scrollview嵌套gridview显示不全的问题

在ScrollView里布局GridView时，GridView会出现显示不完全的问题。这是由于GridView和ScrollView里都有滑动属性，ScrollView不清楚GridView需要多大的高度，从源码的角度说，是因为ScrollView的MeasureSpec的mode为UNSPECIFIED，于是GridView的onMeasure方法拿到的heightMeasureSpec的mode也为UNSPECIFIED。我们看一下GridView中onMeasure方法

@Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // Sets up mListPadding
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

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

        if (widthMode == MeasureSpec.UNSPECIFIED) {
            if (mColumnWidth > 0) {
                widthSize = mColumnWidth + mListPadding.left + mListPadding.right;
            } else {
                widthSize = mListPadding.left + mListPadding.right;
            }
            widthSize += getVerticalScrollbarWidth();
        }

        int childWidth = widthSize - mListPadding.left - mListPadding.right;
        boolean didNotInitiallyFit = determineColumns(childWidth);

        int childHeight = 0;
        int childState = 0;

        mItemCount = mAdapter == null ? 0 : mAdapter.getCount();
        final int count = mItemCount;
        if (count > 0) {
            final View child = obtainView(0, mIsScrap);

            AbsListView.LayoutParams p = (AbsListView.LayoutParams) child.getLayoutParams();
            if (p == null) {
                p = (AbsListView.LayoutParams) generateDefaultLayoutParams();
                child.setLayoutParams(p);
            }
            p.viewType = mAdapter.getItemViewType(0);
            p.isEnabled = mAdapter.isEnabled(0);
            p.forceAdd = true;

            int childHeightSpec = getChildMeasureSpec(
                    MeasureSpec.makeSafeMeasureSpec(MeasureSpec.getSize(heightMeasureSpec),
                            MeasureSpec.UNSPECIFIED), 0, p.height);
            int childWidthSpec = getChildMeasureSpec(
                    MeasureSpec.makeMeasureSpec(mColumnWidth, MeasureSpec.EXACTLY), 0, p.width);
            child.measure(childWidthSpec, childHeightSpec);

            childHeight = child.getMeasuredHeight();
            childState = combineMeasuredStates(childState, child.getMeasuredState());

            if (mRecycler.shouldRecycleViewType(p.viewType)) {
                mRecycler.addScrapView(child, -1);
            }
        }

        if (heightMode == MeasureSpec.UNSPECIFIED) {
            heightSize = mListPadding.top + mListPadding.bottom + childHeight +
                    getVerticalFadingEdgeLength() * 2;
        }

        if (heightMode == MeasureSpec.AT_MOST) {
            int ourSize =  mListPadding.top + mListPadding.bottom;

            final int numColumns = mNumColumns;
            for (int i = 0; i < count; i += numColumns) {
                ourSize += childHeight;
                if (i + numColumns < count) {
                    ourSize += mVerticalSpacing;
                }
                if (ourSize >= heightSize) {
                    ourSize = heightSize;
                    break;
                }
            }
            heightSize = ourSize;
        }

        if (widthMode == MeasureSpec.AT_MOST && mRequestedNumColumns != AUTO_FIT) {
            int ourSize = (mRequestedNumColumns*mColumnWidth)
                    + ((mRequestedNumColumns-1)*mHorizontalSpacing)
                    + mListPadding.left + mListPadding.right;
            if (ourSize > widthSize || didNotInitiallyFit) {
                widthSize |= MEASURED_STATE_TOO_SMALL;
            }
        }

        setMeasuredDimension(widthSize, heightSize);
        mWidthMeasureSpec = widthMeasureSpec;
    }

要解决的这个问题需要重新测量GridView的高度，自定义一个GridView，并重写onMeasure方法，如下

public class CustomGridView extends GridView {

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

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

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

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2,
                MeasureSpec.AT_MOST);
        super.onMeasure(widthMeasureSpec, expandSpec);
    }
}

转载于:https://www.jianshu.com/p/b09078830c4d