引入依赖库

compile 'com.android.support:percent:24.x.x'

主要类

• PercentRelativeLayout(继承自RelativeLayout)
• PercentFrameLayout(继承自FrameLayout )

属性

• layout_widthPercent 设置控件宽度为父容器的宽的百分比
• layout_heightPercent 设置控件高度为父容器的高的百分比
• layout_marginPercent 设置控件外边距为父容器的宽度的百分比
• layout_marginLeftPercent 设置控件与左边控件的距离为父容器的宽度的百分比
• layout_marginTopPercent 设置控件与上方控件的距离为父容器的高度的百分比
• layout_marginRightPercent 设置控件与右边控件的距离为父容器的宽度的百分比
• layout_marginBottomPercent 设置控件与下方控件的距离为父容器的高度的百分比
• layout_marginStartPercent
• layout_marginEndPercent

原来用某些具体单位（如dp）的设置现在都可以用百分比的方式进行设置了，例如设置控件的宽度layout_width原来我们是这样玩的android:layout_width="match_parent"现在用了百分比的属性之后呢，可以这样玩了app:layout_widthPercent="50%"，这里的百分比是相对于父容器而言的。

具体使用

xml文件加入命名空间

xmlns:app="http://schemas.android.com/apk/res-auto"

<android.support.percent.PercentRelativeLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:app="http://schemas.android.com/apk/res-auto"
         android:layout_width="match_parent"
         android:layout_height="match_parent"/>
 
     <ImageView
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_widthPercent="50%"
        app:layout_heightPercent="50%"
        app:layout_marginTopPercent="25%"
        app:layout_marginLeftPercent="25%"/>
 
 </android.support.percent.PercentRelativeLayout/>

自定义PecentLinearLayout

库中并没有提供PecentLinearLayout，想玩PecentLinearLayout就需要自定义了

public class PercentLinearLayout extends LinearLayout
{

    private PercentLayoutHelper mPercentLayoutHelper;

    public PercentLinearLayout(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        mPercentLayoutHelper = new PercentLayoutHelper(this);
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        mPercentLayoutHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mPercentLayoutHelper.handleMeasuredStateTooSmall())
        {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        super.onLayout(changed, l, t, r, b);
        mPercentLayoutHelper.restoreOriginalParams();
    }

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

    public static class LayoutParams extends LinearLayout.LayoutParams
            implements PercentLayoutHelper.PercentLayoutParams
    {
        private PercentLayoutHelper.PercentLayoutInfo mPercentLayoutInfo;

        public LayoutParams(Context c, AttributeSet attrs)
        {
            super(c, attrs);
            mPercentLayoutInfo = PercentLayoutHelper.getPercentLayoutInfo(c, attrs);
        }

        @Override
        public PercentLayoutHelper.PercentLayoutInfo getPercentLayoutInfo()
        {
            return mPercentLayoutInfo;
        }

        @Override
        protected void setBaseAttributes(TypedArray a, int widthAttr, int heightAttr)
        {
            PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
        }

        public LayoutParams(int width, int height) {
            super(width, height);
        }

        public LayoutParams(ViewGroup.LayoutParams source) {
            super(source);
        }

        public LayoutParams(MarginLayoutParams source) {
            super(source);
        }
    }
}

这样我们就有了PecentLinearLayout，原来的LinearLayout的现在都可以用百分比的方式进行设置了。