Android Open Source - android-training-tutorial Pinned Section List View

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The source code is released under:

MIT License

Java Source Code

/*
 * Copyright (C) 2013 Sergej Shafarenka, halfbit.de
 */*from w  w w . java  2s.co m*/
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file kt 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.hb.views;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.PointF;
import android.graphics.Rect;
import android.graphics.drawable.GradientDrawable;
import android.graphics.drawable.GradientDrawable.Orientation;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.accessibility.AccessibilityEvent;
import android.widget.AbsListView;
import android.widget.HeaderViewListAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SectionIndexer;

import com.hb.views.pinnedsection.BuildConfig;

/**
 * ListView, which is capable to pin section views at its top while the rest is still scrolled.
 */
public class PinnedSectionListView extends ListView {

    //-- inner classes

  /** List adapter to be implemented for being used with PinnedSectionListView adapter. */
  public static interface PinnedSectionListAdapter extends ListAdapter {
    /** This method shall return 'true' if views of given type has to be pinned. */
    boolean isItemViewTypePinned(int viewType);
  }

  /** Wrapper class for pinned section view and its position in the list. */
  static class PinnedSection {
    public View view;
    public int position;
    public long id;
  }

  //-- class fields

    // fields used for handling touch events
    private final Rect mTouchRect = new Rect();
    private final PointF mTouchPoint = new PointF();
    private int mTouchSlop;
    private View mTouchTarget;
    private MotionEvent mDownEvent;

    // fields used for drawing shadow under a pinned section
    private GradientDrawable mShadowDrawable;
    private int mSectionsDistanceY;
    private int mShadowHeight;

    /** Delegating listener, can be null. */
    OnScrollListener mDelegateOnScrollListener;

    /** Shadow for being recycled, can be null. */
    PinnedSection mRecycleSection;

    /** shadow instance with a pinned view, can be null. */
    PinnedSection mPinnedSection;

    /** Pinned view Y-translation. We use it to stick pinned view to the next section. */
    int mTranslateY;

  /** Scroll listener which does the magic */
  private final OnScrollListener mOnScrollListener = new OnScrollListener() {

    @Override public void onScrollStateChanged(AbsListView view, int scrollState) {
      if (mDelegateOnScrollListener != null) { // delegate
        mDelegateOnScrollListener.onScrollStateChanged(view, scrollState);
      }
    }

    @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

            if (mDelegateOnScrollListener != null) { // delegate
                mDelegateOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
            }

            // get expected adapter or fail fast
            ListAdapter adapter = getAdapter();
            if (adapter == null || visibleItemCount == 0) return; // nothing to do

            final boolean isFirstVisibleItemSection =
                    isItemViewTypePinned(adapter, adapter.getItemViewType(firstVisibleItem));

            if (isFirstVisibleItemSection) {
                View sectionView = getChildAt(0);
                if (sectionView.getTop() == getPaddingTop()) { // view sticks to the top, no need for pinned shadow
                    destroyPinnedShadow();
                } else { // section doesn't stick to the top, make sure we have a pinned shadow
                    ensureShadowForPosition(firstVisibleItem, firstVisibleItem, visibleItemCount);
                }

            } else { // section is not at the first visible position
                int sectionPosition = findCurrentSectionPosition(firstVisibleItem);
                if (sectionPosition > -1) { // we have section position
                    ensureShadowForPosition(sectionPosition, firstVisibleItem, visibleItemCount);
                } else { // there is no section for the first visible item, destroy shadow
                    destroyPinnedShadow();
                }
            }
    };

  };

  /** Default change observer. */
    private final DataSetObserver mDataSetObserver = new DataSetObserver() {
        @Override public void onChanged() {
            recreatePinnedShadow();
        };
        @Override public void onInvalidated() {
            recreatePinnedShadow();
        }
    };

  //-- constructors

    public PinnedSectionListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView();
    }

    public PinnedSectionListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView();
    }

    private void initView() {
        setOnScrollListener(mOnScrollListener);
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
        initShadow(true);
    }

    //-- public API methods

    public void setShadowVisible(boolean visible) {
        initShadow(visible);
        if (mPinnedSection != null) {
            View v = mPinnedSection.view;
            invalidate(v.getLeft(), v.getTop(), v.getRight(), v.getBottom() + mShadowHeight);
        }
    }

    //-- pinned section drawing methods

    public void initShadow(boolean visible) {
        if (visible) {
            if (mShadowDrawable == null) {
                mShadowDrawable = new GradientDrawable(Orientation.TOP_BOTTOM,
                        new int[] { Color.parseColor("#ffa0a0a0"), Color.parseColor("#50a0a0a0"), Color.parseColor("#00a0a0a0")});
                mShadowHeight = (int) (8 * getResources().getDisplayMetrics().density);
            }
        } else {
            if (mShadowDrawable != null) {
                mShadowDrawable = null;
                mShadowHeight = 0;
            }
        }
    }

  /** Create shadow wrapper with a pinned view for a view at given position */
  void createPinnedShadow(int position) {

    // try to recycle shadow
    PinnedSection pinnedShadow = mRecycleSection;
    mRecycleSection = null;

    // create new shadow, if needed
    if (pinnedShadow == null) pinnedShadow = new PinnedSection();
    // request new view using recycled view, if such
    View pinnedView = getAdapter().getView(position, pinnedShadow.view, PinnedSectionListView.this);

    // read layout parameters
    LayoutParams layoutParams = (LayoutParams) pinnedView.getLayoutParams();
    if (layoutParams == null) { // create default layout params
        layoutParams = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    }

    int heightMode = MeasureSpec.getMode(layoutParams.height);
    int heightSize = MeasureSpec.getSize(layoutParams.height);

    if (heightMode == MeasureSpec.UNSPECIFIED) heightMode = MeasureSpec.EXACTLY;

    int maxHeight = getHeight() - getListPaddingTop() - getListPaddingBottom();
    if (heightSize > maxHeight) heightSize = maxHeight;

    // measure & layout
    int ws = MeasureSpec.makeMeasureSpec(getWidth() - getListPaddingLeft() - getListPaddingRight(), MeasureSpec.EXACTLY);
    int hs = MeasureSpec.makeMeasureSpec(heightSize, heightMode);
    pinnedView.measure(ws, hs);
    pinnedView.layout(0, 0, pinnedView.getMeasuredWidth(), pinnedView.getMeasuredHeight());
    mTranslateY = 0;

    // initialize pinned shadow
    pinnedShadow.view = pinnedView;
    pinnedShadow.position = position;
    pinnedShadow.id = getAdapter().getItemId(position);

    // store pinned shadow
    mPinnedSection = pinnedShadow;
  }

  /** Destroy shadow wrapper for currently pinned view */
  void destroyPinnedShadow() {
      if (mPinnedSection != null) {
          // keep shadow for being recycled later
          mRecycleSection = mPinnedSection;
          mPinnedSection = null;
      }
  }

  /** Makes sure we have an actual pinned shadow for given position. */
    void ensureShadowForPosition(int sectionPosition, int firstVisibleItem, int visibleItemCount) {
        if (visibleItemCount < 2) { // no need for creating shadow at all, we have a single visible item
            destroyPinnedShadow();
            return;
        }

        if (mPinnedSection != null
                && mPinnedSection.position != sectionPosition) { // invalidate shadow, if required
            destroyPinnedShadow();
        }

        if (mPinnedSection == null) { // create shadow, if empty
            createPinnedShadow(sectionPosition);
        }

        // align shadow according to next section position, if needed
        int nextPosition = sectionPosition + 1;
        if (nextPosition < getCount()) {
            int nextSectionPosition = findFirstVisibleSectionPosition(nextPosition,
                    visibleItemCount - (nextPosition - firstVisibleItem));
            if (nextSectionPosition > -1) {
                View nextSectionView = getChildAt(nextSectionPosition - firstVisibleItem);
                final int bottom = mPinnedSection.view.getBottom() + getPaddingTop();
                mSectionsDistanceY = nextSectionView.getTop() - bottom;
                if (mSectionsDistanceY < 0) {
                    // next section overlaps pinned shadow, move it up
                    mTranslateY = mSectionsDistanceY;
                } else {
                    // next section does not overlap with pinned, stick to top
                    mTranslateY = 0;
                }
            } else {
                // no other sections are visible, stick to top
                mTranslateY = 0;
                mSectionsDistanceY = Integer.MAX_VALUE;
            }
        }

    }

  int findFirstVisibleSectionPosition(int firstVisibleItem, int visibleItemCount) {
    ListAdapter adapter = getAdapter();
    for (int childIndex = 0; childIndex < visibleItemCount; childIndex++) {
      int position = firstVisibleItem + childIndex;
      int viewType = adapter.getItemViewType(position);
      if (isItemViewTypePinned(adapter, viewType)) return position;
    }
    return -1;
  }

  int findCurrentSectionPosition(int fromPosition) {
    ListAdapter adapter = getAdapter();

    if (adapter instanceof SectionIndexer) {
      // try fast way by asking section indexer
      SectionIndexer indexer = (SectionIndexer) adapter;
      int sectionPosition = indexer.getSectionForPosition(fromPosition);
      int itemPosition = indexer.getPositionForSection(sectionPosition);
      int typeView = adapter.getItemViewType(itemPosition);
      if (isItemViewTypePinned(adapter, typeView)) {
        return itemPosition;
      } // else, no luck
    }

    // try slow way by looking through to the next section item above
    for (int position=fromPosition; position>=0; position--) {
      int viewType = adapter.getItemViewType(position);
      if (isItemViewTypePinned(adapter, viewType)) return position;
    }
    return -1; // no candidate found
  }

  void recreatePinnedShadow() {
      destroyPinnedShadow();
        ListAdapter adapter = getAdapter();
        if (adapter != null && adapter.getCount() > 0) {
            int firstVisiblePosition = getFirstVisiblePosition();
            int sectionPosition = findCurrentSectionPosition(firstVisiblePosition);
            if (sectionPosition == -1) return; // no views to pin, exit
            ensureShadowForPosition(sectionPosition,
                    firstVisiblePosition, getLastVisiblePosition() - firstVisiblePosition);
        }
  }

  @Override
  public void setOnScrollListener(OnScrollListener listener) {
    if (listener == mOnScrollListener) {
      super.setOnScrollListener(listener);
    } else {
      mDelegateOnScrollListener = listener;
    }
  }

  @Override
  public void onRestoreInstanceState(Parcelable state) {
    super.onRestoreInstanceState(state);
    post(new Runnable() {
      @Override public void run() { // restore pinned view after configuration change
          recreatePinnedShadow();
      }
    });
  }

  @Override
  public void setAdapter(ListAdapter adapter) {

      // assert adapter in debug mode
    if (BuildConfig.DEBUG && adapter != null) {
      if (!(adapter instanceof PinnedSectionListAdapter))
        throw new IllegalArgumentException("Does your adapter implement PinnedSectionListAdapter?");
      if (adapter.getViewTypeCount() < 2)
        throw new IllegalArgumentException("Does your adapter handle at least two types" +
            " of views in getViewTypeCount() method: items and sections?");
    }

    // unregister observer at old adapter and register on new one
    ListAdapter oldAdapter = getAdapter();
    if (oldAdapter != null) oldAdapter.unregisterDataSetObserver(mDataSetObserver);
    if (adapter != null) adapter.registerDataSetObserver(mDataSetObserver);

    // destroy pinned shadow, if new adapter is not same as old one
    if (oldAdapter != adapter) destroyPinnedShadow();

    super.setAdapter(adapter);
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
      super.onLayout(changed, l, t, r, b);
        if (mPinnedSection != null) {
            int parentWidth = r - l - getPaddingLeft() - getPaddingRight();
            int shadowWidth = mPinnedSection.view.getWidth();
            if (parentWidth != shadowWidth) {
                recreatePinnedShadow();
            }
        }
  }

  @Override
  protected void dispatchDraw(Canvas canvas) {
    super.dispatchDraw(canvas);

    if (mPinnedSection != null) {

      // prepare variables
      int pLeft = getListPaddingLeft();
      int pTop = getListPaddingTop();
      View view = mPinnedSection.view;

      // draw child
      canvas.save();

      int clipHeight = view.getHeight() +
              (mShadowDrawable == null ? 0 : Math.min(mShadowHeight, mSectionsDistanceY));
      canvas.clipRect(pLeft, pTop, pLeft + view.getWidth(), pTop + clipHeight);

      canvas.translate(pLeft, pTop + mTranslateY);
      drawChild(canvas, mPinnedSection.view, getDrawingTime());

      if (mShadowDrawable != null && mSectionsDistanceY > 0) {
          mShadowDrawable.setBounds(mPinnedSection.view.getLeft(),
                  mPinnedSection.view.getBottom(),
                  mPinnedSection.view.getRight(),
                  mPinnedSection.view.getBottom() + mShadowHeight);
          mShadowDrawable.draw(canvas);
      }

      canvas.restore();
    }
  }

  //-- touch handling methods

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {

        final float x = ev.getX();
        final float y = ev.getY();
        final int action = ev.getAction();

        if (action == MotionEvent.ACTION_DOWN
                && mTouchTarget == null
                && mPinnedSection != null
                && isPinnedViewTouched(mPinnedSection.view, x, y)) { // create touch target

            // user touched pinned view
            mTouchTarget = mPinnedSection.view;
            mTouchPoint.x = x;
            mTouchPoint.y = y;

            // copy down event for eventually be used later
            mDownEvent = MotionEvent.obtain(ev);
        }

        if (mTouchTarget != null) {
            if (isPinnedViewTouched(mTouchTarget, x, y)) { // forward event to pinned view
                mTouchTarget.dispatchTouchEvent(ev);
            }

            if (action == MotionEvent.ACTION_UP) { // perform onClick on pinned view
                super.dispatchTouchEvent(ev);
                performPinnedItemClick();
                clearTouchTarget();

            } else if (action == MotionEvent.ACTION_CANCEL) { // cancel
                clearTouchTarget();

            } else if (action == MotionEvent.ACTION_MOVE) {
                if (Math.abs(y - mTouchPoint.y) > mTouchSlop) {

                    // cancel sequence on touch target
                    MotionEvent event = MotionEvent.obtain(ev);
                    event.setAction(MotionEvent.ACTION_CANCEL);
                    mTouchTarget.dispatchTouchEvent(event);
                    event.recycle();

                    // provide correct sequence to super class for further handling
                    super.dispatchTouchEvent(mDownEvent);
                    super.dispatchTouchEvent(ev);
                    clearTouchTarget();

                }
            }

            return true;
        }

        // call super if this was not our pinned view
        return super.dispatchTouchEvent(ev);
    }

    private boolean isPinnedViewTouched(View view, float x, float y) {
        view.getHitRect(mTouchRect);

        // by taping top or bottom padding, the list performs on click on a border item.
        // we don't add top padding here to keep behavior consistent.
        mTouchRect.top += mTranslateY;

        mTouchRect.bottom += mTranslateY + getPaddingTop();
        mTouchRect.left += getPaddingLeft();
        mTouchRect.right -= getPaddingRight();
        return mTouchRect.contains((int)x, (int)y);
    }

    private void clearTouchTarget() {
        mTouchTarget = null;
        if (mDownEvent != null) {
            mDownEvent.recycle();
            mDownEvent = null;
        }
    }

    private boolean performPinnedItemClick() {
        if (mPinnedSection == null) return false;

        OnItemClickListener listener = getOnItemClickListener();
        if (listener != null) {
            View view =  mPinnedSection.view;
            playSoundEffect(SoundEffectConstants.CLICK);
            if (view != null) {
                view.sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
            }
            listener.onItemClick(this, view, mPinnedSection.position, mPinnedSection.id);
            return true;
        }
        return false;
    }

    public static boolean isItemViewTypePinned(ListAdapter adapter, int viewType) {
        if (adapter instanceof HeaderViewListAdapter) {
            adapter = ((HeaderViewListAdapter)adapter).getWrappedAdapter();
        }
        return ((PinnedSectionListAdapter) adapter).isItemViewTypePinned(viewType);
    }

}

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