Android自定义View——可以设置最大宽高的FrameLayout

import android.util.DisplayMetrics;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.WindowManager;

/**
* Created by wangxingsheng on 2018/6/8.
*
* 可以设置最大宽高的FrameLayout
* 默认优先比例设置
* 不支持参数小于零
*
*/
public class MaxLayout extends FrameLayout {
private float mMaxHeightRatio = -1f;// 优先级高
private float mMaxHeight = -1f;// 优先级低
private float mMaxWidthRatio = -1f;// 优先级高
private float mMaxWidth = -1f;// 优先级低
private int parentWidth;
private int parentHeight;
private boolean firstHeightRatio = true;//高默认优先比例设置
private boolean firstWidthRatio = true;//宽默认优先比例设置

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

public MaxLayout(Context context, AttributeSet attrs) {
super(context, attrs);
initAttrs(context, attrs);
}

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

private void initAttrs(Context context, AttributeSet attrs) {
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.MaxLayout);
if(a!=null){
firstHeightRatio = a.getBoolean(R.styleable.MaxLayout_first_ratio_height,true);
firstWidthRatio = a.getBoolean(R.styleable.MaxLayout_first_ratio_width,true);
mMaxHeightRatio = a.getFloat(R.styleable.MaxLayout_max_height_ratio, -1f);
mMaxHeight = a.getDimension(R.styleable.MaxLayout_max_height, -1f);
mMaxWidthRatio = a.getFloat(R.styleable.MaxLayout_max_width_ratio, -1f);
mMaxWidth = a.getDimension(R.styleable.MaxLayout_max_width, -1f);
a.recycle();
}
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
initParentWH();
initWH();

int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);

int maxHeightMeasureSpec = MeasureSpec.makeMeasureSpec(heightSize <= mMaxHeight ? heightSize : (int) mMaxHeight, heightMode);

int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int maxWidthMeasureSpec = MeasureSpec.makeMeasureSpec(widthSize <= mMaxWidth ? widthSize : (int) mMaxWidth, widthMode);

super.onMeasure(maxWidthMeasureSpec, maxHeightMeasureSpec);
}

/**
* 计算需要设置的宽高
*/
private void initWH() {
if((firstHeightRatio && mMaxHeightRatio > 0)
|| (!firstHeightRatio && mMaxHeight < 0)){
mMaxHeight = mMaxHeightRatio * parentHeight;
}
if((firstWidthRatio && mMaxWidthRatio > 0)
|| (!firstWidthRatio && mMaxWidth < 0)){
mMaxWidth = mMaxWidthRatio * parentWidth;
}
}

/**
* 获取父控件的宽高
*/
private void initParentWH() {
ViewGroup parent = (ViewGroup) getParent();
if(null != parent){
parentWidth = parent.getWidth();
parentHeight = parent.getHeight();
}else {
WindowManager wm = (WindowManager) getContext()
.getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics dm = new DisplayMetrics();
if (wm != null) {
wm.getDefaultDisplay().getMetrics(dm);
parentWidth = dm.widthPixels;
parentHeight = dm.heightPixels;
}
}
}
}

<declare-styleable name="MaxLayout">
<attr name="max_height_ratio" format="float"/>
<attr name="max_height" format="dimension"/>
<attr name="max_width_ratio" format="float"/>
<attr name="max_width" format="dimension"/>
<attr name="first_ratio_height" format="boolean"/>
<attr name="first_ratio_width" format="boolean"/>
</declare-styleable>