标签：adapter value show == override reg 扩展 bottom 过程
时隔许久，我又要更博了，含蓄的话不多说了，今天我们的主题是这个RecyclerView。至于为什么要加个scrollBar?因为我的业务需求是需要一个实现成这样的,
效果图:（可能看起来比较粗糙，但功能实现了，你可以自定义修改嘛~哈哈哈）
可能我比较老派，我的app 中list的垂直布局还是喜欢用listView ,使用起来简单（可能博主我之前有个通用的adapter不舍得放弃吧，虽然RecyclerView也有通用的adapter，但总感觉显示简单的列表要多写几行代码，有点麻烦，哈哈哈，可能我就想偷懒吧）
但既然今天的是这个RecyclerView那么我们就开始详细的说明下吧~废话不多说切入正题。
先说下我的思路：
一、初始思路（想一个新玩意总得有个过程和弯路嘛），可能跟你想法一样哦
二、现在的实现的思路 （我想了下如果用上面的方案实现的话就，必须写个xml文件，自定义一个ViewGroup，别人使用起来会很麻烦，当然你把他当成类库来用也很简单，而我就不想写xml）
思路也大概说了，那么就来看代码的实现吧。
/** * @author mdm * @Description HobbyRecyclerView * @Version 1.0 */ public class HobbyRecyclerView extends RecyclerView { private RectF mRangeRectf; private Paint mRangPaint; private int showMode = 1; //滚动条宽高 private float scrollBarHeight; private float scrollBarWidth; //柱间隙 private float scrollWidthSpace ; //滚动条宽度的等分比例 private int scrollWidthWeight = 10; //Y轴的偏移值 private float yScrollOffset = 0; //所有的子view的总高度 也就是这个 private float childViewAllHeight; //可视区域的高度 其实这里就是View高度 private float visualHeight; //可视区域的高度/所有的子view的总高度 得出的比例 float range; //recyclerView的每个Item项的宽度 private int childWidth; //判断触摸焦点 private boolean isFocus = false; //手触摸时点的x,y坐标 float x = 0; float y = 0; public HobbyRecyclerView(@NonNull Context context) { super(context); } public HobbyRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) { super(context, attrs); init(context,attrs); } public HobbyRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(context,attrs); } /** * 初始化 * @param context * @param attrs */ private void init(Context context, AttributeSet attrs) { mRangeRectf = new RectF(); // region = new Region(); mRangPaint = new Paint(Paint.ANTI_ALIAS_FLAG); mRangPaint.setStyle(Paint.Style.FILL); TypedArray ta = context.obtainStyledAttributes(attrs,R.styleable.HobbyRecyclerView); showMode = ta.getInteger(R.styleable.HobbyRecyclerView_scrollBarMode,1); ta.recycle(); addOnScrollListener(onScrollListener); } @Override protected void onMeasure(int widthSpec, int heightSpec) { if(showMode != 1){ int width = MeasureSpec.getSize(widthSpec); scrollBarWidth = width / scrollWidthWeight;//取10分之一 scrollWidthSpace = scrollBarWidth / 10; //获取间隙 childWidth = (int) (width - scrollBarWidth); scrollBarWidth = scrollBarWidth - 2 * scrollWidthSpace; for (int i = 0; i < getChildCount(); i++) { measureChild(getChildAt(i),childWidth,heightSpec); getChildAt(i).getLayoutParams().width = childWidth; } setMeasuredDimension(width,heightSpec); }else { super.onMeasure(widthSpec, heightSpec); } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); visualHeight = getMeasuredHeight(); childViewAllHeight = getChildAt(2).getHeight() * getAdapter().getItemCount(); range = 0; if(childViewAllHeight != 0){ range = visualHeight / childViewAllHeight; } scrollBarHeight = range * visualHeight; } @Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); drawRange(canvas); } private void drawRange(Canvas canvas){ if(canvas == null) return; mRangeRectf.set(childWidth + scrollWidthSpace,yScrollOffset,childWidth + scrollBarWidth ,yScrollOffset + scrollBarHeight); if(isFocus) { mRangPaint.setColor(Color.parseColor("#2386BF")); }else{ mRangPaint.setColor(Color.parseColor("#2EB3FF")); } canvas.drawRect(mRangeRectf,mRangPaint); Log.i("tag" , "yScrollOffset ------- " + yScrollOffset); Log.i("tag" , "scrollBarHeight ------- " + scrollBarHeight); Log.i("tag" , "yScrollOffset ------- " + yScrollOffset); } private RecyclerView.OnScrollListener onScrollListener = new OnScrollListener() { @Override public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) { super.onScrollStateChanged(recyclerView, newState); } @Override public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); yScrollOffset += dy * range; } }; @Override public boolean onTouchEvent(MotionEvent event) { switch (event.getAction()){ case MotionEvent.ACTION_DOWN: //获取屏幕上点击的坐标 x = event.getX(); y = event.getY(); if(x >= mRangeRectf.left && x <= mRangeRectf.right && y >= mRangeRectf.top && y <= mRangeRectf.bottom){ isFocus = true; invalidate(); } break; case MotionEvent.ACTION_MOVE: if(x >= mRangeRectf.left && x <= mRangeRectf.right && y >= mRangeRectf.top && y <= mRangeRectf.bottom){ float diffValue = event.getY() - y; scrollBy(0, (int) ((diffValue/visualHeight) * childViewAllHeight)); y = event.getY(); } break; case MotionEvent.ACTION_UP: isFocus = false; invalidate(); break; } if(x >= childWidth && x <= getMeasuredWidth() && y >= 0 && y <= getMeasuredHeight()){ return true; }else return super.onTouchEvent(event); } /** * //当前RcyclerView显示区域的高度。水平列表屏幕从左侧到右侧显示范围 int extent = this.computeHorizontalScrollExtent(); //整体的高度，注意是整体，包括在显示区域之外的。 int range = this.computeHorizontalScrollRange(); //已经向下滚动的距离，为0时表示已处于顶部。 int offset = this.computeHorizontalScrollOffset(); */ }
是不是很简单呢？
ok有什么问题自己看吧。如果你看到最后几行注释了，那么你会疑问，那是因为我看了这个文章
标签：adapter value show == override reg 扩展 bottom 过程
原文地址：https://www.cnblogs.com/woaixingxing/p/10783104.html
