获取视图高度

Question

我想从另一个xml 文件中得到一个View 高度。这些我总是得到 0 作为高度：

fun getHeight(): Int {
    val factory = LayoutInflater.from(context)
    val inflater = context?.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
    val customView = inflater.inflate(R.layout.custom_expandable_helper,null)
    val relativeLayout = customView.findViewById<RelativeLayout>(R.id.container_height)
    val textView = customView.findViewById<TextView>(R.id.tv_height)
    textView.text = complaintText
    val rlp = RelativeLayout(activity)
    rlp.addView(customView)

    activity?.window?.decorView!!.viewTreeObserver.addOnGlobalLayoutListener(object : OnGlobalLayoutListener{
        override fun onGlobalLayout() {
            val obs = relativeLayout.viewTreeObserver
            viewHeight = relativeLayout.height
            obs.removeOnGlobalLayoutListener(this)
        }
    })

    val hei = rlp.height
    relativeLayout.post {
        viewHeight = relativeLayout.height
    }
    return relativeLayout.height
}

在这段代码中，你可以看到很多镜头来获取高度，它们都是 0。

这就是我要膨胀的 xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="12dp"
android:layout_marginStart="12dp"
android:id="@+id/container_height">

<TextView
    android:id="@+id/tv_height"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="@dimen/et_sides"
    android:text="sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample.sample."/>

Answer 1

您应该使用 OnGlobalLayoutListener 来监听视图布局更改，因为当您膨胀视图时，它的大小尚未测量。

附： 抱歉，例如在 JAVA 中

relativeLayout.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                // remove this once the layout measured
                relativeLayout.getViewTreeObserver().removeOnGlobalLayoutListener(this);
                ViewGroup.LayoutParams lp = relativeLayout.getLayoutParams();
                int height = lp.height; // Here we retrieve the measured height

            }
        });

Answer 2

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int parentWidth = MeasureSpec.getSize(widthMeasureSpec);
int parentHeight = MeasureSpec.getSize(heightMeasureSpec);
this.setMeasuredDimension(parentWidth, parentHeight);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

Answer 3

只有在屏幕上布局后，视图才会返回非零高度或宽度。这就是我们使用ViewTreeObserver.OnPreDrawListener、ViewTreeObserver.OnGlobalLayoutListener等的原因。

现在该方法不起作用，因为您只是返回return relativeLayout.height，它始终为零。

换句话说，您的代码中唯一可以获得视图高度的部分是：

activity?.window?.decorView!!.viewTreeObserver.addOnGlobalLayoutListener(object : 
OnGlobalLayoutListener{
        override fun onGlobalLayout() {
            val obs = relativeLayout.viewTreeObserver
            viewHeight = relativeLayout.height
            obs.removeOnGlobalLayoutListener(this)
        }
    })

如果您在其中记录viewHeight，则应该打印正确的视图高度。

试试这个

    val vto = activity?.window?.decorView?.viewTreeObserver?
    vto?.addOnPreDrawListener(object : ViewTreeObserver.OnPreDrawListener {
                override fun onPreDraw(): Boolean {
                vto?.removeOnPreDrawListener(this)
                val viewHeight = relativeLayout.height
                Log.v("logtag", viewHeight)
            }
        })

如果您不打算加载该布局，请执行以下操作：

val view = yourView
val widthSpec = View.MeasureSpec.makeMeasureSpec(parent.width, View.MeasureSpec.EXACTLY)
val heightSpec = View.MeasureSpec.makeMeasureSpec(parent.height, View.MeasureSpec.UNSPECIFIED)

val childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec, parent.paddingLeft+parent.paddingRight,view.layoutParams.width)
val childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec, parent.paddingTop+parent.paddingBottom, view.layoutParams.height)

view.measure(childWidthSpec, childHeightSpec)