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adegardadegard
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Add pinch-to-zoom and double-tap zoom in full screen viewer
1 parent 3aabba8 commit a9fba71

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Lines changed: 222 additions & 2 deletions

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‎app/src/main/java/com/degard/imagecompressor/ZoomableImageView.kt‎

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package com.degard.imagecompressor
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import android.content.Context
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import android.graphics.Matrix
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import android.graphics.PointF
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import android.graphics.drawable.Drawable
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import android.util.AttributeSet
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import android.view.GestureDetector
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import android.view.MotionEvent
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import android.view.ScaleGestureDetector
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import android.view.animation.DecelerateInterpolator
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import android.widget.OverScroller
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import androidx.appcompat.widget.AppCompatImageView
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class ZoomableImageView @JvmOverloads constructor(
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context: Context, attrs: AttributeSet? = null, defStyle: Int = 0
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) : AppCompatImageView(context, attrs, defStyle) {
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private val matrix = Matrix()
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private val savedMatrix = Matrix()
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private val matrixValues = FloatArray(9)
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private var mode = NONE
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private val startPoint = PointF()
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private val midPoint = PointF()
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private var oldDist = 1f
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private var minScale = 1f
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private var maxScale = 5f
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private var currentScale = 1f
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private val scaleDetector = ScaleGestureDetector(context, object : ScaleGestureDetector.SimpleOnScaleGestureListener() {
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override fun onScale(detector: ScaleGestureDetector): Boolean {
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val scaleFactor = detector.scaleFactor
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currentScale *= scaleFactor
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currentScale = currentScale.coerceIn(minScale, maxScale)
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matrix.postScale(scaleFactor, scaleFactor, detector.focusX, detector.focusY)
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constrainMatrix()
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imageMatrix = matrix
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return true
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}
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})
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private val gestureDetector = GestureDetector(context, object : GestureDetector.SimpleOnGestureListener() {
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override fun onDoubleTap(e: MotionEvent): Boolean {
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if (currentScale > 1.5f) {
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resetZoom()
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} else {
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zoomTo(3f, e.x, e.y)
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}
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return true
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}
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override fun onScroll(e1: MotionEvent?, e2: MotionEvent, dx: Float, dy: Float): Boolean {
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if (currentScale > 1f) {
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matrix.postTranslate(-dx, -dy)
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constrainMatrix()
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imageMatrix = matrix
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}
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return true
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}
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})
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private val scroller = OverScroller(context)
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private var scrollAction: Runnable? = null
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init {
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scaleType = ScaleType.MATRIX
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}
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override fun setImageDrawable(drawable: Drawable?) {
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super.setImageDrawable(drawable)
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post { resetZoom() }
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}
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override fun onTouchEvent(event: MotionEvent): Boolean {
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scaleDetector.onTouchEvent(event)
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gestureDetector.onTouchEvent(event)
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when (event.actionMasked) {
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MotionEvent.ACTION_DOWN -> {
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mode = DRAG
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startPoint.set(event.x, event.y)
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savedMatrix.set(matrix)
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stopScroll()
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parent.requestDisallowInterceptTouchEvent(true)
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}
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MotionEvent.ACTION_POINTER_DOWN -> {
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mode = ZOOM
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oldDist = spacing(event)
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midPoint = mid(event)
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savedMatrix.set(matrix)
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parent.requestDisallowInterceptTouchEvent(true)
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}
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MotionEvent.ACTION_MOVE -> {
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if (mode == ZOOM && event.pointerCount >= 2) {
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val newDist = spacing(event)
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if (newDist > 10f) {
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val scale = newDist / oldDist
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matrix.set(savedMatrix)
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currentScale *= scale
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currentScale = currentScale.coerceIn(minScale, maxScale)
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matrix.postScale(scale, scale, midPoint.x, midPoint.y)
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constrainMatrix()
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imageMatrix = matrix
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oldDist = newDist
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}
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}
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}
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MotionEvent.ACTION_UP, MotionEvent.ACTION_POINTER_UP -> {
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mode = NONE
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if (currentScale < minScale) {
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resetZoom()
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}
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if (currentScale <= 1f) {
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parent.requestDisallowInterceptTouchEvent(false)
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}
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}
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}
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return true
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}
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private fun resetZoom() {
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currentScale = minScale
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matrix.reset()
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centerImage()
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imageMatrix = matrix
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}
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private fun zoomTo(targetScale: Float, focusX: Float, focusY: Float) {
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val startScale = currentScale
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val startTime = System.currentTimeMillis()
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val duration = 300L
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scrollAction?.let { removeCallbacks(it) }
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scrollAction = object : Runnable {
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override fun run() {
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val elapsed = System.currentTimeMillis() - startTime
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val t = (elapsed.toFloat() / duration).coerceAtMost(1f)
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val eased = 1f - (1f - t) * (1f - t)
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val newScale = startScale + (targetScale - startScale) * eased
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val factor = newScale / currentScale
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currentScale = newScale
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matrix.postScale(factor, factor, focusX, focusY)
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constrainMatrix()
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imageMatrix = matrix
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if (t < 1f) postOnAnimation(this)
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}
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}
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postOnAnimation(scrollAction!!)
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}
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private fun centerImage() {
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val d = drawable ?: return
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val viewWidth = width.toFloat()
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val viewHeight = height.toFloat()
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val imgWidth = d.intrinsicWidth.toFloat()
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val imgHeight = d.intrinsicHeight.toFloat()
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val scale = minOf(viewWidth / imgWidth, viewHeight / imgHeight, 1f)
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currentScale = scale
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minScale = scale
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val dx = (viewWidth - imgWidth * scale) / 2f
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val dy = (viewHeight - imgHeight * scale) / 2f
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matrix.setScale(scale, scale)
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matrix.postTranslate(dx, dy)
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}
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private fun constrainMatrix() {
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val d = drawable ?: return
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val values = FloatArray(9)
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matrix.getValues(values)
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val scaleX = values[Matrix.MSCALE_X]
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val imgWidth = d.intrinsicWidth * scaleX
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val imgHeight = d.intrinsicHeight * scaleX
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var transX = values[Matrix.MTRANS_X]
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var transY = values[Matrix.MTRANS_Y]
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val viewWidth = width.toFloat()
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val viewHeight = height.toFloat()
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if (imgWidth <= viewWidth) {
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transX = (viewWidth - imgWidth) / 2f
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} else {
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transX = transX.coerceIn(viewWidth - imgWidth, 0f)
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}
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if (imgHeight <= viewHeight) {
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transY = (viewHeight - imgHeight) / 2f
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} else {
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transY = transY.coerceIn(viewHeight - imgHeight, 0f)
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}
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matrix.postTranslate(transX - values[Matrix.MTRANS_X], transY - values[Matrix.MTRANS_Y])
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}
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private fun spacing(event: MotionEvent): Float {
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val x = event.getX(0) - event.getX(1)
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val y = event.getY(0) - event.getY(1)
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return Math.sqrt((x * x + y * y).toDouble()).toFloat()
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}
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private fun mid(event: MotionEvent): PointF {
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val x = event.getX(0) + event.getX(1)
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val y = event.getY(0) + event.getY(1)
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return PointF(x / 2f, y / 2f)
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}
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private fun stopScroll() {
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scrollAction?.let { removeCallbacks(it) }
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scroller.forceFinished(true)
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}
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companion object {
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private const val NONE = 0
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private const val DRAG = 1
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private const val ZOOM = 2
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}
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}

‎app/src/main/res/layout/fullscreen_page.xml‎

Lines changed: 1 addition & 2 deletions
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<?xml version="1.0" encoding="utf-8"?>
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<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
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<com.degard.imagecompressor.ZoomableImageView xmlns:android="http://schemas.android.com/apk/res/android"
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android:id="@+id/ivFull"
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android:layout_width="match_parent"
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android:layout_height="match_parent"
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android:scaleType="fitCenter"
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android:background="#FF000000" />

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