Android 将宽度设置为 ConstraintLayout.LayoutParams.MATCH_PARENT 给出 -1

Question

我在创建弹出窗口时有这段代码

val width = ConstraintLayout.LayoutParams.MATCH_PARENT

弹出窗口显示并具有所需的全宽。但由于某些原因，宽度变量被分配为 -1，我使用该变量填充弹出窗口中的其他内容，以便它们获得负宽度并且不显示。为什么当弹出窗口变满时返回 -1？

Answer 1

public static final int MATCH_PARENT Special value for the height or width requested by a View. MATCH_PARENT means that the view wants to be as big as its parent, minus the parent's padding, if any. Introduced in API Level 8.

Constant Value: -1 (0xffffffff) (+)

要获取特定视图的宽度，您可以执行以下操作：

int width = specificView.getWidth();

Answer 2

视图的宽度（猜测 ConstraintLayout）不是静态的，它取决于呈现视图的设备。在 kotlin 中，您有一种在运行时计算视图尺寸的便捷方法：

view.doOnLayout {
    it.measuredWidth
    it.measuredHeight
}

Android 将宽度设置为 ConstraintLayout.LayoutParams.MATCH_PARENT 给出 -1

Android setting width to ConstraintLayout.LayoutParams.MATCH_PARENT gives -1

android

kotlin

android-constraintlayout