Android实现快速滚动FastScrollView效果 Android实现快速滚动FastScrollVi

先看效果图：

public class FastScrollView extends ScrollView { private Rect mBarRect = new Rect(); private int mScrollExWidth; private int mScrollExHeight; private boolean mScrollStart; private int dx, dy; private int mRightPadding; public FastScrollView(Context context) {super(context); init(); } public FastScrollView(Context context, AttributeSet attrs) {super(context, attrs); init(); } public FastScrollView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr); init(); } private void init() {mScrollExWidth = dip2px(16); //扩展拖动区域宽度，可自行修改mScrollExHeight = dip2px(50); //扩展拖动区域高度，可自行修改} @Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {switch (ev.getAction() & ev.getActionMasked()) {case MotionEvent.ACTION_DOWN://Log.e("fly", "down"); mScrollStart = false; if (canScroll()) {dx = (int) ev.getX(); dy = (int) ev.getY(); float scrollPos = (float) getHeight() / getChildView().getHeight(); int barHeight = (int) (scrollPos * getHeight()); //Log.e("fly", scrollPos+", "+ barHeight); mBarRect.left = getWidth() - mRightPadding - getVerticalScrollbarWidth(); mBarRect.right = getWidth() - mRightPadding; mBarRect.top = (int) (getScrollY() * scrollPos); mBarRect.bottom = mBarRect.top + barHeight; //Dbg.print(mBarRect.left, mBarRect.right, mBarRect.top, mBarRect.bottom, dx, dy); if (dx >= mBarRect.left - mScrollExWidth&& dx < mBarRect.right&& dy >= mBarRect.top - mScrollExHeight&& dy < mBarRect.bottom + mScrollExHeight) {//Log.e("fly", "mScrollStart"); mScrollStart = true; }}break; case MotionEvent.ACTION_MOVE:if (mScrollStart) {int offsetY = (int) ev.getY() - dy; //Log.e("fly", "move: " + ev.getY()); int top = mBarRect.top + offsetY; float scrollPos = (float) top / getHeight(); int scrollY = (int) (scrollPos * getChildView().getHeight()); if (scrollY < 0) {scrollY = 0; }if (scrollY > getChildView().getHeight() - getHeight()) {scrollY = getChildView().getHeight() - getHeight(); }setScrollY(scrollY); return true; }break; }return super.dispatchTouchEvent(ev); } private boolean canScroll() {View child = getChildView(); if (child != null && child.getHeight() > getHeight()) {return true; } else {return false; }} private View getChildView() {if (getChildCount() > 0) {return getChildAt(0); } else {return null; }} private int dip2px(float dpValue) {final float scale = getContext().getResources().getDisplayMetrics().density; return (int) (dpValue * scale + 0.5f); } /*** 这里不用view的paddding，用于预留特殊空隙** @param mRightPadding*/public void setRightPadding(int mRightPadding) {this.mRightPadding = mRightPadding; }}

布局中设置了大滚动条样式，滚动时更加明显：

同理，可以依此制作快速滚动的 HorizontalScrollView。
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