两种图片下拉放大效果实现（自定义CoordinatorLayout以及自定义Recylerview）

一、自定义CoordinatorLayout实现图片放大功能

本文是基于折叠布局实现的图片上拉滑动，下拉图片放大，松手放大的效果，先看下效果图。

实现原理：

1.使用CoordinatorLayout自带效果实现上滑。

2.重写CoordinatorLayout触摸事件，在分发之前判断当前是否是在最顶部，并且是下拉操作。

是：进行图片放大，平移下面布局；松手后执行图片回弹动画，恢复布局。

否：不处理事件，滑动事件自动交给下面的Nestscrollview

代码实现如下：

public class CustomCoordinatorLayout extends CoordinatorLayout {
    private View mZoomView;
    private int mZoomViewWidth;
    private int mZoomViewHeight;

    private float firstPosition;//记录第一次按下的位置
    private boolean isScrolling;//是否正在缩放
    private boolean isScrollDown;//是否下滑

    private float mScrollRate = 0.6f;//缩放系数，缩放系数越大，变化的越大
    private float mReplyRate = 0.3f;//回调系数，越大，回调越慢
    private View mMoveView;
    private View mMoveView2;
    private int height,height2;

    public CustomCoordinatorLayout(@NonNull Context context) {
        super(context);
    }

    public CustomCoordinatorLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public CustomCoordinatorLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public void setmZoomView(View mZoomView) {
        this.mZoomView = mZoomView;
    }

    public void setmMoveView(View mMoveView1,View mMoveView2) {
        this.mMoveView = mMoveView1;
        this.mMoveView2 = mMoveView2;
        height = mMoveView.getMeasuredHeight();
        height2 = mMoveView2.getMeasuredHeight();
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        int[] location = new int[2];
        mZoomView.getLocationOnScreen(location);
        int y = location[1];

        if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) {
            mZoomViewWidth = mZoomView.getMeasuredWidth();
            mZoomViewHeight = mZoomView.getMeasuredHeight();
        }

        switch (ev.getAction()) {
            case MotionEvent.ACTION_UP:
                if(isScrollDown) break;
                //手指离开后恢复图片
                isScrolling = false;
                replyImage();
                break;
            case MotionEvent.ACTION_MOVE:
                if(y != 0) return super.dispatchTouchEvent(ev);
                isScrollDown = false;
                if (!isScrolling) {
                    if (getScrollY() == 0) {
                        firstPosition = ev.getY();// 滚动到顶部时记录位置，否则正常返回
                    } else {
                        break;
                    }
                }
                int distance = (int) ((ev.getY() - firstPosition) * mScrollRate); // 滚动距离乘以一个系数
                if (distance < 0) { // 当前位置比记录位置要小，正常返回
                    isScrollDown = true;
                    break;
                }
                // 处理放大
                isScrolling = true;
                setZoom(distance);

                return super.dispatchTouchEvent(ev);
        }
        return super.dispatchTouchEvent(ev);

    }

    private void scrollDown(float zoom) {
        mMoveView2.setScrollY(-(int)(height2 * ((height2 + zoom) / height2)));
    }

    //回弹动画
    private void replyImage() {
        float distance = mZoomView.getMeasuredWidth() - mZoomViewWidth;
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(distance, 0f).setDuration((long) (distance * mReplyRate));
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                setZoom((Float) animation.getAnimatedValue());
            }

        });
        valueAnimator.start();
        mMoveView.setScrollY(height);
        mMoveView2.setScrollY(height2);
    }

    public void setZoom(float zoom) {
        if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) {
            return;
        }
        ViewGroup.LayoutParams lp = mZoomView.getLayoutParams();
        lp.width = (int) (mZoomViewWidth * ((mZoomViewWidth + zoom) / mZoomViewWidth));
        lp.height = (int) (mZoomViewHeight * ((mZoomViewWidth + zoom) / mZoomViewWidth));
        ((MarginLayoutParams) lp).setMargins(-(lp.width - mZoomViewWidth) / 2, 0, 0, 0);
        mZoomView.setLayoutParams(lp);
        try {
            CollapsingToolbarLayout parent = (CollapsingToolbarLayout) (mMoveView.getParent());
            ViewGroup.LayoutParams layoutParams = parent.getLayoutParams();
            layoutParams.height = lp.height;
            parent.setLayoutParams(layoutParams);
        }catch (Exception e){

        }

    }
}

布局文件结构：

<?xml version="1.0" encoding="utf-8"?>
<com.ingtube.common.widget.CustomCoordinatorLayout 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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:id="@+id/cl_layout">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar_layout"
        android:layout_width="match_parent"
        android:layout_height = "wrap_content"
        >
        <com.google.android.material.appbar.CollapsingToolbarLayout
            android:id="@+id/csl_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fitsSystemWindows="true"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">
　　　　　　//要放大的图片
            <com.facebook.drawee.view.SimpleDraweeView
                android:id="@+id/mine_iv_avatar"
                android:layout_width="match_parent"
                android:layout_height="230dp"
                android:alpha="0.4"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"
                />

　　　　　　//平移布局一
            <RelativeLayout
                android:id="@+id/rl_layout"
                android:layout_width="match_parent"
                android:layout_height="230dp"
                android:layout_gravity="bottom"
                app:layout_collapseMode="parallax"
                app:layout_collapseParallaxMultiplier="0"
                >

                <LinearLayout
                    android:id="@+id/mine_ll_name"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="24dp"
                    android:layout_marginTop="50dp"
                    android:gravity="center_vertical">

                    <TextView
                        android:id="@+id/mine_tv_name"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:maxLines="1"
                        android:textColor="@color/yt_color_white"
                        android:textSize="@dimen/yt_text_name"
                        android:textStyle="normal"
                        tools:text="节操君" />

                    <ImageView
                        android:id="@+id/iv_ensure_icon"
                        android:layout_width="20dp"
                        android:layout_height="20dp"
                        android:layout_marginStart="14dp"
                        android:src="@drawable/ic_ensure_icon" />
                </LinearLayout>

                <TextView
                    android:id="@+id/mine_tv_info"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/mine_ll_name"
                    android:layout_alignStart="@id/mine_ll_name"
                    android:layout_marginTop="6dp"
                    android:alpha="0.6"
                    android:background="@drawable/shape_bg_gray_round_stroke"
                    android:paddingLeft="6dp"
                    android:paddingTop="2dp"
                    android:paddingEnd="6dp"
                    android:paddingBottom="2dp"
                    android:text="我的主页"
                    android:textColor="@color/yt_color_white"
                    android:textSize="@dimen/yt_text_t1" />

                <View
                    android:id="@+id/v_personal_info_dot"
                    android:layout_width="8dp"
                    android:layout_height="8dp"
                    android:layout_alignTop="@+id/mine_tv_info"
                    android:layout_alignEnd="@+id/mine_tv_info"
                    android:background="@drawable/shape_red_dot" />

                <TextView
                    android:id="@+id/tv_mine_user_setting"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_alignBottom="@id/mine_tv_info"
                    android:layout_marginStart="8dp"
                    android:layout_toEndOf="@+id/mine_tv_info"
                    android:alpha="0.6"
                    android:background="@drawable/shape_bg_gray_round_stroke"
                    android:paddingStart="6dp"
                    android:paddingTop="2dp"
                    android:paddingEnd="6dp"
                    android:paddingBottom="2dp"
                    android:text="编辑主页"
                    android:textColor="@color/yt_color_white"
                    android:textSize="@dimen/yt_text_t1" />

    　　　　//代码省略
        　　...
            </RelativeLayout>
        </com.google.android.material.appbar.CollapsingToolbarLayout>

    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:id="@+id/nestedScrollView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true"
        app:layout_behavior="@string/appbar_scrolling_view_behavior”>

　　　　//平移布局二
        <LinearLayout
            android:id="@+id/ll_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            >
    　　　　//代码省略
            ...

        </LinearLayout>
    </androidx.core.widget.NestedScrollView>

</com.ingtube.common.widget.CustomCoordinatorLayout>

使用就非常简单了，在代码中设置要放大的view以及需要平移的view就可以了。

 private fun zoomImage() {
        cl_layout.setmMoveView(rl_layout,ll_layout)
        cl_layout.setmZoomView(mine_iv_avatar)
    }

以上只是个例子用于实现特定布局的动画效果，实际应用可根据场景来自定义view进行操作。

二、自定义recylerView实现图片放大效果

实现效果如下：

实现原理：

重写recylerview的onTouchEvent方法，在顶部往下滑的时候，进行第一个item图片放大及布局下移操作。

好处：多布局中自带滑动，不用处理其他item的滑动，流畅程度100%

代码实现如下：

public class ZoomRecyclerView extends RecyclerView {

    private View mZoomView;
    private int mZoomViewWidth;
    private int mZoomViewHeight;
    private int mViewParentHeight;
    private float mScrollRate = 0.3f;//缩放系数，缩放系数越大，变化的越大
    private float mReplyRate = 0.3f;//回调系数，越大，回调越慢
    // 记录首次按下位置
    private float mFirstPosition = 0;
    // 是否正在放大
    private Boolean mScaling = false;
    LinearLayoutManager mLinearLayoutManager ;

    public ZoomRecyclerView( Context context) {
        super(context);
    }

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

    public ZoomRecyclerView( Context context,  AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public void setZoomView(SimpleDraweeView v, LinearLayoutManager linearLayoutManager) {
        this.mZoomView = v;
        mLinearLayoutManager = linearLayoutManager ;

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if(mZoomView !=null){
            if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) {
                mZoomViewWidth = mZoomView.getMeasuredWidth();
                mZoomViewHeight = mZoomView.getMeasuredHeight();
            }
            if(mViewParentHeight <= 0) {
                try {
                    RelativeLayout parent = (RelativeLayout) mZoomView.getParent();
                    ViewGroup.LayoutParams layoutParams = parent.getLayoutParams();
                    mViewParentHeight = layoutParams.height;
                }catch (Exception e){}

            }
            //判断触摸事件
            switch (event.getAction()) {
                //触摸结束
                case MotionEvent.ACTION_UP:
                    mScaling = false;
                    replyImage();
                    break;
                //触摸中
                case MotionEvent.ACTION_MOVE:
                    //判断是否正在放大 mScaling 的默认值为false
                    if (!mScaling) {
                        //当图片也就是第一个item完全可见的时候，记录触摸屏幕的位置
                        if (mLinearLayoutManager.findViewByPosition(mLinearLayoutManager.findFirstVisibleItemPosition()).getTop() == 0) {
                            //记录首次按下位置
                            mFirstPosition = event.getY();
                        } else {
                            break;
                        }
                    }
                    // 滚动距离乘以一个系数
                    int distance = (int) ((event.getY() - mFirstPosition) * mScrollRate);
                    if (distance < 0) {
                        break;
                    }
                    // 处理放大
                    mScaling = true;
                    setZoom(distance);
                default:
                    break;
            }
        }

        return super.onTouchEvent(event);
    }

    private void setZoom(float distance) {
        if (mZoomViewWidth <= 0 || mZoomViewHeight <= 0) {
            return;
        }
        ViewGroup.LayoutParams lp = mZoomView.getLayoutParams();

        lp.width = (int) (mZoomViewWidth * ((mZoomViewWidth + distance) / mZoomViewWidth));
        lp.height = (int) (mZoomViewHeight * ((mZoomViewWidth + distance) / mZoomViewWidth));
        mZoomView.setLayoutParams(lp);
        try {
            RelativeLayout parent = (RelativeLayout)mZoomView.getParent();
            ViewGroup.LayoutParams layoutParams = parent.getLayoutParams();
            layoutParams.height = (int) (mViewParentHeight * ((mZoomViewWidth + distance) / mZoomViewWidth));
            parent.setLayoutParams(layoutParams);
        }catch (Exception e){

        }
    }

    /**
     * 图片回弹动画
     */
    private void replyImage() {
        float distance = mZoomView.getMeasuredWidth() - mZoomViewWidth;
        ValueAnimator valueAnimator = ValueAnimator.ofFloat(distance, 0f).setDuration((long) (distance * mReplyRate));
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                setZoom((Float) animation.getAnimatedValue());
            }

        });
        valueAnimator.start();

    }

布局很简单：

<?xml version="1.0" encoding="utf-8"?>
<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"
    android:orientation="vertical">

    <com.ingtube.common.widget.ZoomRecyclerView
        android:id="@+id/rv_personal_info"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</RelativeLayout>

使用也非常简单了。

实现recylerview的滑动监听，在布局为0的时候，设置图片放大及布局下移操作。

 rv_personal_info.addOnScrollListener(object : RecyclerView.OnScrollListener() {
            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
                this@PersonalInfoActivity.scrollY = recyclerView.computeVerticalScrollOffset()

                    if (scrollY == 0 && pageItems.size != 0) {
                       rv_personal_info.setZoomView(personalPageHeadViewBinder!!.getZoomView(), rv_personal_info.layoutManager as? LinearLayoutManager)
                    }
                }catch (e:Exception){
                    e.printStackTrace()
                }
            }
        })