Created
July 7, 2019 20:23
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ViewPager with support animation wrap_content
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<?xml version="1.0" encoding="utf-8"?> | |
<resources> | |
<declare-styleable name="ViewPager"> | |
<attr name="enableAnimation" format="boolean" /> | |
<attr name="animationDuration" format="integer" /> | |
</declare-styleable> | |
</resources> |
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<one.xcorp.widget.ViewPager | |
android:id="@+id/wt_content" | |
android:layout_width="match_parent" | |
android:layout_height="wrap_content" | |
app:enableAnimation="true" /> |
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package one.xcorp.widget | |
import android.animation.ValueAnimator | |
import android.content.Context | |
import android.util.AttributeSet | |
import android.view.View | |
import android.view.ViewGroup.LayoutParams.MATCH_PARENT | |
import android.view.ViewGroup.LayoutParams.WRAP_CONTENT | |
import one.xcorp.widget.R | |
import kotlin.properties.Delegates.observable | |
class ViewPager : android.support.v4.view.ViewPager { | |
var enableAnimation by observable(false) { _, _, enable -> | |
if (enable) { | |
addOnPageChangeListener(onPageChangeListener) | |
} else { | |
removeOnPageChangeListener(onPageChangeListener) | |
} | |
} | |
private var animationDuration = 0L | |
private var animator: ValueAnimator? = null | |
constructor (context: Context) : super(context) { | |
init(context, null) | |
} | |
constructor (context: Context, attrs: AttributeSet?) : super(context, attrs) { | |
init(context, attrs) | |
} | |
private fun init(context: Context, attrs: AttributeSet?) { | |
context.theme.obtainStyledAttributes( | |
attrs, | |
R.styleable.ViewPager, | |
0, | |
0 | |
).apply { | |
try { | |
enableAnimation = getBoolean( | |
R.styleable.ViewPager_enableAnimation, | |
enableAnimation | |
) | |
animationDuration = getInteger( | |
R.styleable.ViewPager_animationDuration, | |
resources.getInteger(android.R.integer.config_shortAnimTime) | |
).toLong() | |
} finally { | |
recycle() | |
} | |
} | |
} | |
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) { | |
val heightMode = MeasureSpec.getMode(heightMeasureSpec) | |
val measuredHeight = if (heightMode == MeasureSpec.EXACTLY) { | |
MeasureSpec.getSize(heightMeasureSpec) | |
} else { | |
val currentViewHeight = findViewByPosition(currentItem)?.also { | |
measureView(it) | |
}?.measuredHeight ?: 0 | |
if (heightMode != MeasureSpec.AT_MOST) { | |
currentViewHeight | |
} else { | |
Math.min( | |
currentViewHeight, | |
MeasureSpec.getSize(heightMeasureSpec) | |
) | |
} | |
} | |
super.onMeasure( | |
widthMeasureSpec, | |
MeasureSpec.makeMeasureSpec(measuredHeight, MeasureSpec.EXACTLY) | |
) | |
} | |
private fun measureView(view: View) = with(view) { | |
val horizontalMode: Int | |
val horizontalSize: Int | |
when (layoutParams.width) { | |
MATCH_PARENT -> { | |
horizontalMode = MeasureSpec.EXACTLY | |
horizontalSize = this@ViewPager.measuredWidth | |
} | |
WRAP_CONTENT -> { | |
horizontalMode = MeasureSpec.UNSPECIFIED | |
horizontalSize = 0 | |
} | |
else -> { | |
horizontalMode = MeasureSpec.EXACTLY | |
horizontalSize = layoutParams.width | |
} | |
} | |
val verticalMode: Int | |
val verticalSize: Int | |
when (layoutParams.height) { | |
MATCH_PARENT -> { | |
verticalMode = MeasureSpec.EXACTLY | |
verticalSize = this@ViewPager.measuredHeight | |
} | |
WRAP_CONTENT -> { | |
verticalMode = MeasureSpec.UNSPECIFIED | |
verticalSize = 0 | |
} | |
else -> { | |
verticalMode = MeasureSpec.EXACTLY | |
verticalSize = layoutParams.height | |
} | |
} | |
val horizontalMeasureSpec = MeasureSpec.makeMeasureSpec(horizontalSize, horizontalMode) | |
val verticalMeasureSpec = MeasureSpec.makeMeasureSpec(verticalSize, verticalMode) | |
measure(horizontalMeasureSpec, verticalMeasureSpec) | |
} | |
private fun findViewByPosition(position: Int): View? { | |
for (i in 0 until childCount) { | |
val childView = getChildAt(i) | |
val childLayoutParams = childView.layoutParams as LayoutParams | |
val childPosition by lazy { | |
val field = childLayoutParams.javaClass.getDeclaredField("position") | |
field.isAccessible = true | |
field.get(childLayoutParams) as Int | |
} | |
if (!childLayoutParams.isDecor && position == childPosition) { | |
return childView | |
} | |
} | |
return null | |
} | |
private fun animateContentHeight(childView: View, fromHeight: Int, toHeight: Int) { | |
animator?.cancel() | |
if (fromHeight == toHeight) { | |
return | |
} | |
animator = ValueAnimator.ofInt(fromHeight, toHeight).apply { | |
addUpdateListener { | |
measureView(childView) | |
if (childView.measuredHeight != toHeight) { | |
animateContentHeight(childView, height, childView.measuredHeight) | |
} else { | |
layoutParams.height = animatedValue as Int | |
requestLayout() | |
} | |
} | |
duration = animationDuration | |
start() | |
} | |
} | |
private val onPageChangeListener = object : OnPageChangeListener { | |
override fun onPageScrollStateChanged(state: Int) { | |
/* do nothing */ | |
} | |
override fun onPageScrolled( | |
position: Int, | |
positionOffset: Float, | |
positionOffsetPixels: Int | |
) { | |
/* do nothing */ | |
} | |
override fun onPageSelected(position: Int) { | |
if (!isAttachedToWindow) { | |
return | |
} | |
findViewByPosition(position)?.let { childView -> | |
measureView(childView) | |
animateContentHeight(childView, height, childView.measuredHeight) | |
} | |
} | |
} | |
} |
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