我有这个容器类，用于制作其中一个尺寸，宽度或高度，另一个尺寸的比例。例如，我想要一个16：9的布局容器，其宽度为“match_parent”。但是，当使用高度作为“match_parent”时，Android似乎没有正确地重新布局。当我将高度设置为宽度的比例时，一切都很好！反之亦然，它不起作用。这是怎么回事？
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());
}
}
要查看它的实际效果，请使用以下布局：
<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>
这将是我的活动：
记录输出：
I/Ratio (9445): /onMeasure
I/Ratio (9445): mw: 1087, mh: 670
I/Ratio (9445): /onMeasure
I/Ratio (9445): mw: 655, mh: 404
I/Ratio (9445): /onLayout
I/Ratio (9445): l: 0, t: 133, r:1087, b:537
I/Ratio (9445): mw: 655, mh:404
I/Ratio (9445): w: 1087, mw:404 <--- NO reason this should not be 655
为什么Android不尊重我最新的measuredWidth而是使用旧版本但最新高度？
编辑：已更新。使RatioLayout NOT 的父级成为RelativeLayout，但LinearLayout或FrameLayout为我提供了正确的行为。出于某种原因，RelativeLayout正在“缓存”measuredWidth并且不使用最新的。
编辑2： RelativeLayout.onLayout中的这条评论似乎证实了我的“它的缓存”，我认为这是一个错误
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// The layout has actually already been performed and the positions
// cached. Apply the cached values to the children.
int count = getChildCount();
// TODO: we need to find another way to implement RelativeLayout
// This implementation cannot handle every case
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
最终编辑好的。我放弃。这是RelativeLayout中的一个合法错误。这段代码修复了它，但它会产生toRightOf属性的问题。我找到的工作是将此RatioLayout嵌套到另一个ViewGroup，如LinerLayout。那些好奇的代码
@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);
}
答案 0 :(得分：1)
我实际上已经尝试过你正在尝试做的事情，也就是说，让View尽可能大，同时保留一些宽高比（即正方形或4：3或类似的东西）这一点）。
我的问题是当我的视图处于ScrollView时，大小计算错误。我无法解决这个问题，但我会在下面发布我的代码以防它有所帮助。它与您的代码非常相似，但我继承自FrameLayout，最后我会调用super.onMeasure()。
我仔细检查了我正在使用它的项目，我确实将它作为RelativeLayout的直接子项。
爪哇：
/**
* 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)));
}
}
attrs.xml：
<resources>
<declare-styleable name="RatioFrameLayout">
<attr name="ratio" format="string|reference" />
</declare-styleable>
</resources>