Class ZoomableImageView


  • public class ZoomableImageView
    extends java.lang.Object
    ZoomableImageView is a simple class that enhances an ImageView with the capability to zoom in and out.
    Author:
    Pawel Dube

    Requirements and limitations:

    • the imageview has to be populated with a bitmap. Other content will not work.
    • WIDTH AND HEIGHT OF THE IMAGEVIEW MUST BE SET TO "MATCH_PARENT". When set to "wrap_content", the view will shrink when the bitmap inside the view shrinks due to zooming!

    Gestures:

    this class catches the usual "zoom in" and "zoom out" gestures:
    • zoom in = move two pointers (e.g. two fingers) away from each other while touching the screen
    • zoom out = move two pointers (e.g. two fingers) closer to each other while touching the screen

    moving one pointer (e.g. one finger) while touching the screen moves the scaled bitmap within the imageview

    Notes:

    • this class always "consumes" the provided motionEvent, because the underlying ScaleGestureDetector does so. Therefore, there are NEVER any "unused" events after this class has been called. However, this is not a limitation, see example how to use.

    How to use:

    1. create an instance of ZoomableImageView providing Context, the imageview and the bitmap,
    2. and optionally override "onGestureFinished" to catch the results once a gesture is done. If you do not need to further react after a zoom/move gesture, you can skip this.
    3. Register an OnTouchListerner and handle over the motionEvent to the ZoomableImageView.

    That's all.


    mapImageView = (ImageView) findViewById(R.id.map); zoomableImageView = new ZoomableImageView(getApplicationContext(),mapImageView,BitmapFactory.decodeResource(getResources(),R.drawable.germany_nc,null)){
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  ZoomableImageView.SPRITEFIXPOINT
      Static class that holds values how to fix a sprite to the underlying bitmap.
    • Constructor Summary

      Constructors 
      Constructor Description
      ZoomableImageView​(Context context, ImageView imageView, Bitmap bitmap)
      Initializes this class.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int addSpite​(Bitmap bitmap, float x, float y, int fixpoint)
      Sprite concept: a "sprite" is a small bitmap/icon that is fixed to an absolute position on top of the underlying bitmap.
      float getRelativeXFocus()
      Returns the current focus as a relative position, returns a value between 0 (=left border of the bitmap) and 1 (=right border of the bitmap).
      float getRelativeYFocus()
      Returns the current focus as a relative position, returns a value between 0 (=left top of the bitmap) and 1 (=bottom of the bitmap).
      float getXFocus()
      Returns the absolute focus x coordinate in pixels.
      float getYFocus()
      Returns the absolute focus y coordinate in pixels.
      void onGestureFinished​(float scaleFactor, float lastPressX, float lastPressY, float xFocus, float yFocus, float xFocusRelative, float yFocusRelative, RectF currentlyVisibleArea)
      Always called when a gesture (zoom or movement) finished.
      Override this method to do something once a zoom / movement inside the imageview finished.
      The focus is the visible center coordinate.
      boolean onTouchEvent​(MotionEvent motionEvent)
      Use this method to supply all motionEvents from the imageview to this class.
      void redrawBitmap()
      Redraws the bitmap inside the imageview.
      void restoreZoomViewState​(Bundle zoomViewState)  
      Bundle saveZoomViewState()  
      void setScaleRange​(float min, float max)
      Optional method to set the min and max scale range.
      Example: setScaleRange(0.25,1); sets a maximum zoom in of 4x and a maximum zoom out to the original size.
      void updateBitmap​(Bitmap newbitmap)
      Updates the bitmap with a new one.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • scaleFactor

        public float scaleFactor
        The current zoom:
        1 = no zoom,
        values below 1 mean the bitmap is zoomed in (enlarged)
        values above 1 mean the bitmap is zoomed out (shrunk).
        Values above 1 are discouraged and may lead to unexpected behaviour of the imageview/bitmap.

        Notice: this value is only accurate once a scale gesture finished. During a scale gesture, it holds the scale factor from the beginning of the gesture. In other words: it is updated at the end of the gesture, and not while a gesture is being performed.

        Override onGestureFinished to get the results of a gesture.

      • xFocus

        public float xFocus
        The current focus (=center) visible. Both variables refer to the x/y coordinates of the underlying bitmap.
      • yFocus

        public float yFocus
      • minScaleRange

        public float minScaleRange
        Default max. zoom factor, 0.25f = 4x zoom.
      • maxScaleRange

        public float maxScaleRange
        Default min. zoom factor, values above 1 are discouraged.
      • temporaryVisibleArea

        public RectF temporaryVisibleArea
        Holds the borders of the visible area of the bimap. May be null before first gestures.
      • lastPressX

        public float lastPressX
      • lastPressY

        public float lastPressY
      • zoomGestureListener

        public de.kaffeemitkoffein.tinyweatherforecastgermany.ZoomableImageView.ZoomGestureListener zoomGestureListener
      • scaleGestureDetector

        public ScaleGestureDetector scaleGestureDetector
      • STATE_SCALEFACTOR

        public static final java.lang.String STATE_SCALEFACTOR
        See Also:
        Constant Field Values
    • Constructor Detail

      • ZoomableImageView

        public ZoomableImageView​(Context context,
                                 ImageView imageView,
                                 Bitmap bitmap)
        Initializes this class. Values must not be null.
        Parameters:
        context - the application context
        imageView - the imageview
        bitmap - the bitmap to be used in the imageview
    • Method Detail

      • setScaleRange

        public void setScaleRange​(float min,
                                  float max)
        Optional method to set the min and max scale range.
        Example: setScaleRange(0.25,1); sets a maximum zoom in of 4x and a maximum zoom out to the original size.
        Parameters:
        min - the max. zoom, must be lower than max (e.g. 0.25 means a max. zoom of 4x).
        max - the min. zoom, typically 1 (original size). Values above 1 are discouraged.
      • updateBitmap

        public void updateBitmap​(Bitmap newbitmap)
        Updates the bitmap with a new one. If the old and new bitmap have the same width and height, the current zoom values and the focus are preserved.
        Parameters:
        newbitmap - the new bitmap, must not be null
      • addSpite

        public int addSpite​(Bitmap bitmap,
                            float x,
                            float y,
                            int fixpoint)
        Sprite concept: a "sprite" is a small bitmap/icon that is fixed to an absolute position on top of the underlying bitmap. When the underlying bitmap gets zoomed in or out, the sprite does NOT zoom but always keeps the same size. It remains at the same (relative) position fixed to the underlying bitmap. Got it? Adds a sprite.
        Parameters:
        bitmap - the bitmap holding the sprite. May not be null.
        x - x-position (on the underlying bitmap) where to fix the sprite
        y - y-position (on the underlying bitmap) where to fix the sprite
        fixpoint - how to fix the sprite, see SPRITEFIXPOINT class
        Returns:
        number of the sprite
      • onGestureFinished

        public void onGestureFinished​(float scaleFactor,
                                      float lastPressX,
                                      float lastPressY,
                                      float xFocus,
                                      float yFocus,
                                      float xFocusRelative,
                                      float yFocusRelative,
                                      RectF currentlyVisibleArea)
        Always called when a gesture (zoom or movement) finished.
        Override this method to do something once a zoom / movement inside the imageview finished.
        The focus is the visible center coordinate.
        Parameters:
        scaleFactor - the current scale factor
        lastPressX - the absolute x of last pointer/touch, reference is the whole bitmap
        lastPressY - the absolute y of last pointer/touch, reference is the whole bitmap
        xFocus - the absolute x focus in pixels, reference is the whole bitmap
        yFocus - the absolute y focus in pixels, reference is the whole bitmap
        xFocusRelative - the relative x focus (0 <= xFocusRelative <= 1), reference is the whole bitmap
        yFocusRelative - the relative y focus (0 <= yFocusRelative <= 1), reference is the whole bitmap
        currentlyVisibleArea - rectangle holding the coordinates of the visible area in pixels
      • getRelativeXFocus

        public float getRelativeXFocus()
        Returns the current focus as a relative position, returns a value between 0 (=left border of the bitmap) and 1 (=right border of the bitmap). The position refers to the bitmap.
        The focus is the visible center coordinate.
        Returns:
        the relative x coordinate of the focus, 0 <= x <= 1
      • getRelativeYFocus

        public float getRelativeYFocus()
        Returns the current focus as a relative position, returns a value between 0 (=left top of the bitmap) and 1 (=bottom of the bitmap). The position refers to the bitmap.
        The focus is the visible center coordinate.
        Returns:
        the relative y coordinate of the focus, 0 <= y <= 1
      • getXFocus

        public float getXFocus()
        Returns the absolute focus x coordinate in pixels. The coordinate refers to the bitmap size in pixels.
        The focus is the visible center coordinate.
        Returns:
        absolute x coordinate
      • getYFocus

        public float getYFocus()
        Returns the absolute focus y coordinate in pixels. The coordinate refers to the bitmap size in pixels.
        The focus is the visible center coordinate.
        Returns:
        absolute y coordinate
      • onTouchEvent

        public boolean onTouchEvent​(MotionEvent motionEvent)
        Use this method to supply all motionEvents from the imageview to this class. This is typically called from an OnTouchListener that is attached to the imageview. See example above.
        Parameters:
        motionEvent -
        Returns:
        if the motionEvent was used, always returns TRUE.
      • redrawBitmap

        public void redrawBitmap()
        Redraws the bitmap inside the imageview. Uses the currently set scale factor.
      • saveZoomViewState

        public Bundle saveZoomViewState()
      • restoreZoomViewState

        public void restoreZoomViewState​(Bundle zoomViewState)