如何从自定义视图中访问layout_height？

Question

我有一个自定义视图,我只想访问xml布局值layout_height.

我目前正在获取该信息并在onMeasure期间存储它,但这仅在视图首次绘制时发生.我的视图是XY图,它需要尽早知道它的高度,以便它可以开始执行计算.

The view is on the fourth page of a viewFlipper layout, so the user may not flip to it for a while, but when they do flip to it, I would like the view to already contain data, which requires that I have the height to make the calculations.

Thanks!!!

Answer 1

工作:)...你需要改变"android"为" http://schemas.android.com/apk/res/android "

public CustomView(final Context context, AttributeSet attrs) {
    super(context, attrs);
    String height = attrs.getAttributeValue("http://schemas.android.com/apk/res/android", "layout_height");
    //further logic of your choice..
}

Answer 2

你可以使用这个：

public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);

    int[] systemAttrs = {android.R.attr.layout_height};
    TypedArray a = context.obtainStyledAttributes(attrs, systemAttrs);
    int height = a.getDimensionPixelSize(0, ViewGroup.LayoutParams.WRAP_CONTENT);
    a.recycle();
}

Answer 3

从 public View(Context context, AttributeSet attrs)构造函数文档：

从 XML 扩充视图时调用的构造函数。当从 XML 文件构造视图时调用它，提供在 XML 文件中指定的属性。

因此，要实现您需要的功能，请为您的自定义视图提供一个构造函数，该构造函数将 Attributes 作为参数，即：

public CustomView(final Context context, AttributeSet attrs) {
    super(context, attrs);
    String height = attrs.getAttributeValue("android", "layout_height");
    //further logic of your choice..
}

Answer 4

\xe2\x80\xa2Kotlin Version

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针对此问题编写的答案并未完全涵盖该问题。事实上，他们正在互相补足。总结一下答案，首先我们应该检查getAttributeValue返回值，然后如果layout_height定义为维度值，则使用以下方法检索它getDimensionPixelSize：

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val layoutHeight = attrs?.getAttributeValue("http://schemas.android.com/apk/res/android", "layout_height")\nvar height = 0\nwhen {\n    layoutHeight.equals(ViewGroup.LayoutParams.MATCH_PARENT.toString()) -> \n        height = ViewGroup.LayoutParams.MATCH_PARENT\n    layoutHeight.equals(ViewGroup.LayoutParams.WRAP_CONTENT.toString()) -> \n        height = ViewGroup.LayoutParams.WRAP_CONTENT\n    else -> context.obtainStyledAttributes(attrs, intArrayOf(android.R.attr.layout_height)).apply {\n        height = getDimensionPixelSize(0, ViewGroup.LayoutParams.WRAP_CONTENT)\n        recycle()\n    }\n}\n\n// Further to do something with `height`:\nwhen (height) {\n    ViewGroup.LayoutParams.MATCH_PARENT -> {\n        // defined as `MATCH_PARENT`\n    }\n    ViewGroup.LayoutParams.WRAP_CONTENT -> {\n        // defined as `WRAP_CONTENT`\n    }\n    in 0 until Int.MAX_VALUE -> {\n        // defined as dimension values (here in pixels)\n    }\n}\n

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