给RecycleView定制个分割线吧。

本文介绍了如何在Android的RecycleView中自定义分割线,从使用margin做分割线过渡到自定义绘制。在实践中遇到宽度增大时分割线消失的问题,通过逐步调试,发现是空间预留不足导致。寻求解决此类问题的方法。

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RecycleView使用了这么久,一直都是用margin做分割,一方面是自己比较懒,一方面是为了高效开发,一直没有自定义过。最近比较有空,就尝试写写。纸上得来终觉浅,还真的遇到不少问题。
首先来一次正确的打开方式:

public class DividerItemDecoration extends RecyclerView.ItemDecoration
{

    /**
        * RecyclerView的布局方向,默认先赋值
        * 为纵向布局
        * RecyclerView 布局可横向,也可纵向
        * 横向和纵向对应的分割想画法不一样
        * */
    private int mOrientation = LinearLayoutManager.VERTICAL ;

    private static final int[] ATTRS = new int[] { android.R.attr.listDivider };
    /**
     * item之间分割线的drawable
     */
    private Drawable mDivider;
    /**
     * 构造方法传入布局方向,不可不传
     * @param context
     * @param orientation
     */
    public DividerItemDecoration(Context context,int orientation) {
        this.mOrientation = orientation;
        if(orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL){
            throw new IllegalArgumentException("请传入正确的参数") ;
        }
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if(mOrientation == LinearLayoutManager.VERTICAL){
            drawVertical(c,parent) ;
        }else {
            drawHorizontal(c,parent) ;
        }
    }

    /**
     * 绘制纵向 item 分割线
     * @param canvas
     * @param parent
     */
    private void drawVertical(Canvas canvas,RecyclerView parent){
        final int left = parent.getPaddingLeft() ;
        final int right = parent.getMeasuredWidth() - parent.getPaddingRight() ;
        final int childSize = parent.getChildCount() ;
        for(int i = 0 ; i < childSize ; i ++){
            final View child = parent.getChildAt( i ) ;
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int top = child.getBottom() + layoutParams.bottomMargin ;
            final int bottom = top +  mDivider.getIntrinsicHeight() ;
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
    }

    /**
     * 绘制横向 item 分割线
     * @param canvas
     * @param parent
     */
    private void drawHorizontal(Canvas canvas,RecyclerView parent){
        final int top = parent.getPaddingTop() ;
        final int bottom = parent.getMeasuredHeight() - parent.getPaddingBottom() ;
        final int childSize = parent.getChildCount() ;
        for(int i = 0 ; i < childSize ; i ++){
            final View child = parent.getChildAt( i ) ;
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + layoutParams.rightMargin ;
            final int right = left + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
    }

    /**
     * 设置item便宜的size
     * @param outRect
     * @param view
     * @param parent
     * @param state
     */
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if(mOrientation == LinearLayoutManager.VERTICAL){
            outRect.set(0,0,0, mDivider.getIntrinsicHeight());
        }else {
            outRect.set(0,0, mDivider.getIntrinsicHeight(),0);
        }
    }
}

代码基本copy自网上;

  • 那么问题来了,如果我想简单设置个高度,不用系统的listDivider,自己画一个巨型分割线该怎么实现呢?我的做法如下:
public class DividerItemDecoration extends RecyclerView.ItemDecoration
{

    /*
    * RecyclerView的布局方向,默认先赋值
    * 为纵向布局
    * RecyclerView 布局可横向,也可纵向
    * 横向和纵向对应的分割想画法不一样
    * */
    private int mOrientation = LinearLayoutManager.VERTICAL ;

    /**
     * item之间分割线的size,默认为1
     */
    private int mItemSize = 1 ;

    /**
     * 绘制item分割线的画笔,和设置其属性
     * 来绘制个性分割线
     */
    private Paint mPaint ;

    /**
     * 构造方法传入布局方向,不可不传
     * @param context
     * @param orientation
     */
    public DividerItemDecoration(Context context,int orientation) {
        this.mOrientation = orientation;
        if(orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL){
            throw new IllegalArgumentException("请传入正确的参数") ;
        }
        mItemSize = (int) TypedValue.applyDimension(mItemSize, TypedValue.COMPLEX_UNIT_DIP, context.getResources().getDisplayMetrics());
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG) ;
        mPaint.setColor(Color.BLUE);
         /*设置填充*/
        mPaint.setStyle(Paint.Style.FILL);
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if(mOrientation == LinearLayoutManager.VERTICAL){
            drawVertical(c,parent) ;
        }else {
            drawHorizontal(c,parent) ;
        }
    }

    /**
     * 绘制纵向 item 分割线
     * @param canvas
     * @param parent
     */
    private void drawVertical(Canvas canvas,RecyclerView parent){
        final int left = parent.getPaddingLeft() ;
        final int right = parent.getWidth() - parent.getPaddingRight() ;
        final int childSize = parent.getChildCount() ;
        for(int i = 0 ; i < childSize ; i ++){
            final View child = parent.getChildAt( i ) ;
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int top = child.getBottom() + layoutParams.bottomMargin ;
            final int bottom = top + mItemSize ;
            canvas.drawRect(left,top,right,bottom,mPaint);
        }
    }

    /**
     * 绘制横向 item 分割线
     * @param canvas
     * @param parent
     */
    private void drawHorizontal(Canvas canvas,RecyclerView parent){
        final int top = parent.getPaddingTop() ;
        final int bottom = parent.getHeight() - parent.getPaddingBottom() ;
        final int childSize = parent.getChildCount() ;
        for(int i = 0 ; i < childSize ; i ++){
            final View child = parent.getChildAt( i ) ;
            RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + layoutParams.rightMargin ;
            final int right = left + mItemSize ;
            canvas.drawRect(left,top,right,bottom,mPaint);
        }
    }

    /**
     * 设置item分割线的size
     * @param outRect
     * @param view
     * @param parent
     * @param state
     */
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if(mOrientation == LinearLayoutManager.VERTICAL){
            outRect.set(0,0,0,mItemSize);
        }else {
            outRect.set(0,0,mItemSize,0);
        }
    }
}

ok,运行:
mItemSize=1
mItemSize=1的时候,
貌似正常
增大宽度

    private int mItemSize = 5 ;

ok,运行:
这里写图片描述
貌似还是正常
继续增大宽度

    private int mItemSize = 6 ;

ok,运行:
这里写图片描述

我们的分割线被谁吃了!

为了看是没画出来还是没留出偏移空间,继续增大宽度

    private int mItemSize = 100 ;

ok,运行:
这里写图片描述
还是这样,item之间的空隙并没有增加。
why?
- 我这个小菜鸟期待大神给我指点迷津。。。help me~

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