Android仿微信聊天图片的放大缩小功能

<?xml version="1.0" encoding="utf-8"?>
<framelayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <imagebutton
        android:id="@+id/thumb_button_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginright="1dp"
        android:contentdescription="@string/description_image_1"
        android:scaletype="centercrop"
        android:src="@drawable/ic_main_img" />
</framelayout>

<framelayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <androidx.recyclerview.widget.recyclerview
        android:id="@+id/rv_room"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layoutmanager="androidx.recyclerview.widget.linearlayoutmanager"
        tools:itemcount="3"
        tools:listitem="@layout/item_zoom"/>
    <!-- this initially hidden imageview holds the zoomed version of
         the preceding images. without transformations applied, it fills the entire
         screen. to achieve the zoom animation, this view's bounds are animated
         from the bounds of the preceding thumbnail button to its final laid-out
         bounds.
         -->
    <imageview
        android:id="@+id/expanded_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="invisible"
        android:contentdescription="@string/description_zoom_touch_close" />
</framelayout>

class zoomadapter: recyclerview.adapter<zoomadapter.vh>() {
    var itemclick: ( (view) -> unit ) ?= null
    inner class vh(binding: itemzoombinding): recyclerview.viewholder(binding.root)
    override fun oncreateviewholder(parent: viewgroup, viewtype: int): vh {
        val layoutinflater = layoutinflater.from(parent.context)
        val binding = itemzoombinding.inflate(layoutinflater,parent,false)
        binding.thumbbutton1.setonclicklistener {
            itemclick?.invoke(it)
        }
        return vh(binding)
    }
    override fun onbindviewholder(holder: vh, position: int) {
    }
    override fun getitemcount(): int = 3
}

/**
 * 仿写微信应用中图片放大缩小效果
 */
class zoomactivity: fragmentactivity() {
    // hold a reference to the current animator so that it can be canceled
    // midway.
    private var currentanimator: animator? = null
    // the system "short" animation time duration in milliseconds. this duration
    // is ideal for subtle animations or animations that occur frequently.
    private var shortanimationduration: int = 0
    private val binding: activityzoomlistbinding by lazy {
        activityzoomlistbinding.inflate(layoutinflater)
    }
    private val adapter = zoomadapter()
    override fun oncreate(savedinstancestate: bundle?) {
        super.oncreate(savedinstancestate)
        setcontentview(binding.root)
        // retrieve and cache the system's default "short" animation time.
        shortanimationduration = resources.getinteger(android.r.integer.config_shortanimtime)
        initview()
    }
    private fun initview(){
        binding.rvroom.adapter = adapter
        // hook up taps on the thumbnail views.
        adapter.itemclick = {
            zoomimagefromthumb(it, r.drawable.ic_main_img)
        }
    }
    private fun zoomimagefromthumb(thumbview: view, imageresid: int) {
        // if there's an animation in progress, cancel it immediately and
        // proceed with this one.
        currentanimator?.cancel()
        // load the high-resolution "zoomed-in" image.
        binding.expandedimage.setimageresource(imageresid)
        // calculate the starting and ending bounds for the zoomed-in image.
        val startboundsint = rect()
        val finalboundsint = rect()
        val globaloffset = point()
        // the start bounds are the global visible rectangle of the thumbnail,
        // and the final bounds are the global visible rectangle of the
        // container view. set the container view's offset as the origin for the
        // bounds, since that's the origin for the positioning animation
        // properties (x, y).
        thumbview.getglobalvisiblerect(startboundsint)
        binding.container.getglobalvisiblerect(finalboundsint, globaloffset)
        startboundsint.offset(-globaloffset.x, -globaloffset.y)
        finalboundsint.offset(-globaloffset.x, -globaloffset.y)
        val startbounds = rectf(startboundsint)
        val finalbounds = rectf(finalboundsint)
        // using the "center crop" technique, adjust the start bounds to be the
        // same aspect ratio as the final bounds. this prevents unwanted
        // stretching during the animation. calculate the start scaling factor.
        // the end scaling factor is always 1.0.
        val startscale: float
        if ((finalbounds.width() / finalbounds.height() > startbounds.width() / startbounds.height())) {
            // extend start bounds horizontally.
            startscale = startbounds.height() / finalbounds.height()
            val startwidth: float = startscale * finalbounds.width()
            val deltawidth: float = (startwidth - startbounds.width()) / 2
            startbounds.left -= deltawidth.toint()
            startbounds.right += deltawidth.toint()
        } else {
            // extend start bounds vertically.
            startscale = startbounds.width() / finalbounds.width()
            val startheight: float = startscale * finalbounds.height()
            val deltaheight: float = (startheight - startbounds.height()) / 2f
            startbounds.top -= deltaheight.toint()
            startbounds.bottom += deltaheight.toint()
        }
        // hide the thumbnail and show the zoomed-in view. when the animation
        // begins, it positions the zoomed-in view in the place of the
        // thumbnail.
        thumbview.alpha = 0f
        animatezoomtolargeimage(startbounds, finalbounds, startscale)
        setdismisslargeimageanimation(thumbview, startbounds, startscale)
    }
    private fun animatezoomtolargeimage(startbounds: rectf, finalbounds: rectf, startscale: float) {
        binding.expandedimage.visibility = view.visible
        // set the pivot point for scale_x and scale_y transformations to the
        // top-left corner of the zoomed-in view. the default is the center of
        // the view.
        binding.expandedimage.pivotx = 0f
        binding.expandedimage.pivoty = 0f
        // construct and run the parallel animation of the four translation and
        // scale properties: x, y, scale_x, and scale_y.
        currentanimator = animatorset().apply {
            play(
                objectanimator.offloat(
                    binding.expandedimage,
                    view.x,
                    startbounds.left,
                    finalbounds.left)
            ).apply {
                with(objectanimator.offloat(binding.expandedimage, view.y, startbounds.top, finalbounds.top))
                with(objectanimator.offloat(binding.expandedimage, view.scale_x, startscale, 1f))
                with(objectanimator.offloat(binding.expandedimage, view.scale_y, startscale, 1f))
            }
            duration = shortanimationduration.tolong()
            interpolator = decelerateinterpolator()
            addlistener(object : animatorlisteneradapter() {
                override fun onanimationend(animation: animator) {
                    currentanimator = null
                }
                override fun onanimationcancel(animation: animator) {
                    currentanimator = null
                }
            })
            start()
        }
    }
    private fun setdismisslargeimageanimation(thumbview: view, startbounds: rectf, startscale: float) {
        // when the zoomed-in image is tapped, it zooms down to the original
        // bounds and shows the thumbnail instead of the expanded image.
        binding.expandedimage.setonclicklistener {
            currentanimator?.cancel()
            // animate the four positioning and sizing properties in parallel,
            // back to their original values.
            currentanimator = animatorset().apply {
                play(objectanimator.offloat(binding.expandedimage, view.x, startbounds.left)).apply {
                    with(objectanimator.offloat(binding.expandedimage, view.y, startbounds.top))
                    with(objectanimator.offloat(binding.expandedimage, view.scale_x, startscale))
                    with(objectanimator.offloat(binding.expandedimage, view.scale_y, startscale))
                }
                duration = shortanimationduration.tolong()
                interpolator = decelerateinterpolator()
                addlistener(object : animatorlisteneradapter() {
                    override fun onanimationend(animation: animator) {
                        thumbview.alpha = 1f
                        binding.expandedimage.visibility = view.gone
                        currentanimator = null
                    }
                    override fun onanimationcancel(animation: animator) {
                        thumbview.alpha = 1f
                        binding.expandedimage.visibility = view.gone
                        currentanimator = null
                    }
                })
                start()
            }
        }
    }
}