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Scaleable / zoomable imageview for Xamarin Android
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Android.Content;
using Android.Graphics;
using Android.Util;
using Android.Views;
using Android.Widget;
namespace Droid
{
public class ScaleImageViewGestureDetector : GestureDetector.SimpleOnGestureListener
{
readonly ScaleImageView _scaleImageView;
public ScaleImageViewGestureDetector(ScaleImageView scaleImageView)
{
_scaleImageView = scaleImageView;
}
public override bool OnDown(MotionEvent e)
{
return true;
}
public override bool OnDoubleTap(MotionEvent e)
{
_scaleImageView.MaxZoomTo((int)e.GetX(), (int)e.GetY());
_scaleImageView.Cutting();
return true;
}
}
public class ScaleImageView : ImageView, View.IOnTouchListener, INotifyPropertyChanged
{
Matrix _matrix;
float[] _matrixValues = new float[9];
int _width;
int _height;
int _intrinsicWidth;
int _intrinsicHeight;
float _scale;
float _minScale;
float _previousDistance;
int _previousMoveX;
int _previousMoveY;
bool _isScaling;
GestureDetector _gestureDetector;
public float MaxScale { get; set; } = 2.0f;
bool _isScaled;
public bool IsScaled
{
get
{
return _isScaled;
}
private set
{
_isScaled = value;
OnPropertyChanged();
}
}
public float Scale
{
get { return GetValue(_matrix, Matrix.MscaleX); }
}
public float TranslateX
{
get { return GetValue(_matrix, Matrix.MtransX); }
}
public float TranslateY
{
get { return GetValue(_matrix, Matrix.MtransY); }
}
public event PropertyChangedEventHandler PropertyChanged;
public ScaleImageView(Context context, IAttributeSet attrs) :
base(context, attrs)
{
Initialize();
}
public ScaleImageView(Context context, IAttributeSet attrs, int defStyle) :
base(context, attrs, defStyle)
{
Initialize();
}
public override void SetImageBitmap(Bitmap bm)
{
base.SetImageBitmap(bm);
Initialize();
}
public override void SetImageResource(int resId)
{
base.SetImageResource(resId);
Initialize();
}
void Initialize()
{
SetScaleType(ScaleType.Matrix);
_matrix = new Matrix();
if (Drawable != null)
{
_intrinsicWidth = Drawable.IntrinsicWidth;
_intrinsicHeight = Drawable.IntrinsicHeight;
SetOnTouchListener(this);
}
_gestureDetector = new GestureDetector(Context, new ScaleImageViewGestureDetector(this));
}
protected override bool SetFrame(int l, int t, int r, int b)
{
_width = r - l;
_height = b - t;
_matrix.Reset();
var r_norm = r - l;
_scale = (float)r_norm / (float)_intrinsicWidth;
var paddingHeight = 0;
var paddingWidth = 0;
if (_scale * _intrinsicHeight > _height)
{
_scale = (float)_height / (float)_intrinsicHeight;
_matrix.PostScale(_scale, _scale);
paddingWidth = (r - _width) / 2;
}
else
{
_matrix.PostScale(_scale, _scale);
paddingHeight = (b - _height) / 2;
}
_matrix.PostTranslate(paddingWidth, paddingHeight);
ImageMatrix = _matrix;
_minScale = _scale;
Cutting();
return base.SetFrame(l, t, r, b);
}
float GetValue(Matrix matrix, int whichValue)
{
matrix.GetValues(_matrixValues);
return _matrixValues[whichValue];
}
public void MaxZoomTo(int x, int y)
{
if (_minScale != Scale && (Scale - _minScale) > 0.1f)
{
var scale = _minScale / Scale;
ZoomTo(scale, x, y);
}
else
{
var scale = MaxScale / Scale;
ZoomTo(scale, x, y);
}
}
public void ZoomTo(float scale, int x, int y)
{
if (Scale * scale < _minScale)
{
scale = _minScale / Scale;
}
else
{
if (scale >= 1 && Scale * scale > MaxScale)
{
scale = MaxScale / Scale;
}
}
_matrix.PostScale(scale, scale);
//move to center
_matrix.PostTranslate(-(_width * scale - _width) / 2, -(_height * scale - _height) / 2);
//move x and y distance
_matrix.PostTranslate(-(x - (_width / 2)) * scale, 0);
_matrix.PostTranslate(0, -(y - (_height / 2)) * scale);
ImageMatrix = _matrix;
}
public void Cutting()
{
var width = (int)(_intrinsicWidth * Scale);
var height = (int)(_intrinsicHeight * Scale);
if (TranslateX < -(width - _width))
{
_matrix.PostTranslate(-(TranslateX + width - _width), 0);
}
if (TranslateX > 0)
{
_matrix.PostTranslate(-TranslateX, 0);
}
if (TranslateY < -(height - _height))
{
_matrix.PostTranslate(0, -(TranslateY + height - _height));
}
if (TranslateY > 0)
{
_matrix.PostTranslate(0, -TranslateY);
}
if (width < _width)
{
_matrix.PostTranslate((_width - width) / 2, 0);
}
if (height < _height)
{
_matrix.PostTranslate(0, (_height - height) / 2);
}
ImageMatrix = _matrix;
IsScaled = Scale > _minScale;
}
float Distance(float x0, float x1, float y0, float y1)
{
var x = x0 - x1;
var y = y0 - y1;
return (float)Math.Sqrt(x * x + y * y);
}
float DispDistance()
{
return (float)Math.Sqrt(_width * _width + _height * _height);
}
public override bool OnTouchEvent(MotionEvent e)
{
if (_gestureDetector.OnTouchEvent(e))
{
_previousMoveX = (int)e.GetX();
_previousMoveY = (int)e.GetY();
return true;
}
var touchCount = e.PointerCount;
switch (e.Action)
{
case MotionEventActions.Down:
case MotionEventActions.Pointer1Down:
case MotionEventActions.Pointer2Down:
{
if (touchCount >= 2)
{
var distance = Distance(e.GetX(0), e.GetX(1), e.GetY(0), e.GetY(1));
_previousDistance = distance;
_isScaling = true;
}
}
break;
case MotionEventActions.Move:
{
if (touchCount >= 2 && _isScaling)
{
var distance = Distance(e.GetX(0), e.GetX(1), e.GetY(0), e.GetY(1));
var scale = (distance - _previousDistance) / DispDistance();
_previousDistance = distance;
scale += 1;
scale = scale * scale;
ZoomTo(scale, _width / 2, _height / 2);
Cutting();
}
else if (!_isScaling)
{
var distanceX = _previousMoveX - (int)e.GetX();
var distanceY = _previousMoveY - (int)e.GetY();
_previousMoveX = (int)e.GetX();
_previousMoveY = (int)e.GetY();
_matrix.PostTranslate(-distanceX, -distanceY);
Cutting();
}
}
break;
case MotionEventActions.Up:
case MotionEventActions.Pointer1Up:
case MotionEventActions.Pointer2Up:
{
if (touchCount <= 1)
{
_isScaling = false;
}
}
break;
}
return true;
}
public bool OnTouch(View v, MotionEvent e)
{
return OnTouchEvent(e);
}
public void OnPropertyChanged([CallerMemberName]string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
@dehghani-mehdi

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@dehghani-mehdi dehghani-mehdi commented Jun 23, 2018

Doesn't work here

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