Android实现展开收起动画的悬浮按钮

效果图：

实现原理

    利用属性动画的特性，动态地改变控件宽度。

    这里唯一要注意的坑点在于我们一定要拿到准确的子控件（即内部几个view）的宽度与高度 才能精准地对要伸展以及收缩的宽度进行控制。同时，为了不让子控件内部由于文字挤压所带来的换行影响，这里可以设置textview的maxLine属性为1。

    由于现在需求急于上线，这里先直接上代码了~等忙完这阵子再来细细分享实现过程中遇到的坑以及一些代码逻辑的实现原理。

Coding Time

class ExpandAnimationView : LinearLayout {

    private lateinit var mImageView: ImageView

    private val mAnimatorSet = AnimatorSet()

    private var mExpandWidth = 0

    private val mExpandContainer = LinearLayout(context)

    private val mExpandItems = listOf(ExpandItem(R.drawable.ic_next, "收起"), ExpandItem(R.drawable.ic_share, "分享"))

    private var mIsExpanding = false

    private var mClickListener: OnExpandViewClickListener? = null

    constructor(context: Context): this(context, null)

    constructor(context: Context, attrs: AttributeSet?): super (context, attrs)

    init {
        // 设置父级控件的属性
        orientation = HORIZONTAL
        gravity = Gravity.CENTER_VERTICAL
        background = ResourcesCompat.getDrawable(context.resources, R.drawable.bg_expand_view, null)
        mImageView = ImageView(context)
        addView(mImageView)
        mImageView.apply {
            layoutParams = LinearLayout.LayoutParams(dip2px(25F), dip2px(25F))
            val p = layoutParams as LayoutParams
            p.setMargins(dip2px(13F), dip2px(13F), dip2px(13F), dip2px(13F))
            layoutParams = p
            setImageResource(R.drawable.ic_add)
        }

        setOnClickListener {
            mImageView.performClick()
        }

        mImageView.setOnClickListener {
            startAnimation()
        }

        // 设置扩展的子控件的属性
        initExpandView()
    }

    private fun initExpandView() {
        if (mExpandItems.isEmpty()) return

        addView(mExpandContainer, 0)

        mExpandContainer.layoutParams = LinearLayout.LayoutParams(0, LayoutParams.MATCH_PARENT)
        val containerParam = mExpandContainer.layoutParams as LayoutParams
        mExpandContainer.gravity = Gravity.CENTER_VERTICAL

        for ((index, item) in mExpandItems.withIndex()) {
            val textView = TextView(context)
            textView.apply {
                gravity = Gravity.CENTER_VERTICAL
                textView.textSize = 13F
                textView.setTextColor(Color.WHITE)
                textView.text = item.text
                textView.maxLines = 1