Recycleview侧边添加拖拽控件

本文主要是介绍Recycleview侧边添加拖拽控件，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

一.概述
为了满足recycleview数据过多时,能够快速滑动到指定位置,特意自定义了一个控件,用来实现该功能,先看下效果图:
这里写图片描述

二.创建一个SlideBar类继承View

1.重写onMeasue方法:

  @Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);int width = getMySize(MeasureSpec.getSize(widthMeasureSpec), widthMeasureSpec);int height = getMySize(MeasureSpec.getSize(heightMeasureSpec), heightMeasureSpec);//设置控件的大小setMeasuredDimension(width, height);}private int getMySize(int defaultSize, int measureSpec) {int mySize = defaultSize;int mode = MeasureSpec.getMode(measureSpec);int size = MeasureSpec.getSize(measureSpec);switch (mode) {case MeasureSpec.UNSPECIFIED: {//如果没有指定大小，就设置为默认大小mySize = defaultSize;break;}case MeasureSpec.AT_MOST: {//如果测量模式是最大取值为size//我们将大小取最大值,你也可以取其他值mySize = size;break;}case MeasureSpec.EXACTLY: {//如果是固定的大小，那就不要去改变它mySize = size;break;}}return mySize;}

自定义控件继承view一般都需要重写onMeasuer方法,这个方法目的就是测量控件的大小而已.
2.重写onDraw方法:

  @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);//加载拖拽图片Bitmap bitmap =BitmapFactory.decodeResource(getResources(), R.mipmap.title_scroll_n);//分别得到图片的宽,高int height = bitmap.getHeight();mWidth = bitmap.getWidth();//记录宽,高中的较大值用来滑动的时候判断mSlideBarHeight = height > mWidth ? height : mWidth;//将图片画出来canvas.drawBitmap(bitmap,getMeasuredWidth()- mWidth,0,mPaint);}

ondraw方法主要就是滑出我们的view需要显示的内容,我们这里就只要显示拖拽图片即可.

3.重写onTouchEvent(MotionEvent event)方法:

@Overridepublic boolean onTouchEvent(MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN://记录按下的x,y坐标float downX = event.getX();mDownY = event.getY();//如果按下的位置不是拖拽图片就不响应事件if (downX > getMeasuredWidth() || downX < getMeasuredWidth()- mWidth|| mDownY > Math.abs(getScrollY()) + mSlideBarHeight|| mDownY < Math.abs(getScrollY())) {return false;}break;case MotionEvent.ACTION_MOVE://计算滑动的距离的百分百float diffY = move(event);//滑动拖拽图片scrollBy(0, -(int) diffY);mDownY = event.getY();break;case MotionEvent.ACTION_UP:move(event);break;case MotionEvent.ACTION_OUTSIDE:move(event);break;}return true;}private float move(MotionEvent event) {float diffY = event.getY() - mDownY;//判断界限if (getScrollY() - diffY > 0) {diffY = getScrollY();}if (getScrollY() - diffY < -(getMeasuredHeight()-mSlideBarHeight)) {diffY = getScrollY() + getMeasuredHeight()-mSlideBarHeight;}//已经滑动的距离int scrollHeight = getScrollY() - (int) diffY;//求出滑动的距离占View的高度的百分比float progress = Math.abs(scrollHeight)*1.0f / (getMeasuredHeight()-mSlideBarHeight);//使得返回的position的范围在0~size之间if (progress >= 0 && progress <= 1) {//计算已经滑动的距离,应该时recycleview滑动到的位置int position = (int) Math.ceil(progress * size);if (mOnTouchingChangedListener != null) {mOnTouchingChangedListener.onTouchingChanged(position);}}return diffY;}