Android getMeasuredHeight 返回错误值！ [英] Android getMeasuredHeight returns wrong values !

问题描述

我正在尝试确定某些 UI 元素的实际尺寸(以像素为单位)！

I'm trying to determine the real dimension in pixels of some UI elements !

这些元素是从一个 .xml 文件中膨胀出来的，并用倾斜宽度和高度初始化，这样 GUI 最终将支持多种屏幕尺寸和 dpi (android 规范推荐).

Those elements are inflated from a .xml file and are initialized with dip width and height so that the GUI will eventually support multiple screen size and dpi (as recommended by android specs).

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="150dip"
android:orientation="vertical">
    
<ImageView
    android:id="@+id/TlFrame" 
    android:layout_width="110dip" 
    android:layout_height="90dip"
    android:src="@drawable/timeline_nodrawing"
    android:layout_margin="0dip"
    android:padding="0dip"/></LinearLayout>

前面的 xml 代表一个框架.但我确实在水平布局中动态添加了许多内容:

This previous xml represent one frame. But I do add many dynamically inside a horizontal layout describe here :

<HorizontalScrollView 
        android:id="@+id/TlScroller"
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_margin="0dip"
        android:padding="0dip"
        android:scrollbars="none"
        android:fillViewport="false"
        android:scrollbarFadeDuration="0"
        android:scrollbarDefaultDelayBeforeFade="0"
        android:fadingEdgeLength="0dip"
        android:scaleType="centerInside">
        
        <!-- HorizontalScrollView can only host one direct child -->
        <LinearLayout 
            android:id="@+id/TimelineContent" 
            android:layout_width="fill_parent" 
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:layout_alignParentTop="true"
            android:layout_alignParentLeft="true"
            android:layout_margin="0dip"
            android:padding="0dip"
            android:scaleType="centerInside"/>
   
    </HorizontalScrollView > 

定义在我的java代码中添加一帧的方法:

The method defined to add one frame inside my java code :

private void addNewFrame()
{       
    LayoutInflater inflater     = (LayoutInflater) _parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    ViewGroup root      = (ViewGroup) inflater.inflate(R.layout.tl_frame, null);
    TextView frameNumber = (TextView) root.findViewById(R.id.FrameNumber);
    Integer val = new Integer(_nFramesDisplayed+1); //+1 to display ids starting from one on the user side 
    frameNumber.setText(val.toString());
    
    ++_nFramesDisplayed;
    _content.addView(root);
// _content variable is initialized like this in c_tor
// _content = (LinearLayout) _parent.findViewById(R.id.TimelineContent);
}

然后在我的代码中，我尝试以像素为单位获得实际的实际大小，因为我需要它来在其上绘制一些 opengl 内容.

Then inside my code, I try to get the actual real size in pixel because I need this to draw some opengl stuff over it.

LayoutInflater inflater     = (LayoutInflater) _parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    ViewGroup root      = (ViewGroup) inflater.inflate(R.layout.tl_frame, null);
    ImageView frame = (ImageView) root.findViewById(R.id.TlFrame);
    
    frame.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
    frame.measure(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

    final int w = frame.getMeasuredWidth();
    final int h = frame.getMeasuredHeight();

似乎一切正常，只是这些值比 ImageView 的实际像素大小大得多.

Everything seems to work fine except that those values are way bigger than the actual pixel size of the ImageView.

来自 getWindowManager().getDefaultDisplay().getMetrics(metrics) 的报告信息；如下:密度 = 1,5密度Dpi = 240宽度像素 = 600高度像素 = 1024

Reported infos from getWindowManager().getDefaultDisplay().getMetrics(metrics); are the following : density = 1,5 densityDpi = 240 widthPixel = 600 heightPixel = 1024

现在，我知道 android 的规则是:pixel = dip * (dpi/160).但是返回的值没有任何意义.对于 (90dip X 110dip) 的 ImageView，measure() 方法的返回值是 (270 x 218)，我假设它以像素为单位！

Now, I know the rule from android is : pixel = dip * (dpi /160). But nothing makes any sense with the value returned. For that ImageView of (90dip X 110dip), the returned values of the measure() method is (270 x 218) which I assumed is in pixel !

有人知道为什么吗?返回值是否以像素为单位?

Anyone has any idea why ? Is the value returned in pixel ?

顺便说一句:我一直在测试相同的代码，但使用的是 TextView 而不是 ImageView，一切似乎都运行良好！为什么！?！?

By the way : I've been testing the same code but with a TextView instead than an ImageView and everything seems to be working fine ! Why !?!?

推荐答案

您错误地调用了 measure.

measure 需要 MeasureSpec 由 MeasureSpec.makeMeasureSpec 特别打包的值.measure 忽略 LayoutParams.执行测量的父级应根据自己的测量和布局策略以及子级的 LayoutParams 创建 MeasureSpec.

measure takes MeasureSpec values which are specially packed by MeasureSpec.makeMeasureSpec. measure ignores LayoutParams. The parent doing the measuring is expected to create a MeasureSpec based on its own measurement and layout strategy and the child's LayoutParams.

如果您想测量 WRAP_CONTENT 通常在大多数布局中的工作方式，请像这样调用 measure:

If you want to measure the way that WRAP_CONTENT usually works in most layouts, call measure like this:

frame.measure(MeasureSpec.makeMeasureSpec(maxWidth, MeasureSpec.AT_MOST),
        MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.AT_MOST));

如果您没有最大值(例如，如果您正在编写具有无限空间的 ScrollView 之类的内容)，您可以使用 UNSPECIFIED 模式:

If you don't have max values (for example if you're writing something like a ScrollView that has infinite space) you can use the UNSPECIFIED mode:

frame.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
        MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));

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