Android 仿淘宝、京东商品详情页向上拖动查看图文详情控件DEMO详解
一、淘宝商品详情页效果
我们的效果
二、实现思路
使用两个scrollView,两个scrollView 竖直排列,通过自定义viewGroup来控制两个scrollView的竖直排列,以及滑动事件的处理。如下图
三、具体实现
1、继承viewGroup自定义布局View 重写onMeasure()和onLayout方法,在onLayout方法中完成对两个子ScrollView的竖直排列布局,代码如下:
布局文件:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.baoyunlong.view.pulluptoloadmore.MainActivity"> <com.baoyunlong.view.pulluptoloadmore.PullUpToLoadMore android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <com.baoyunlong.view.pulluptoloadmore.MyScrollView android:layout_width="match_parent" android:layout_height="match_parent" android:fillViewport="true"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <ImageView android:scaleType="fitXY" android:src="@drawable/a1" android:layout_width="match_parent" android:layout_height="180dp" /> <TextView android:text="这里是标题" android:textSize="18dp" android:layout_marginRight="10dp" android:layout_marginLeft="10dp" android:layout_marginTop="10dp" android:layout_width="match_parent" android:layout_height="wrap_content" /> <TextView android:layout_marginTop="10dp" android:text="子标题" android:layout_marginLeft="10dp" android:layout_marginRight="10dp" android:textSize="18dp" android:layout_width="match_parent" android:layout_height="wrap_content" /> .............. <LinearLayout android:layout_height="0dp" android:layout_weight="1" android:gravity="bottom" android:layout_width="match_parent"> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:height="50dp" android:background="#b11" android:gravity="center" android:text="继续拖动查看图文详情" android:textColor="#000" /> </LinearLayout> </LinearLayout> </com.baoyunlong.view.pulluptoloadmore.MyScrollView> <com.baoyunlong.view.pulluptoloadmore.MyScrollView android:layout_width="match_parent" android:layout_height="match_parent" android:fillViewport="true"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:orientation="vertical"> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/a1" /> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/a3" /> ......... </LinearLayout> </com.baoyunlong.view.pulluptoloadmore.MyScrollView> </com.baoyunlong.view.pulluptoloadmore.PullUpToLoadMore> </RelativeLayout>
代码:
public class PullUpToLoadMore extends ViewGroup { public PullUpToLoadMore(Context context) { super(context); } public PullUpToLoadMore(Context context, AttributeSet attrs) { super(context, attrs); } public PullUpToLoadMore(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); measureChildren(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int childCount = getChildCount(); int childTop = t; for (int i = 0; i < childCount; i++) { View child = getChildAt(i); child.layout(l, childTop, r, childTop + child.getMeasuredHeight()); childTop += child.getMeasuredHeight(); } } }
2、处理滑动事件
规则如下 :
(1)、当处于第一屏时 第一个ScrollView已经滑动到底部并且滑动方向是往上滑动,这个时候滑动事件应该交给父view处理也就是拦截事件让onInterceptTouchEvent返回true.然后父view通过scrollBy()方法滚动,显示出第二个scrollView。
(2)、当处于第二屏时 第二个ScrollView已经滑动到顶部并且滑动方向是往下滑动,这个时候滑动事件交给父view处理,根据滑动事件显示出第一个ScrollView。
(3)、当手指离开屏幕时,根据滑动速度来决定是回弹到第一个ScrollView还是第二个ScrollView,通过VelocityTracker来获取滑动速度。
3、一些细节的处理
(1)、如果仔细看观察淘宝的实现效果你会发现,当你滑动到刚刚看到 “继续拖动,查看图文详情”的时候,手指抬起,然后再按下重新向上拖动你会发现,第二页并不会划出来,而是停留在了“继续拖动,查看图文详情”的底部,京东的效果也是一样。这样用户体验不太好,我们来优化一下。其实通过查看ScrollView的源码可以看出来,这是因为ScrollView类的onTouchEvent方法的默认实现,调用了parent.requestDisallowInterceptTouchEvent(true)方法 阻止了我们拦截事件,导致我们父view的onInterceptTouchEvent方法无法执行,也就拦截不到事件,拦截不到事件我们的onTouchEvent就无法执行,onTouchEvent无法执行,我们写在onTouchEvent里面的滚动逻辑就执行不到了,导致了上面我们看到的划不动的效果。解决方法就是,我们需要重写dispatchTouchEvent()方法,防止子view干扰我们,这样我们滑动的时候就可以一气呵成了。代码如下:
@Override public boolean dispatchTouchEvent(MotionEvent ev) { //防止子View禁止父view拦截事件 this.requestDisallowInterceptTouchEvent(false); return super.dispatchTouchEvent(ev); }
(2)、监听ScrollView滑动事件的问题
ScrollView没有提供滚动事件的监听方法,也就没法判断是否滚动到了顶部,或者底部,这里我们继承ScrollView 自己实现滚动事件监听。
/** * Created by baoyunlong on 16/6/8. */ public class MyScrollView extends ScrollView { private static String TAG=MyScrollView.class.getName(); public void setScrollListener(ScrollListener scrollListener) { this.mScrollListener = scrollListener; } private ScrollListener mScrollListener; public MyScrollView(Context context) { super(context); } public MyScrollView(Context context, AttributeSet attrs) { super(context, attrs); } public MyScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override public boolean onTouchEvent(MotionEvent ev) { switch (ev.getAction()){ case MotionEvent.ACTION_MOVE: if(mScrollListener!=null){ int contentHeight=getChildAt(0).getHeight(); int scrollHeight=getHeight(); int scrollY=getScrollY(); mScrollListener.onScroll(scrollY); if(scrollY+scrollHeight>=contentHeight||contentHeight<=scrollHeight){ mScrollListener.onScrollToBottom(); }else { mScrollListener.notBottom(); } if(scrollY==0){ mScrollListener.onScrollToTop(); } } break; } boolean result=super.onTouchEvent(ev); requestDisallowInterceptTouchEvent(false); return result; } public interface ScrollListener{ void onScrollToBottom(); void onScrollToTop(); void onScroll(int scrollY); void notBottom(); }
4、完整代码如下
/** * Created by baoyunlong on 16/6/8. */ public class PullUpToLoadMore extends ViewGroup { public static String TAG = PullUpToLoadMore.class.getName(); MyScrollView topScrollView, bottomScrollView; VelocityTracker velocityTracker = VelocityTracker.obtain(); Scroller scroller = new Scroller(getContext()); int currPosition = 0; int position1Y; int lastY; public int scaledTouchSlop;//最小滑动距离 int speed = 200; boolean isIntercept; public boolean bottomScrollVIewIsInTop = false; public boolean topScrollViewIsBottom = false; public PullUpToLoadMore(Context context) { super(context); init(); } public PullUpToLoadMore(Context context, AttributeSet attrs) { super(context, attrs); init(); } public PullUpToLoadMore(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(); } private void init() { post(new Runnable() { @Override public void run() { topScrollView = (MyScrollView) getChildAt(0); bottomScrollView = (MyScrollView) getChildAt(1); topScrollView.setScrollListener(new MyScrollView.ScrollListener() { @Override public void onScrollToBottom() { topScrollViewIsBottom = true; } @Override public void onScrollToTop() { } @Override public void onScroll(int scrollY) { } @Override public void notBottom() { topScrollViewIsBottom = false; } }); bottomScrollView.setScrollListener(new MyScrollView.ScrollListener() { @Override public void onScrollToBottom() { } @Override public void onScrollToTop() { } @Override public void onScroll(int scrollY) { if (scrollY == 0) { bottomScrollVIewIsInTop = true; } else { bottomScrollVIewIsInTop = false; } } @Override public void notBottom() { } }); position1Y = topScrollView.getBottom(); scaledTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); } }); } @Override public boolean dispatchTouchEvent(MotionEvent ev) { //防止子View禁止父view拦截事件 this.requestDisallowInterceptTouchEvent(false); return super.dispatchTouchEvent(ev); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { int y = (int) ev.getY(); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: lastY = y; break; case MotionEvent.ACTION_MOVE: //判断是否已经滚动到了底部 if (topScrollViewIsBottom) { int dy = lastY - y; //判断是否是向上滑动和是否在第一屏 if (dy > 0 && currPosition == 0) { if (dy >= scaledTouchSlop) { isIntercept = true;//拦截事件 lastY=y; } } } if (bottomScrollVIewIsInTop) { int dy = lastY - y; //判断是否是向下滑动和是否在第二屏 if (dy < 0 && currPosition == 1) { if (Math.abs(dy) >= scaledTouchSlop) { isIntercept = true; } } } break; } return isIntercept; } @Override public boolean onTouchEvent(MotionEvent event) { int y = (int) event.getY(); velocityTracker.addMovement(event); switch (event.getAction()) { case MotionEvent.ACTION_MOVE: int dy = lastY - y; if (getScrollY() + dy < 0) { dy = getScrollY() + dy + Math.abs(getScrollY() + dy); } if (getScrollY() + dy + getHeight() > bottomScrollView.getBottom()) { dy = dy - (getScrollY() + dy - (bottomScrollView.getBottom() - getHeight())); } scrollBy(0, dy); break; case MotionEvent.ACTION_UP: isIntercept = false; velocityTracker.computeCurrentVelocity(1000); float yVelocity = velocityTracker.getYVelocity(); if (currPosition == 0) { if (yVelocity < 0 && yVelocity < -speed) { smoothScroll(position1Y); currPosition = 1; } else { smoothScroll(0); } } else { if (yVelocity > 0 && yVelocity > speed) { smoothScroll(0); currPosition = 0; } else { smoothScroll(position1Y); } } break; } lastY = y; return true; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); measureChildren(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int childCount = getChildCount(); int childTop = t; for (int i = 0; i < childCount; i++) { View child = getChildAt(i); child.layout(l, childTop, r, childTop + child.getMeasuredHeight()); childTop += child.getMeasuredHeight(); } } //通过Scroller实现弹性滑动 private void smoothScroll(int tartY) { int dy = tartY - getScrollY(); scroller.startScroll(getScrollX(), getScrollY(), 0, dy); invalidate(); } @Override public void computeScroll() { if (scroller.computeScrollOffset()) { scrollTo(scroller.getCurrX(), scroller.getCurrY()); postInvalidate(); } } }
源码:
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