我有个问题。我创建了一个CustomView,可以在其中拖放视图,但现在我还想为其添加缩放/旋转功能。现在,这里是创建的OnTouchEvent,用于在其中移动视图:
public override bool OnTouchEvent(MotionEvent e)
{
float x = e.RawX;
float y = e.RawY;
var dragView = Element as DraggableView.DraggableView;
switch (e.Action)
{
case MotionEventActions.Down:
if (dragView.DragMode == DragMode.Touch)
{
if (!touchedDown)
{
if (firstTime)
{
originalX = GetX();
originalY = GetY();
firstTime = false;
}
dragView.DragStarted();
}
TextMoved = false;
touchedDown = true;
stopwatch.Start();
}
dX = x - this.GetX();
dY = y - this.GetY();
break;
case MotionEventActions.Move:
if (touchedDown)
{
if (dragView.DragDirection == DragDirectionType.All || dragView.DragDirection == DragDirectionType.Horizontal)
{
SetX(x - dX);
}
if (dragView.DragDirection == DragDirectionType.All || dragView.DragDirection == DragDirectionType.Vertical)
{
SetY(y - dY);
}
TextMoved = true;
}
break;
case MotionEventActions.Up:
touchedDown = false;
if(TextMoved == true)
{
dragView.DragEnded();
}
else
{
MessagingCenter.Send<object, DraggableView.DraggableView>(this, "EditSelectedText", dragView);
}
break;
case MotionEventActions.Cancel:
touchedDown = false;
break;
}
return base.OnTouchEvent(e);
}
但是现在我还需要“缩放/旋转”功能。问题是我已经为我的skiasharp位图创建了它,但这不是skiasharp,所以我不能使用它。
没有skiasharp,如何在OnTouchEvent中实现此功能?
有一个关于ScaleAndRotate的xamarin-forms-samples ,但是与无关TouchEvent
。我找到了一种方法,可以使用PanGestureRecognizer和PinchGestureRecognizer来实现它。
创建一个ScaleAndRotateContainer ContentView,其中包含PanGestureRecognizer
和PinchGestureRecognizer
:
public class ScaleAndRotateContainer : ContentView
{
double currentScale = 1;
double startScale = 1;
double xOffset = 0;
double yOffset = 0;
double rotateNum = 1;
public ScaleAndRotateContainer()
{
var pinchGesture = new PinchGestureRecognizer ();
pinchGesture.PinchUpdated += OnPinchUpdated;
var panGesture = new PanGestureRecognizer();
panGesture.PanUpdated += PanGesture_PanUpdated;
GestureRecognizers.Add (pinchGesture);
GestureRecognizers.Add(panGesture);
}
private void PanGesture_PanUpdated(object sender, PanUpdatedEventArgs e)
{
rotateNum++;
this.RotateTo(rotateNum);
this.AnchorX = 0.5;
this.AnchorY = 0.5;
}
void OnPinchUpdated (object sender, PinchGestureUpdatedEventArgs e)
{
if (e.Status == GestureStatus.Started) {
// Store the current scale factor applied to the wrapped user interface element,
// and zero the components for the center point of the translate transform.
startScale = Content.Scale;
Content.AnchorX = 0;
Content.AnchorY = 0;
}
if (e.Status == GestureStatus.Running) {
// Calculate the scale factor to be applied.
currentScale += (e.Scale - 1) * startScale;
currentScale = Math.Max (1, currentScale);
// The ScaleOrigin is in relative coordinates to the wrapped user interface element,
// so get the X pixel coordinate.
double renderedX = Content.X + xOffset;
double deltaX = renderedX / Width;
double deltaWidth = Width / (Content.Width * startScale);
double originX = (e.ScaleOrigin.X - deltaX) * deltaWidth;
// The ScaleOrigin is in relative coordinates to the wrapped user interface element,
// so get the Y pixel coordinate.
double renderedY = Content.Y + yOffset;
double deltaY = renderedY / Height;
double deltaHeight = Height / (Content.Height * startScale);
double originY = (e.ScaleOrigin.Y - deltaY) * deltaHeight;
// Calculate the transformed element pixel coordinates.
double targetX = xOffset - (originX * Content.Width) * (currentScale - startScale);
double targetY = yOffset - (originY * Content.Height) * (currentScale - startScale);
// Apply translation based on the change in origin.
Content.TranslationX = targetX.Clamp (-Content.Width * (currentScale - 1), 0);
Content.TranslationY = targetY.Clamp (-Content.Height * (currentScale - 1), 0);
// Apply scale factor
Content.Scale = currentScale;
}
if (e.Status == GestureStatus.Completed) {
// Store the translation delta's of the wrapped user interface element.
xOffset = Content.TranslationX;
yOffset = Content.TranslationY;
}
}
}
然后在Xaml中将其用于ContentPage:
xmlns:local="clr-namespace:PinchGesture;assembly=YourNameSpace"
<local:ScaleAndRotateContainer>
<local:ScaleAndRotateContainer.Content>
<StackLayout HorizontalOptions="Center" VerticalOptions="Center" >
<Label Text="Hello Xamarin.Forms!" />
<Image Source="waterfront.jpg" />
</StackLayout>
</local:ScaleAndRotateContainer.Content>
</local:ScaleAndRotateContainer>
效果:
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