RecyclerView 动态调整高度， 调整item高度

1. RecyclerView 高度动态调整 

solution ( RecyclerView的高度控制都在 LayoutManager 中)

LinearLayoutManager exceptionLayoutManager = new LinearLayoutManager(this){

            @Override
            public void onMeasure( recycler,  state, int widthSpec, int heightSpec) {

                    View view = (0);
                    if (view != null) {
                        measureChild(view, widthSpec, heightSpec);
                        //int measuredWidth = (widthSpec);
                        int measuredHeight = ();
                        int showHeight = measuredHeight * ();
                        if(() >= 5){
                            showHeight = measuredHeight * 5;
                        }
                        setMeasuredDimension(widthSpec, showHeight);
                    }
            }
};

(false);
(false);
(exceptionLayoutManager);
(new DefaultItemAnimator());

/buobao/blog/651279

1.1
(false)
(false)

@Override
public void onMeasure( recycler,  state, int widthSpec,int heightSpec) {
    View view = (0);
    measureChild(view, widthSpec, heightSpec);
    int measuredWidth = (widthSpec);
    int measuredHeight = ();
    setMeasuredDimension(measuredWidth, measuredHeight);
}

1.2这里获取了view的高度，也就是item布局的高度，所以item的布局需要设定固定的高度，否则获取为0。其次，
这两个设置不能少，否则报错，这里和中的调用顺序有关，源码：

protected void onMeasure(int widthSpec, int heightSpec) {
    if (mLayout == null) {
        defaultOnMeasure(widthSpec, heightSpec);
        return;
    }
    if () {     //这里为true会进入该分支
        final int widthMode = (widthSpec);
        final int heightMode = (heightSpec);
        final boolean skipMeasure = widthMode == 
                && heightMode == ;
        (mRecycler, mState, widthSpec, heightSpec);   //在调用mLayout的onMeasure方法时（被自定义复写的方法），为0，造成越界异常
        if (skipMeasure || mAdapter == null) {
            return;
        }
        if ( == State.STEP_START) {
            dispatchLayoutStep1();
        }
        // set dimensions in 2nd step. Pre-layout should happen with old dimensions for
        // consistency
        (widthSpec, heightSpec);
         = true;
        dispatchLayoutStep2();

        // now we can get the width and height from the children.
        (widthSpec, heightSpec);

        // if RecyclerView has non-exact width and height and if there is at least one child
        // which also has non-exact width & height, we have to re-measure.
        if (()) {
            (
                    (getMeasuredWidth(), ),
                    (getMeasuredHeight(), ));
             = true;
            dispatchLayoutStep2();
            // now we can get the width and height from the children.
            (widthSpec, heightSpec);
        }
    } else {
        if (mHasFixedSize) {   //这里不设置为false会造成与上面相同的问题
            (mRecycler, mState, widthSpec, heightSpec);
            return;
        }
        // custom onMeasure
        if (mAdapterUpdateDuringMeasure) {
            eatRequestLayout();
            processAdapterUpdatesAndSetAnimationFlags();

            if () {
                 = true;
            } else {
                // consume remaining updates to provide a consistent state with the layout pass.
                ();
                 = false;
            }
            mAdapterUpdateDuringMeasure = false;
            resumeRequestLayout(false);
        }

        if (mAdapter != null) {
             = ();
        } else {
             = 0;
        }
        eatRequestLayout();
        (mRecycler, mState, widthSpec, heightSpec);   //在这里调用时才会有值，这与mLayout中获取当前item布局的方式有关：View view = (0);
        resumeRequestLayout(false);
         = false; // clear
    }
}

2. 关于RecyclerView的宽高调整 /crazyman2010/article/details/54315109

设置ItemView的间隔高宽

重写ItemDecoration的getItemOffsets函数即可：

(new () {
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent,  state) {
        (outRect, view, parent, state);
        (4, 4, 4, 4);//设置itemView中内容相对边框左，上，右，下距离
    }
});

3. ItemView适应RecyclerView

RecyclerView大小固定的情况下，根据RecyclerView的宽高设置ItemView的宽高，以达到recyclerview刚好显示N行/列数据的目的： 
在原理是先计算出RecyclerView的宽高，然后在Adapter的onCreateViewHolder中设置view的高度： 
比如一个垂直列表，希望recyclerview刚好显示三行，这样写：

@Override
public  onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = (()).inflate(布局文件, parent, false);
    ().height = mRecyclerViewHeight/3;
    return new ServiceItemViewHolder(view);
}