/*
* Copyright (C) 2013 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 org.getlantern.dynamicgridview;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.TypeEvaluator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
/**
* The dynamic listview is an extension of listview that supports cell dragging
* and swapping.
*
* This layout is in charge of positioning the hover cell in the correct
* location on the screen in response to user touch events. It uses the position
* of the hover cell to determine when two cells should be swapped. If two cells
* should be swapped, all the corresponding data set and layout changes are
* handled here.
*
* If no cell is selected, all the touch events are passed down to the listview
* and behave normally. If one of the items in the listview experiences a long
* press event, the contents of its current visible state are captured as a
* bitmap and its visibility is set to INVISIBLE. A hover cell is then created
* and added to this layout as an overlaying BitmapDrawable above the listview.
* Once the hover cell is translated some distance to signify an item swap, a
* data set change accompanied by animation takes place. When the user releases
* the hover cell, it animates into its corresponding position in the listview.
*
* When the hover cell is either above or below the bounds of the listview, this
* listview also scrolls on its own so as to reveal additional content.
*/
public class DynamicListView extends ListView {
private final int SMOOTH_SCROLL_AMOUNT_AT_EDGE = 15;
private final int MOVE_DURATION = 150;
private final int LINE_THICKNESS = 15;
private int mLastEventY = -1;
private int mDownY = -1;
private int mDownX = -1;
private int mTotalOffset = 0;
private boolean mCellIsMobile = false;
private boolean mIsMobileScrolling = false;
private int mSmoothScrollAmountAtEdge = 0;
private final int INVALID_ID = -1;
private long mAboveItemId = INVALID_ID;
private long mMobileItemId = INVALID_ID;
private long mBelowItemId = INVALID_ID;
private BitmapDrawable mHoverCell;
private Rect mHoverCellCurrentBounds;
private Rect mHoverCellOriginalBounds;
private final int INVALID_POINTER_ID = -1;
private int mActivePointerId = INVALID_POINTER_ID;
private boolean mIsWaitingForScrollFinish = false;
private int mScrollState = OnScrollListener.SCROLL_STATE_IDLE;
/**
* Listens for long clicks on any items in the listview. When a cell has
* been selected, the hover cell is created and set up.
*/
private final AdapterView.OnItemLongClickListener mOnItemLongClickListener = new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(final AdapterView<?> arg0, final View arg1, final int pos, final long id) {
mTotalOffset = 0;
final int position = pointToPosition(mDownX, mDownY);
final int itemNum = position - getFirstVisiblePosition();
final View selectedView = getChildAt(itemNum);
mMobileItemId = getAdapter().getItemId(position);
mHoverCell = getAndAddHoverView(selectedView);
selectedView.setVisibility(INVISIBLE);
mCellIsMobile = true;
updateNeighborViewsForID(mMobileItemId);
return true;
}
};
/**
* This TypeEvaluator is used to animate the BitmapDrawable back to its
* final location when the user lifts his finger by modifying the
* BitmapDrawable's bounds.
*/
private final static TypeEvaluator<Rect> sBoundEvaluator = new TypeEvaluator<Rect>() {
@Override
public Rect evaluate(final float fraction, final Rect startValue, final Rect endValue) {
return new Rect(interpolate(startValue.left, endValue.left, fraction), interpolate(startValue.top,
endValue.top, fraction), interpolate(startValue.right, endValue.right, fraction), interpolate(
startValue.bottom, endValue.bottom, fraction));
}
public int interpolate(final int start, final int end, final float fraction) {
return (int) (start + fraction * (end - start));
}
};
/**
* This scroll listener is added to the listview in order to handle cell
* swapping when the cell is either at the top or bottom edge of the
* listview. If the hover cell is at either edge of the listview, the
* listview will begin scrolling. As scrolling takes place, the listview
* continuously checks if new cells became visible and determines whether
* they are potential candidates for a cell swap.
*/
private final AbsListView.OnScrollListener mScrollListener = new AbsListView.OnScrollListener() {
private int mPreviousFirstVisibleItem = -1;
private int mPreviousVisibleItemCount = -1;
private int mCurrentFirstVisibleItem;
private int mCurrentVisibleItemCount;
private int mCurrentScrollState;
/**
* Determines if the listview scrolled up enough to reveal a new cell at
* the top of the list. If so, then the appropriate parameters are
* updated.
*/
public void checkAndHandleFirstVisibleCellChange() {
if (mCurrentFirstVisibleItem != mPreviousFirstVisibleItem) {
if (mCellIsMobile && mMobileItemId != INVALID_ID) {
updateNeighborViewsForID(mMobileItemId);
handleCellSwitch();
}
}
}
/**
* Determines if the listview scrolled down enough to reveal a new cell
* at the bottom of the list. If so, then the appropriate parameters are
* updated.
*/
public void checkAndHandleLastVisibleCellChange() {
final int currentLastVisibleItem = mCurrentFirstVisibleItem + mCurrentVisibleItemCount;
final int previousLastVisibleItem = mPreviousFirstVisibleItem + mPreviousVisibleItemCount;
if (currentLastVisibleItem != previousLastVisibleItem) {
if (mCellIsMobile && mMobileItemId != INVALID_ID) {
updateNeighborViewsForID(mMobileItemId);
handleCellSwitch();
}
}
}
@Override
public void onScroll(final AbsListView view, final int firstVisibleItem, final int visibleItemCount,
final int totalItemCount) {
mCurrentFirstVisibleItem = firstVisibleItem;
mCurrentVisibleItemCount = visibleItemCount;
mPreviousFirstVisibleItem = mPreviousFirstVisibleItem == -1 ? mCurrentFirstVisibleItem
: mPreviousFirstVisibleItem;
mPreviousVisibleItemCount = mPreviousVisibleItemCount == -1 ? mCurrentVisibleItemCount
: mPreviousVisibleItemCount;
checkAndHandleFirstVisibleCellChange();
checkAndHandleLastVisibleCellChange();
mPreviousFirstVisibleItem = mCurrentFirstVisibleItem;
mPreviousVisibleItemCount = mCurrentVisibleItemCount;
}
@Override
public void onScrollStateChanged(final AbsListView view, final int scrollState) {
mCurrentScrollState = scrollState;
mScrollState = scrollState;
isScrollCompleted();
}
/**
* This method is in charge of invoking 1 of 2 actions. Firstly, if the
* listview is in a state of scrolling invoked by the hover cell being
* outside the bounds of the listview, then this scrolling event is
* continued. Secondly, if the hover cell has already been released,
* this invokes the animation for the hover cell to return to its
* correct position after the listview has entered an idle scroll state.
*/
private void isScrollCompleted() {
if (mCurrentVisibleItemCount > 0 && mCurrentScrollState == SCROLL_STATE_IDLE) {
if (mCellIsMobile && mIsMobileScrolling) {
handleMobileCellScroll();
} else if (mIsWaitingForScrollFinish) {
touchEventsEnded();
}
}
}
};
public DynamicListView(final Context context) {
super(context);
init(context);
}
public DynamicListView(final Context context, final AttributeSet attrs) {
super(context, attrs);
init(context);
}
public DynamicListView(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
init(context);
}
/** Retrieves the position in the list corresponding to itemID */
public int getPositionForID(final long itemID) {
final View v = getViewForID(itemID);
if (v == null)
return -1;
else
return getPositionForView(v);
}
/** Retrieves the view in the list corresponding to itemID */
public View getViewForID(final long itemID) {
final int firstVisiblePosition = getFirstVisiblePosition();
final ListAdapter adapter = getAdapter();
for (int i = 0; i < getChildCount(); i++) {
final View v = getChildAt(i);
final int position = firstVisiblePosition + i;
final long id = adapter.getItemId(position);
if (id == itemID) return v;
}
return null;
}
/**
* This method is in charge of determining if the hover cell is above or
* below the bounds of the listview. If so, the listview does an appropriate
* upward or downward smooth scroll so as to reveal new items.
*/
public boolean handleMobileCellScroll(final Rect r) {
final int offset = computeVerticalScrollOffset();
final int height = getHeight();
final int extent = computeVerticalScrollExtent();
final int range = computeVerticalScrollRange();
final int hoverViewTop = r.top;
final int hoverHeight = r.height();
if (hoverViewTop <= 0 && offset > 0) {
smoothScrollBy(-mSmoothScrollAmountAtEdge, 0);
return true;
}
if (hoverViewTop + hoverHeight >= height && offset + extent < range) {
smoothScrollBy(mSmoothScrollAmountAtEdge, 0);
return true;
}
return false;
}
public void init(final Context context) {
setOnItemLongClickListener(mOnItemLongClickListener);
setOnScrollListener(mScrollListener);
final DisplayMetrics metrics = context.getResources().getDisplayMetrics();
mSmoothScrollAmountAtEdge = (int) (SMOOTH_SCROLL_AMOUNT_AT_EDGE / metrics.density);
}
@Override
public boolean onTouchEvent(final MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
mDownX = (int) event.getX();
mDownY = (int) event.getY();
mActivePointerId = event.getPointerId(0);
break;
case MotionEvent.ACTION_MOVE:
if (mActivePointerId == INVALID_POINTER_ID) {
break;
}
int pointerIndex = event.findPointerIndex(mActivePointerId);
mLastEventY = (int) event.getY(pointerIndex);
final int deltaY = mLastEventY - mDownY;
if (mCellIsMobile) {
mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mHoverCellOriginalBounds.top
+ deltaY + mTotalOffset);
mHoverCell.setBounds(mHoverCellCurrentBounds);
invalidate();
handleCellSwitch();
mIsMobileScrolling = false;
handleMobileCellScroll();
return false;
}
break;
case MotionEvent.ACTION_UP:
touchEventsEnded();
break;
case MotionEvent.ACTION_CANCEL:
touchEventsCancelled();
break;
case MotionEvent.ACTION_POINTER_UP:
/*
* If a multitouch event took place and the original touch
* dictating the movement of the hover cell has ended, then the
* dragging event ends and the hover cell is animated to its
* corresponding position in the listview.
*/
pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = event.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
touchEventsEnded();
}
break;
default:
break;
}
return super.onTouchEvent(event);
}
@Override
public void setAdapter(final ListAdapter adapter) {
if (!(adapter instanceof DraggableAdapter))
throw new IllegalArgumentException("Adapter have to implement DraggableAdapter");
super.setAdapter(adapter);
}
/**
* dispatchDraw gets invoked when all the child views are about to be drawn.
* By overriding this method, the hover cell (BitmapDrawable) can be drawn
* over the listview's items whenever the listview is redrawn.
*/
@Override
protected void dispatchDraw(final Canvas canvas) {
super.dispatchDraw(canvas);
if (mHoverCell != null) {
mHoverCell.draw(canvas);
}
}
/**
* Creates the hover cell with the appropriate bitmap and of appropriate
* size. The hover cell's BitmapDrawable is drawn on top of the bitmap every
* single time an invalidate call is made.
*/
private BitmapDrawable getAndAddHoverView(final View v) {
final int w = v.getWidth();
final int h = v.getHeight();
final int top = v.getTop();
final int left = v.getLeft();
final Bitmap b = getBitmapWithBorder(v);
final BitmapDrawable drawable = new BitmapDrawable(getResources(), b);
mHoverCellOriginalBounds = new Rect(left, top, left + w, top + h);
mHoverCellCurrentBounds = new Rect(mHoverCellOriginalBounds);
drawable.setBounds(mHoverCellCurrentBounds);
return drawable;
}
/** Returns a bitmap showing a screenshot of the view passed in. */
private Bitmap getBitmapFromView(final View v) {
final Bitmap bitmap = Bitmap.createBitmap(v.getWidth(), v.getHeight(), Bitmap.Config.ARGB_8888);
final Canvas canvas = new Canvas(bitmap);
v.draw(canvas);
return bitmap;
}
/** Draws a black border over the screenshot of the view passed in. */
private Bitmap getBitmapWithBorder(final View v) {
final Bitmap bitmap = getBitmapFromView(v);
final Canvas can = new Canvas(bitmap);
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final Paint paint = new Paint();
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(LINE_THICKNESS);
paint.setColor(Color.BLACK);
can.drawBitmap(bitmap, 0, 0, null);
can.drawRect(rect, paint);
return bitmap;
}
/**
* This method determines whether the hover cell has been shifted far enough
* to invoke a cell swap. If so, then the respective cell swap candidate is
* determined and the data set is changed. Upon posting a notification of
* the data set change, a layout is invoked to place the cells in the right
* place. Using a ViewTreeObserver and a corresponding OnPreDrawListener, we
* can offset the cell being swapped to where it previously was and then
* animate it to its new position.
*/
private void handleCellSwitch() {
final int deltaY = mLastEventY - mDownY;
final int deltaYTotal = mHoverCellOriginalBounds.top + mTotalOffset + deltaY;
final View belowView = getViewForID(mBelowItemId);
final View mobileView = getViewForID(mMobileItemId);
final View aboveView = getViewForID(mAboveItemId);
final boolean isBelow = belowView != null && deltaYTotal > belowView.getTop();
final boolean isAbove = aboveView != null && deltaYTotal < aboveView.getTop();
if (isBelow || isAbove) {
final long switchItemID = isBelow ? mBelowItemId : mAboveItemId;
final View switchView = isBelow ? belowView : aboveView;
final int originalItem = getPositionForView(mobileView);
if (switchView == null) {
updateNeighborViewsForID(mMobileItemId);
return;
}
final int newItemPosition = getPositionForID(switchItemID);
((DraggableAdapter) getAdapter()).swapElements(originalItem, newItemPosition);
mDownY = mLastEventY;
final int switchViewStartTop = switchView.getTop();
mobileView.setVisibility(View.VISIBLE);
switchView.setVisibility(View.INVISIBLE);
updateNeighborViewsForID(mMobileItemId);
final ViewTreeObserver observer = getViewTreeObserver();
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
observer.removeOnPreDrawListener(this);
final View switchView = getViewForID(switchItemID);
mTotalOffset += deltaY;
final int switchViewNewTop = switchView.getTop();
final int delta = switchViewStartTop - switchViewNewTop;
switchView.setTranslationY(delta);
final ObjectAnimator animator = ObjectAnimator.ofFloat(switchView, View.TRANSLATION_Y, 0);
animator.setDuration(MOVE_DURATION);
animator.start();
return true;
}
});
}
}
/**
* Determines whether this listview is in a scrolling state invoked by the
* fact that the hover cell is out of the bounds of the listview;
*/
private void handleMobileCellScroll() {
mIsMobileScrolling = handleMobileCellScroll(mHoverCellCurrentBounds);
}
/**
* Resets all the appropriate fields to a default state.
*/
private void touchEventsCancelled() {
final View mobileView = getViewForID(mMobileItemId);
if (mCellIsMobile) {
mAboveItemId = INVALID_ID;
mMobileItemId = INVALID_ID;
mBelowItemId = INVALID_ID;
mobileView.setVisibility(VISIBLE);
mHoverCell = null;
invalidate();
}
mCellIsMobile = false;
mIsMobileScrolling = false;
mActivePointerId = INVALID_POINTER_ID;
}
/**
* Resets all the appropriate fields to a default state while also animating
* the hover cell back to its correct location.
*/
private void touchEventsEnded() {
final View mobileView = getViewForID(mMobileItemId);
if (mCellIsMobile || mIsWaitingForScrollFinish) {
mCellIsMobile = false;
mIsWaitingForScrollFinish = false;
mIsMobileScrolling = false;
mActivePointerId = INVALID_POINTER_ID;
// If the autoscroller has not completed scrolling, we need to wait
// for it to
// finish in order to determine the final location of where the
// hover cell
// should be animated to.
if (mScrollState != OnScrollListener.SCROLL_STATE_IDLE) {
mIsWaitingForScrollFinish = true;
return;
}
mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mobileView.getTop());
final ObjectAnimator hoverViewAnimator = ObjectAnimator.ofObject(mHoverCell, "bounds", sBoundEvaluator,
mHoverCellCurrentBounds);
hoverViewAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(final ValueAnimator valueAnimator) {
invalidate();
}
});
hoverViewAnimator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(final Animator animation) {
mAboveItemId = INVALID_ID;
mMobileItemId = INVALID_ID;
mBelowItemId = INVALID_ID;
mobileView.setVisibility(VISIBLE);
mHoverCell = null;
setEnabled(true);
invalidate();
}
@Override
public void onAnimationStart(final Animator animation) {
setEnabled(false);
}
});
hoverViewAnimator.start();
} else {
touchEventsCancelled();
}
}
/**
* Stores a reference to the views above and below the item currently
* corresponding to the hover cell. It is important to note that if this
* item is either at the top or bottom of the list, mAboveItemId or
* mBelowItemId may be invalid.
*/
private void updateNeighborViewsForID(final long itemID) {
final int position = getPositionForID(itemID);
final ListAdapter adapter = getAdapter();
mAboveItemId = adapter.getItemId(position - 1);
mBelowItemId = adapter.getItemId(position + 1);
}
}