y < bottom) {
          bottom = header.y;
        } else if (header.state == TOP || header.state == FADING) {
          int newTop = header.y + header.height;
          if (newTop > top) {
            top = newTop;
          }
        }
      }
    }

    if (hasVisibleHeaders) {
      canvas.save();
    }

    super.dispatchDraw(canvas);

    if (hasVisibleHeaders) {
      canvas.restore();

      // If the first item is visible and if it has a positive top that is greater than the
      // first header's assigned y-value, use that for the first header's y value. This way,
      // the header inherits any padding applied to the list view.
      if (mSize > 0 && getFirstVisiblePosition() == 0) {
        View firstChild = getChildAt(0);
        PinnedHeader firstHeader = mHeaders[0];

        if (firstHeader != null) {
          int firstHeaderTop = firstChild != null ? firstChild.getTop() : 0;
          firstHeader.y = Math.max(firstHeader.y, firstHeaderTop);
        }
      }

      // First draw top headers, then the bottom ones to handle the Z axis correctly
      for (int i = mSize; --i >= 0; ) {
        PinnedHeader header = mHeaders[i];
        if (header.visible && (header.state == TOP || header.state == FADING)) {
          drawHeader(canvas, header, currentTime);
        }
      }

      for (int i = 0; i < mSize; i++) {
        PinnedHeader header = mHeaders[i];
        if (header.visible && header.state == BOTTOM) {
          drawHeader(canvas, header, currentTime);
        }
      }
    }

    invalidateIfAnimating();
  }

  private void drawHeader(Canvas canvas, PinnedHeader header, long currentTime) {
    if (header.animating) {
      int timeLeft = (int) (header.targetTime - currentTime);
      if (timeLeft <= 0) {
        header.y = header.targetY;
        header.visible = header.targetVisible;
        header.animating = false;
      } else {
        header.y =
            header.targetY + (header.sourceY - header.targetY) * timeLeft / mAnimationDuration;
      }
    }
    if (header.visible) {
      View view = header.view;
      int saveCount = canvas.save();
      int translateX =
          ViewUtil.isViewLayoutRtl(this)
              ? getWidth() - mHeaderPaddingStart - view.getWidth()
              : mHeaderPaddingStart;
      canvas.translate(translateX, header.y);
      if (header.state == FADING) {
        mBounds.set(0, 0, view.getWidth(), view.getHeight());
        canvas.saveLayerAlpha(mBounds, header.alpha);
      }
      view.draw(canvas);
      canvas.restoreToCount(saveCount);
    }
  }

  /** Adapter interface. The list adapter must implement this interface. */
  public interface PinnedHeaderAdapter {

    /** Returns the overall number of pinned headers, visible or not. */
    int getPinnedHeaderCount();

    /** Creates or updates the pinned header view. */
    View getPinnedHeaderView(int viewIndex, View convertView, ViewGroup parent);

    /**
     * Configures the pinned headers to match the visible list items. The adapter should call {@link
     * PinnedHeaderListView#setHeaderPinnedAtTop}, {@link
     * PinnedHeaderListView#setHeaderPinnedAtBottom}, {@link PinnedHeaderListView#setFadingHeader}
     * or {@link PinnedHeaderListView#setHeaderInvisible}, for each header that needs to change its
     * position or visibility.
     */
    void configurePinnedHeaders(PinnedHeaderListView listView);

    /**
     * Returns the list position to scroll to if the pinned header is touched. Return -1 if the list
     * does not need to be scrolled.
     */
    int getScrollPositionForHeader(int viewIndex);
  }

  private static final class PinnedHeader {

    View view;
    boolean visible;
    int y;
    int height;
    int alpha;
    int state;

    boolean animating;
    boolean targetVisible;
    int sourceY;
    int targetY;
    long targetTime;
  }
}