Java tutorial
/* * 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 ucsc.hci.rankit; 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.content.Intent; 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.BaseAdapter; import android.widget.ListView; import java.util.ArrayList; import static android.support.v4.app.ActivityCompat.startActivity; /** * 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 = 5; public ArrayList<RankObjects> mObjectList; 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; public DynamicListView(Context context) { super(context); init(context); } public DynamicListView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context); } public DynamicListView(Context context, AttributeSet attrs) { super(context, attrs); init(context); } public void init(Context context) { // This is no longer needed, as now we initiate drag onTouchEvent. // setOnItemLongClickListener(mOnItemLongClickListener); setOnScrollListener(mScrollListener); DisplayMetrics metrics = context.getResources().getDisplayMetrics(); mSmoothScrollAmountAtEdge = (int) (SMOOTH_SCROLL_AMOUNT_AT_EDGE / metrics.density); } /** * 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 OnItemLongClickListener mOnItemLongClickListener = new OnItemLongClickListener() { public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int pos, long id) { mTotalOffset = 0; int position = pointToPosition(mDownX, mDownY); int itemNum = position - getFirstVisiblePosition(); View selectedView = getChildAt(itemNum); mMobileItemId = getAdapter().getItemId(position); mHoverCell = getAndAddHoverView(selectedView); selectedView.setVisibility(INVISIBLE); mCellIsMobile = true; updateNeighborViewsForID(mMobileItemId); return true; } }; */ /** * 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(View v) { int w = 10; int h = 10; int top = 10; int left = 10; try { w = v.getWidth(); h = v.getHeight(); top = v.getTop(); left = v.getLeft(); } catch (Exception e) { e.printStackTrace(); } Bitmap b = getBitmapWithBorder(v); BitmapDrawable drawable = new BitmapDrawable(getResources(), b); mHoverCellOriginalBounds = new Rect(left, top, left + w, top + h); mHoverCellCurrentBounds = new Rect(mHoverCellOriginalBounds); drawable.setBounds(mHoverCellCurrentBounds); return drawable; } /** Draws a black border over the screenshot of the view passed in. */ private Bitmap getBitmapWithBorder(View v) { Bitmap bitmap = getBitmapFromView(v); Canvas can = new Canvas(bitmap); Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); Paint paint = new Paint(); paint.setStyle(Paint.Style.STROKE); paint.setStrokeWidth(LINE_THICKNESS); paint.setColor(Color.WHITE); can.drawBitmap(bitmap, 0, 0, null); can.drawRect(rect, paint); return bitmap; } /** Returns a bitmap showing a screenshot of the view passed in. */ private Bitmap getBitmapFromView(View v) { Bitmap bitmap = Bitmap.createBitmap(10, 10, Bitmap.Config.ARGB_8888); try { bitmap = Bitmap.createBitmap(v.getWidth(), v.getHeight(), Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(bitmap); v.draw(canvas); } catch (Exception e) { e.printStackTrace(); //intent.putExtra(USERS_CALL_STRING,UsersCallString); //Intent intentnow = new Intent(RankItApp.getAppContext(), MenuPageActivity.class); //startActivity(MenuPageActivity.intent_global); } return bitmap; } /** * 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(long itemID) { int position = getPositionForID(itemID); StableArrayAdapter adapter = ((StableArrayAdapter) getAdapter()); mAboveItemId = adapter.getItemId(position - 1); mBelowItemId = adapter.getItemId(position + 1); } /** Retrieves the view in the list corresponding to itemID */ public View getViewForID(long itemID) { int firstVisiblePosition = getFirstVisiblePosition(); StableArrayAdapter adapter = ((StableArrayAdapter) getAdapter()); for (int i = 0; i < getChildCount(); i++) { View v = getChildAt(i); int position = firstVisiblePosition + i; long id = adapter.getItemId(position); if (id == itemID) { return v; } } return null; } /** Retrieves the position in the list corresponding to itemID */ public int getPositionForID(long itemID) { View v = getViewForID(itemID); if (v == null) { return -1; } else { return getPositionForView(v); } } /** * 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(Canvas canvas) { super.dispatchDraw(canvas); if (mHoverCell != null) { mHoverCell.draw(canvas); } } @Override public boolean onTouchEvent(MotionEvent event) { switch (event.getAction() & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: mDownX = (int) event.getX(); mDownY = (int) event.getY(); mActivePointerId = event.getPointerId(0); // This part has been copied from OnItemLongClickListener code above (which has now // been commented out). mTotalOffset = 0; int position = pointToPosition(mDownX, mDownY); int itemNum = position - getFirstVisiblePosition(); View selectedView = getChildAt(itemNum); mMobileItemId = getAdapter().getItemId(position); mHoverCell = getAndAddHoverView(selectedView); selectedView.setVisibility(INVISIBLE); mCellIsMobile = true; updateNeighborViewsForID(mMobileItemId); // End of copy-paste from OnItemLongClickListener break; case MotionEvent.ACTION_MOVE: if (mActivePointerId == INVALID_POINTER_ID) { break; } int pointerIndex = event.findPointerIndex(mActivePointerId); mLastEventY = (int) event.getY(pointerIndex); int deltaY = mLastEventY - mDownY; if (mCellIsMobile) { mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mHoverCellOriginalBounds.top + deltaY + mTotalOffset); try { mHoverCell.setBounds(mHoverCellCurrentBounds); } catch (Exception e) { e.printStackTrace(); } 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); } /** * 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; int deltaYTotal = mHoverCellOriginalBounds.top + mTotalOffset + deltaY; View belowView = getViewForID(mBelowItemId); View mobileView = getViewForID(mMobileItemId); View aboveView = getViewForID(mAboveItemId); boolean isBelow = (belowView != null) && (deltaYTotal > belowView.getTop()); boolean isAbove = (aboveView != null) && (deltaYTotal < aboveView.getTop()); if (isBelow || isAbove) { final long switchItemID = isBelow ? mBelowItemId : mAboveItemId; View switchView = isBelow ? belowView : aboveView; final int originalItem = getPositionForView(mobileView); if (switchView == null) { updateNeighborViewsForID(mMobileItemId); return; } swapElements(mObjectList, originalItem, getPositionForView(switchView)); ((BaseAdapter) getAdapter()).notifyDataSetChanged(); mDownY = mLastEventY; final int switchViewStartTop = switchView.getTop(); // if (android.os.Build.VERSION.SDK_INT <= android.os.Build.VERSION_CODES.KITKAT) { mobileView.setVisibility(View.VISIBLE); switchView.setVisibility(View.INVISIBLE); // } // else { // mobileView.setVisibility(View.INVISIBLE); // switchView.setVisibility(View.VISIBLE); // } updateNeighborViewsForID(mMobileItemId); final ViewTreeObserver observer = getViewTreeObserver(); observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() { public boolean onPreDraw() { observer.removeOnPreDrawListener(this); View switchView = getViewForID(switchItemID); mTotalOffset += deltaY; int switchViewNewTop = switchView.getTop(); int delta = switchViewStartTop - switchViewNewTop; switchView.setTranslationY(delta); ObjectAnimator animator = ObjectAnimator.ofFloat(switchView, View.TRANSLATION_Y, 0); animator.setDuration(MOVE_DURATION); animator.start(); return true; } }); } } private void swapElements(ArrayList arrayList, int indexOne, int indexTwo) { Object temp = arrayList.get(indexOne); arrayList.set(indexOne, arrayList.get(indexTwo)); arrayList.set(indexTwo, temp); } /** * 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; } try { mHoverCellCurrentBounds.offsetTo(mHoverCellOriginalBounds.left, mobileView.getTop()); } catch (Exception e) { e.printStackTrace(); } ObjectAnimator hoverViewAnimator = ObjectAnimator.ofObject(mHoverCell, "bounds", sBoundEvaluator, mHoverCellCurrentBounds); hoverViewAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator valueAnimator) { invalidate(); } }); hoverViewAnimator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationStart(Animator animation) { setEnabled(false); } @Override public void onAnimationEnd(Animator animation) { mAboveItemId = INVALID_ID; mMobileItemId = INVALID_ID; mBelowItemId = INVALID_ID; mobileView.setVisibility(VISIBLE); mHoverCell = null; setEnabled(true); invalidate(); } }); try { hoverViewAnimator.start(); } catch (Exception e) { e.printStackTrace(); } } else { touchEventsCancelled(); } } /** * Resets all the appropriate fields to a default state. */ private void touchEventsCancelled() { 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; // readyToMove = 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>() { public Rect evaluate(float fraction, Rect startValue, 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(int start, int end, float fraction) { return (int) (start + fraction * (end - start)); } }; /** * 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); } /** * 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(Rect r) { int offset = computeVerticalScrollOffset(); int height = getHeight(); int extent = computeVerticalScrollExtent(); int range = computeVerticalScrollRange(); int hoverViewTop = r.top; 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 setObjectList(ArrayList<RankObjects> objectList) { mObjectList = objectList; } /** * 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 OnScrollListener mScrollListener = new OnScrollListener() { private int mPreviousFirstVisibleItem = -1; private int mPreviousVisibleItemCount = -1; private int mCurrentFirstVisibleItem; private int mCurrentVisibleItemCount; private int mCurrentScrollState; public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, 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(AbsListView view, 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(); } } } /** * 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() { int currentLastVisibleItem = mCurrentFirstVisibleItem + mCurrentVisibleItemCount; int previousLastVisibleItem = mPreviousFirstVisibleItem + mPreviousVisibleItemCount; if (currentLastVisibleItem != previousLastVisibleItem) { if (mCellIsMobile && mMobileItemId != INVALID_ID) { updateNeighborViewsForID(mMobileItemId); handleCellSwitch(); } } } }; }