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1.需要实现的效果图如下:
实现方式主要有两种:
1)、ScrollView内嵌软件介绍+ViewPager+ViewPager中是ScrollView,这种方式呢,纯原生,没有涉及到自定义控件,但是这样嵌套呢,涉及到测量以及事件的冲突处理。
2)、将做外层的ScrollView改为了自定义的一个控件,继承自LinearLayout,叫做StickyNavLayout,利用NestedScrolling特性:子view和父view共同消费滑动来实现。
详细代码如下:
import android.animation.ValueAnimator;
import android.content.Context;
import android.support.v4.view.NestedScrollingParent;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.animation.Interpolator;
import android.widget.LinearLayout;
import android.widget.OverScroller;public class StickyNavLayout extends LinearLayout implements NestedScrollingParent
{private static final String TAG = "StickyNavLayout";/*首先子View需要找到一个支持NestedScrollingParent的父View,
告知父View我准备开始和你一起处理滑动事件了,
一般情况下都是在onTouchEvent的ACTION_DOWN中调用public boolean startNestedScroll(int axes),
然后父View就会被回调public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes)
和public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes)onStartNestedScroll可以理解是父View的一个验证机制,
父View可以在此方法中根据滑动方向等信息决定是否要和子View一起处理此次滑动,
只有在onStartNestedScroll返回true的时候才会接着调用onNestedScrollAccepted*/@Overridepublic boolean onStartNestedScroll(View child, View target, int nestedScrollAxes){Log.e(TAG, "onStartNestedScroll");return true;}
/*父View接受了子View的邀请,可以在此方法中做一些初始化的操作*/@Overridepublic void onNestedScrollAccepted(View child, View target, int nestedScrollAxes){Log.e(TAG, "onNestedScrollAccepted");}
/*
* 随着ACTION_UP或者ACTION_CANCEL的到来,子View需要调用public void stopNestedScroll()
* 来告知父View本次NestedScrollig结束,父View对应的会被回调public void onStopNestedScroll(View target),
* 可以在此方法中做一些对应停止的逻辑操作比如资源释放等
* */@Overridepublic void onStopNestedScroll(View target){Log.e(TAG, "onStopNestedScroll");}
/*
* 父View处理完后,接下来子View就要进自己的滑动操作了,滑动完成后子View还需要调用public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow)
* 将自己的滑动结果再次传递给父View,父View对应的会被回调public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed),但这步操作有一个前提,
* 就是父View没有将滑动值全部消耗掉,因为父View全部消耗掉,子View就不应该再进行滑动了,这一步也就没有必要了
*
* */@Overridepublic void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed){Log.e(TAG, "onNestedScroll");}
/*
* 每次子View在滑动前都需要将滑动细节传递给父View,
* 一般情况下是在ACTION_MOVE中调用public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow),
* 然后父View就会被回调public void onNestedPreScroll(View target, int dx, int dy, int[] consumed)
* dx dy代表本次滑动 x y方向的距离,consumed需要子View创建并传递给父View,
* 如果父View选择要消耗掉滑动的值就需要通过此数组传递给子View,consumed[0]:x轴消费的距离;consumed[1]:y轴消费的距离
* */@Overridepublic void onNestedPreScroll(View target, int dx, int dy, int[] consumed){Log.e(TAG, "onNestedPreScroll");Log.e(TAG, "onNestedPreScroll scrollY=" + getScrollY());Log.e(TAG, "onNestedPreScroll dy=" + dy);boolean hiddenTop = dy > 0 && getScrollY() < mTopViewHeight;boolean showTop = dy < 0 && getScrollY() >= 0 && !ViewCompat.canScrollVertically(target, -1);if (hiddenTop || showTop){scrollBy(0, dy);consumed[1] = dy;}}private int TOP_CHILD_FLING_THRESHOLD = 3;/** 如果产生了fling,就需要子View在stopNestedScroll前调用public boolean dispatchNestedPreFling(View target, float velocityX, float velocityY)* 和public boolean dispatchNestedFling(View target, float velocityX, float velocityY, boolean consumed),* 父View对应的会被回调public boolean onNestedPreFling(View target, float velocityX, float velocityY)* 和public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed)*参数consumed代表子View是否消耗掉了fling,fling不存在部分消耗,一旦被消耗就是指全部*返回值代表父View是否消耗掉了fling* */@Overridepublic boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed){Log.e(TAG, "onNestedFling, velocityX=" + velocityX + ",velocityY=" + velocityY);//如果是recyclerView 根据判断第一个元素是哪个位置可以判断是否消耗//这里判断如果第一个元素的位置是大于TOP_CHILD_FLING_THRESHOLD的//认为已经被消耗,在animateScroll里不会对velocityY<0时做处理if (target instanceof RecyclerView && velocityY < 0) {final RecyclerView recyclerView = (RecyclerView) target;final View firstChild = recyclerView.getChildAt(0);final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);Log.d(TAG,"onNestedFling childAdapterPosition" + childAdapterPosition);consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;}if (!consumed) {animateScroll(velocityY, computeDuration(0),consumed);} else {animateScroll(velocityY, computeDuration(velocityY),consumed);}return true;}@Overridepublic boolean onNestedPreFling(View target, float velocityX, float velocityY){//不做拦截 可以传递给子Viewreturn false;}@Overridepublic int getNestedScrollAxes(){Log.e(TAG, "getNestedScrollAxes");return 0;}/*** 根据速度计算滚动动画持续时间* @param velocityY* @return*/private int computeDuration(float velocityY) {final int distance;if (velocityY > 0) {distance = Math.abs(mTop.getHeight() - getScrollY());} else {distance = Math.abs(mTop.getHeight() - (mTop.getHeight() - getScrollY()));}final int duration;velocityY = Math.abs(velocityY);if (velocityY > 0) {duration = 3 * Math.round(1000 * (distance / velocityY));} else {final float distanceRatio = (float) distance / getHeight();duration = (int) ((distanceRatio + 1) * 150);}return duration;}private void animateScroll(float velocityY, final int duration,boolean consumed) {final int currentOffset = getScrollY();final int topHeight = mTop.getHeight();if (mOffsetAnimator == null) {mOffsetAnimator = new ValueAnimator();mOffsetAnimator.setInterpolator(mInterpolator);mOffsetAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {@Overridepublic void onAnimationUpdate(ValueAnimator animation) {if (animation.getAnimatedValue() instanceof Integer) {scrollTo(0, (Integer) animation.getAnimatedValue());}}});} else {mOffsetAnimator.cancel();}mOffsetAnimator.setDuration(Math.min(duration, 600));if (velocityY >= 0) {mOffsetAnimator.setIntValues(currentOffset, topHeight);mOffsetAnimator.start();}else {//如果子View没有消耗down事件 那么就让自身滑倒0位置if(!consumed){mOffsetAnimator.setIntValues(currentOffset, 0);mOffsetAnimator.start();}}}private View mTop;private View mNav;private ViewPager mViewPager;private int mTopViewHeight;private OverScroller mScroller;private VelocityTracker mVelocityTracker;private ValueAnimator mOffsetAnimator;private Interpolator mInterpolator;private int mTouchSlop;private int mMaximumVelocity, mMinimumVelocity;private float mLastY;private boolean mDragging;public StickyNavLayout(Context context, AttributeSet attrs){super(context, attrs);setOrientation(LinearLayout.VERTICAL);mScroller = new OverScroller(context);mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();mMaximumVelocity = ViewConfiguration.get(context).getScaledMaximumFlingVelocity();mMinimumVelocity = ViewConfiguration.get(context).getScaledMinimumFlingVelocity();}private void initVelocityTrackerIfNotExists(){if (mVelocityTracker == null){mVelocityTracker = VelocityTracker.obtain();}}private void recycleVelocityTracker(){if (mVelocityTracker != null){mVelocityTracker.recycle();mVelocityTracker = null;}}// @Override
// public boolean onTouchEvent(MotionEvent event)
// {
// initVelocityTrackerIfNotExists();
// mVelocityTracker.addMovement(event);
// int action = event.getAction();
// float y = event.getY();
//
// switch (action)
// {
// case MotionEvent.ACTION_DOWN:
// if (!mScroller.isFinished())
// mScroller.abortAnimation();
// mLastY = y;
// return true;
// case MotionEvent.ACTION_MOVE:
// float dy = y - mLastY;
//
// if (!mDragging && Math.abs(dy) > mTouchSlop)
// {
// mDragging = true;
// }
// if (mDragging)
// {
// scrollBy(0, (int) -dy);
// }
//
// mLastY = y;
// break;
// case MotionEvent.ACTION_CANCEL:
// mDragging = false;
// recycleVelocityTracker();
// if (!mScroller.isFinished())
// {
// mScroller.abortAnimation();
// }
// break;
// case MotionEvent.ACTION_UP:
// mDragging = false;
// mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
// int velocityY = (int) mVelocityTracker.getYVelocity();
// if (Math.abs(velocityY) > mMinimumVelocity)
// {
// fling(-velocityY);
// }
// recycleVelocityTracker();
// break;
// }
//
// return super.onTouchEvent(event);
// }@Overrideprotected void onFinishInflate(){super.onFinishInflate();mTop = findViewById(R.id.id_stickynavlayout_topview);mNav = findViewById(R.id.id_stickynavlayout_indicator);View view = findViewById(R.id.id_stickynavlayout_viewpager);if (!(view instanceof ViewPager)){throw new RuntimeException("id_stickynavlayout_viewpager show used by ViewPager !");}mViewPager = (ViewPager) view;}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){//不限制顶部的高度super.onMeasure(widthMeasureSpec, heightMeasureSpec);getChildAt(0).measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));ViewGroup.LayoutParams params = mViewPager.getLayoutParams();params.height = getMeasuredHeight() - mNav.getMeasuredHeight();setMeasuredDimension(getMeasuredWidth(), mTop.getMeasuredHeight() + mNav.getMeasuredHeight() + mViewPager.getMeasuredHeight());}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh){super.onSizeChanged(w, h, oldw, oldh);mTopViewHeight = mTop.getMeasuredHeight();}public void fling(int velocityY){mScroller.fling(0, getScrollY(), 0, velocityY, 0, 0, 0, mTopViewHeight);invalidate();}@Overridepublic void scrollTo(int x, int y){if (y < 0){y = 0;}if (y > mTopViewHeight){y = mTopViewHeight;}if (y != getScrollY()){super.scrollTo(x, y);}}@Overridepublic void computeScroll(){Log.d(TAG,"computeScroll getCurrY():" + mScroller.getCurrY());if (mScroller.computeScrollOffset()){scrollTo(0, mScroller.getCurrY());invalidate();}}}
主要原理就是,子View和父view一起处理一个滑动事件。在public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) 中获取父view在x,y轴上要滑动的距离,并调用scrollBy(0, dy); 不断进行滑动。
对Fling的滑动,则在public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed)中获取到y轴的滑动速度,并利用ValueAnimator .addUpdateListener 获取不断变化的y轴值,调用scrollTo来进行滑动操作。
2.使用
详情页布局如下:
<com.zhy.view.StickyNavLayout xmlns:tools="http://schemas.android.com/tools" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <RelativeLayout android:id="@id/id_stickynavlayout_topview" android:layout_width="match_parent" android:layout_height="300dp" android:background="#4400ff00" > <TextView android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:text="软件介绍" android:textSize="30sp" android:textStyle="bold" /> </RelativeLayout> <com.zhy.view.SimpleViewPagerIndicator android:id="@id/id_stickynavlayout_indicator" android:layout_width="match_parent" android:layout_height="50dp" android:background="#ffffffff" > </com.zhy.view.SimpleViewPagerIndicator> <android.support.v4.view.ViewPager android:id="@id/id_stickynavlayout_viewpager" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="#44ff0000" > </android.support.v4.view.ViewPager> </com.zhy.view.StickyNavLayout>
最外层是父view StickyNavLayout 再往下,依次是header, viewpageIndicator, 和viewpager
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