我有这个容器类,用于制作其他尺寸的一个尺寸,宽度或高度,其他尺寸的比例.例如,我想要一个16：9布局容器,其宽度为“match_parent”.但是,当将高度用作“match_parent”时,Android似乎没有正确的重新发送.当我将高度设置为一个比例的宽度一切都很好！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,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());
}
}
要查看它的行动,使用这样的布局：
<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不符合我最新的measuredWidth,但使用较旧的版本,但最新的高度？
编辑：更新.使RatioLayout的父级不是RelativeLayout,但是LinearLayout或FrameLayout给出了正确的行为.由于某些原因RelativeLayout是“缓存”measuredWidth并且不使用最新的.
编辑2：RelativeLayout.onLayout中的这个评论似乎证实了我的“缓存”,我认为这是一个bug
@Override
protected void onLayout(boolean changed,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) {
最后编辑好的我放弃.这是RelativeLayout中的一个合法的错误.这种代码修复它,但它会导致toRightOf属性的问题.我发现的工作是将此RatioLayout嵌入另一个ViewGroup,如LinerLayout.那些好奇的代码
@Override
protected void onMeasure(int 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",e);
} catch (IllegalAccessException e) {
Log.e("Ration",e);
}
}
int mw = getMeasuredWidth();
int mh = getMeasuredHeight();
lastWidth = mw;
Log.i("Ratio",mh: " + mh);
}
解决方法
我实际上试图做你以前尝试做的,也就是说,使视图尽可能大,同时保留一些宽高比(即平方或4：3或类似的东西).
我的问题是当我的View在一个ScrollView中时,它的大小计算不正确.我无法弄清楚这一点,但是我会发布我的代码,以防万一有帮助.这与你的代码非常相似,但是我从FrameLayout继承,最后调用super.onMeasure().
我仔细检查了我正在使用的项目,实际上它是RelativeLayout的直接孩子.
Java的：
/**
* 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,int defStyle)
{
super(context,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>
