/*
* Copyright (C) 2011 Patrik Åkerfeldt
*
* 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.taptwo.android.widget;
import java.util.EnumSet;
import java.util.LinkedList;
import org.taptwo.android.widget.viewflow.R;
import android.content.Context;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.widget.AbsListView;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.Scroller;
/**
* A horizontally scrollable {@link ViewGroup} with items populated from an
* {@link Adapter}. The ViewFlow uses a buffer to store loaded {@link View}s in.
* The default size of the buffer is 3 elements on both sides of the currently
* visible {@link View}, making up a total buffer size of 3 * 2 + 1 = 7. The
* buffer size can be changed using the {@code sidebuffer} xml attribute.
*
*/
public class ViewFlow extends AdapterView<Adapter> {
private static final int SNAP_VELOCITY = 1000;
private static final int INVALID_SCREEN = -1;
private final static int TOUCH_STATE_REST = 0;
private final static int TOUCH_STATE_SCROLLING = 1;
private LinkedList<View> mLoadedViews;
private LinkedList<View> mRecycledViews;
private int mCurrentBufferIndex;
private int mCurrentAdapterIndex;
private int mSideBuffer = 2;
private Scroller mScroller;
private VelocityTracker mVelocityTracker;
private int mTouchState = TOUCH_STATE_REST;
private float mLastMotionX;
private int mTouchSlop;
private int mMaximumVelocity;
private int mCurrentScreen;
private int mNextScreen = INVALID_SCREEN;
private boolean mFirstLayout = true;
private ViewSwitchListener mViewSwitchListener;
private ViewLazyInitializeListener mViewInitializeListener;
private EnumSet<LazyInit> mLazyInit = EnumSet.allOf(LazyInit.class);
private Adapter mAdapter;
private int mLastScrollDirection;
private AdapterDataSetObserver mDataSetObserver;
private FlowIndicator mIndicator;
private int mLastOrientation = -1;
private OnGlobalLayoutListener orientationChangeListener = new OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
getViewTreeObserver().removeGlobalOnLayoutListener(
orientationChangeListener);
setSelection(mCurrentAdapterIndex);
}
};
/**
* Receives call backs when a new {@link View} has been scrolled to.
*/
public static interface ViewSwitchListener {
/**
* This method is called when a new View has been scrolled to.
*
* @param view
* the {@link View} currently in focus.
* @param position
* The position in the adapter of the {@link View} currently in focus.
*/
void onSwitched(View view, int position);
}
public static interface ViewLazyInitializeListener {
void onViewLazyInitialize(View view, int position);
}
enum LazyInit {
LEFT, RIGHT
}
public ViewFlow(Context context) {
super(context);
mSideBuffer = 3;
init();
}
public ViewFlow(Context context, int sideBuffer) {
super(context);
mSideBuffer = sideBuffer;
init();
}
public ViewFlow(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray styledAttrs = context.obtainStyledAttributes(attrs,
R.styleable.ViewFlow);
mSideBuffer = styledAttrs.getInt(R.styleable.ViewFlow_sidebuffer, 3);
init();
}
private void init() {
mLoadedViews = new LinkedList<View>();
mRecycledViews = new LinkedList<View>();
mScroller = new Scroller(getContext());
final ViewConfiguration configuration = ViewConfiguration
.get(getContext());
mTouchSlop = configuration.getScaledTouchSlop();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
public void onConfigurationChanged(Configuration newConfig) {
if (newConfig.orientation != mLastOrientation) {
mLastOrientation = newConfig.orientation;
getViewTreeObserver().addOnGlobalLayoutListener(orientationChangeListener);
}
}
public int getViewsCount() {
return mAdapter.getCount();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
final int width = MeasureSpec.getSize(widthMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode != MeasureSpec.EXACTLY && !isInEditMode()) {
throw new IllegalStateException(
"ViewFlow can only be used in EXACTLY mode.");
}
final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (heightMode != MeasureSpec.EXACTLY && !isInEditMode()) {
throw new IllegalStateException(
"ViewFlow can only be used in EXACTLY mode.");
}
// The children are given the same width and height as the workspace
final int count = getChildCount();
for (int i = 0; i < count; i++) {
getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
}
if (mFirstLayout) {
mScroller.startScroll(0, 0, mCurrentScreen * width, 0, 0);
mFirstLayout = false;
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
int childLeft = 0;
final int count = getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != View.GONE) {
final int childWidth = child.getMeasuredWidth();
child.layout(childLeft, 0, childLeft + childWidth,
child.getMeasuredHeight());
childLeft += childWidth;
}
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (getChildCount() == 0)
return false;
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
final float x = ev.getX();
switch (action) {
case MotionEvent.ACTION_DOWN:
/*
* If being flinged and user touches, stop the fling. isFinished
* will be false if being flinged.
*/
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
// Remember where the motion event started
mLastMotionX = x;
mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
: TOUCH_STATE_SCROLLING;
break;
case MotionEvent.ACTION_MOVE:
final int deltaX = (int) (mLastMotionX - x);
boolean xMoved = Math.abs(deltaX) > mTouchSlop;
if (xMoved) {
// Scroll if the user moved far enough along the X axis
mTouchState = TOUCH_STATE_SCROLLING;
if (mViewInitializeListener != null)
initializeView(deltaX);
}
if (mTouchState == TOUCH_STATE_SCROLLING) {
// Scroll to follow the motion event
mLastMotionX = x;
final int scrollX = getScrollX();
if (deltaX < 0) {
if (scrollX > 0) {
scrollBy(Math.max(-scrollX, deltaX), 0);
}
} else if (deltaX > 0) {
final int availableToScroll = getChildAt(
getChildCount() - 1).getRight()
- scrollX - getWidth();
if (availableToScroll > 0) {
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
}
return true;
}
break;
case MotionEvent.ACTION_UP:
if (mTouchState == TOUCH_STATE_SCROLLING) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int velocityX = (int) velocityTracker.getXVelocity();
if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
// Fling hard enough to move left
snapToScreen(mCurrentScreen - 1);
} else if (velocityX < -SNAP_VELOCITY
&& mCurrentScreen < getChildCount() - 1) {
// Fling hard enough to move right
snapToScreen(mCurrentScreen + 1);
} else {
snapToDestination();
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
mTouchState = TOUCH_STATE_REST;
break;
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
}
return false;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (getChildCount() == 0)
return false;
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
final float x = ev.getX();
switch (action) {
case MotionEvent.ACTION_DOWN:
/*
* If being flinged and user touches, stop the fling. isFinished
* will be false if being flinged.
*/
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
// Remember where the motion event started
mLastMotionX = x;
mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
: TOUCH_STATE_SCROLLING;
break;
case MotionEvent.ACTION_MOVE:
final int deltaX = (int) (mLastMotionX - x);
boolean xMoved = Math.abs(deltaX) > mTouchSlop;
if (xMoved) {
// Scroll if the user moved far enough along the X axis
mTouchState = TOUCH_STATE_SCROLLING;
if (mViewInitializeListener != null)
initializeView(deltaX);
}
if (mTouchState == TOUCH_STATE_SCROLLING) {
// Scroll to follow the motion event
mLastMotionX = x;
final int scrollX = getScrollX();
if (deltaX < 0) {
if (scrollX > 0) {
scrollBy(Math.max(-scrollX, deltaX), 0);
}
} else if (deltaX > 0) {
final int availableToScroll = getChildAt(
getChildCount() - 1).getRight()
- scrollX - getWidth();
if (availableToScroll > 0) {
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
}
return true;
}
break;
case MotionEvent.ACTION_UP:
if (mTouchState == TOUCH_STATE_SCROLLING) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int velocityX = (int) velocityTracker.getXVelocity();
if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
// Fling hard enough to move left
snapToScreen(mCurrentScreen - 1);
} else if (velocityX < -SNAP_VELOCITY
&& mCurrentScreen < getChildCount() - 1) {
// Fling hard enough to move right
snapToScreen(mCurrentScreen + 1);
} else {
snapToDestination();
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
mTouchState = TOUCH_STATE_REST;
break;
case MotionEvent.ACTION_CANCEL:
snapToDestination();
mTouchState = TOUCH_STATE_REST;
}
return true;
}
private void initializeView(final float direction) {
if (direction > 0) {
if (mLazyInit.contains(LazyInit.RIGHT)) {
mLazyInit.remove(LazyInit.RIGHT);
if (mCurrentBufferIndex+1 < mLoadedViews.size())
mViewInitializeListener.onViewLazyInitialize(mLoadedViews.get(mCurrentBufferIndex + 1), mCurrentAdapterIndex + 1);
}
} else {
if (mLazyInit.contains(LazyInit.LEFT)) {
mLazyInit.remove(LazyInit.LEFT);
if (mCurrentBufferIndex > 0)
mViewInitializeListener.onViewLazyInitialize(mLoadedViews.get(mCurrentBufferIndex - 1), mCurrentAdapterIndex - 1);
}
}
}
@Override
protected void onScrollChanged(int h, int v, int oldh, int oldv) {
super.onScrollChanged(h, v, oldh, oldv);
if (mIndicator != null) {
/*
* The actual horizontal scroll origin does typically not match the
* perceived one. Therefore, we need to calculate the perceived
* horizontal scroll origin here, since we use a view buffer.
*/
int hPerceived = h + (mCurrentAdapterIndex - mCurrentBufferIndex)
* getWidth();
mIndicator.onScrolled(hPerceived, v, oldh, oldv);
}
}
private void snapToDestination() {
final int screenWidth = getWidth();
final int whichScreen = (getScrollX() + (screenWidth / 2))
/ screenWidth;
snapToScreen(whichScreen);
}
private void snapToScreen(int whichScreen) {
mLastScrollDirection = whichScreen - mCurrentScreen;
if (!mScroller.isFinished())
return;
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
mNextScreen = whichScreen;
final int newX = whichScreen * getWidth();
final int delta = newX - getScrollX();
mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta) * 2);
invalidate();
}
@Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();
} else if (mNextScreen != INVALID_SCREEN) {
mCurrentScreen = Math.max(0,
Math.min(mNextScreen, getChildCount() - 1));
mNextScreen = INVALID_SCREEN;
postViewSwitched(mLastScrollDirection);
}
}
/**
* Scroll to the {@link View} in the view buffer specified by the index.
*
* @param indexInBuffer
* Index of the view in the view buffer.
*/
private void setVisibleView(int indexInBuffer, boolean uiThread) {
mCurrentScreen = Math.max(0,
Math.min(indexInBuffer, getChildCount() - 1));
int dx = (mCurrentScreen * getWidth()) - mScroller.getCurrX();
mScroller.startScroll(mScroller.getCurrX(), mScroller.getCurrY(), dx,
0, 0);
if(dx == 0)
onScrollChanged(mScroller.getCurrX() + dx, mScroller.getCurrY(), mScroller.getCurrX() + dx, mScroller.getCurrY());
if (uiThread)
invalidate();
else
postInvalidate();
}
/**
* Set the listener that will receive notifications every time the {code
* ViewFlow} scrolls.
*
* @param l
* the scroll listener
*/
public void setOnViewSwitchListener(ViewSwitchListener l) {
mViewSwitchListener = l;
}
public void setOnViewLazyInitializeListener(ViewLazyInitializeListener l) {
mViewInitializeListener = l;
}
@Override
public Adapter getAdapter() {
return mAdapter;
}
@Override
public void setAdapter(Adapter adapter) {
setAdapter(adapter, 0);
}
public void setAdapter(Adapter adapter, int initialPosition) {
if (mAdapter != null) {
mAdapter.unregisterDataSetObserver(mDataSetObserver);
}
mAdapter = adapter;
if (mAdapter != null) {
mDataSetObserver = new AdapterDataSetObserver();
mAdapter.registerDataSetObserver(mDataSetObserver);
}
if (mAdapter == null || mAdapter.getCount() == 0)
return;
setSelection(initialPosition);
}
@Override
public View getSelectedView() {
return (mCurrentBufferIndex < mLoadedViews.size() ? mLoadedViews
.get(mCurrentBufferIndex) : null);
}
@Override
public int getSelectedItemPosition() {
return mCurrentAdapterIndex;
}
/**
* Set the FlowIndicator
*
* @param flowIndicator
*/
public void setFlowIndicator(FlowIndicator flowIndicator) {
mIndicator = flowIndicator;
mIndicator.setViewFlow(this);
}
protected void recycleViews() {
while (!mLoadedViews.isEmpty())
recycleView(mLoadedViews.remove());
}
protected void recycleView(View v) {
if (v == null)
return;
mRecycledViews.add(v);
detachViewFromParent(v);
}
protected View getRecycledView() {
return (mRecycledViews.isEmpty() ? null : mRecycledViews.remove(0));
}
@Override
public void setSelection(int position) {
mNextScreen = INVALID_SCREEN;
mScroller.forceFinished(true);
if (mAdapter == null)
return;
position = Math.max(position, 0);
position = Math.min(position, mAdapter.getCount()-1);
recycleViews();
View currentView = makeAndAddView(position, true);
mLoadedViews.addLast(currentView);
if (mViewInitializeListener != null)
mViewInitializeListener.onViewLazyInitialize(currentView, position);
for(int offset = 1; mSideBuffer - offset >= 0; offset++) {
int leftIndex = position - offset;
int rightIndex = position + offset;
if(leftIndex >= 0)
mLoadedViews.addFirst(makeAndAddView(leftIndex, false));
if(rightIndex < mAdapter.getCount())
mLoadedViews.addLast(makeAndAddView(rightIndex, true));
}
mCurrentBufferIndex = mLoadedViews.indexOf(currentView);
mCurrentAdapterIndex = position;
requestLayout();
setVisibleView(mCurrentBufferIndex, false);
if (mIndicator != null) {
mIndicator.onSwitched(currentView, mCurrentAdapterIndex);
}
if (mViewSwitchListener != null) {
mViewSwitchListener.onSwitched(currentView, mCurrentAdapterIndex);
}
}
private void resetFocus() {
logBuffer();
recycleViews();
removeAllViewsInLayout();
mLazyInit.addAll(EnumSet.allOf(LazyInit.class));
for (int i = Math.max(0, mCurrentAdapterIndex - mSideBuffer); i < Math
.min(mAdapter.getCount(), mCurrentAdapterIndex + mSideBuffer
+ 1); i++) {
mLoadedViews.addLast(makeAndAddView(i, true));
if (i == mCurrentAdapterIndex) {
mCurrentBufferIndex = mLoadedViews.size() - 1;
if (mViewInitializeListener != null)
mViewInitializeListener.onViewLazyInitialize(mLoadedViews.getLast(), mCurrentAdapterIndex);
}
}
logBuffer();
requestLayout();
}
private void postViewSwitched(int direction) {
if (direction == 0)
return;
if (direction > 0) { // to the right
mCurrentAdapterIndex++;
mCurrentBufferIndex++;
mLazyInit.remove(LazyInit.LEFT);
mLazyInit.add(LazyInit.RIGHT);
// Recycle view outside buffer range
if (mCurrentAdapterIndex > mSideBuffer) {
recycleView(mLoadedViews.removeFirst());
mCurrentBufferIndex--;
}
// Add new view to buffer
int newBufferIndex = mCurrentAdapterIndex + mSideBuffer;
if (newBufferIndex < mAdapter.getCount())
mLoadedViews.addLast(makeAndAddView(newBufferIndex, true));
} else { // to the left
mCurrentAdapterIndex--;
mCurrentBufferIndex--;
mLazyInit.add(LazyInit.LEFT);
mLazyInit.remove(LazyInit.RIGHT);
// Recycle view outside buffer range
if (mAdapter.getCount() - 1 - mCurrentAdapterIndex > mSideBuffer) {
recycleView(mLoadedViews.removeLast());
}
// Add new view to buffer
int newBufferIndex = mCurrentAdapterIndex - mSideBuffer;
if (newBufferIndex > -1) {
mLoadedViews.addFirst(makeAndAddView(newBufferIndex, false));
mCurrentBufferIndex++;
}
}
requestLayout();
setVisibleView(mCurrentBufferIndex, true);
if (mIndicator != null) {
mIndicator.onSwitched(mLoadedViews.get(mCurrentBufferIndex),
mCurrentAdapterIndex);
}
if (mViewSwitchListener != null) {
mViewSwitchListener
.onSwitched(mLoadedViews.get(mCurrentBufferIndex),
mCurrentAdapterIndex);
}
logBuffer();
}
private View setupChild(View child, boolean addToEnd, boolean recycle) {
ViewGroup.LayoutParams p = (ViewGroup.LayoutParams) child
.getLayoutParams();
if (p == null) {
p = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT, 0);
}
if (recycle)
attachViewToParent(child, (addToEnd ? -1 : 0), p);
else
addViewInLayout(child, (addToEnd ? -1 : 0), p, true);
return child;
}
private View makeAndAddView(int position, boolean addToEnd) {
return makeAndAddView(position, addToEnd, getRecycledView());
}
private View makeAndAddView(int position, boolean addToEnd, View convertView) {
View view = mAdapter.getView(position, convertView, this);
if(view != convertView)
mRecycledViews.add(convertView);
return setupChild(view, addToEnd, view == convertView);
}
class AdapterDataSetObserver extends DataSetObserver {
@Override
public void onChanged() {
View v = getChildAt(mCurrentBufferIndex);
if (v != null) {
for (int index = 0; index < mAdapter.getCount(); index++) {
if (v.equals(mAdapter.getItem(index))) {
mCurrentAdapterIndex = index;
break;
}
}
}
resetFocus();
}
@Override
public void onInvalidated() {
// Not yet implemented!
}
}
private void logBuffer() {
Log.d("viewflow", "Size of mLoadedViews: " + mLoadedViews.size() +
", Size of mRecycledViews: " + mRecycledViews.size() +
", X: " + mScroller.getCurrX() + ", Y: " + mScroller.getCurrY());
Log.d("viewflow", "IndexInAdapter: " + mCurrentAdapterIndex
+ ", IndexInBuffer: " + mCurrentBufferIndex);
}
}