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DoubleSwipeDetector.cs
C#
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/*
* Copyright (C) 2010 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.
*/
 
using System;
 
using Android.Runtime;
using Android.Content;
using Android.Util;
using Android.Views;
 
namespace FriendTab
{
public class DoubleSwipeDetector
{
public interface IOnScaleGestureListener {
 
bool OnScale(DoubleSwipeDetector detector);
 
bool OnScaleBegin(DoubleSwipeDetector detector);
 
void OnScaleEnd(DoubleSwipeDetector detector);
}
 
public class SimpleOnScaleGestureListener : IOnScaleGestureListener {
 
public bool OnScale(DoubleSwipeDetector detector) {
return false;
}
 
public bool OnScaleBegin(DoubleSwipeDetector detector) {
return true;
}
 
public void OnScaleEnd(DoubleSwipeDetector detector) {
// Intentionally empty
}
}
 
private static float PRESSURE_THRESHOLD = 0.67f;
 
private Context mContext;
private IOnScaleGestureListener mListener;
private bool mGestureInProgress;
 
private MotionEvent mPrevEvent;
private MotionEvent mCurrEvent;
 
private float mFocusX;
private float mFocusY;
private float mPrevFingerDiffX;
private float mPrevFingerDiffY;
private float mCurrFingerDiffX;
private float mCurrFingerDiffY;
private float mCurrLen;
private float mPrevLen;
private float mScaleFactor;
private float mCurrPressure;
private float mPrevPressure;
private long mTimeDelta;
 
private bool mInvalidGesture;
 
// Pointer IDs currently responsible for the two fingers controlling the gesture
private int mActiveId0;
private int mActiveId1;
private bool mActive0MostRecent;
 
public DoubleSwipeDetector (Context context, IOnScaleGestureListener listener) {
mContext = context;
mListener = listener;
}
 
public bool OnTouchEvent (MotionEvent evt) {
var action = evt.ActionMasked;
 
if (action == MotionEventActions.Down) {
reset(); // Start fresh
}
 
bool handled = true;
if (mInvalidGesture) {
handled = false;
} else if (!mGestureInProgress) {
switch (action) {
case MotionEventActions.Down: {
mActiveId0 = evt.GetPointerId(0);
mActive0MostRecent = true;
}
break;
 
case MotionEventActions.Up:
reset();
break;
 
case MotionEventActions.PointerDown: {
// We have a new multi-finger gesture
if (mPrevEvent != null) mPrevEvent.Recycle();
mPrevEvent = MotionEvent.Obtain(evt);
mTimeDelta = 0;
 
int index1 = evt.ActionIndex;
int index0 = evt.FindPointerIndex(mActiveId0);
mActiveId1 = evt.GetPointerId(index1);
if (index0 < 0 || index0 == index1) {
// Probably someone sending us a broken evt stream.
index0 = findNewActiveIndex(evt, mActiveId1, -1);
mActiveId0 = evt.GetPointerId(index0);
}
mActive0MostRecent = false;
 
setContext(evt);
 
mGestureInProgress = mListener.OnScaleBegin(this);
break;
}
}
} else {
// Transform gesture in progress - attempt to handle it
switch (action) {
case MotionEventActions.Down: {
// End the old gesture and begin a new one with the most recent two fingers.
mListener.OnScaleEnd(this);
int oldActive0 = mActiveId0;
int oldActive1 = mActiveId1;
reset();
 
mPrevEvent = MotionEvent.Obtain(evt);
mActiveId0 = mActive0MostRecent ? oldActive0 : oldActive1;
mActiveId1 = evt.GetPointerId(evt.ActionIndex);
mActive0MostRecent = false;
 
int index0 = evt.FindPointerIndex (mActiveId0);
if (index0 < 0 || mActiveId0 == mActiveId1) {
index0 = findNewActiveIndex(evt, mActiveId1, -1);
mActiveId0 = evt.GetPointerId(index0);
}
 
setContext(evt);
 
mGestureInProgress = mListener.OnScaleBegin(this);
}
break;
 
case MotionEventActions.PointerUp: {
int pointerCount = evt.PointerCount;
int actionIndex = evt.ActionIndex;
int actionId = evt.GetPointerId(actionIndex);
 
bool gestureEnded = false;
if (pointerCount > 2) {
if (actionId == mActiveId0) {
int newIndex = findNewActiveIndex(evt, mActiveId1, actionIndex);
if (newIndex >= 0) {
mListener.OnScaleEnd(this);
mActiveId0 = evt.GetPointerId(newIndex);
mActive0MostRecent = true;
mPrevEvent = MotionEvent.Obtain(evt);
setContext(evt);
mGestureInProgress = mListener.OnScaleBegin(this);
} else {
gestureEnded = true;
}
} else if (actionId == mActiveId1) {
int newIndex = findNewActiveIndex(evt, mActiveId0, actionIndex);
if (newIndex >= 0) {
mListener.OnScaleEnd(this);
mActiveId1 = evt.GetPointerId(newIndex);
mActive0MostRecent = false;
mPrevEvent = MotionEvent.Obtain(evt);
setContext(evt);
mGestureInProgress = mListener.OnScaleBegin(this);
} else {
gestureEnded = true;
}
}
mPrevEvent.Recycle();
mPrevEvent = MotionEvent.Obtain(evt);
setContext(evt);
} else {
gestureEnded = true;
}
 
if (gestureEnded) {
// Gesture ended
setContext(evt);
 
// Set focus point to the remaining finger
int activeId = actionId == mActiveId0 ? mActiveId1 : mActiveId0;
int index = evt.FindPointerIndex(activeId);
mFocusX = evt.GetX(index);
mFocusY = evt.GetY(index);
 
mListener.OnScaleEnd(this);
reset();
mActiveId0 = activeId;
mActive0MostRecent = true;
}
}
break;
 
case MotionEventActions.Cancel:
mListener.OnScaleEnd(this);
reset();
break;
 
case MotionEventActions.Up:
reset();
break;
 
case MotionEventActions.Move: {
setContext(evt);
 
// Only accept the evt if our relative pressure is within
// a certain limit - this can help filter shaky data as a
// finger is lifted.
if (mCurrPressure / mPrevPressure > PRESSURE_THRESHOLD) {
bool updatePrevious = mListener.OnScale(this);
 
if (updatePrevious) {
mPrevEvent.Recycle();
mPrevEvent = MotionEvent.Obtain(evt);
}
}
}
break;
}
}
 
return handled;
}
 
private int findNewActiveIndex(MotionEvent ev, int otherActiveId, int removedPointerIndex) {
int pointerCount = ev.PointerCount;
 
// It's ok if this isn't found and returns -1, it simply won't match.
int otherActiveIndex = ev.FindPointerIndex(otherActiveId);
 
// Pick a new id and update tracking state.
for (int i = 0; i < pointerCount; i++) {
if (i != removedPointerIndex && i != otherActiveIndex) {
return i;
}
}
return -1;
}
 
private void setContext(MotionEvent curr) {
if (mCurrEvent != null) {
mCurrEvent.Recycle();
}
mCurrEvent = MotionEvent.Obtain(curr);
 
mCurrLen = -1;
mPrevLen = -1;
mScaleFactor = -1;
 
MotionEvent prev = mPrevEvent;
 
int prevIndex0 = prev.FindPointerIndex(mActiveId0);
int prevIndex1 = prev.FindPointerIndex(mActiveId1);
int currIndex0 = curr.FindPointerIndex(mActiveId0);
int currIndex1 = curr.FindPointerIndex(mActiveId1);
 
if (prevIndex0 < 0 || prevIndex1 < 0 || currIndex0 < 0 || currIndex1 < 0) {
mInvalidGesture = true;
if (mGestureInProgress) {
mListener.OnScaleEnd(this);
}
return;
}
 
float px0 = prev.GetX(prevIndex0);
float py0 = prev.GetY(prevIndex0);
float px1 = prev.GetX(prevIndex1);
float py1 = prev.GetY(prevIndex1);
float cx0 = curr.GetX(currIndex0);
float cy0 = curr.GetY(currIndex0);
float cx1 = curr.GetX(currIndex1);
float cy1 = curr.GetY(currIndex1);
 
float pvx = px1 - px0;
float pvy = py1 - py0;
float cvx = cx1 - cx0;
float cvy = cy1 - cy0;
mPrevFingerDiffX = pvx;
mPrevFingerDiffY = pvy;
mCurrFingerDiffX = cvx;
mCurrFingerDiffY = cvy;
 
mFocusX = cx0 + cvx * 0.5f;
mFocusY = cy0 + cvy * 0.5f;
mTimeDelta = curr.EventTime - prev.EventTime;
mCurrPressure = curr.GetPressure(currIndex0) + curr.GetPressure(currIndex1);
mPrevPressure = prev.GetPressure(prevIndex0) + prev.GetPressure(prevIndex1);
}
 
private void reset() {
if (mPrevEvent != null) {
mPrevEvent.Recycle();
mPrevEvent = null;
}
if (mCurrEvent != null) {
mCurrEvent.Recycle();
mCurrEvent = null;
}
mGestureInProgress = false;
mActiveId0 = -1;
mActiveId1 = -1;
mInvalidGesture = false;
}
 
public bool IsInProgress {
get {
return mGestureInProgress;
}
}
 
public float FocusX {
get {
return mFocusX;
}
}
 
public float FocusY {
get {
return mFocusY;
}
}
 
public float CurrentSpan {
get {
if (mCurrLen == -1) {
float cvx = mCurrFingerDiffX;
float cvy = mCurrFingerDiffY;
mCurrLen = (float)Math.Sqrt (cvx * cvx + cvy * cvy);
}
return mCurrLen;
}
}
 
public float CurrentSpanX {
get {
return mCurrFingerDiffX;
}
}
 
public float CurrentSpanY {
get {
return mCurrFingerDiffY;
}
}
 
public float PreviousSpan {
get {
if (mPrevLen == -1) {
float pvx = mPrevFingerDiffX;
float pvy = mPrevFingerDiffY;
mPrevLen = (float)Math.Sqrt (pvx * pvx + pvy * pvy);
}
return mPrevLen;
}
}
 
public float PreviousSpanX {
get {
return mPrevFingerDiffX;
}
}
 
public float PreviousSpanY {
get {
return mPrevFingerDiffY;
}
}
 
public float ScaleFactor {
get {
if (mScaleFactor == -1) {
mScaleFactor = CurrentSpan / PreviousSpan;
}
return mScaleFactor;
}
}
 
public long TimeDelta {
get {
return mTimeDelta;
}
}
 
public long EventTime {
get {
return mCurrEvent.EventTime;
}
}
}
}
ExpandHelper.cs
C#
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/*
* Copyright (C) 2012 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.
*/
 
using System;
 
using Android.Animation;
using Android.Content;
using Android.Views;
using Android.Util;
 
namespace Foo
{
public class ExpandHelper : Java.Lang.Object
{
public interface Callback
{
View GetChildAtRawPosition(float x, float y);
View GetChildAtPosition(float x, float y);
bool CanChildBeExpanded(View v);
bool SetUserExpandedChild(View v, bool userxpanded);
}
 
const string Tag = "ExpandHelper";
protected const bool Debug = false;
const long ExpandDuration = 250;
const long GlowDuration = 150;
 
// Set to false to disable focus-based gestures (two-finger pull).
const bool UseDrag = true;
// Set to false to disable scale-based gestures (both horizontal and vertical).
const bool UseSpan = false;
// Both gestures types may be active at the same time.
// At least one gesture type should be active.
// A variant of the screwdriver gesture will emerge from either gesture type.
 
// amount of overstretch for maximum brightness expressed in U
// 2f: maximum brightness is stretching a 1U to 3U, or a 4U to 6U
const float StretchInterval = 2f;
 
// level of glow for a touch, without overstretch
// overstretch fills the range (GLOW_BASE, 1.0]
const float GlowBase = 0.5f;
 
Context context;
 
bool stretching;
View eventSource;
View currView;
View currViewTopGlow;
View currViewBottomGlow;
float oldHeight;
float naturalHeight;
float initialTouchFocusY;
float initialTouchSpan;
Callback callback;
DoubleSwipeDetector detector;
ViewScaler scaler;
//ObjectAnimator scaleAnimation;
ValueAnimator scaleAnimation;
AnimatorSet glowAnimationSet;
ObjectAnimator glowTopAnimation;
ObjectAnimator glowBottomAnimation;
 
int smallSize;
int largeSize;
float maximumStretch;
 
GravityFlags gravity;
 
class ViewScaler
{
View mView;
ViewGroup.LayoutParams pars;
 
public ViewScaler() {}
 
public void SetView(View v)
{
mView = v;
pars = v.LayoutParameters;
}
 
public float Height {
get {
int height = mView.LayoutParameters.Height;
if (height < 0) {
height = mView.MeasuredHeight;
}
return (float) height;
}
set {
mView.Visibility = value == 0 ? ViewStates.Invisible : ViewStates.Visible;
pars.Height = (int)value;
mView.RequestLayout ();
}
}
 
public int GetNaturalHeight (int maximum)
{
ViewGroup.LayoutParams lp = mView.LayoutParameters;
int oldHeight = lp.Height;
lp.Height = ViewGroup.LayoutParams.WrapContent;
mView.LayoutParameters = lp;
mView.Measure (
View.MeasureSpec.MakeMeasureSpec(mView.MeasuredWidth, MeasureSpecMode.Exactly),
View.MeasureSpec.MakeMeasureSpec(maximum, MeasureSpecMode.AtMost));
lp.Height = oldHeight;
mView.LayoutParameters = lp;
var height = mView.MeasuredHeight;
return height;
}
}
 
class AnimatorListener : AnimatorListenerAdapter
{
public override void OnAnimationStart(Animator animation)
{
View target = (View) ((ObjectAnimator) animation).Target;
if (target.Alpha <= 0.0f)
target.Visibility = ViewStates.Visible;
}
 
public override void OnAnimationEnd(Animator animation)
{
View target = (View) ((ObjectAnimator) animation).Target;
if (target.Alpha <= 0.0f)
target.Visibility = ViewStates.Invisible;
}
}
 
class GestureDetector : DoubleSwipeDetector.IOnScaleGestureListener
{
ExpandHelper parent;
 
public GestureDetector (ExpandHelper parent)
{
this.parent = parent;
}
 
public bool OnScaleBegin (DoubleSwipeDetector detector)
{
float x = detector.FocusX;
float y = detector.FocusY;
 
View v = null;
if (parent.eventSource != null) {
int[] location = new int[2];
parent.eventSource.GetLocationOnScreen(location);
x += (float) location[0];
y += (float) location[1];
v = parent.callback.GetChildAtRawPosition(x, y);
} else {
v = parent.callback.GetChildAtPosition(x, y);
}
 
// your fingers have to be somewhat close to the bounds of the view in question
parent.initialTouchFocusY = detector.FocusY;
parent.initialTouchSpan = Math.Abs(detector.CurrentSpan);
 
parent.stretching = parent.InitScale(v);
return parent.stretching;
}
 
public bool OnScale (DoubleSwipeDetector detector)
{
// are we scaling or dragging?
float span = Math.Abs(detector.CurrentSpan) - parent.initialTouchSpan;
span *= UseSpan ? 1f : 0f;
float drag = detector.FocusY - parent.initialTouchFocusY;
drag *= UseDrag ? 1f : 0f;
drag *= parent.gravity == GravityFlags.Bottom ? -1f : 1f;
float pull = Math.Abs(drag) + Math.Abs(span) + 1f;
float hand = drag * Math.Abs(drag) / pull + span * Math.Abs(span) / pull;
 
hand = hand + parent.oldHeight;
float target = hand;
 
hand = hand < parent.smallSize ? parent.smallSize : (hand > parent.largeSize ? parent.largeSize : hand);
hand = hand > parent.naturalHeight ? parent.naturalHeight : hand;
 
parent.scaler.Height = hand;
 
// glow if overscale
float stretch = (float) Math.Abs((target - hand) / parent.maximumStretch);
float strength = 1f / (1f + (float) Math.Pow(Math.E, -1 * ((8f * stretch) - 5f)));
parent.SetGlow(GlowBase + strength * (1f - GlowBase));
return true;
}
 
public void OnScaleEnd(DoubleSwipeDetector detector)
{
parent.FinishScale(false);
}
}
 
public ExpandHelper(Context context, Callback callback, int small, int large) {
this.smallSize = small;
this.maximumStretch = Math.Max (smallSize, 1) * StretchInterval;
this.largeSize = large;
this.context = context;
this.callback = callback;
this.scaler = new ViewScaler();
this.gravity = GravityFlags.Top;
 
//this.scaleAnimation = ObjectAnimator.OfFloat (scaler, "Height", 0f);
this.scaleAnimation = ValueAnimator.OfFloat (0f);
this.scaleAnimation.Update += (sender, e) => scaler.Height = (float)e.Animation.AnimatedValue;
this.scaleAnimation.SetDuration (ExpandDuration);
 
AnimatorListenerAdapter glowVisibilityController = new AnimatorListener ();
glowTopAnimation = ObjectAnimator.OfFloat (null, "alpha", 0f);
glowTopAnimation.AddListener (glowVisibilityController);
glowBottomAnimation = ObjectAnimator.OfFloat (null, "alpha", 0f);
glowBottomAnimation.AddListener (glowVisibilityController);
glowAnimationSet = new AnimatorSet();
glowAnimationSet.Play (glowTopAnimation).With(glowBottomAnimation);
glowAnimationSet.SetDuration(GlowDuration);
 
detector = new DoubleSwipeDetector(context, new GestureDetector (this));
}
 
public bool Progressing {
get {
return detector.IsInProgress;
}
}
 
public void SetEventSource (View eventSource)
{
this.eventSource = eventSource;
}
 
public void SetGravity (GravityFlags gravity)
{
this.gravity = gravity;
}
 
public void SetGlow (float glow)
{
if (!glowAnimationSet.IsRunning || glow == 0f) {
if (glowAnimationSet.IsRunning) {
glowAnimationSet.Cancel ();
}
if (currViewTopGlow != null && currViewBottomGlow != null) {
if (glow == 0f || currViewTopGlow.Alpha == 0f) {
// animate glow in and out
glowTopAnimation.SetTarget(currViewTopGlow);
glowBottomAnimation.SetTarget(currViewBottomGlow);
glowTopAnimation.SetFloatValues(glow);
glowBottomAnimation.SetFloatValues(glow);
glowAnimationSet.SetupStartValues();
glowAnimationSet.Start();
} else {
// set it explicitly in reponse to touches.
currViewTopGlow.Alpha = glow;
currViewBottomGlow.Alpha = glow;
HandleGlowVisibility();
}
}
}
}
 
void HandleGlowVisibility ()
{
currViewTopGlow.Visibility = currViewTopGlow.Alpha <= 0.0f ? ViewStates.Invisible : ViewStates.Visible;
currViewBottomGlow.Visibility = currViewBottomGlow.Alpha <= 0.0f ? ViewStates.Invisible : ViewStates.Visible;
}
 
public bool OnInterceptTouchEvent (MotionEvent ev)
{
stretching = detector.OnTouchEvent(ev);
return stretching;
}
 
public bool OnTouchEvent (MotionEvent ev)
{
var action = ev.Action;
if (stretching)
detector.OnTouchEvent(ev);
switch (action) {
case MotionEventActions.Up:
case MotionEventActions.Cancel:
stretching = false;
ClearView();
break;
}
return true;
}
 
bool InitScale (View v)
{
if (v != null) {
stretching = true;
SetView(v);
SetGlow(GlowBase);
scaler.SetView(v);
oldHeight = scaler.Height;
if (callback.CanChildBeExpanded(v))
naturalHeight = scaler.GetNaturalHeight(largeSize);
else
naturalHeight = oldHeight;
v.Parent.RequestDisallowInterceptTouchEvent (true);
}
return stretching;
}
 
void FinishScale (bool force) {
float h = scaler.Height;
bool wasClosed = (oldHeight == smallSize);
if (wasClosed) {
h = (force || h > smallSize) ? naturalHeight : smallSize;
} else {
h = (force || h < naturalHeight) ? smallSize : naturalHeight;
}
if (scaleAnimation.IsRunning) {
scaleAnimation.Cancel();
}
scaleAnimation.SetFloatValues (scaler.Height, h);
scaleAnimation.Start();
stretching = false;
SetGlow(0f);
callback.SetUserExpandedChild(currView, h == naturalHeight);
 
ClearView();
}
 
void ClearView ()
{
currView = null;
currViewTopGlow = null;
currViewBottomGlow = null;
}
 
void SetView (View v)
{
currView = v;
ViewGroup g = v as ViewGroup;
if (g == null)
g = v.Parent.Parent as ViewGroup;
if (g != null) {
currViewTopGlow = g.FindViewById(Resource.Id.TopGlow);
currViewBottomGlow = g.FindViewById(Resource.Id.BottomGlow);
}
}
}
}
ExpandableListView.cs
C#
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Util;
using Android.Views;
using Android.Widget;
 
namespace Foo
{
public class ExpandableListView : ListView, ExpandHelper.Callback
{
ExpandHelper expandHelper;
bool expandoRequested;
 
public ExpandableListView (Context context) :
base (context)
{
Initialize ();
}
 
public ExpandableListView (Context context, IAttributeSet attrs) :
base (context, attrs)
{
Initialize ();
}
 
public ExpandableListView (Context context, IAttributeSet attrs, int defStyle) :
base (context, attrs, defStyle)
{
Initialize ();
}
 
void Initialize ()
{
Focusable = false;
FocusableInTouchMode = false;
DescendantFocusability = DescendantFocusability.BlockDescendants;
LongClickable = false;
Clickable = false;
SetSelector (Android.Resource.Color.Transparent);
expandHelper = new ExpandHelper (Context, this, 0, ActivityItemAdapter.MapHeight);
expandHelper.SetEventSource (this);
}
 
public override bool OnInterceptTouchEvent (MotionEvent ev)
{
expandoRequested = expandHelper.OnInterceptTouchEvent (ev);
return expandoRequested;
}
 
public override bool OnTouchEvent (MotionEvent e)
{
expandHelper.OnTouchEvent (e);
return expandHelper.Progressing || e.PointerCount == 2 || base.OnTouchEvent (e);
}
 
public View GetChildAtRawPosition (float x, float y)
{
var index = GetItemPositionFromRawYCoordinates ((int)y);
if (index == -1)
return null;
var view = GetChildAt (index);
return view.FindViewById (Resource.Id.MapPicture);
}
 
public View GetChildAtPosition (float x, float y)
{
return GetChildAtRawPosition (x, y);
}
 
public bool CanChildBeExpanded (View v)
{
var activityItem = GetActivityItemFromChildView (v);
return activityItem != null && activityItem.Expandable;
}
 
public bool SetUserExpandedChild (View v, bool userxpanded)
{
var activityItem = GetActivityItemFromChildView (v);
if (activityItem != null)
activityItem.Expanded = userxpanded;
return activityItem != null;
}
 
ActivityItem GetActivityItemFromChildView (View v)
{
ActivityItem item = v as ActivityItem;
if (item != null)
return item;
var parent = v.Parent;
while (parent != null && (item = parent as ActivityItem) == null)
parent = parent.Parent;
return item;
}
 
int GetItemPositionFromRawYCoordinates (int rawY)
{
int total = LastVisiblePosition - FirstVisiblePosition + 1;
 
int[] coords = new int[2];
for (int i = 0; i < total; i++) {
var child = GetChildAt (i);
child.GetLocationOnScreen (coords);
int top = coords[1];
int bottom = top + child.Height;
if ((rawY >= top) && (rawY <= bottom))
return i;
}
 
return -1;
}
}
}

Hello..

Your example of Expandable Listview is so good.

I want to implement functionality same like you. so can you please provide me some more code. so i can implement this kind of functionality .

Thanks
Harshad

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