Android RelativeLayout未正确更新自定义视图的宽度

我有一个容器类，用来制作一个维度，宽度或高度，与另一个维度的比率。例如，我想要一个宽度为“match_parent”的16:9布局容器。然而，当使用高度作为“匹配父对象”时，Android似乎没有正确地重新显示自己。当我将高度设置为宽度的比率时，一切都很好！反之亦然，则不起作用。发生什么事了

public class RatioLayout extends ViewGroup {

private float ratio = 1.6222f; // 4 x 3 default. 1.78 is 16 x 9
public float getRatio() { return ratio; }
public void setRatio(float ratio) {
    this.ratio = ratio;
    requestLayout();
}

public RatioLayout(Context context) {
    this(context, null);
}

public RatioLayout(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public RatioLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    Log.i("Ratio", "/onMeasure");
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

//      int exactly = MeasureSpec.EXACTLY; // 1073741824    
//      int atMost = MeasureSpec.AT_MOST; // -2147483648
//      int unspec = MeasureSpec.UNSPECIFIED; // 0

    width = Math.round(height * ratio);
    widthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
    heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

    setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);

    int mw = getMeasuredWidth();
    int mh = getMeasuredHeight();
    Log.i("Ratio", "mw: " + mw + ", mh: " + mh);
}


@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    Log.i("Ratio", "/onLayout");
    Log.i("Ratio", "l: " + l + ", t: " + t + ", r:" + r + ", b:" + b);
    Log.i("Ratio", "mw: " + getMeasuredWidth() + ", mh:" + getMeasuredHeight());
    Log.i("Ratio", "w: " + getWidth() + ", mw:" + getHeight());
}

}

要查看它的运行情况，请使用如下布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

<com.example.RatioLayout
    android:id="@+id/image"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_marginBottom="100dp"
    android:layout_marginTop="100dp"
    android:background="#FFFF00FF" />

</RelativeLayout>

最终编辑确定。我放弃了。这是相对论中的一个合法错误。这段代码在某种程度上修复了它，但它在属性的定义方面产生了问题。我发现的解决方法是将此RatioLayout嵌套到另一个视图组（如LinerLayout）中。那些好奇的人的密码

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    Log.i("Ratio", "/onMeasure");
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

//      int exactly = MeasureSpec.EXACTLY; // 1073741824    
//      int atMost = MeasureSpec.AT_MOST; // -2147483648
//      int unspec = MeasureSpec.UNSPECIFIED; // 0

    width = Math.round(height * ratio);
    widthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
    heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

    setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);

    if (getParent() instanceof RelativeLayout) {
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)getLayoutParams();
        Class<?> clazz = RelativeLayout.LayoutParams.class;
        try {
            Field left = clazz.getDeclaredField("mLeft");
            Field right = clazz.getDeclaredField("mRight");
            left.setAccessible(true);
            right.setAccessible(true);
            int l = left.getInt(params);
            if (l == -1) l = params.leftMargin; // if the value is uninitialized, set it to 0;
            if (l == -1) l = 0; // if the value is uninitialized, set it to 0;
            // setting this seems to break the layout_marginLeft properties.
            right.setInt(params, l + getMeasuredWidth());
        } catch (NoSuchFieldException e) {
            Log.e("Ration", "error", e);
        } catch (IllegalArgumentException e) {
            Log.e("Ration", "error", e);
        } catch (IllegalAccessException e) {
            Log.e("Ration", "error", e);
        }
    }

    int mw = getMeasuredWidth();
    int mh = getMeasuredHeight();
    lastWidth = mw;
    Log.i("Ratio", "mw: " + mw + ", mh: " + mh);
}

@覆盖
测量时的保护空隙（内部宽度测量等级、内部高度测量等级）{
对数i（“比率”，即“测量值”）；
int width=MeasureSpec.getSize（widthmasurespec）；
int height=MeasureSpec.getSize（heightMeasureSpec）；
int widthMode=MeasureSpec.getMode（widthmasurespec）；
int heightMode=MeasureSpec.getMode（heightMeasureSpec）；
//int-justice=MeasureSpec.justice；//1073741824
//int atMost=MeasureSpec.AT_MOST；//-2147483648
//int unspec=MeasureSpec.UNSPECIFIED；//0
宽度=数学圆（高度*比率）；
widthMeasureSpec=MeasureSpec.MakeMasureSpec（宽度，精确测量）；
heightMeasureSpec=MeasureSpec.MakeMasureSpec（高度，精确测量）；
设置测量尺寸（宽度测量等级、高度测量等级）；
if（getParent（）instanceof RelativeLayout）{
RelativeLayout.LayoutParams params=（RelativeLayout.LayoutParams）getLayoutParams（）；
clazz类=RelativeLayout.LayoutParams.Class；
试一试{
字段左=clazz.getDeclaredField（“mLeft”）；
字段右侧=clazz.getDeclaredField（“mRight”）；
left.setAccessible（true）；
对。setAccessible（true）；
int l=left.getInt（参数）；
如果（l==-1）l=params.leftMargin；//如果该值未初始化，则将其设置为0；
如果（l==-1）l=0；//如果该值未初始化，则将其设置为0；
//设置此选项似乎会破坏布局\u marginLeft属性。
right.setInt（params，l+getMeasuredWidth（））；
}捕获（无此字段例外）{
Log.e（“定量”、“错误”，e）；
}捕获（IllegalArgumentException e）{
Log.e（“定量”、“错误”，e）；
}捕获（非法访问例外e）{
Log.e（“定量”、“错误”，e）；
}
}
int mw=getMeasuredWidth（）；
int mh=getMeasuredHeight（）；
最后宽度=兆瓦；
对数i（“比率”，“mw:+mw+”，mh:+mh）；
}

实际上，我已经试着做了您之前想做的事情，也就是说，使

视图尽量大，同时保留一些纵横比（即正方形或4:3或类似的东西）

我的问题是，当我的视图位于
滚动视图中时，大小计算不正确。我无法理解这一点，但我会在下面发布我的代码，以防万一。它与您的代码非常相似，但我继承了
FrameLayout
，最后调用了
super.onMeasure（）

我仔细检查了我在中使用它的项目，实际上它是
RelativeLayout
的直接子项目

爪哇：

attrs.xml
：

<resources>
    <declare-styleable name="RatioFrameLayout">
        <attr name="ratio" format="string|reference" />
    </declare-styleable>
</resources>



@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    Log.i("Ratio", "/onMeasure");
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

//      int exactly = MeasureSpec.EXACTLY; // 1073741824    
//      int atMost = MeasureSpec.AT_MOST; // -2147483648
//      int unspec = MeasureSpec.UNSPECIFIED; // 0

    width = Math.round(height * ratio);
    widthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
    heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

    setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);

    if (getParent() instanceof RelativeLayout) {
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)getLayoutParams();
        Class<?> clazz = RelativeLayout.LayoutParams.class;
        try {
            Field left = clazz.getDeclaredField("mLeft");
            Field right = clazz.getDeclaredField("mRight");
            left.setAccessible(true);
            right.setAccessible(true);
            int l = left.getInt(params);
            if (l == -1) l = params.leftMargin; // if the value is uninitialized, set it to 0;
            if (l == -1) l = 0; // if the value is uninitialized, set it to 0;
            // setting this seems to break the layout_marginLeft properties.
            right.setInt(params, l + getMeasuredWidth());
        } catch (NoSuchFieldException e) {
            Log.e("Ration", "error", e);
        } catch (IllegalArgumentException e) {
            Log.e("Ration", "error", e);
        } catch (IllegalAccessException e) {
            Log.e("Ration", "error", e);
        }
    }

    int mw = getMeasuredWidth();
    int mh = getMeasuredHeight();
    lastWidth = mw;
    Log.i("Ratio", "mw: " + mw + ", mh: " + mh);
}

/**
 * A FrameLayout which tries to be as big as possible while maintaining a given ratio between its width and height.
 * Formula: Height = Width / ratio;
 * Usage:
 * 1) Set layout_width and layout_height to "match_parent"
 * 2) For 4:3 for example, set ratio to 4/3 = 1.333333 etc. Or don't specify, and it will be square by default.
 */
public class RatioFrameLayout extends FrameLayout
{
    private final static float DEFAULT_RATIO = 1f;

    private float ratio;
    private boolean measured = false;

    public RatioFrameLayout(Context context)
    {
        super(context);
    }

    public RatioFrameLayout(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        readAttributes(context, attrs);
    }

    public RatioFrameLayout(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        readAttributes(context, attrs);
    }

    private void readAttributes(Context context, AttributeSet attrs)
    {
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RatioFrameLayout);

        String value = a.getString(R.styleable.RatioFrameLayout_ratio);
        try
        {
            ratio = Float.parseFloat(value);
        }
        catch (Exception e)
        {
            ratio = DEFAULT_RATIO;
        }

        a.recycle();
    }

    public float getRatio()
    {
        return ratio;
    }

    public void setRatio(float ratio)
    {
        this.ratio = ratio;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int targetWidth = getMeasuredWidth();
        int targetHeight = Math.round((float)getMeasuredWidth() / ratio);

        if (targetHeight > getMeasuredHeight() && getMeasuredHeight() != 0)
        {
            targetWidth = Math.round(getMeasuredHeight() * ratio);
            targetHeight = getMeasuredHeight();
        }

        super.onMeasure(MeasureSpec.makeMeasureSpec(targetWidth, MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(targetHeight, MeasureSpec.EXACTLY));
    }

    private void printMeasureSpec(String description, int value)
    {
        int mode = MeasureSpec.getMode(value);
        String modeName = mode == MeasureSpec.AT_MOST ? "AT_MOST"
                : mode == MeasureSpec.EXACTLY ? "EXACTLY" : "UNSPECIFIED";
        DLog.d(String.format("Measure spec for %s, mode = %s, size = %d", description, modeName, MeasureSpec.getSize(value)));
    }
}

<resources>
    <declare-styleable name="RatioFrameLayout">
        <attr name="ratio" format="string|reference" />
    </declare-styleable>
</resources>