Android（Java/Kotlin）在任何地方Showing

最近做一个项目，项目中好几处用到了popwindow，于是乎想简单的封装下popwindow，最初想着用MeasureSpec来获取暂未显示的view的宽高：

public static void showPopwindow(View anchor){
.....
binding.root.measure(makeDropDownMeasureSpec(AppUtils.dip2px(context, 254f)),
                makeDropDownMeasureSpec(ViewGroup.LayoutParams.WRAP_CONTENT))
        val offsetY: Int =
                binding.root.measuredHeight + anchor.height
        Log.d(TAG,
                "xyInfo==>" + offsetY + "|" + binding.root.measuredHeight + "|" + anchor.height)
        mPopWindow.showAsDropDown(anchor, 0, -offsetY, Gravity.END)
}

    private fun makeDropDownMeasureSpec(measureSpec: Int): Int {
        val mode: Int = if (measureSpec == ViewGroup.LayoutParams.WRAP_CONTENT) {
            View.MeasureSpec.AT_MOST
        } else {
            View.MeasureSpec.EXACTLY
        }
        return View.MeasureSpec.makeMeasureSpec(View.MeasureSpec.getSize(measureSpec), mode)
    }

 }

但如上方式，在手机上实际显示的效果发现位置不对，offsetY的值偏小了，日志打印出来不是预期的高度，想到popwindow的contentView都是在使用时才通过Layoutinflater初始化的可能测量无法精准，于是乎想到了另一种实现：
采用addOnGlobalLayoutListener来精确/准确获取View的大小（因为这时view已经初始化），果然完美解决，现在只需要简单就能实现在你想要的任何地方显示popwindow了。

public static void showPopwindow(View anchor){
......
binding.getRoot().getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                binding.getRoot().getViewTreeObserver().removeOnGlobalLayoutListener(this);
                binding.getRoot().setVisibility(View.VISIBLE);
                int mWidth = binding.getRoot().getWidth();
                int mHeight = binding.getRoot().getHeight();
                Log.d("mPopWindowLocation", "xyInfo==>" + mPopWindow.isShowing() + "|" + binding.getRoot().getHeight() + "|" + anchor.getHeight());
                if (mPopWindow.isShowing()) {
                    mPopWindow.update(anchor, 0, -(mHeight + anchor.getHeight()), mWidth, mHeight);
                }
            }
        });
        binding.getRoot().setVisibility(View.INVISIBLE);
        mPopWindow.showAsDropDown(anchor, 0, 0, Gravity.END);
}

传统的Layoutinflater方式下上面的方式应该已经是正常工作了，但在用databinding的Layoutinflater时，其实应为databinding的机制问题，View中的getWidth 或者getHeight方法其实返回的依旧是之前的数据，databing过后的margin啊，padding啊并没有更新，所以测出来的数据并不对，应此在用databingding的方式下应该对如上实现方式做调整：

    private fun showPopwindow(anchor: View) {
   
val binding: DialogAttachmentLayoutBinding =
                DataBindingUtil.inflate(LayoutInflater.from(context),
                        R.layout.dialog_attachment_layout,
                        null,
                        false)
        binding.theme = SDKProviderDelegate.getTheme().value
        val mPopWindow = PopupWindow(binding.root,
                AppUtils.dip2px(context, 254f),
                ViewGroup.LayoutParams.WRAP_CONTENT, true)
//new implementation:
binding.root.viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
            override fun onGlobalLayout() {
                binding.root.viewTreeObserver.removeOnGlobalLayoutListener(this)
                binding.root.visibility = View.VISIBLE
                var mHeight = 0
                val viewParent = (binding.root as ViewGroup)
                for (i in 0 until viewParent.childCount) {
                    val child: View = viewParent.getChildAt(i)
                    val lp: ViewGroup.LayoutParams = child.layoutParams
                    val widthMeasureMode = if (lp.width == ViewGroup.LayoutParams.WRAP_CONTENT) MeasureSpec.AT_MOST else MeasureSpec.EXACTLY
                    val heightMeasureMode = if (lp.height == ViewGroup.LayoutParams.WRAP_CONTENT) MeasureSpec.AT_MOST else MeasureSpec.EXACTLY
                    val widthMeasure = MeasureSpec.makeMeasureSpec(binding.root.width, widthMeasureMode)
                    val heightMeasure = MeasureSpec.makeMeasureSpec(binding.root.height, heightMeasureMode)
                    child.measure(widthMeasure, heightMeasure)
                    mHeight += child.measuredHeight
                }
                mHeight = (mHeight + binding.root.paddingTop + binding.root.paddingBottom)
                Log.d("mPopWindowLocation", "xyInfo==>" + mPopWindow.isShowing + "|" + binding.root.height + "|" + mHeight)
                if (mPopWindow.isShowing) {
                    mPopWindow.update(anchor, 0, -(anchor.top + anchor.height + mHeight), -1, -1)
                }
            }
        })
        binding.root.visibility = View.INVISIBLE
        mPopWindow.showAsDropDown(anchor, 0, 0, Gravity.END)
    }

现在工作良好，所以看自己的项目决定采用哪种解决方法吧。
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