Google 官方提供百分比布局，但是也有一定的局限性，例如不能设置与父容器的间距以及子容器的pading,通过源码可以看出，布局的位置摆放通过layoutParams去设置，可以通过generateLayoutParams去自定义实现layoutparms然后根据。

package com.gui.screenadapter.percentlayout;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;

public class PercentLayout extends RelativeLayout {

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

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

    public PercentLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //获取父容器的尺寸
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            ViewGroup.LayoutParams params = child.getLayoutParams();
            //如果说是百分比布局属性
            if (checkLayoutParams(params)){
                LayoutParams lp = (LayoutParams)params;
                 float widthPercent = lp.widthPercent;
                 float heightPercent = lp.heightPercent;
                 float marginLeftPercent = lp.marginLeftPercent;
                 float marginRightPercent= lp.marginRightPercent;
                 float marginTopPercent= lp.marginTopPercent;
                 float marginBottomPercent = lp.marginBottomPercent;

                 if (widthPercent > 0){
                     params.width = (int) (widthSize * widthPercent);
                 }

                if (heightPercent > 0){
                    params.height = (int) (heightSize * heightPercent);
                }

                if (marginLeftPercent > 0){
                    ((LayoutParams) params).leftMargin = (int) (widthSize * marginLeftPercent);
                }

                if (marginRightPercent > 0){
                    ((LayoutParams) params).rightMargin = (int) (widthSize * marginRightPercent);
                }

                if (marginTopPercent > 0){
                    ((LayoutParams) params).topMargin = (int) (heightSize * marginTopPercent);
                }

                if (marginBottomPercent > 0){
                    ((LayoutParams) params).bottomMargin = (int) (heightSize * marginBottomPercent);
                }

            }
        }

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof LayoutParams;
    }

    public LayoutParams generateLayoutParams(AttributeSet attrs){
        return new LayoutParams(getContext(), attrs);
    }

    public static class LayoutParams extends RelativeLayout.LayoutParams{

        public float widthPercent;
        public float heightPercent;
        private float marginLeftPercent;
        private float marginRightPercent;
        private float marginTopPercent;
        private float marginBottomPercent;

        public LayoutParams(Context c, AttributeSet attrs) {
            super(c, attrs);
            //解析自定义属性
            TypedArray a = c.obtainStyledAttributes(attrs,R.styleable.PercentLayout);
            widthPercent = a.getFloat(R.styleable.PercentLayout_widthPercent, 0);
            heightPercent = a.getFloat(R.styleable.PercentLayout_heightPercent, 0);
            marginLeftPercent = a.getFloat(R.styleable.PercentLayout_marginLeftPercent, 0);
            marginRightPercent = a.getFloat(R.styleable.PercentLayout_marginRightPercent, 0);
            marginTopPercent = a.getFloat(R.styleable.PercentLayout_marginTopPercent, 0);
            marginBottomPercent = a.getFloat(R.styleable.PercentLayout_marginBottomPercent, 0);
            a.recycle();
        }
    }
}

上面的关键是：

1.重写父类 generateLayoutParams 然后结合自定义属性
2.根据checkLayoutParams判断是不是自定义layoutparams
3.重写onMeasure 遍历子view去设置属性