最近接到一个需求，需要实现可以自动折叠的TextView，如下图所示：
fte3p-rxvyq.gif
重点主要有两个：如何测量文本显示的行数；动画适合实现；
下面就先就这两个问题展示一下核心代码
测量文本行数
这里主要通过StaticLayout来得到文本的行数等信息：
/**
* 根据[source]创建一个[StaticLayout]对象，用于辅助计算文本可显示行数、高度等
*/
private fun <T : CharSequence> createStaticLayout(source: T): Layout =
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
StaticLayout.Builder.obtain(source, 0, source.length, paint, mMeasuredWidth)
.setAlignment(Layout.Alignment.ALIGN_NORMAL)
.setIncludePad(includeFontPadding)
.setLineSpacing(lineSpacingExtra, lineSpacingMultiplier)
.build()
} else {
@Suppress("DEPRECATION")
StaticLayout(
source,
paint,
mMeasuredWidth,
Layout.Alignment.ALIGN_NORMAL,
lineSpacingMultiplier,
lineSpacingExtra,
includeFontPadding
)
}
canFold = layout.lineCount > mFoldedLines //lineCount 文本行数
mExpandedHeight = createStaticLayout(mExpandedText).height + paddingTop + paddingBottom //height 文本高度
实现动画
通过属性动画可以实现折叠和展开效果：
private fun createAnimation(
start: Int,
end: Int,
startCallback: (() -> Unit)?,
endCallback: (() -> Unit)?
): ObjectAnimator {
val animator = ObjectAnimator.ofInt(this, "layoutHeight", start, end)
animator.duration = mDuration
animator.interpolator = AccelerateDecelerateInterpolator()
animator.addListener(object : Animator.AnimatorListener {
override fun onAnimationStart(animation: Animator?) {
isAnimating = true
startCallback?.invoke()
}
override fun onAnimationEnd(animation: Animator?) {
isAnimating = false
endCallback?.invoke()
}
override fun onAnimationCancel(animation: Animator?) {
}
override fun onAnimationRepeat(animation: Animator?) {
}
})
return animator
}
手动支持CLickableSpann
这里“展开”和“折叠”按钮是通过SpannableString实现，要实现点击事件除了加上ClikableSpann是不行的，看到网上的方法一般都是设置一个LinkMovementMethod，但是这样的话当使用动画的时候，文本整体都被向上挪动了，最后也是在网上找的解决方案：重写onTouch方法来自己实现对clickableSpann的支持：
/**
* 重写方法以支持ClickSpan的点击事件
* 直接设置LinkMovementMethod的话会导致TextView可以滑动，当执行折叠动画时整个文本会被向上推，达不到预期效果
*/
@SuppressLint("ClickableViewAccessibility")
override fun onTouchEvent(event: MotionEvent?): Boolean {
val curText = text
val action = event?.action
when {
curText is Spanned && (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_DOWN) -> {
val x = (event.x - totalPaddingLeft + scrollX).toInt()
val y = (event.y - totalPaddingTop + scrollY).toInt()
val line = layout.getLineForVertical(y)
val off = layout.getOffsetForHorizontal(line, x.toFloat())
val link = curText.getSpans(off, off, ClickableSpan::class.java)
if (link.isNotEmpty()) {
if (action == MotionEvent.ACTION_UP) link[0].onClick(this)
return true
}
}
else -> return super.onTouchEvent(event)
}
return super.onTouchEvent(event)
}
完整代码
class ExpandableTextView(context: Context, attrs: AttributeSet?, defStyleAttr: Int) :
AppCompatTextView(context, attrs, defStyleAttr) {
private var mOriginText: CharSequence? = null
private var mExpandedText: SpannableStringBuilder = createSpannableStringBuilder("")
private var mFoldedText: SpannableStringBuilder = createSpannableStringBuilder("")
private var mMeasuredWidth: Int = 0
private var mFoldedHeight: Int = 0 //折叠后的高度
private var mFoldAnimator: Animator? = null //折叠动画
private var mExpandedHeight: Int = 0
private var mExpandAnimator: Animator? = null
/**
* 折叠行数阈值，本文行数超过阈值时才可已折叠
*/
private val mFoldedLines: Int
private val mSuffixTextColor: Int
private val mFoldedSuffix: SpannableString //折叠状态下的文本后缀
private val mExpandedSuffix: SpannableString//展开状态下的文本后缀
private var canFold: Boolean = true
private var isFolded: Boolean = false
private val mDuration: Long
private var isAnimating: Boolean = false
@Suppress("unused")
var layoutHeight: Int = 0
set(value) {
field = value
Log.d(TAG, "set layoutHeight: $value")
layoutParams.height = value
requestLayout()
}
constructor(context: Context) : this(context, null)
constructor(context: Context, attrs: AttributeSet?) : this(context, attrs, 0)
init {
val typedValue = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView)
mOriginText = typedValue.getString(R.styleable.ExpandableTextView_expandableText)
mDuration = typedValue.getInt(
R.styleable.ExpandableTextView_expandDuration,
DEFAULT_DURATION_TIME
).toLong()
mFoldedLines = typedValue.getInt(
R.styleable.ExpandableTextView_foldLines,
DEFAULT_EXPANDABLE_LINES
)
mSuffixTextColor = typedValue.getColor(
R.styleable.ExpandableTextView_suffixTextColor,
DEFAULT_SUFFIX_TEXT_COLOR
)
val foldSuffix = typedValue.getString(R.styleable.ExpandableTextView_foldedSuffixText)
?: DEFAULT_ACTION_TEXT_EXPAND
mFoldedSuffix = createClickedSpannableString(
ELLIPSIS_STRING + foldSuffix,
ELLIPSIS_STRING.length
)
val expandText = typedValue.getString(R.styleable.ExpandableTextView_expandedSuffixText)
?: DEFAULT_ACTION_TEXT_FOLD
mExpandedSuffix = createClickedSpannableString(expandText)
//取消clickableSpan点击背景
highlightColor = Color.argb(0, 0, 0, 0)
typedValue.recycle()
}
/**
* 设置原始文本
* 若文本所需显示的函数小于[mFoldedLines]，则不会做任何处理，
* 否则文本可以展开与折叠
*
* @param text TextView所需显示的原始文本
*/
fun setExpandableText(text: CharSequence) {
mOriginText = text
if (mMeasuredWidth <= 0) return
val layout = createStaticLayout(text)
canFold = layout.lineCount > mFoldedLines
isFolded = canFold
if (canFold) {
buildExpandableText(layout)
setText(if (isFolded) mFoldedText else mExpandedText)
} else {
setText(mOriginText)
}
}
/**
* 展开/折叠
*/
fun toggleExpand() {
if (!canFold || isAnimating) return
isFolded = !isFolded
if (isFolded) {
mFoldAnimator?.start()
} else {
mExpandAnimator?.start()
}
}
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
if ((mMeasuredWidth == 0 || mMeasuredWidth != measuredWidth) && !isAnimating) {
Log.d(TAG, "width $mMeasuredWidth changed to $measuredWidth , $canFold")
mMeasuredWidth = measuredWidth
if (canFold) mOriginText?.let { setExpandableText(it) }
}
}
/**
* 重写方法以支持ClickSpan的点击事件
* 直接设置LinkMovementMethod的话会导致TextView可以滑动，当执行折叠动画时整个文本会被向上推，达不到预期效果
*/
@SuppressLint("ClickableViewAccessibility")
override fun onTouchEvent(event: MotionEvent?): Boolean {
val curText = text
val action = event?.action
when {
curText is Spanned && (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_DOWN) -> {
val x = (event.x - totalPaddingLeft + scrollX).toInt()
val y = (event.y - totalPaddingTop + scrollY).toInt()
val line = layout.getLineForVertical(y)
val off = layout.getOffsetForHorizontal(line, x.toFloat())
val link = curText.getSpans(off, off, ClickableSpan::class.java)
if (link.isNotEmpty()) {
if (action == MotionEvent.ACTION_UP) link[0].onClick(this)
return true
}
}
else -> return super.onTouchEvent(event)
}
return super.onTouchEvent(event)
}
/**
* 构建展开/折叠状态下的文本
*/
private fun buildExpandableText(originLayout: Layout) {
if (TextUtils.isEmpty(mOriginText)) return
mExpandedText = createSpannableStringBuilder(mOriginText!!).append(mExpandedSuffix)
mExpandedHeight = createStaticLayout(mExpandedText).height + paddingTop + paddingBottom
Log.d(TAG, "build ExpandedText: $mExpandedText")
val lineEnd = originLayout.getLineEnd(mFoldedLines - 1)
var foldText = mOriginText!!.subSequence(0, lineEnd)
var builder = createSpannableStringBuilder(foldText).append(mFoldedSuffix)
while (createStaticLayout(builder).lineCount > mFoldedLines) {
foldText = foldText.subSequence(0, foldText.length - 1)
builder = createSpannableStringBuilder(foldText).append(mFoldedSuffix)
}
// val foldText =
// mOriginText!!.subSequence(0, lineEnd - mFoldedSuffix.length - 1)
// mFoldedText = createSpannableStringBuilder(foldText).append(mFoldedSuffix)
mFoldedText = createSpannableStringBuilder(builder)
mFoldedHeight = createStaticLayout(mFoldedText).height + paddingTop + paddingBottom
Log.d(TAG, "build FoldedText: $mFoldedText")
mFoldAnimator = createAnimation(mExpandedHeight, mFoldedHeight, null, {
text = mFoldedText
})
mExpandAnimator = createAnimation(mFoldedHeight, mExpandedHeight, {
text = mExpandedText
}, null)
}
/**
* 根据[source]创建一个[StaticLayout]对象，用于辅助计算文本可显示行数、高度等
*/
private fun <T : CharSequence> createStaticLayout(source: T): Layout =
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
StaticLayout.Builder.obtain(source, 0, source.length, paint, mMeasuredWidth)
.setAlignment(Layout.Alignment.ALIGN_NORMAL)
.setIncludePad(includeFontPadding)
.setLineSpacing(lineSpacingExtra, lineSpacingMultiplier)
.build()
} else {
@Suppress("DEPRECATION")
StaticLayout(
source,
paint,
mMeasuredWidth,
Layout.Alignment.ALIGN_NORMAL,
lineSpacingMultiplier,
lineSpacingExtra,
includeFontPadding
)
}
private fun createClickedSpannableString(
charSequence: CharSequence, start: Int = 0
): SpannableString = SpannableString(charSequence).apply {
setSpan(object : ClickableSpan() {
override fun onClick(widget: View) {
toggleExpand()
}
override fun updateDrawState(ds: TextPaint) {
super.updateDrawState(ds)
ds.color = mSuffixTextColor
ds.isUnderlineText = false
}
}, start, charSequence.length, Spanned.SPAN_EXCLUSIVE_INCLUSIVE)
}
private fun createSpannableStringBuilder(charSequence: CharSequence) =
SpannableStringBuilder(charSequence)
private fun createAnimation(
start: Int,
end: Int,
startCallback: (() -> Unit)?,
endCallback: (() -> Unit)?
): ObjectAnimator {
val animator = ObjectAnimator.ofInt(this, "layoutHeight", start, end)
animator.duration = mDuration
animator.interpolator = AccelerateDecelerateInterpolator()
animator.addListener(object : Animator.AnimatorListener {
override fun onAnimationStart(animation: Animator?) {
isAnimating = true
startCallback?.invoke()
}
override fun onAnimationEnd(animation: Animator?) {
isAnimating = false
endCallback?.invoke()
}
override fun onAnimationCancel(animation: Animator?) {
}
override fun onAnimationRepeat(animation: Animator?) {
}
})
return animator
}
companion object {
const val TAG = "ExpandableTextView"
val ELLIPSIS_STRING = String(charArrayOf('\u2026')) //省略号
const val DEFAULT_EXPANDABLE_LINES = 4
const val DEFAULT_DURATION_TIME = 300
val DEFAULT_SUFFIX_TEXT_COLOR = Color.rgb(255, 97, 46)
const val DEFAULT_ACTION_TEXT_FOLD = "收起"
const val DEFAULT_ACTION_TEXT_EXPAND = "展开"
}
}
github:ExpandableTextView
参考文章
需求做完了之后蛮久才补的笔记，还有些博客实在找不到了 = =
