//(edit: removed complexities around fling velocity and transitions;
now just decelerates like the standard gallery)
package com.droidful.flinggallery;
import android.content.Context;
import android.view.GestureDetector;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
import android.view.animation.Transformation;
import android.widget.Adapter;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
public class FlingGallery extends FrameLayout
{
// Constants
private final int swipe_min_distance = 120;
private final int swipe_max_off_path = 250;
private final int swipe_threshold_veloicty = 400;
// Properties
private int mViewPaddingWidth = 0;
private int mAnimationDuration = 400;
private float mSnapBorderRatio = 0.4f;
private boolean mIsGalleryCircular = true;
// Members
private int mGalleryWidth = 0;
private boolean mIsTouched = false;
private boolean mIsDragging = false;
private float mCurrentOffset = 0.0f;
private int mFlingDirection = 0;
private int mCurrentPosition = 0;
private int mCurrentViewNumber = 0;
private Context mContext;
private Adapter mAdapter;
private FlingGalleryView[] mViews;
private FlingGalleryAnimation mAnimation;
private GestureDetector mGestureDetector;
private Interpolator mDecelerateInterpolater;
public FlingGallery(Context context)
{
super(context);
mContext = context;
mAdapter = null;
mViews = new FlingGalleryView[3];
mViews[0] = new FlingGalleryView(0, this);
mViews[1] = new FlingGalleryView(1, this);
mViews[2] = new FlingGalleryView(2, this);
mAnimation = new FlingGalleryAnimation();
mGestureDetector = new GestureDetector(new
FlingGestureDetector());
mDecelerateInterpolater =
AnimationUtils.loadInterpolator(mContext,
android.R.anim.decelerate_interpolator);
AnimationUtils.loadInterpolator(mContext,
android.R.anim.linear_interpolator);
}
public void setPaddingWidth(int viewPaddingWidth)
{
mViewPaddingWidth = viewPaddingWidth;
}
public void setAnimationDuration(int animationDuration)
{
mAnimationDuration = animationDuration;
}
public void setSnapBorderRatio(float snapBorderRatio)
{
mSnapBorderRatio = snapBorderRatio;
}
public void setIsGalleryCircular(boolean isGalleryCircular)
{
if (mIsGalleryCircular != isGalleryCircular)
{
mIsGalleryCircular = isGalleryCircular;
if (mCurrentPosition == getFirstPosition())
{
// We need to reload the view immediately to
the left to change it
to circular view or blank
mViews[getPrevViewNumber(mCurrentViewNumber)].recycleView(getPrevPosition(mCurrentPosition));
}
if (mCurrentPosition == getLastPosition())
{
// We need to reload the view immediately to
the right to change
it to circular view or blank
mViews[getNextViewNumber(mCurrentViewNumber)].recycleView(getNextPosition(mCurrentPosition));
}
}
}
public int getGalleryCount()
{
return (mAdapter == null) ? 0 : mAdapter.getCount();
}
public int getFirstPosition()
{
return 0;
}
public int getLastPosition()
{
return (getGalleryCount() == 0) ? 0 : getGalleryCount() - 1;
}
private int getPrevPosition(int relativePosition)
{
int prevPosition = relativePosition - 1;
if (prevPosition < getFirstPosition())
{
prevPosition = getFirstPosition() - 1;
if (mIsGalleryCircular == true)
{
prevPosition = getLastPosition();
}
}
return prevPosition;
}
private int getNextPosition(int relativePosition)
{
int nextPosition = relativePosition + 1;
if (nextPosition > getLastPosition())
{
nextPosition = getLastPosition() + 1;
if (mIsGalleryCircular == true)
{
nextPosition = getFirstPosition();
}
}
return nextPosition;
}
private int getPrevViewNumber(int relativeViewNumber)
{
return (relativeViewNumber == 0) ? 2 : relativeViewNumber - 1;
}
private int getNextViewNumber(int relativeViewNumber)
{
return (relativeViewNumber == 2) ? 0 : relativeViewNumber + 1;
}
@Override
protected void onLayout(boolean changed, int left, int top, int
right, int bottom)
{
super.onLayout(changed, left, top, right, bottom);
// Calculate our view width
mGalleryWidth = right - left;
if (changed == true)
{
// Position views at correct starting offsets
mViews[0].setOffset(0, 0, mCurrentViewNumber);
mViews[1].setOffset(0, 0, mCurrentViewNumber);
mViews[2].setOffset(0, 0, mCurrentViewNumber);
}
}
public void setAdapter(Adapter adapter)
{
mAdapter = adapter;
mCurrentPosition = 0;
mCurrentViewNumber = 0;
// Load the initial views from adapter
mViews[0].recycleView(mCurrentPosition);
mViews[1].recycleView(getNextPosition(mCurrentPosition));
mViews[2].recycleView(getPrevPosition(mCurrentPosition));
// Position views at correct starting offsets
mViews[0].setOffset(0, 0, mCurrentViewNumber);
mViews[1].setOffset(0, 0, mCurrentViewNumber);
mViews[2].setOffset(0, 0, mCurrentViewNumber);
}
private int getViewOffset(int viewNumber, int relativeViewNumber)
{
// Determine width including configured padding width
int offsetWidth = mGalleryWidth + mViewPaddingWidth;
// Position the previous view one measured width to left
if (viewNumber == getPrevViewNumber(relativeViewNumber))
{
return offsetWidth;
}
// Position the next view one measured width to the right
if (viewNumber == getNextViewNumber(relativeViewNumber))
{
return offsetWidth * -1;
}
return 0;
}
void movePrevious()
{
// Note: We prevent movement if an animation is running so that
we
don't
// get too ahead of ourselves. We could allow it but given that
a
second
// movement while an existing animation is in progress would
involve
the
// off-screen view we would need to update the animation code as
well
if (false == mAnimation.mIsRunningAnimation)
{
// Slide to previous view
mFlingDirection = 1;
processGesture();
}
}
void moveNext()
{
if (false == mAnimation.mIsRunningAnimation)
{
// Slide to next view
mFlingDirection = -1;
processGesture();
}
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
switch (keyCode)
{
case KeyEvent.KEYCODE_DPAD_LEFT:
movePrevious();
return true;
case KeyEvent.KEYCODE_DPAD_RIGHT:
moveNext();
return true;
case KeyEvent.KEYCODE_DPAD_CENTER:
case KeyEvent.KEYCODE_ENTER:
}
return super.onKeyDown(keyCode, event);
}
public boolean onGalleryTouchEvent(MotionEvent event)
{
boolean consumed = mGestureDetector.onTouchEvent(event);
if (event.getAction() == MotionEvent.ACTION_UP)
{
if (mIsTouched || mIsDragging)
{
processScrollSnap();
processGesture();
}
}
return consumed;
}
void processGesture()
{
int newViewNumber = mCurrentViewNumber;
int reloadViewNumber = 0;
int reloadPosition = 0;
mIsTouched = false;
mIsDragging = false;
if (mFlingDirection > 0)
{
if (mCurrentPosition > getFirstPosition() ||
mIsGalleryCircular ==
true)
{
// Determine previous view and outgoing view to
recycle
newViewNumber =
getPrevViewNumber(mCurrentViewNumber);
mCurrentPosition =
getPrevPosition(mCurrentPosition);
reloadViewNumber =
getNextViewNumber(mCurrentViewNumber);
reloadPosition =
getPrevPosition(mCurrentPosition);
}
}
if (mFlingDirection < 0)
{
if (mCurrentPosition < getLastPosition() ||
mIsGalleryCircular ==
true)
{
// Determine the next view and outgoing view to
recycle
newViewNumber =
getNextViewNumber(mCurrentViewNumber);
mCurrentPosition =
getNextPosition(mCurrentPosition);
reloadViewNumber =
getPrevViewNumber(mCurrentViewNumber);
reloadPosition =
getNextPosition(mCurrentPosition);
}
}
if (newViewNumber != mCurrentViewNumber)
{
mCurrentViewNumber = newViewNumber;
// Reload outgoing view from adapter in new position
mViews[reloadViewNumber].recycleView(reloadPosition);
}
// Ensure input focus on the current view
mViews[mCurrentViewNumber].requestFocus();
// Run the slide animations for view transitions
mAnimation.prepareAnimation(mCurrentViewNumber);
this.startAnimation(mAnimation);
// Reset fling state
mFlingDirection = 0;
}
void processScrollSnap()
{
// Snap to next view if scrolled passed snap position
float rollEdgeWidth = mGalleryWidth * mSnapBorderRatio;
int rollOffset = mGalleryWidth - (int) rollEdgeWidth;
int currentOffset =
mViews[mCurrentViewNumber].getCurrentOffset();
if (currentOffset <= rollOffset * -1)
{
// Snap to previous view
mFlingDirection = 1;
}
if (currentOffset >= rollOffset)
{
// Snap to next view
mFlingDirection = -1;
}
}
private class FlingGalleryView
{
private int mViewNumber;
private FrameLayout mParentLayout;
private FrameLayout mInvalidLayout = null;
private LinearLayout mInternalLayout = null;
private View mExternalView = null;
public FlingGalleryView(int viewNumber, FrameLayout
parentLayout)
{
mViewNumber = viewNumber;
mParentLayout = parentLayout;
// Invalid layout is used when outside gallery
mInvalidLayout = new FrameLayout(mContext);
mInvalidLayout.setLayoutParams(new
LinearLayout.LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
// Internal layout is permanent for duration
mInternalLayout = new LinearLayout(mContext);
mInternalLayout.setLayoutParams(new
LinearLayout.LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
mParentLayout.addView(mInternalLayout);
}
public void recycleView(int newPosition)
{
if (mExternalView != null)
{
mInternalLayout.removeView(mExternalView);
}
if (mAdapter != null)
{
mExternalView = mInvalidLayout;
if (newPosition >= getFirstPosition() &&
newPosition <=
getLastPosition())
{
mExternalView =
mAdapter.getView(newPosition, mExternalView,
mInternalLayout);
}
}
if (mExternalView != null)
{
mInternalLayout.addView(mExternalView, new
LinearLayout.LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
}
}
public void setOffset(int xOffset, int yOffset, int
relativeViewNumber)
{
// Scroll the target view relative to its own position
relative to
currently displayed view
mInternalLayout.scrollTo(getViewOffset(mViewNumber,
relativeViewNumber) + xOffset, yOffset);
}
public int getCurrentOffset()
{
// Return the current scroll position
return mInternalLayout.getScrollX();
}
public void requestFocus()
{
mInternalLayout.requestFocus();
}
}
private class FlingGalleryAnimation extends Animation
{
private boolean mIsRunningAnimation;
private int mRelativeViewNumber;
private int mInitialOffset;
private int mTargetOffset;
private int mTargetDistance;
public FlingGalleryAnimation()
{
mIsRunningAnimation = false;
mRelativeViewNumber = 0;
mInitialOffset = 0;
mTargetOffset = 0;
mTargetDistance = 0;
}
void prepareAnimation(int relativeViewNumber)
{
mRelativeViewNumber = relativeViewNumber;
// Note: In this implementation the targetOffset will
always be
zero
// as we are centering the view; we only include the
calculations of
// targetOffset and targetDistance for use in future
implementations
mInitialOffset =
mViews[mRelativeViewNumber].getCurrentOffset();
mTargetOffset = getViewOffset(mRelativeViewNumber,
mRelativeViewNumber);
mTargetDistance = mTargetOffset - mInitialOffset;
// Configure base animation properties
this.setDuration(mAnimationDuration);
this.setInterpolator(mDecelerateInterpolater);
}
@Override
protected void applyTransformation(float interpolatedTime,
Transformation transformation)
{
// Ensure interpolatedTime does not over-shoot then calculate
new offset
interpolatedTime = (interpolatedTime > 1.0f) ? 1.0f :
interpolatedTime;
int offset = mInitialOffset + (int) (mTargetDistance *
interpolatedTime);
for (int viewNumber = 0; viewNumber < 3; viewNumber++)
{
// We only need to animate two views as the
other view will always
be off-screen
// as long as we don't allow additional
movements while an
animation is in progress
if ((mTargetDistance > 0 && viewNumber !=
getNextViewNumber(mRelativeViewNumber)) ||
(mTargetDistance < 0 && viewNumber !=
getPrevViewNumber(mRelativeViewNumber)))
{
mViews[viewNumber].setOffset(offset, 0,
mRelativeViewNumber);
}
}
}
@Override
public boolean getTransformation(long currentTime,
Transformation outTransformation)
{
mIsRunningAnimation = true;
if (super.getTransformation(currentTime, outTransformation)
== false)
{
// Perform final adjustment to offsets to cleanup
animation
mViews[0].setOffset(mTargetOffset, 0,
mRelativeViewNumber);
mViews[1].setOffset(mTargetOffset, 0,
mRelativeViewNumber);
mViews[2].setOffset(mTargetOffset, 0,
mRelativeViewNumber);
mIsRunningAnimation = false;
}
// Cancel if the screen touched
if (mIsTouched || mIsDragging)
{
mIsRunningAnimation = false;
}
return mIsRunningAnimation;
}
}
private class FlingGestureDetector extends
GestureDetector.SimpleOnGestureListener
{
@Override
public boolean onDown(MotionEvent e)
{
// Stop animation
mIsTouched = true;
// Reset fling state
mFlingDirection = 0;
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float
distanceX, float distanceY)
{
if (mIsDragging == false)
{
// Stop animation
mIsTouched = true;
// Reconfigure scroll
mIsDragging = true;
mFlingDirection = 0;
mCurrentOffset =
mViews[mCurrentViewNumber].getCurrentOffset();
}
if (e2.getAction() == MotionEvent.ACTION_MOVE)
{
int scrollOffset = Math.round(mCurrentOffset +
e1.getX() -
e2.getX());
// We can't scroll more than the width of our own frame
layout
if (scrollOffset >= mGalleryWidth) scrollOffset =
mGalleryWidth;
if (scrollOffset <= mGalleryWidth * -1) scrollOffset =
mGalleryWidth * -1;
mViews[0].setOffset(scrollOffset, 0,
mCurrentViewNumber);
mViews[1].setOffset(scrollOffset, 0,
mCurrentViewNumber);
mViews[2].setOffset(scrollOffset, 0,
mCurrentViewNumber);
}
return false;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float
velocityX, float velocityY)
{
if (Math.abs(e1.getY() - e2.getY()) <= swipe_max_off_path)
{
if (e2.getX() - e1.getX() > swipe_min_distance &&
Math.abs(velocityX) > swipe_threshold_veloicty)
{
// Fling to previous view
mFlingDirection = 1;
Math.abs(velocityX);
}
if(e1.getX() - e2.getX() > swipe_min_distance &&
Math.abs(velocityX) > swipe_threshold_veloicty)
{
// Fling to next view
mFlingDirection = -1;
Math.abs(velocityX);
}
if (mFlingDirection != 0)
{
// Process immediately
processGesture();
}
}
return false;
}
@Override
public void onLongPress(MotionEvent e)
{
// Finalise scrolling
mFlingDirection = 0;
processGesture();
}
@Override
public void onShowPress(MotionEvent e)
{
}
@Override
public boolean onSingleTapUp(MotionEvent e)
{
// Reset fling state
mFlingDirection = 0;
return false;
}
}
}
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