Java tutorial
/* * The MIT License (MIT) * * Copyright (c) 2015 cpoopc * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ package com.app.gongza.libs.view.scrollablelayout; import android.annotation.TargetApi; import android.content.Context; import android.os.Build; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.widget.LinearLayout; import android.widget.Scroller; /** * Created by cpoopc(303727604@qq.com) on 2015-02-10. */ public class ScrollableLayout extends LinearLayout { private final String tag = "cp:scrollableLayout"; private float mDownX; private float mDownY; private float mLastY; private int minY = 0; private int maxY = 0; private int mHeadHeight; private int mExpandHeight; private int mTouchSlop; private int mMinimumVelocity; private int mMaximumVelocity; // ? private DIRECTION mDirection; private int mCurY; private int mLastScrollerY; private boolean needCheckUpdown; private boolean updown; private boolean mDisallowIntercept; private boolean isClickHead; private boolean isClickHeadExpand; private View mHeadView; private ViewPager childViewPager; private Scroller mScroller; private VelocityTracker mVelocityTracker; /** * ? * */ enum DIRECTION { UP, // ? DOWN// ? } public interface OnScrollListener { void onScroll(int currentY, int maxY); } private OnScrollListener onScrollListener; public void setOnScrollListener(OnScrollListener onScrollListener) { this.onScrollListener = onScrollListener; } private ScrollableHelper mHelper; public ScrollableHelper getHelper() { return mHelper; } public ScrollableLayout(Context context) { super(context); init(context); } public ScrollableLayout(Context context, AttributeSet attrs) { super(context, attrs); init(context); } @TargetApi(Build.VERSION_CODES.HONEYCOMB) public ScrollableLayout(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(context); } @TargetApi(Build.VERSION_CODES.LOLLIPOP) public ScrollableLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); init(context); } private void init(Context context) { mHelper = new ScrollableHelper(); mScroller = new Scroller(context); final ViewConfiguration configuration = ViewConfiguration.get(context); mTouchSlop = configuration.getScaledTouchSlop(); mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); } public boolean isSticked() { return mCurY == maxY; } /** * * * @param expandHeight */ public void setClickHeadExpand(int expandHeight) { mExpandHeight = expandHeight; } public int getMaxY() { return maxY; } public boolean isHeadTop() { return mCurY == minY; } public boolean canPtr() { return updown && mCurY == minY && mHelper.isTop(); } public void requestScrollableLayoutDisallowInterceptTouchEvent(boolean disallowIntercept) { super.requestDisallowInterceptTouchEvent(disallowIntercept); mDisallowIntercept = disallowIntercept; } @Override public boolean dispatchTouchEvent(MotionEvent ev) { float currentX = ev.getX(); float currentY = ev.getY(); float deltaY; int shiftX = (int) Math.abs(currentX - mDownX); int shiftY = (int) Math.abs(currentY - mDownY); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mDisallowIntercept = false; needCheckUpdown = true; updown = true; mDownX = currentX; mDownY = currentY; mLastY = currentY; checkIsClickHead((int) currentY, mHeadHeight, getScrollY()); checkIsClickHeadExpand((int) currentY, mHeadHeight, getScrollY()); initOrResetVelocityTracker(); mVelocityTracker.addMovement(ev); mScroller.forceFinished(true); break; case MotionEvent.ACTION_MOVE: if (mDisallowIntercept) { break; } initVelocityTrackerIfNotExists(); mVelocityTracker.addMovement(ev); deltaY = mLastY - currentY; if (needCheckUpdown) { if (shiftX > mTouchSlop && shiftX > shiftY) { needCheckUpdown = false; updown = false; } else if (shiftY > mTouchSlop && shiftY > shiftX) { needCheckUpdown = false; updown = true; } } if (updown && shiftY > mTouchSlop && shiftY > shiftX && (!isSticked() || mHelper.isTop() || isClickHeadExpand)) { if (childViewPager != null) { childViewPager.requestDisallowInterceptTouchEvent(true); } scrollBy(0, (int) (deltaY + 0.5)); } mLastY = currentY; break; case MotionEvent.ACTION_UP: if (updown && shiftY > shiftX && shiftY > mTouchSlop) { mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); float yVelocity = -mVelocityTracker.getYVelocity(); boolean dislowChild = false; if (Math.abs(yVelocity) > mMinimumVelocity) { mDirection = yVelocity > 0 ? DIRECTION.UP : DIRECTION.DOWN; if ((mDirection == DIRECTION.UP && isSticked()) || (!isSticked() && getScrollY() == 0 && mDirection == DIRECTION.DOWN)) { dislowChild = true; } else { mScroller.fling(0, getScrollY(), 0, (int) yVelocity, 0, 0, -Integer.MAX_VALUE, Integer.MAX_VALUE); mScroller.computeScrollOffset(); mLastScrollerY = getScrollY(); invalidate(); } } if (!dislowChild && (isClickHead || !isSticked())) { int action = ev.getAction(); ev.setAction(MotionEvent.ACTION_CANCEL); boolean dispathResult = super.dispatchTouchEvent(ev); ev.setAction(action); return dispathResult; } } break; default: break; } super.dispatchTouchEvent(ev); return true; } private int getScrollerVelocity(int distance, int duration) { if (mScroller == null) { return 0; } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) { return (int) mScroller.getCurrVelocity(); } else { return distance / duration; } } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { final int currY = mScroller.getCurrY(); if (mDirection == DIRECTION.UP) { // ? if (isSticked()) { int distance = mScroller.getFinalY() - currY; int duration = calcDuration(mScroller.getDuration(), mScroller.timePassed()); mHelper.smoothScrollBy(getScrollerVelocity(distance, duration), distance, duration); mScroller.forceFinished(true); return; } else { scrollTo(0, currY); } } else { // ? if (mHelper.isTop() || isClickHeadExpand) { int deltaY = (currY - mLastScrollerY); int toY = getScrollY() + deltaY; scrollTo(0, toY); if (mCurY <= minY) { mScroller.forceFinished(true); return; } } invalidate(); } mLastScrollerY = currY; } } @Override public void scrollBy(int x, int y) { int scrollY = getScrollY(); int toY = scrollY + y; if (toY >= maxY) { toY = maxY; } else if (toY <= minY) { toY = minY; } y = toY - scrollY; super.scrollBy(x, y); } @Override public void scrollTo(int x, int y) { if (y >= maxY) { y = maxY; } else if (y <= minY) { y = minY; } mCurY = y; if (onScrollListener != null) { onScrollListener.onScroll(y, maxY); } super.scrollTo(x, y); } private void initOrResetVelocityTracker() { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } else { mVelocityTracker.clear(); } } private void initVelocityTrackerIfNotExists() { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } } private void recycleVelocityTracker() { if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } private void checkIsClickHead(int downY, int headHeight, int scrollY) { isClickHead = downY + scrollY <= headHeight; } private void checkIsClickHeadExpand(int downY, int headHeight, int scrollY) { if (mExpandHeight <= 0) { isClickHeadExpand = false; } isClickHeadExpand = downY + scrollY <= headHeight + mExpandHeight; } private int calcDuration(int duration, int timepass) { return duration - timepass; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { mHeadView = getChildAt(0); measureChildWithMargins(mHeadView, widthMeasureSpec, 0, MeasureSpec.UNSPECIFIED, 0); maxY = mHeadView.getMeasuredHeight(); mHeadHeight = mHeadView.getMeasuredHeight(); super.onMeasure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(MeasureSpec.getSize(heightMeasureSpec) + maxY, MeasureSpec.EXACTLY)); } @Override protected void onFinishInflate() { if (mHeadView != null && !mHeadView.isClickable()) { mHeadView.setClickable(true); } int childCount = getChildCount(); for (int i = 0; i < childCount; i++) { View childAt = getChildAt(i); if (childAt != null && childAt instanceof ViewPager) { childViewPager = (ViewPager) childAt; } } super.onFinishInflate(); } }