仿美团详情滑动界面，并兼容NestedScroll嵌套 源码实例

package xiaochen.you.meituan.widget; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Canvas; import android.graphics.Rect; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.support.v4.view.AccessibilityDelegateCompat; import android.support.v4.view.InputDeviceCompat; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.NestedScrollingChild; import android.support.v4.view.NestedScrollingChildHelper; import android.support.v4.view.NestedScrollingParent; import android.support.v4.view.NestedScrollingParentHelper; import android.support.v4.view.ScrollingView; import android.support.v4.view.VelocityTrackerCompat; import android.support.v4.view.ViewCompat; import android.support.v4.view.accessibility.AccessibilityEventCompat; import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat; import android.support.v4.view.accessibility.AccessibilityRecordCompat; import android.support.v4.widget.EdgeEffectCompat; import android.support.v4.widget.ScrollerCompat; import android.util.AttributeSet; import android.util.Log; import android.util.TypedValue; import android.view.FocusFinder; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.ViewParent; import android.view.accessibility.AccessibilityEvent; import android.view.animation.AnimationUtils; import android.widget.FrameLayout; import android.widget.ScrollView; import java.util.List; /** * Created by you on 2017/3/29. */ public class NestedScrollView extends FrameLayout implements NestedScrollingParent, NestedScrollingChild, ScrollingView { /** * 支持向下滑动偏移 */ static final int PULLDOWN_SCALE = 2; /** * 向下越界滑动时的滑动比例 */ static final int PULLDOWN_SCROLL = 3; static final int ANIMATED_SCROLL_GAP = 250; static final float MAX_SCROLL_FACTOR = 0.5f; private static final String TAG = "NestedScrollView"; /** * Interface definition for a callback to be invoked when the scroll * X or Y positions of a view change. * * <p>This version of the interface works on all versions of Android, back to API v4.</p> * * @see #setOnScrollChangeListener(OnScrollChangeListener) */ public interface OnScrollChangeListener { /** * Called when the scroll position of a view changes. * * @param v The view whose scroll position has changed. * @param scrollX Current horizontal scroll origin. * @param scrollY Current vertical scroll origin. * @param oldScrollX Previous horizontal scroll origin. * @param oldScrollY Previous vertical scroll origin. */ void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY); } private long mLastScroll; private final Rect mTempRect = new Rect(); private ScrollerCompat mScroller; private EdgeEffectCompat mEdgeGlowTop; private EdgeEffectCompat mEdgeGlowBottom; /** * Position of the last motion event. */ private int mLastMotionY; /** * True when the layout has changed but the traversal has not come through yet. * Ideally the view hierarchy would keep track of this for us. */ private boolean mIsLayoutDirty = true; private boolean mIsLaidOut = false; /** * The child to give focus to in the event that a child has requested focus while the * layout is dirty. This prevents the scroll from being wrong if the child has not been * laid out before requesting focus. */ private View mChildToScrollTo = null; /** * True if the user is currently dragging this ScrollView around. This is * not the same as 'is being flinged', which can be checked by * mScroller.isFinished() (flinging begins when the user lifts his finger). */ private boolean mIsBeingDragged = false; /** * Determines speed during touch scrolling */ private VelocityTracker mVelocityTracker; /** * When set to true, the scroll view measure its child to make it fill the currently * visible area. */ private boolean mFillViewport; /** * Whether arrow scrolling is animated. */ private boolean mSmoothScrollingEnabled = true; private int mTouchSlop; private int mMinimumVelocity; private int mMaximumVelocity; /** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */ private int mActivePointerId = INVALID_POINTER; /** * Used during scrolling to retrieve the new offset within the window. */ private final int[] mScrollOffset = new int[2]; private final int[] mScrollConsumed = new int[2]; private int mNestedYOffset; /** * Sentinel value for no current active pointer. * Used by {@link #mActivePointerId}. */ private static final int INVALID_POINTER = -1; private SavedState mSavedState; private static final AccessibilityDelegate ACCESSIBILITY_DELEGATE = new AccessibilityDelegate(); private static final int[] SCROLLVIEW_STYLEABLE = new int[] { android.R.attr.fillViewport }; private final NestedScrollingParentHelper mParentHelper; private final NestedScrollingChildHelper mChildHelper; private float mVerticalScrollFactor; private OnScrollChangeListener mOnScrollChangeListener; public NestedScrollView(Context context) { this(context, null); } public NestedScrollView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public NestedScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); initScrollView(); final TypedArray a = context.obtainStyledAttributes( attrs, SCROLLVIEW_STYLEABLE, defStyleAttr, 0); setFillViewport(a.getBoolean(0, false)); a.recycle(); mParentHelper = new NestedScrollingParentHelper(this); mChildHelper = new NestedScrollingChildHelper(this); // ...because why else would you be using this widget? setNestedScrollingEnabled(true); ViewCompat.setAccessibilityDelegate(this, ACCESSIBILITY_DELEGATE); } // NestedScrollingChild @Override public void setNestedScrollingEnabled(boolean enabled) { mChildHelper.setNestedScrollingEnabled(enabled); } @Override public boolean isNestedScrollingEnabled() { return mChildHelper.isNestedScrollingEnabled(); } @Override public boolean startNestedScroll(int axes) { return mChildHelper.startNestedScroll(axes); } @Override public void stopNestedScroll() { mChildHelper.stopNestedScroll(); } @Override public boolean hasNestedScrollingParent() { return mChildHelper.hasNestedScrollingParent(); } @Override public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) { return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow); } @Override public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) { return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow); } @Over