Java tutorial
/* * Copyright (C) 2013 Sergej Shafarenka, halfbit.de * * 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.dm.xz.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.support.v4.BuildConfig; 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) { layoutParams = (LayoutParams) generateDefaultLayoutParams(); pinnedView.setLayoutParams(layoutParams); } 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(); int adapterDataCount = adapter.getCount(); if (getLastVisiblePosition() >= adapterDataCount) return -1; // dataset has changed, no candidate if (firstVisibleItem + visibleItemCount >= adapterDataCount) {//added to prevent index Outofbound (in case) visibleItemCount = adapterDataCount - firstVisibleItem; } 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 (fromPosition >= adapter.getCount()) return -1; // dataset has changed, no candidate 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 && getAdapter().isEnabled(mPinnedSection.position)) { 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); } }