二阶贝塞尔曲线之波浪图(二)

谁践踏了优雅 2022-06-14 07:30 130阅读 0赞

昨天我写了[二阶贝塞尔曲线之波浪图][Link 1]之后，结果装逼失败。理由是大佬说这个波浪图的效果很生硬，一般情况下波浪图是配合手势使用的。因此决定改写该控件，实现利用手势实现波浪图。先来一张效果图：

![这里写图片描述][SouthEast]

实现思路如下：

1.  在RecyclerView的onTouch事件中，获取当前页面加载的最后一个可见item的下标Position，确认RecyclerView是否加载到底部？
2.  上述确认加载到到底部后，处理onTouch事件（判断是长按事件还是点击事件）
3.  在长按事件中将滑动过程中的X值传给自定义控件，然后自定义控件根据x值绘制贝塞尔曲线并显示控件；
4.  在手势抬起后调用自定义控件方法，重置参数并隐藏控件

一、我本来打算在RecyclerView的item布局文件中自定义控件，但是发现获取不到控件，后来想了一下，这样会把最后一项Item布局撑大，于是还是加在了根布局上。  
RecyclerView获取最后一个可见Item有两个方法，但是都需要实现同一个抽象类RecyclerView.OnScrollListener，然后我们可以使用一个boolean的标志位来记录RecyclerView是否加载到底部？代码如下：

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                    @Override
                    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                        super.onScrollStateChanged(recyclerView, newState);
                        //当滚动结束
                        if(newState == RecyclerView.SCROLL_STATE_IDLE){
                             //当前分页加载的demo数据最多只有41条，所以下标值是40
                            check =((LinearLayoutManager)mRecyclerView.getLayoutManager()).findLastVisibleItemPosition() == 40;
                        }
                    }
    
                    @Override
                    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                        super.onScrolled(recyclerView, dx, dy);
                        //得到当前显示的最后一个item的view
                        View lastChildView = recyclerView.getLayoutManager().getChildAt(recyclerView.getLayoutManager().getChildCount()-1);
                        //当前分页加载的demo数据最多只有41条，所以下标值是40
                        check  = recyclerView.getLayoutManager().getPosition(lastChildView) == 40;
                    }
                });

二、在onTouch事件判断当前事件为触摸还是还是点击、长按等其它事件，其实这个方法一般就两种：

1.  通过触摸的时间来判断
2.  通过滑动的距离来判断

由于为了不影响长按事件，这里选择通过滑动距离来判断，代码如下：

@Override
        public boolean onTouch(View v, MotionEvent event) {
    
            if(check){
                switch (event.getAction()){
                    case MotionEvent.ACTION_DOWN:
                        downX = event.getX();
                        downY = event.getY();
                        break;
                    case MotionEvent.ACTION_MOVE:
                        float moveX = event.getX();
                        float moveY = event.getY();
                        if (Math.abs(moveX - downX) > dp5 && Math.abs(moveY - downY) > dp5) {
                            waveView.setPoint(moveX);
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                    case MotionEvent.ACTION_CANCEL:
                        float upX = event.getX();
                        float upY = event.getY();
                        //加载到顶部后的点击或者长按事件
                        if (Math.abs(upX - downX) < dp5 && Math.abs(upY - downY) < dp5) {
                           return false;
                        }
    
                        break;
                }
                return true;
            }
            return false;
        }

三、在长按事件中将滑动过程中的X值传给自定义控件，然后自定义控件根据x值绘制贝塞尔曲线并显示控件。整个过程就是自定义控件有一个公共方法接收参数，并刷新视图。虽然自定义控件的核心还是绘制贝塞尔曲线，但是一些参数有了变化，这里做一个说明。

![这里写图片描述][SouthEast 1]  
![这里写图片描述][SouthEast 2]  
制图技术实在不行，因此将就看吧，看不懂就看源码：

/** * Created by 魏兴 on 2017/6/12. */
    
    public class WaveView extends View { 
    
        private static final String TAG = "WaveView";
        //波浪画笔
        private Paint mPaint;
    
    
        //波浪Path类
        private Path mPath;
    
        private float controlpoint;
    
    
        //波纹的中间轴
        private int mCenterY;
    
        //屏幕高度
        private int mScreenHeight;
        //屏幕宽度
        private int mScreenWidth;
    
        public WaveView(Context context) {
            super(context);
            init();
        }
    
        public WaveView(Context context, AttributeSet attrs, int defStyleAttr) {
            super(context, attrs, defStyleAttr);
            init();
        }
    
        public WaveView(Context context, AttributeSet attrs) {
            super(context, attrs);
            init();
        }
    
        private void init() {
            mPath = new Path();
            mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
            mPaint.setColor(Color.LTGRAY);
            mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    
    
    
        }
    
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            mScreenHeight = h;
            mScreenWidth = w;
    
            mCenterY = mScreenHeight * 3/ 5;
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
    
            mPath.reset();
    
            int start;
            int end;
            boolean isLeft = true;
            if(controlpoint>=mScreenWidth/2){
    
                isLeft = false;
            }
            start = isLeft ? mCenterY/3:mCenterY;
            end =  isLeft ? mCenterY:mCenterY/3;
    
            mPath.moveTo(0, start);
            mPath.quadTo(controlpoint,mCenterY/3, mScreenWidth,end);
    
            //填充矩形
            mPath.lineTo(mScreenWidth, mScreenHeight);
            mPath.lineTo(0, mScreenHeight);
            mPath.close();
            canvas.drawPath(mPath, mPaint);
        }
    
        public void setPoint(float x ){
    
            this.controlpoint = x;
            setVisibility(VISIBLE);
            invalidate();
        }
    
        public void rest(){
            this.controlpoint = 0;
            setVisibility(GONE);
        }
    
    }

感觉手势抬起以后贝塞尔曲线的图形直接隐藏还是很生硬，加一个动画：

@Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
    
            mPath.reset();
    
            int startY;
            int endY;
            boolean isLeft = true;
            if(controlpoint>=mScreenWidth/2){
    
                isLeft = false;
            }
    
            startY = isLeft ? mCenterY/3:mCenterY;
            endY =  isLeft ? mCenterY:mCenterY/3;
    
            mPath.moveTo(0, startY+offset);
            mPath.quadTo(controlpoint,0+offset, mScreenWidth,endY+offset);
            Log.e(TAG, "onDraw: "+(startY)+" " +0+" "+endY);
            //填充矩形
            mPath.lineTo(mScreenWidth, mScreenHeight);
            mPath.lineTo(0, mScreenHeight);
            mPath.close();
            canvas.drawPath(mPath, mPaint);
        }
    
        public void setPoint(float x ){
            if(!isRestting){
                this.controlpoint = x;
                setVisibility(VISIBLE);
                invalidate();
            }
    
        }
        private boolean isRestting = false;
        public void rest(){
    // setVisibility(GONE);
    // controlpoint = 0;
            isRestting = true;
            ValueAnimator animator = ValueAnimator.ofInt(0, mScreenHeight);
            animator.setDuration(400);
            animator.setInterpolator(new LinearInterpolator());
            animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                @Override
                public void onAnimationUpdate(ValueAnimator animation) {
                    offset = (int) animation.getAnimatedValue();
                    postInvalidate();
                }
            });
    
            animator.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) {
    
                }
    
                @Override
                public void onAnimationEnd(Animator animation) {
                    setVisibility(GONE);
                    controlpoint = 0;
                    mScreenHeight = height;
                    mCenterY = mScreenHeight * 3/ 5;
                    offset = 0;
                    isRestting = false;
                }
    
                @Override
                public void onAnimationCancel(Animator animation) {
    
                }
    
                @Override
                public void onAnimationRepeat(Animator animation) {
    
                }
            });
            animator.start();
        }

再看看效果：

![这里写图片描述][SouthEast 3]

### **[源码][Link 2]** ###

## **参考资料：** ##

### **[Recyclerview中最后一个可见Item的位置以及是否滑动到底部][Recyclerview_Item]** ###

[Link 1]: http://blog.csdn.net/vicent_9920/article/details/73129384
[SouthEast]: /images/20220614/7f8dcff7f2f648b3b80a8f1c217e6dbb.png
[SouthEast 1]: /images/20220614/b08a1eb9b00a45e6bb768af25ef39117.png
[SouthEast 2]: /images/20220614/00f8928addf5411ab2ffd88fe01f0c7d.png
[SouthEast 3]: /images/20220614/2d3143c965ed468485673b98b2c899bb.png
[Link 2]: https://github.com/Vicent9920/StudyAndroid/blob/master/app/src/main/java/cn/com/luckytry/demos/paged/PagedActivity.java
[Recyclerview_Item]: http://blog.csdn.net/zhangyalong_android/article/details/54289419