FullyGridLayoutManager.java

package moe.feng.bilinyan.util;

import android.content.Context;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.view.ViewGroup;

public class FullyGridLayoutManager extends GridLayoutManager {

	public FullyGridLayoutManager(Context context, int spanCount) {
		super(context, spanCount);
	}

	public FullyGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {
		super(context, spanCount, orientation, reverseLayout);
	}

	private int[] mMeasuredDimension = new int[2];

	@Override
	public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {
		final int widthMode = View.MeasureSpec.getMode(widthSpec);
		final int heightMode = View.MeasureSpec.getMode(heightSpec);
		final int widthSize = View.MeasureSpec.getSize(widthSpec);
		final int heightSize = View.MeasureSpec.getSize(heightSpec);

		int width = 0;
		int height = 0;
		int count = getItemCount();
		int span = getSpanCount();
		for (int i = 0; i < count; i++) {
			measureScrapChild(recycler, i,
					View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
					View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
					mMeasuredDimension);

			if (getOrientation() == HORIZONTAL) {
				if (i % span == 0) {
					width = width + mMeasuredDimension[0];
				}
				if (i == 0) {
					height = mMeasuredDimension[1];
				}
			} else {
				if (i % span == 0) {
					height = height + mMeasuredDimension[1];
				}
				if (i == 0) {
					width = mMeasuredDimension[0];
				}
			}
		}

		switch (widthMode) {
			case View.MeasureSpec.EXACTLY:
				width = widthSize;
			case View.MeasureSpec.AT_MOST:
			case View.MeasureSpec.UNSPECIFIED:
		}

		switch (heightMode) {
			case View.MeasureSpec.EXACTLY:
				height = heightSize;
			case View.MeasureSpec.AT_MOST:
			case View.MeasureSpec.UNSPECIFIED:
		}

		setMeasuredDimension(width, height);
	}

	private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
	                               int heightSpec, int[] measuredDimension) {
		if (position < getItemCount()) {
			try {
				View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException
				if (view != null) {
					RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
					int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
							getPaddingLeft() + getPaddingRight(), p.width);
					int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
							getPaddingTop() + getPaddingBottom(), p.height);
					view.measure(childWidthSpec, childHeightSpec);
					measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
					measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
					recycler.recycleView(view);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}

}