Android仿高德首页三段式滑动

最近发现很多app都使用了三段式滑动,比如说高德的首页和某宝等物流信息都是使用的三段式滑动方式,谷歌其实给了我们很好的2段式滑动,就是BottomSheet,所以这次我也是在这个原理基础上做了一个小小的修改来实现我们今天想要的效果。

高德的效果

gaode_300.gif

实现的效果

fgaode_300.gif

我们实现的效果和高德差距不是很大,也很顺滑。具体实现其实就是集成CoordinatorLayout.Behavior

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.zwl.mybehaviordemo.gaode;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Build.VERSION;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.ViewParent;

import androidx.annotation.NonNull;
import androidx.annotation.RestrictTo;
import androidx.annotation.RestrictTo.Scope;
import androidx.annotation.VisibleForTesting;
import androidx.coordinatorlayout.widget.CoordinatorLayout;
import androidx.coordinatorlayout.widget.CoordinatorLayout.Behavior;
import androidx.core.math.MathUtils;
import androidx.core.view.ViewCompat;
import androidx.customview.view.AbsSavedState;
import androidx.customview.widget.ViewDragHelper;
import androidx.customview.widget.ViewDragHelper.Callback;

import com.zwl.mybehaviordemo.R;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;

/**
 * 高德首页滑动效果
 *
 * @author yixiaolunhui
 */
public class GaoDeBottomSheetBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {
    public static final int STATE_DRAGGING = 1;
    public static final int STATE_SETTLING = 2;
    public static final int STATE_EXPANDED = 3;
    public static final int STATE_COLLAPSED = 4;
    public static final int STATE_HIDDEN = 5;
    public static final int STATE_HALF_EXPANDED = 6;
    public static final int PEEK_HEIGHT_AUTO = -1;
    private static final float HIDE_THRESHOLD = 0.5F;
    private static final float HIDE_FRICTION = 0.1F;
    public static final int MIDDLE_HEIGHT_AUTO = -1;
    private boolean fitToContents = true;
    private float maximumVelocity;
    private int peekHeight;
    private boolean peekHeightAuto;
    private int peekHeightMin;
    private int lastPeekHeight;
    int fitToContentsOffset;
    int halfExpandedOffset;
    int collapsedOffset;
    boolean hideable;
    private boolean skipCollapsed;
    int state = STATE_COLLAPSED;
    ViewDragHelper viewDragHelper;
    private boolean ignoreEvents;
    private int lastNestedScrollDy;
    private boolean nestedScrolled;
    int parentHeight;
    WeakReference<V> viewRef;
    WeakReference<View> nestedScrollingChildRef;
    private GaoDeBottomSheetBehavior.BottomSheetCallback callback;
    private VelocityTracker velocityTracker;
    int activePointerId;
    private int initialY;
    boolean touchingScrollingChild;
    private Map<View, Integer> importantForAccessibilityMap;
    private final Callback dragCallback;


    private int mMiddleHeight;
    private boolean mMiddleHeightAuto;

    public GaoDeBottomSheetBehavior() {
        this.dragCallback = new NamelessClass_1();
    }

    public GaoDeBottomSheetBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.dragCallback = new NamelessClass_1();
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BottomSheetBehavior_Layout);
        TypedValue value = a.peekValue(R.styleable.BottomSheetBehavior_Layout_behavior_peekHeight);
        if (value != null && value.data == -1) {
            this.setPeekHeight(value.data);
        } else {
            this.setPeekHeight(a.getDimensionPixelSize(R.styleable.BottomSheetBehavior_Layout_behavior_peekHeight, -1));
        }

        this.setHideable(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_hideAble, false));
        this.setFitToContents(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_fitToContents, true));
        this.setSkipCollapsed(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_skipCollapse, false));
        setMiddleHeight(a.getDimensionPixelSize(R.styleable.BottomSheetBehavior_Layout_behavior_middleHeight, MIDDLE_HEIGHT_AUTO));

        a.recycle();
        ViewConfiguration configuration = ViewConfiguration.get(context);
        this.maximumVelocity = (float) configuration.getScaledMaximumFlingVelocity();
    }

    class NamelessClass_1 extends Callback {
        NamelessClass_1() {
        }

        @Override
        public boolean tryCaptureView(@NonNull View child, int pointerId) {
            if (GaoDeBottomSheetBehavior.this.state == STATE_DRAGGING) {
                return false;
            } else if (GaoDeBottomSheetBehavior.this.touchingScrollingChild) {
                return false;
            } else {
                if (GaoDeBottomSheetBehavior.this.state == 3 && GaoDeBottomSheetBehavior.this.activePointerId == pointerId) {
                    View scroll = (View) GaoDeBottomSheetBehavior.this.nestedScrollingChildRef.get();
                    if (scroll != null && scroll.canScrollVertically(-1)) {
                        return false;
                    }
                }

                return GaoDeBottomSheetBehavior.this.viewRef != null && GaoDeBottomSheetBehavior.this.viewRef.get() == child;
            }
        }

        @Override
        public void onViewPositionChanged(@NonNull View changedView, int left, int top, int dx, int dy) {
            GaoDeBottomSheetBehavior.this.dispatchOnSlide(top);
        }

        @Override
        public void onViewDragStateChanged(int state) {
            if (state == 1) {
                GaoDeBottomSheetBehavior.this.setStateInternal(STATE_DRAGGING);
            }

        }

        @Override
        public void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) {
            int top;
            byte targetState;
            int currentTop;
            if (yvel < 0.0F) {
                if (GaoDeBottomSheetBehavior.this.fitToContents) {
                    currentTop = releasedChild.getTop();

                    if (currentTop < (collapsedOffset + HIDE_THRESHOLD) && currentTop >= halfExpandedOffset) {
                        top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;
                        targetState = STATE_HALF_EXPANDED;
                    } else {
                        top = GaoDeBottomSheetBehavior.this.fitToContentsOffset;
                        targetState = STATE_EXPANDED;
                    }

                } else {
                    currentTop = releasedChild.getTop();
                    if (currentTop > GaoDeBottomSheetBehavior.this.halfExpandedOffset) {
                        top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;
                        targetState = STATE_HALF_EXPANDED;
                    } else {
                        top = 0;
                        targetState = STATE_EXPANDED;
                    }
                }
            } else if (!GaoDeBottomSheetBehavior.this.hideable || !GaoDeBottomSheetBehavior.this.shouldHide(releasedChild, yvel) || releasedChild.getTop() <= GaoDeBottomSheetBehavior.this.collapsedOffset && Math.abs(xvel) >= Math.abs(yvel)) {
                if (yvel != 0.0F && Math.abs(xvel) <= Math.abs(yvel)) {
                    currentTop = releasedChild.getTop();
                    if (currentTop < halfExpandedOffset) {
                        top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;
                        targetState = STATE_HALF_EXPANDED;
                    } else {
                        top = GaoDeBottomSheetBehavior.this.collapsedOffset;
                        targetState = STATE_COLLAPSED;
                    }

                } else {
                    currentTop = releasedChild.getTop();
                    if (GaoDeBottomSheetBehavior.this.fitToContents) {
                        if (Math.abs(currentTop - GaoDeBottomSheetBehavior.this.fitToContentsOffset) < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) {
                            top = GaoDeBottomSheetBehavior.this.fitToContentsOffset;
                            targetState = STATE_EXPANDED;
                        } else {
                            top = GaoDeBottomSheetBehavior.this.collapsedOffset;
                            targetState = STATE_COLLAPSED;
                        }
                    } else if (currentTop < GaoDeBottomSheetBehavior.this.halfExpandedOffset) {
                        if (currentTop < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) {
                            top = 0;
                            targetState = STATE_EXPANDED;
                        } else {
                            top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;
                            targetState = STATE_HALF_EXPANDED;
                        }
                    } else if (Math.abs(currentTop - GaoDeBottomSheetBehavior.this.halfExpandedOffset) < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) {
                        top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;
                        targetState = STATE_HALF_EXPANDED;
                    } else {
                        top = GaoDeBottomSheetBehavior.this.collapsedOffset;
                        targetState = STATE_COLLAPSED;
                    }
                }
            } else {
                top = GaoDeBottomSheetBehavior.this.parentHeight;
                targetState = STATE_HIDDEN;
            }

            if (GaoDeBottomSheetBehavior.this.viewDragHelper.settleCapturedViewAt(releasedChild.getLeft(), top)) {
                GaoDeBottomSheetBehavior.this.setStateInternal(STATE_SETTLING);
                ViewCompat.postOnAnimation(releasedChild, GaoDeBottomSheetBehavior.this.new SettleRunnable(releasedChild, targetState));
            } else {
                GaoDeBottomSheetBehavior.this.setStateInternal(targetState);
            }

        }

        @Override
        public int clampViewPositionVertical(@NonNull View child, int top, int dy) {
            return MathUtils.clamp(top, GaoDeBottomSheetBehavior.this.getExpandedOffset(), GaoDeBottomSheetBehavior.this.hideable ? GaoDeBottomSheetBehavior.this.parentHeight : GaoDeBottomSheetBehavior.this.collapsedOffset);
        }

        @Override
        public int clampViewPositionHorizontal(@NonNull View child, int left, int dx) {
            return child.getLeft();
        }

        @Override
        public int getViewVerticalDragRange(@NonNull View child) {
            return GaoDeBottomSheetBehavior.this.hideable ? GaoDeBottomSheetBehavior.this.parentHeight : GaoDeBottomSheetBehavior.this.collapsedOffset;
        }
    }

    @Override
    public Parcelable onSaveInstanceState(CoordinatorLayout parent, V child) {
        return new GaoDeBottomSheetBehavior.SavedState(super.onSaveInstanceState(parent, child), this.state);
    }

    @Override
    public void onRestoreInstanceState(CoordinatorLayout parent, V child, Parcelable state) {
        GaoDeBottomSheetBehavior.SavedState ss = (GaoDeBottomSheetBehavior.SavedState) state;
        super.onRestoreInstanceState(parent, child, ss.getSuperState());
        if (ss.state != STATE_DRAGGING && ss.state != STATE_SETTLING) {
            this.state = ss.state;
        } else {
            this.state = STATE_COLLAPSED;
        }

    }

    @Override
    public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
        if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child)) {
            child.setFitsSystemWindows(true);
        }

        int savedTop = child.getTop();
        parent.onLayoutChild(child, layoutDirection);
        this.parentHeight = parent.getHeight();
        if (this.peekHeightAuto) {
            if (this.peekHeightMin == 0) {
                this.peekHeightMin = parent.getResources().getDimensionPixelSize(R.dimen.design_bottom_sheet_peek_height_min);
            }

            this.lastPeekHeight = Math.max(this.peekHeightMin, this.parentHeight - parent.getWidth() * 9 / 16);
        } else {
            this.lastPeekHeight = this.peekHeight;
        }
        if (mMiddleHeightAuto) {
            mMiddleHeight = this.parentHeight;
        }
        this.fitToContentsOffset = Math.max(0, this.parentHeight - child.getHeight());
        this.halfExpandedOffset = this.parentHeight - mMiddleHeight;
        this.calculateCollapsedOffset();
        if (this.state == STATE_EXPANDED) {
            ViewCompat.offsetTopAndBottom(child, this.getExpandedOffset());
        } else if (this.state == STATE_HALF_EXPANDED) {
            ViewCompat.offsetTopAndBottom(child, this.halfExpandedOffset);
        } else if (this.hideable && this.state == STATE_HIDDEN) {
            ViewCompat.offsetTopAndBottom(child, this.parentHeight);
        } else if (this.state == STATE_COLLAPSED) {
            ViewCompat.offsetTopAndBottom(child, this.collapsedOffset);
        } else if (this.state == STATE_DRAGGING || this.state == STATE_SETTLING) {
            ViewCompat.offsetTopAndBottom(child, savedTop - child.getTop());
        }

        if (this.viewDragHelper == null) {
            this.viewDragHelper = ViewDragHelper.create(parent, this.dragCallback);
        }

        this.viewRef = new WeakReference(child);
        this.nestedScrollingChildRef = new WeakReference(this.findScrollingChild(child));
        return true;
    }

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) {
        if (!child.isShown()) {
            this.ignoreEvents = true;
            return false;
        } else {
            int action = event.getActionMasked();
            if (action == 0) {
                this.reset();
            }

            if (this.velocityTracker == null) {
                this.velocityTracker = VelocityTracker.obtain();
            }

            this.velocityTracker.addMovement(event);
            switch (action) {
                case 0:
                    int initialX = (int) event.getX();
                    this.initialY = (int) event.getY();
                    View scroll = this.nestedScrollingChildRef != null ? (View) this.nestedScrollingChildRef.get() : null;
                    if (scroll != null && parent.isPointInChildBounds(scroll, initialX, this.initialY)) {
                        this.activePointerId = event.getPointerId(event.getActionIndex());
                        this.touchingScrollingChild = true;
                    }

                    this.ignoreEvents = this.activePointerId == -1 && !parent.isPointInChildBounds(child, initialX, this.initialY);
                    break;
                case 1:
                case 3:
                    this.touchingScrollingChild = false;
                    this.activePointerId = -1;
                    if (this.ignoreEvents) {
                        this.ignoreEvents = false;
                        return false;
                    }
                case 2:
            }

            if (!this.ignoreEvents && this.viewDragHelper != null && this.viewDragHelper.shouldInterceptTouchEvent(event)) {
                return true;
            } else {
                View scroll = this.nestedScrollingChildRef != null ? (View) this.nestedScrollingChildRef.get() : null;
                return action == 2 && scroll != null && !this.ignoreEvents && this.state != 1 && !parent.isPointInChildBounds(scroll, (int) event.getX(), (int) event.getY()) && this.viewDragHelper != null && Math.abs((float) this.initialY - event.getY()) > (float) this.viewDragHelper.getTouchSlop();
            }
        }
    }

    @Override
    public boolean onTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) {
        if (!child.isShown()) {
            return false;
        } else {
            int action = event.getActionMasked();
            if (this.state == STATE_DRAGGING && action == 0) {
                return true;
            } else {
                if (this.viewDragHelper != null) {
                    this.viewDragHelper.processTouchEvent(event);
                }

                if (action == 0) {
                    this.reset();
                }

                if (this.velocityTracker == null) {
                    this.velocityTracker = VelocityTracker.obtain();
                }

                this.velocityTracker.addMovement(event);
                if (action == 2 && !this.ignoreEvents && Math.abs((float) this.initialY - event.getY()) > (float) this.viewDragHelper.getTouchSlop()) {
                    this.viewDragHelper.captureChildView(child, event.getPointerId(event.getActionIndex()));
                }

                return !this.ignoreEvents;
            }
        }
    }

    @Override
    public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View directTargetChild, @NonNull View target, int axes, int type) {
        this.lastNestedScrollDy = 0;
        this.nestedScrolled = false;
        return (axes & 2) != 0;
    }

    @Override
    public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int dx, int dy, @NonNull int[] consumed, int type) {
        if (type != 1) {
            View scrollingChild = (View) this.nestedScrollingChildRef.get();
            if (target == scrollingChild) {
                int currentTop = child.getTop();
                int newTop = currentTop - dy;
                if (dy > 0) {
                    if (newTop < this.getExpandedOffset()) {
                        consumed[1] = currentTop - this.getExpandedOffset();
                        ViewCompat.offsetTopAndBottom(child, -consumed[1]);
                        this.setStateInternal(STATE_EXPANDED);
                    } else {
                        consumed[1] = dy;
                        ViewCompat.offsetTopAndBottom(child, -dy);
                        this.setStateInternal(STATE_DRAGGING);
                    }
                } else if (dy < 0 && !target.canScrollVertically(-1)) {
                    if (newTop > this.collapsedOffset && !this.hideable) {
                        consumed[1] = currentTop - this.collapsedOffset;
                        ViewCompat.offsetTopAndBottom(child, -consumed[1]);
                        this.setStateInternal(STATE_COLLAPSED);
                    } else {
                        consumed[1] = dy;
                        ViewCompat.offsetTopAndBottom(child, -dy);
                        this.setStateInternal(STATE_DRAGGING);
                    }
                }

                this.dispatchOnSlide(child.getTop());
                this.lastNestedScrollDy = dy;
                this.nestedScrolled = true;
            }
        }
    }

    @Override
    public void onStopNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int type) {
        if (child.getTop() == this.getExpandedOffset()) {
            this.setStateInternal(STATE_EXPANDED);
        } else if (target == this.nestedScrollingChildRef.get() && this.nestedScrolled) {
            int top;
            byte targetState;
            if (this.lastNestedScrollDy > 0) {
                int currentTop = child.getTop();
                if (currentTop <= collapsedOffset - HIDE_THRESHOLD && currentTop >= halfExpandedOffset) {
                    top = this.halfExpandedOffset;
                    targetState = STATE_HALF_EXPANDED;

                } else {
                    top = this.getExpandedOffset();
                    targetState = STATE_EXPANDED;
                }

            } else if (this.hideable && this.shouldHide(child, this.getYVelocity())) {
                top = this.parentHeight;
                targetState = STATE_HIDDEN;
            } else if (this.lastNestedScrollDy == 0) {
                int currentTop = child.getTop();
                if (this.fitToContents) {
                    if (Math.abs(currentTop - this.fitToContentsOffset) < Math.abs(currentTop - this.collapsedOffset)) {
                        top = this.fitToContentsOffset;
                        targetState = STATE_EXPANDED;
                    } else {
                        top = this.collapsedOffset;
                        targetState = STATE_COLLAPSED;
                    }
                } else if (currentTop < this.halfExpandedOffset) {
                    if (currentTop < Math.abs(currentTop - this.collapsedOffset)) {
                        top = 0;
                        targetState = STATE_EXPANDED;
                    } else {
                        top = this.halfExpandedOffset;
                        targetState = STATE_HALF_EXPANDED;
                    }
                } else if (Math.abs(currentTop - this.halfExpandedOffset) < Math.abs(currentTop - this.collapsedOffset)) {
                    top = this.halfExpandedOffset;
                    targetState = STATE_HALF_EXPANDED;
                } else {
                    top = this.collapsedOffset;
                    targetState = STATE_COLLAPSED;
                }
            } else {
                int currentTop = child.getTop();
                if (currentTop <= halfExpandedOffset + HIDE_THRESHOLD && currentTop > HIDE_THRESHOLD) {
                    top = this.halfExpandedOffset;
                    targetState = STATE_HALF_EXPANDED;
                } else {
                    top = this.collapsedOffset;
                    targetState = STATE_COLLAPSED;
                }
            }

            if (this.viewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
                this.setStateInternal(STATE_SETTLING);
                ViewCompat.postOnAnimation(child, new GaoDeBottomSheetBehavior.SettleRunnable(child, targetState));
            } else {
                this.setStateInternal(targetState);
            }

            this.nestedScrolled = false;
        }
    }

    @Override
    public boolean onNestedPreFling(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, float velocityX, float velocityY) {
        return target == this.nestedScrollingChildRef.get() && (this.state != STATE_EXPANDED || super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY));
    }

    public boolean isFitToContents() {
        return this.fitToContents;
    }

    public void setFitToContents(boolean fitToContents) {
        if (this.fitToContents != fitToContents) {
            this.fitToContents = fitToContents;
            if (this.viewRef != null) {
                this.calculateCollapsedOffset();
            }

            this.setStateInternal(this.fitToContents && this.state == STATE_HALF_EXPANDED ? STATE_HALF_EXPANDED : this.state);
        }
    }

    public final void setPeekHeight(int peekHeight) {
        boolean layout = false;
        if (peekHeight == -1) {
            if (!this.peekHeightAuto) {
                this.peekHeightAuto = true;
                layout = true;
            }
        } else if (this.peekHeightAuto || this.peekHeight != peekHeight) {
            this.peekHeightAuto = false;
            this.peekHeight = Math.max(0, peekHeight);
            this.collapsedOffset = this.parentHeight - peekHeight;
            layout = true;
        }

        if (layout && this.state == STATE_COLLAPSED && this.viewRef != null) {
            V view = (V) this.viewRef.get();
            if (view != null) {
                view.requestLayout();
            }
        }

    }

    public final void setMiddleHeight(int middleHeight) {
        boolean layout = false;
        if (middleHeight == PEEK_HEIGHT_AUTO) {
            if (!mMiddleHeightAuto) {
                mMiddleHeightAuto = true;
                layout = true;
            }
        } else if (mMiddleHeightAuto || mMiddleHeight != middleHeight) {
            mMiddleHeightAuto = false;
            mMiddleHeight = Math.max(0, middleHeight);
            layout = true;
        }
        if (layout && this.state == STATE_COLLAPSED && viewRef != null) {
            V view = viewRef.get();
            if (view != null) {
                view.requestLayout();
            }
        }
    }

    public final int getPeekHeight() {
        return this.peekHeightAuto ? -1 : this.peekHeight;
    }

    public final int getMiddleHeight() {
        return this.mMiddleHeightAuto ? -1 : this.mMiddleHeight;
    }

    public final int getParentHeight() {
        return this.parentHeight;
    }

    public void setHideable(boolean hideable) {
        this.hideable = hideable;
    }

    public boolean isHideable() {
        return this.hideable;
    }

    public void setSkipCollapsed(boolean skipCollapsed) {
        this.skipCollapsed = skipCollapsed;
    }

    public boolean getSkipCollapsed() {
        return this.skipCollapsed;
    }

    public void setBottomSheetCallback(GaoDeBottomSheetBehavior.BottomSheetCallback callback) {
        this.callback = callback;
    }

    public final void setState(final int state) {
        if (state != this.state) {
            if (this.viewRef == null) {
                if (state == STATE_COLLAPSED || state == STATE_EXPANDED || state == STATE_HALF_EXPANDED || this.hideable && state == STATE_HIDDEN) {
                    this.state = state;
                }

            } else {
                final V child = (V) this.viewRef.get();
                if (child != null) {
                    ViewParent parent = child.getParent();
                    if (parent != null && parent.isLayoutRequested() && ViewCompat.isAttachedToWindow(child)) {
                        child.post(new Runnable() {
                            @Override
                            public void run() {
                                GaoDeBottomSheetBehavior.this.startSettlingAnimation(child, state);
                            }
                        });
                    } else {
                        this.startSettlingAnimation(child, state);
                    }

                }
            }
        }
    }

    public final int getState() {
        return this.state;
    }

    void setStateInternal(int state) {
        if (this.state != state) {
            this.state = state;
            if (state != STATE_HALF_EXPANDED && state != STATE_EXPANDED) {
                if (state == STATE_HIDDEN || state == STATE_COLLAPSED) {
                    this.updateImportantForAccessibility(false);
                }
            } else {
                this.updateImportantForAccessibility(true);
            }

            View bottomSheet = (View) this.viewRef.get();
            if (bottomSheet != null && this.callback != null) {
                this.callback.onStateChanged(bottomSheet, state);
            }

        }
    }

    private void calculateCollapsedOffset() {
        if (this.fitToContents) {
            this.collapsedOffset = Math.max(this.parentHeight - this.lastPeekHeight, this.fitToContentsOffset);
        } else {
            this.collapsedOffset = this.parentHeight - this.lastPeekHeight;
        }

    }

    private void reset() {
        this.activePointerId = -1;
        if (this.velocityTracker != null) {
            this.velocityTracker.recycle();
            this.velocityTracker = null;
        }

    }

    boolean shouldHide(View child, float yvel) {
        if (this.skipCollapsed) {
            return true;
        } else if (child.getTop() < this.collapsedOffset) {
            return false;
        } else {
            float newTop = (float) child.getTop() + yvel * HIDE_FRICTION;
            return Math.abs(newTop - (float) this.collapsedOffset) / (float) this.peekHeight > HIDE_THRESHOLD;
        }
    }

    @VisibleForTesting
    View findScrollingChild(View view) {
        if (ViewCompat.isNestedScrollingEnabled(view)) {
            return view;
        } else {
            if (view instanceof ViewGroup) {
                ViewGroup group = (ViewGroup) view;
                int i = 0;

                for (int count = group.getChildCount(); i < count; ++i) {
                    View scrollingChild = this.findScrollingChild(group.getChildAt(i));
                    if (scrollingChild != null) {
                        return scrollingChild;
                    }
                }
            }

            return null;
        }
    }

    private float getYVelocity() {
        if (this.velocityTracker == null) {
            return 0.0F;
        } else {
            this.velocityTracker.computeCurrentVelocity(1000, this.maximumVelocity);
            return this.velocityTracker.getYVelocity(this.activePointerId);
        }
    }

    private int getExpandedOffset() {
        return this.fitToContents ? this.fitToContentsOffset : 0;
    }

    void startSettlingAnimation(View child, int state) {
        int top;
        if (state == STATE_COLLAPSED) {
            top = this.collapsedOffset;
        } else if (state == STATE_HALF_EXPANDED) {
            top = this.halfExpandedOffset;
        } else if (state == STATE_EXPANDED) {
            top = this.getExpandedOffset();
        } else {
            if (!this.hideable || state != STATE_HIDDEN) {
                throw new IllegalArgumentException("Illegal state argument: " + state);
            }

            top = this.parentHeight;
        }

        if (this.viewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
            this.setStateInternal(STATE_SETTLING);
            ViewCompat.postOnAnimation(child, new GaoDeBottomSheetBehavior.SettleRunnable(child, state));
        } else {
            this.setStateInternal(state);
        }

    }

    void dispatchOnSlide(int top) {
        View bottomSheet = (View) this.viewRef.get();
        if (bottomSheet != null && this.callback != null) {
            if (top > this.collapsedOffset) {
                this.callback.onSlide(bottomSheet, (float) (this.collapsedOffset - top) / (float) (this.parentHeight - this.collapsedOffset));
            } else {
                this.callback.onSlide(bottomSheet, (float) (this.collapsedOffset - top) / (float) (this.collapsedOffset - this.getExpandedOffset()));
            }
        }

    }

    @VisibleForTesting
    int getPeekHeightMin() {
        return this.peekHeightMin;
    }

    public static <V extends View> GaoDeBottomSheetBehavior<V> from(V view) {
        LayoutParams params = view.getLayoutParams();
        if (!(params instanceof CoordinatorLayout.LayoutParams)) {
            throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
        } else {
            Behavior behavior = ((CoordinatorLayout.LayoutParams) params).getBehavior();
            if (!(behavior instanceof GaoDeBottomSheetBehavior)) {
                throw new IllegalArgumentException("The view is not associated with BottomSheetBehavior");
            } else {
                return (GaoDeBottomSheetBehavior) behavior;
            }
        }
    }

    @SuppressLint("WrongConstant")
    private void updateImportantForAccessibility(boolean expanded) {
        if (this.viewRef != null) {
            ViewParent viewParent = ((View) this.viewRef.get()).getParent();
            if (viewParent instanceof CoordinatorLayout) {
                CoordinatorLayout parent = (CoordinatorLayout) viewParent;
                int childCount = parent.getChildCount();
                if (VERSION.SDK_INT >= 16 && expanded) {
                    if (this.importantForAccessibilityMap != null) {
                        return;
                    }

                    this.importantForAccessibilityMap = new HashMap(childCount);
                }

                for (int i = 0; i < childCount; ++i) {
                    View child = parent.getChildAt(i);
                    if (child != this.viewRef.get()) {
                        if (!expanded) {
                            if (this.importantForAccessibilityMap != null && this.importantForAccessibilityMap.containsKey(child)) {
                                ViewCompat.setImportantForAccessibility(child, (Integer) this.importantForAccessibilityMap.get(child));
                            }
                        } else {
                            if (VERSION.SDK_INT >= 16) {
                                this.importantForAccessibilityMap.put(child, child.getImportantForAccessibility());
                            }

                            ViewCompat.setImportantForAccessibility(child, 4);
                        }
                    }
                }

                if (!expanded) {
                    this.importantForAccessibilityMap = null;
                }

            }
        }
    }

    protected static class SavedState extends AbsSavedState {
        final int state;
        public static final Creator<GaoDeBottomSheetBehavior.SavedState> CREATOR = new ClassLoaderCreator<GaoDeBottomSheetBehavior.SavedState>() {
            @Override
            public GaoDeBottomSheetBehavior.SavedState createFromParcel(Parcel in, ClassLoader loader) {
                return new GaoDeBottomSheetBehavior.SavedState(in, loader);
            }

            @Override
            public GaoDeBottomSheetBehavior.SavedState createFromParcel(Parcel in) {
                return new GaoDeBottomSheetBehavior.SavedState(in, (ClassLoader) null);
            }

            @Override
            public GaoDeBottomSheetBehavior.SavedState[] newArray(int size) {
                return new GaoDeBottomSheetBehavior.SavedState[size];
            }
        };

        public SavedState(Parcel source) {
            this(source, (ClassLoader) null);
        }

        public SavedState(Parcel source, ClassLoader loader) {
            super(source, loader);
            this.state = source.readInt();
        }

        public SavedState(Parcelable superState, int state) {
            super(superState);
            this.state = state;
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeInt(this.state);
        }
    }

    private class SettleRunnable implements Runnable {
        private final View view;
        private final int targetState;

        SettleRunnable(View view, int targetState) {
            this.view = view;
            this.targetState = targetState;
        }

        @Override
        public void run() {
            if (GaoDeBottomSheetBehavior.this.viewDragHelper != null && GaoDeBottomSheetBehavior.this.viewDragHelper.continueSettling(true)) {
                ViewCompat.postOnAnimation(this.view, this);
            } else {
                GaoDeBottomSheetBehavior.this.setStateInternal(this.targetState);
            }

        }
    }

    @Retention(RetentionPolicy.SOURCE)
    @RestrictTo({Scope.LIBRARY_GROUP})
    public @interface State {
    }

    public abstract static class BottomSheetCallback {
        public BottomSheetCallback() {
        }

        public abstract void onStateChanged(@NonNull View var1, int var2);

        public abstract void onSlide(@NonNull View var1, float var2);
    }
}

使用的时候直接设置

    <androidx.appcompat.widget.LinearLayoutCompat
            android:id="@+id/bottom_sheet"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@android:color/white"
            android:orientation="vertical"
            android:visibility="visible"
            app:behavior_hideable="false"
            app:behavior_middleHeight="200dp"
            app:behavior_peekHeight="80dp"
          app:layout_behavior=".gaode.GaoDeBottomSheetBehavior"
            tools:ignore="MissingPrefix">
         //....
    </androidx.appcompat.widget.LinearLayoutCompat>

对于按钮滑动及通明度渐变隐藏显示也是通过实现behavior,因为比较的简单直接上代码

package com.zwl.mybehaviordemo.gaode;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.appcompat.widget.LinearLayoutCompat;
import androidx.coordinatorlayout.widget.CoordinatorLayout;
import androidx.core.view.ViewCompat;

import com.zwl.mybehaviordemo.R;

/**
 * 高德首页按钮处理
 *
 * @author yixiaolunhui
 */
public class GaoDeBtnBehavior extends CoordinatorLayout.Behavior {

    private View rightActions;
    private View topActions;

    public GaoDeBtnBehavior() {
    }

    public GaoDeBtnBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onLayoutChild(@NonNull CoordinatorLayout parent, @NonNull View child, int layoutDirection) {
        if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child)) {
            child.setFitsSystemWindows(true);
        }
        if (rightActions == null) {
            rightActions = parent.findViewById(R.id.rightActions);
        }
        if (topActions == null) {
            topActions = parent.findViewById(R.id.topActions);
        }
        return super.onLayoutChild(parent, child, layoutDirection);
    }

    @Override
    public boolean layoutDependsOn(@NonNull CoordinatorLayout parent, @NonNull View child, @NonNull View dependency) {
        return dependency instanceof LinearLayoutCompat || super.layoutDependsOn(parent, child, dependency);
    }

    @Override
    public boolean onDependentViewChanged(@NonNull CoordinatorLayout parent, @NonNull View child, @NonNull View dependency) {
        //判断当前dependency 是内容布局
        if (dependency instanceof LinearLayoutCompat && dependency.getId() == R.id.bottom_sheet) {
            if (rightActions != null) {
                GaoDeBottomSheetBehavior behavior = GaoDeBottomSheetBehavior.from(dependency);
                int middleHeight = behavior.getParentHeight() - behavior.getMiddleHeight() - rightActions.getMeasuredHeight();
                CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) rightActions.getLayoutParams();
                int newY = dependency.getTop() - rightActions.getHeight() - layoutParams.bottomMargin;
                if (newY >= middleHeight) {
                    rightActions.setTranslationY(newY - layoutParams.bottomMargin);
                } else {
                    rightActions.setTranslationY(middleHeight);
                }
                int offset = behavior.getParentHeight() - behavior.getMiddleHeight() - layoutParams.bottomMargin - dependency.getTop();
                float alpha = 1f - offset * 1.0f / rightActions.getHeight();

                rightActions.setAlpha(alpha);
                if (topActions != null) {
                    topActions.setAlpha(alpha);
                }
            }
        }
        return super.onDependentViewChanged(parent, child, dependency);
    }

}

github:https://github.com/yixiaolunhui/FGaoDeIndexDemo
好了,话不多说,一笑轮回~~~~~

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