自定义ScrollView实现图片下拉放大（弹性效果）+ 悬浮框

曾经终败给现在 2022-06-05 07:09 259阅读 0赞

**效果图：**

![Center][]

MyScrollView

package com.bwie.com.wangruixin1509c20171121;
    
    import android.content.Context;
    import android.graphics.Rect;
    import android.os.Handler;
    import android.util.AttributeSet;
    import android.view.MotionEvent;
    import android.widget.ImageView;
    import android.widget.ScrollView;
    import android.widget.Scroller;
    
    /** * Created by Wangrx on 2017/11/21. */ public class MyScrollView extends ScrollView{
        private OnScrollListener onScrollListener;
        private int lastScrollY;
    
        private static final int LEN = 0xc8;
        private static final int DURATION = 500;
        private static final int MAX_DY = 200;
        private Scroller mScroller;
        TouchTool tool;
        int left, top;
        float startX, startY, currentX, currentY;
        int imageViewH;
        int rootW, rootH;
        ImageView imageView;
        boolean scrollerType;
    
        public MyScrollView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
    
        }
    
        public MyScrollView(Context context, AttributeSet attrs) {
            super(context, attrs);
            mScroller = new Scroller(context);
        }
    
        public MyScrollView(Context context) {
            super(context);
    
        }
    
    
        public void setImageView(ImageView imageView) {
            this.imageView = imageView;
        }
    
        @Override protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {
    
            return 0;
        }
    
        private int[] li = new int[2];
        private int[] li2 = new int[2];
        private float lastLy;
        private boolean startIsTop = true;
    
        @Override public boolean dispatchTouchEvent(MotionEvent event) {
            super.dispatchTouchEvent(event);
            int action = event.getAction();
            if (!mScroller.isFinished()) {
                return super.onTouchEvent(event);
            }
            currentX = event.getX();
            currentY = event.getY();
            imageView.getLocationInWindow(li);
            getLocationOnScreen(li2);
            imageView.getTop();
            switch (action) {
                case MotionEvent.ACTION_DOWN:
                    if (li[1] != li2[1]) {
      // 判断开始触摸时，imageview和窗口顶部对齐没 startIsTop = false;
                    }
                    left = imageView.getLeft();
                    top = imageView.getBottom();
                    rootW = getWidth();
                    rootH = getHeight();
                    imageViewH = imageView.getHeight();
                    startX = currentX;
                    startY = currentY;
                    tool = new TouchTool(imageView.getLeft(), imageView.getBottom(), imageView.getLeft(),
                            imageView.getBottom() + LEN);
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (!startIsTop && li[1] == li2[1]) {
                        startY = currentY;
                        startIsTop = true;
                    }
                    if (imageView.isShown() && imageView.getTop() >= 0) {
                        if (tool != null) {
                            int t = tool.getScrollY(currentY - startY);
                            if (!scrollerType && currentY < lastLy && imageView.getHeight() > imageViewH) {
                                scrollTo(0, 0);
                                imageView.getLocationInWindow(li);
                                getLocationOnScreen(li2);
                                android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
                                params.height = t;
                                imageView.setLayoutParams(params);
                                if (imageView.getHeight() == imageViewH && li[1] == li2[1]) {
                                    scrollerType = true;
                                }
                                if (startIsTop && li[1] != li2[1]) {
                                    startIsTop = false;
                                }
                            }
                            if (t >= top && t <= imageView.getBottom() + LEN && li[1] == li2[1] && currentY > lastLy) {
                                android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
                                params.height = t;
                                imageView.setLayoutParams(params);
                            }
                        }
                        scrollerType = false;
                    }
    
                    lastLy = currentY;
                    break;
                case MotionEvent.ACTION_UP:
                    if (li[1] == li2[1]) {
                        scrollerType = true;
                        mScroller.startScroll(imageView.getLeft(), imageView.getBottom(), 0 - imageView.getLeft(),
                                imageViewH - imageView.getBottom(), DURATION);
                        invalidate();
                    }
                    startIsTop = true;
                    break;
            }
    
            return true;
        }
    
    
    
        @Override public void computeScroll() {
            super.computeScroll();
            if (mScroller.computeScrollOffset()) {
                int x = mScroller.getCurrX();
                int y = mScroller.getCurrY();
                imageView.layout(0, 0, x + imageView.getWidth(), y);
                invalidate();
                if (!mScroller.isFinished() && scrollerType && y > MAX_DY) {
                    android.view.ViewGroup.LayoutParams params = imageView.getLayoutParams();
                    params.height = y;
                    imageView.setLayoutParams(params);
                }
            }
        }
    
        public class TouchTool {
    
            private int startX, startY;
    
            public TouchTool(int startX, int startY, int endX, int endY) {
                super();
                this.startX = startX;
                this.startY = startY;
            }
    
            public int getScrollX(float dx) {
                int xx = (int) (startX + dx / 2.5F);
                return xx;
            }
    
            public int getScrollY(float dy) {
                int yy = (int) (startY + dy / 2.5F);
                return yy;
            }
        }
    
    
        /** * 设置滚动接口 * @param onScrollListener */ public void setOnScrollListener(OnScrollListener onScrollListener){
            this.onScrollListener = onScrollListener;
        }
        /** * 用于用户手指离开MyScrollView的时候获取MyScrollView滚动的Y距离，然后回调给onScroll方法中 */ private Handler handler = new Handler() {
    
            public void handleMessage(android.os.Message msg) {
                int scrollY = MyScrollView.this.getScrollY();
    
                //此时的距离和记录下的距离不相等，在隔5毫秒给handler发送消息 if(lastScrollY != scrollY){
                    lastScrollY = scrollY;
                    handler.sendMessageDelayed(handler.obtainMessage(), 5);
                }
                if(onScrollListener != null){
                    onScrollListener.onScroll(scrollY);
                }
    
            }
    
        };
    
        @Override public boolean onTouchEvent(MotionEvent ev) {
            if(onScrollListener != null){
                onScrollListener.onScroll(lastScrollY = this.getScrollY());
            }
            switch(ev.getAction()){
                case MotionEvent.ACTION_UP:
                    handler.sendMessageDelayed(handler.obtainMessage(), 20);
                    break;
            }
            return super.onTouchEvent(ev);
        }
    
        /** * 滚动的回调接口 */ public interface OnScrollListener{
            /** * 回调方法， 返回MyScrollView滑动的Y方向距离 */ public void onScroll(int scrollY);
        }
    }

MainActivity

package com.bwie.com.wangruixin1509c20171121;
    
    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;
    import android.widget.ListAdapter;
    import android.widget.ListView;
    import android.widget.RelativeLayout;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class MainActivity extends AppCompatActivity {
    
        private ListView listView;
        private ImageView imageView;
    // private RelativeLayout relativeLayout; private RelativeLayout relativeLayout2;
        private MyScrollView dampView;
    
        private List<String> list = new ArrayList<>();
        @Override protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            initView();
    // initData(); //设置可拉伸的头部ImageView dampView.setImageView(imageView);
    
    // //setAdapter // listView.setAdapter(new ArrayAdapter<String>(this, // android.R.layout.simple_list_item_1, list)); //动态设置ListView单条的高度，解决与scollView的滑动冲突 setListViewHeightBasedOnChildren(listView);
    
            dampView.setOnScrollListener(new MyScrollView.OnScrollListener() {
                @Override public void onScroll(int scrollY) {
                    if (scrollY >= imageView.getHeight()){
    // relativeLayout.setVisibility(View.GONE); relativeLayout2.setVisibility(View.VISIBLE);
                    }else {
    // relativeLayout.setVisibility(View.VISIBLE); relativeLayout2.setVisibility(View.GONE);
                    }
                }
            });
        }
    // //假数据 // private void initData() { // for (int i = 0; i < 100; i++) { // list.add(i, i + ""); // } // } //查找控件 private void initView() {
            dampView = (MyScrollView) findViewById(R.id.dampView);
            listView = (ListView) findViewById(R.id.listView);
            imageView = (ImageView) findViewById(R.id.imageView);
    // relativeLayout = (RelativeLayout) findViewById(R.id.relativeLayout); relativeLayout2 = (RelativeLayout) findViewById(R.id.relativeLayout2);
    
        }
    
    
        //动态设置ListView单条的高度，解决与scollView的滑动冲突 public void setListViewHeightBasedOnChildren(ListView listView) {
            // 获取ListView对应的Adapter ListAdapter listAdapter = listView.getAdapter();
            if (listAdapter == null) {
                return;
            }
    
            int totalHeight = 0;
            for (int i = 0, len = listAdapter.getCount(); i < len; i++) {
                // listAdapter.getCount()返回数据项的数目 View listItem = listAdapter.getView(i, null, listView);
                // 计算子项View 的宽高 listItem.measure(0, 0);
                // 统计所有子项的总高度 totalHeight += listItem.getMeasuredHeight();
            }
    
            ViewGroup.LayoutParams params = listView.getLayoutParams();
            params.height = totalHeight+ (listView.getDividerHeight() * (listAdapter.getCount() - 1));
            // listView.getDividerHeight()获取子项间分隔符占用的高度 // params.height最后得到整个ListView完整显示需要的高度 listView.setLayoutParams(params);
        }
    }

activity\_main.xml

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.bwie.com.wangruixin1509c20171121.MainActivity">
    
        <com.bwie.com.wangruixin1509c20171121.MyScrollView android:id="@+id/dampView"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
    
            <LinearLayout android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="vertical">
    
                <ImageView android:id="@+id/imageView"
                    android:layout_width="match_parent"
                    android:layout_height="300dp"
                    android:background="@mipmap/i" />
    
                           <ListView android:id="@+id/listView"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:entries="@array/entry"></ListView>
            </LinearLayout>
        </com.bwie.com.wangruixin1509c20171121.MyScrollView>
    
        <RelativeLayout android:id="@+id/relativeLayout2"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:background="@color/colorAccent"
            android:visibility="gone">
    
            <TextView android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:gravity="center"
                android:text="固定在顶部" />
        </RelativeLayout>
    
    </RelativeLayout>

[Center]: /images/20220605/c9e245febc484c37a1bba9253cfd3984.png