Android时间轴控件-WheelView

在做时间轴或者某些类型的选择时，有时候设计师会给我们出类似下面的效果：

因此，我们就需要重新自定义scrollview,，也就是移动端常用的时间轴控件：WheelView

实现方式直接上代码：

public class WheelView extends ScrollView {
    public static final String TAG = WheelView.class.getSimpleName();

    public static class OnWheelViewListener {
        public void onSelected(int selectedIndex, String item) {
        }
    }


    private Context context;
//    private ScrollView scrollView;

    private LinearLayout views;

    public WheelView(Context context) {
        super(context);
        init(context);
    }

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

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

    //    String[] items;
    List items;

    private List getItems() {
        return items;
    }

    public void setItems(List list) {
        if (null == items) {
            items = new ArrayList();
        }
        items.clear();
        items.addAll(list);

        // 前面和后面补全
        for (int i = 0; i < offset; i++) {
            items.add(0, "");
            items.add("");
        }
        initData();
    }


    // 每页显示的数量
    public static final int OFF_SET_DEFAULT = 1;
    int offset = OFF_SET_DEFAULT; // 偏移量（需要在最前面和最后面补全）

    int displayItemCount;
    int selectedIndex = 1; //
    int itemHeight = 0;//每个条目的高度
    int textSize = 20;//每个条目的字体大小

    public int getOffset() {
        return offset;
    }

    public void setOffset(int offset) {
        this.offset = offset;
    }

    public void setTextSize(int textSize) {
        this.textSize = textSize;
    }

    private void init(Context context) {
        this.context = context;

//        scrollView = ((ScrollView)this.getParent());
//        Log.d(TAG, "scrollview: " + scrollView);
        Log.d(TAG, "parent: " + this.getParent());
//        this.setOrientation(VERTICAL);
        this.setVerticalScrollBarEnabled(false);

        views = new LinearLayout(context);
        views.setOrientation(LinearLayout.VERTICAL);
        this.addView(views);

        scrollerTask = new Runnable() {

            public void run() {

                int newY = getScrollY();
                if (initialY - newY == 0) { // stopped
                    final int remainder = initialY % itemHeight;
                    final int divided = initialY / itemHeight;
//                    Log.d(TAG, "initialY: " + initialY);
//                    Log.d(TAG, "remainder: " + remainder + ", divided: " + divided);
                    if (remainder == 0) {
                        selectedIndex = divided + offset;

                        onSeletedCallBack();
                    } else {
                        if (remainder > itemHeight / 2) {
                            WheelView.this.post(new Runnable() {
                                @Override
                                public void run() {
                                    WheelView.this.smoothScrollTo(0, initialY - remainder + itemHeight);
                                    selectedIndex = divided + offset + 1;
                                    onSeletedCallBack();
                                }
                            });
                        } else {
                            WheelView.this.post(new Runnable() {
                                @Override
                                public void run() {
                                    WheelView.this.smoothScrollTo(0, initialY - remainder);
                                    selectedIndex = divided + offset;
                                    onSeletedCallBack();
                                }
                            });
                        }


                    }


                } else {
                    initialY = getScrollY();
                    WheelView.this.postDelayed(scrollerTask, newCheck);
                }
            }
        };


    }

    int initialY;

    Runnable scrollerTask;
    int newCheck = 50;

    public void startScrollerTask() {

        initialY = getScrollY();
        this.postDelayed(scrollerTask, newCheck);
    }

    private void initData() {
        displayItemCount = offset * 2 + 1;

        for (String item : items) {
            views.addView(createView(item));
        }

        refreshItemView(0);
    }

    private TextView createView(String item) {
        TextView tv = new TextView(context);
        tv.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        tv.setSingleLine(true);
        tv.setTextSize(TypedValue.COMPLEX_UNIT_SP, textSize);
        tv.setText(item);
        tv.setGravity(Gravity.CENTER);
        int padding = dip2px(15);
        tv.setPadding(padding, padding, padding, padding);
        if (0 == itemHeight) {
            itemHeight = getViewMeasuredHeight(tv);
            Log.d(TAG, "itemHeight: " + itemHeight);
            views.setLayoutParams(new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, itemHeight * displayItemCount));
            LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) this.getLayoutParams();
            this.setLayoutParams(new LinearLayout.LayoutParams(lp.width, itemHeight * displayItemCount));
        }
        return tv;
    }


    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);

//        Log.d(TAG, "l: " + l + ", t: " + t + ", oldl: " + oldl + ", oldt: " + oldt);

//        try {
//            Field field = ScrollView.class.getDeclaredField("mScroller");
//            field.setAccessible(true);
//            OverScroller mScroller = (OverScroller) field.get(this);
//
//
//            if(mScroller.isFinished()){
//                Log.d(TAG, "isFinished...");
//            }
//
//        } catch (Exception e) {
//            e.printStackTrace();
//        }


        refreshItemView(t);

        if (t > oldt) {
//            Log.d(TAG, "向下滚动");
            scrollDirection = SCROLL_DIRECTION_DOWN;
        } else {
//            Log.d(TAG, "向上滚动");
            scrollDirection = SCROLL_DIRECTION_UP;

        }
    }

    private void refreshItemView(int y) {
        int position = y / itemHeight + offset;
        int remainder = y % itemHeight;
        int divided = y / itemHeight;

        if (remainder == 0) {
            position = divided + offset;
        } else {
            if (remainder > itemHeight / 2) {
                position = divided + offset + 1;
            }

//            if(remainder > itemHeight / 2){
//                if(scrollDirection == SCROLL_DIRECTION_DOWN){
//                    position = divided + offset;
//                    Log.d(TAG, ">down...position: " + position);
//                }else if(scrollDirection == SCROLL_DIRECTION_UP){
//                    position = divided + offset + 1;
//                    Log.d(TAG, ">up...position: " + position);
//                }
//            }else{
////                position = y / itemHeight + offset;
//                if(scrollDirection == SCROLL_DIRECTION_DOWN){
//                    position = divided + offset;
//                    Log.d(TAG, "> 2, View.MeasureSpec.AT_MOST);
        view.measure(width, expandSpec);
        return view.getMeasuredHeight();
    }

}

外面设置属性和传数据的使用方式如下：

val layout_wheelview = findViewById(R.id.layout_wheelview).apply {
           //设置选中的字体颜色
            setCheckTextColor(Color.BLACK)
            //设置条目字体大小
            setTextSize(18)
            //设置列表数据
            setItems(listContent)
            //添加滑动监听
            onWheelViewListener = object : WheelView.OnWheelViewListener() {
                override fun onSelected(selectedIndex: Int, item: String) {
                }
            }
        }

外面获取当前选中的条目：

layout_wheelview.seletedIndex