GitHub repo and demo video: https://github.com/xulihang/misc/tree/master/b4x/b4j/snapAndShowGuides
B4X:
#Region Project Attributes
#MainFormWidth: 600
#MainFormHeight: 600
#End Region
Sub Process_Globals
Private fx As JFX
Private MainForm As Form
Private xui As XUI
Private Button1 As Button
Private Button2 As Button
Type PositionData (PressedX As Double, PressedY As Double,linesShown As Boolean)
Type Line (X0 As Double, Y0 As Double, X1 As Double, Y1 As Double)
Private ImageView1 As ImageView
Private Pane1 As Pane
End Sub
Sub AppStart (Form1 As Form, Args() As String)
MainForm = Form1
MainForm.RootPane.LoadLayout("Layout1")
MainForm.Show
ImageView1.PickOnBounds = False
End Sub
Private Sub Button2_MouseDragged (EventData As MouseEvent)
HandleButtonDragged(Sender,EventData)
End Sub
Private Sub Button2_MousePressed (EventData As MouseEvent)
HandleButtonPressed(Sender,EventData)
End Sub
Private Sub Button1_MouseDragged (EventData As MouseEvent)
HandleButtonDragged(Sender,EventData)
End Sub
Private Sub Button1_MousePressed (EventData As MouseEvent)
HandleButtonPressed(Sender,EventData)
End Sub
Private Sub HandleButtonPressed(btn As Button,EventData As MouseEvent)
Dim btn As Button = Sender
Dim pd As PositionData
Dim event As JavaObject = EventData
pd.PressedX = event.RunMethod("getSceneX",Null)
pd.PressedY = event.RunMethod("getSceneY",Null)
pd.linesShown = False
btn.Tag = pd
End Sub
Private Sub HandleButtonDragged(btn As Button,EventData As MouseEvent)
Dim btn As Button = Sender
Dim event As JavaObject = EventData
Dim pd As PositionData = btn.Tag
Dim XDiff As Double= event.RunMethod("getSceneX",Null) - pd.pressedX
Dim YDiff As Double= event.RunMethod("getSceneY",Null) - pd.pressedY
btn.Left = XDiff+btn.Left
btn.Top = YDiff+btn.Top
If pd.linesShown = True Then
If XDiff < 0 Then
XDiff = XDiff - 2
Else
XDiff = XDiff + 2
End If
If YDiff < 0 Then
YDiff = YDiff - 2
Else
YDiff = YDiff + 2
End If
pd.linesShown = False
End If
pd.PressedX = event.RunMethod("getSceneX",Null)
pd.PressedY = event.RunMethod("getSceneY",Null)
Dim snapped As Boolean = SnapAndShowGuideLines(btn,XDiff,YDiff)
If snapped Then
pd.linesShown = True
End If
End Sub
Private Sub SnapAndShowGuideLines(n As Node,XDiff As Double,YDiff As Double) As Boolean
Dim snapped As Boolean
Dim bc As BitmapCreator
bc.Initialize(Pane1.Width,Pane1.Height)
Dim left As Double = n.Left
Dim top As Double = n.Top
Dim right As Double = n.Left + n.PrefWidth
Dim bottom As Double = n.top + n.PrefHeight
Dim centerX As Double = n.Left + n.PrefWidth/2
Dim centerX As Double = n.Left + n.PrefWidth/2
Dim centerY As Double = n.top + n.PrefHeight/2
Dim shapes As List = GetShapes(n)
Dim linesToDraw As List
linesToDraw.Initialize
For Each shape As B4XRect In shapes
If Abs(shape.Left - left) < 3 And Abs(XDiff) < 2 Then 'left
If shape.Left <> left Then
n.Left = shape.Left 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = shape.Left
l.Y0 = Min(n.Top,shape.Top)
l.X1 = shape.Left
l.Y1 = Max(n.Top+n.PrefHeight,shape.Bottom)
linesToDraw.Add(l)
End If
If Abs(shape.Right - right) < 3 And Abs(XDiff) < 2 Then ' right
If shape.Right <> right Then
n.Left = shape.Right - n.PrefWidth 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = shape.Right
l.Y0 = Min(n.Top,shape.Top)
l.X1 = shape.Right
l.Y1 = Max(n.Top+n.PrefHeight,shape.Bottom)
linesToDraw.Add(l)
End If
If Abs(shape.Right - left) < 3 And Abs(XDiff) < 2 Then ' left and right
If shape.Right <> left Then
n.Left = shape.Right 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = shape.Right
l.Y0 = Min(n.Top,shape.Top)
l.X1 = shape.Right
l.Y1 = Max(n.Top+n.PrefHeight,shape.Bottom)
linesToDraw.Add(l)
End If
If Abs(shape.Left - right) < 3 And Abs(XDiff) < 2 Then ' right and left
If shape.Left <> right Then
n.Left = shape.Left - n.PrefWidth 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = shape.Left
l.Y0 = Min(n.Top,shape.Top)
l.X1 = shape.Left
l.Y1 = Max(n.Top+n.PrefHeight,shape.Bottom)
linesToDraw.Add(l)
End If
If Abs(shape.CenterX - centerX) < 3 And Abs(XDiff) < 2 Then 'centerx
If shape.CenterX <> centerX Then
n.Left = shape.CenterX - n.PrefWidth/2 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = shape.centerX
l.Y0 = Min(n.Top,shape.Top)
l.X1 = shape.centerX
l.Y1 = Max(n.Top+n.PrefHeight,shape.Bottom)
linesToDraw.Add(l)
End If
If Abs(shape.Top - top) < 3 And Abs(YDiff) < 2 Then 'top
If shape.Top <> top Then
n.Top = shape.Top 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = Min(n.Left,shape.Left)
l.Y0 = shape.Top
l.X1 = Max(n.Left+n.PrefWidth,shape.Right)
l.Y1 = shape.Top
linesToDraw.Add(l)
End If
If Abs(shape.Bottom - bottom) < 3 And Abs(YDiff) < 2 Then 'bottom
If shape.Bottom <> bottom Then
n.Top = shape.Bottom - n.PrefHeight 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = Min(n.Left,shape.Left)
l.Y0 = shape.Bottom
l.X1 = Max(n.Left+n.PrefWidth,shape.Right)
l.Y1 = shape.Bottom
linesToDraw.Add(l)
End If
If Abs(shape.Top - bottom) < 3 And Abs(YDiff) < 2 Then 'top and bottom
If shape.Top <> bottom Then
n.Top = shape.Top - n.PrefHeight 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = Min(n.Left,shape.Left)
l.Y0 = shape.Top
l.X1 = Max(n.Left+n.PrefWidth,shape.Right)
l.Y1 = shape.Top
linesToDraw.Add(l)
End If
If Abs(shape.Bottom - top) < 3 And Abs(YDiff) < 2 Then 'bottom and top
If shape.Bottom <> top Then
n.Top = shape.Bottom 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = Min(n.Left,shape.Left)
l.Y0 = shape.Bottom
l.X1 = Max(n.Left+n.PrefWidth,shape.Right)
l.Y1 = shape.Bottom
linesToDraw.Add(l)
End If
If Abs(shape.CenterY - centerY) < 3 And Abs(YDiff) < 2 Then 'centery
If shape.CenterY <> centerY Then
n.Top = shape.centerY - n.PrefHeight/2 'snap
snapped = True
End If
Dim l As Line
l.Initialize
l.X0 = Min(n.Left,shape.Left)
l.Y0 = shape.centerY
l.X1 = Max(n.Left+n.PrefWidth,shape.Right)
l.Y1 = shape.centerY
linesToDraw.Add(l)
End If
Next
If linesToDraw.Size>0 Then
For Each l As Line In linesToDraw
bc.DrawLine(l.X0,l.Y0,l.X1,l.Y1,xui.Color_Red,1)
Next
End If
ImageView1.SetImage(bc.Bitmap)
Return snapped
End Sub
Private Sub GetShapes(n As Node) As List
Dim shapes As List
shapes.Initialize
Dim paneRect As B4XRect
paneRect.Initialize(0,0,Pane1.Width,Pane1.Height)
shapes.Add(paneRect)
For Each nodeForComparing As Node In Array(Button1,Button2)
If n <> nodeForComparing Then
Dim r As B4XRect
r.Initialize(nodeForComparing.Left,nodeForComparing.Top, _
nodeForComparing.Left+nodeForComparing.PrefWidth, _
nodeForComparing.Top+nodeForComparing.PrefHeight)
shapes.Add(r)
End If
Next
Return shapes
End Sub
