ScrollView与RecyclerView冲突及异常情况处理

昨天再写项目的时候，有一个布局需要ScrollView嵌套RecyclerView，效果展示的时候RecyclerView的滑动会出现卡顿的样子，ScrollView也滑动不流畅。产生的原因是ScrollView与RecyclerView冲突引起的。

解决方法：先自定义LinearLayoutManager，重新测量；再自定义ScrollView，横向不拦截，竖向拦截；

（1）.自定义LinearLayoutManager:

public class FullyLinearLayoutManager extends LinearLayoutManager {        private static final String TAG = FullyLinearLayoutManager.class.getSimpleName();        public FullyLinearLayoutManager(Context context) {          super(context);      }        public FullyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {          super(context, 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);            Log.i(TAG, "onMeasure called. \nwidthMode " + widthMode                  + " \nheightMode " + heightSpec                  + " \nwidthSize " + widthSize                  + " \nheightSize " + heightSize                  + " \ngetItemCount() " + getItemCount());            int width = 0;          int height = 0;          for (int i = 0; i < getItemCount(); i++) {              measureScrapChild(recycler, i,                      View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                      View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                      mMeasuredDimension);                if (getOrientation() == HORIZONTAL) {                  width = width + mMeasuredDimension[0];                  if (i == 0) {                      height = mMeasuredDimension[1];                  }              } else {                  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) {          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();          } finally {          }      }  }  

（2）.自定义ScrollView

public class MyScrollview extends ScrollView{    private int downX;    private int downY;    private int mTouchSlop;    public MyScrollview(Context context) {        this(context,null);    }    public MyScrollview(Context context, AttributeSet attrs) {        this(context, attrs,-1);     }     public MyScrollview(Context context, AttributeSet attrs, int defStyleAttr) {          super(context, attrs, defStyleAttr);          mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();     }    @Override    public boolean onInterceptTouchEvent(MotionEvent e) {        int action = e.getAction();        switch (action) {            case MotionEvent.ACTION_DOWN:                downX = (int) e.getRawX();                downY = (int) e.getRawY();                break;            case MotionEvent.ACTION_MOVE:                int moveY = (int) e.getRawY();                if (Math.abs(moveY - downY) > mTouchSlop) {                    return true;                }        }        return super.onInterceptTouchEvent(e);    }}

（3）.上面弄好，会出现另外一个问题，RecyclerView条目加载不完全。

如何解决呢？

第一种就是固定recyclerView条目的个数；

第二种就是在recyclerView的外层再嵌套一层相对布局或者线性布局。

        <RelativeLayout            android:layout_width="match_parent"            android:layout_weight="1"            android:layout_height="0dp">            <android.support.v7.widget.RecyclerView                android:id="@+id/recycler_front"                android:layout_width="match_parent"                android:layout_height="match_parent"/>        </RelativeLayout>