Android 主页下拉放大效果

继承NestedScrollView 实现可滑动的效果， 在onInterceptTouchEvent 中处理了横向滑动，在需要处理的时候直接调用setNeedScroll为flase时即可

package com.sumansoul.onmat.curricula.widget;


import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.ScrollView;

import androidx.core.widget.NestedScrollView;

/**
 *  下拉放大第一个view
 * @author anxinlong
 * @since 2023/5/13 12:56 PM
 */
public class AmplifyFirstScrollView extends NestedScrollView implements View.OnTouchListener {

    // 记录首次按下位置
    private float mFirstPosition = 0;
    // 是否正在放大
    private Boolean mScaling = false;

    private View dropZoomView;
    private int dropZoomViewWidth;
    private int dropZoomViewHeight;

    private boolean isNeedScroll = true;

    private int scaledTouchSlop;
    public AmplifyFirstScrollView(Context context) {
        super(context);
    }

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

    public AmplifyFirstScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        scaledTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        init();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    }

    private void init() {
        setOverScrollMode(OVER_SCROLL_NEVER);
        if (getChildAt(0) != null) {
            ViewGroup vg = (ViewGroup) getChildAt(0);
            if (vg.getChildAt(0) != null) {
                dropZoomView = vg.getChildAt(0);
                setOnTouchListener(this);

            }
        }
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (dropZoomViewWidth <= 0 || dropZoomViewHeight <= 0) {
            dropZoomViewWidth = dropZoomView.getMeasuredWidth();
            dropZoomViewHeight = dropZoomView.getMeasuredHeight();
        }
        switch (event.getAction()) {
            case MotionEvent.ACTION_UP:
                //手指离开后恢复图片
                mScaling = false;
                replyImage();
                break;
            case MotionEvent.ACTION_MOVE:
                if (!mScaling) {
                    if (getScrollY() == 0) {
                        mFirstPosition = event.getY();// 滚动到顶部时记录位置，否则正常返回
                    } else {
                        break;
                    }
                }
                int distance = (int) ((event.getY() - mFirstPosition) * 0.6); // 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
                    break;
                }

                // 处理放大
                mScaling = true;
                setZoom(1 + distance);
                return true; // 返回true表示已经完成触摸事件，不再处理
        }
        return false;
    }
    private float xDistance, yDistance, xLast, yLast;
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.i("TAG", "onInterceptTouchEvent: ");
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                xDistance = yDistance = 0f;
                xLast = ev.getX();
                yLast = ev.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                final float curX = ev.getX();
                final float curY = ev.getY();

                xDistance += Math.abs(curX - xLast);
                yDistance += Math.abs(curY - yLast);
                xLast = curX;
                yLast = curY;
                Log.e("SiberiaDante", "xDistance ：" + xDistance + "---yDistance:" + yDistance);
                return !(xDistance >= yDistance || yDistance < scaledTouchSlop) && isNeedScroll;

        }
        return super.onInterceptTouchEvent(ev);
    }

    // 回弹动画 (使用了属性动画)
    public void replyImage() {
        final float distance = dropZoomView.getMeasuredWidth() - dropZoomViewWidth;

        // 设置动画
        ValueAnimator anim = ObjectAnimator.ofFloat(0.0F, 1.0F).setDuration((long) (distance * 0.7));

        anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float cVal = (Float) animation.getAnimatedValue();
                setZoom(distance - ((distance) * cVal));
            }
        });
        anim.start();

    }

    //缩放
    public void setZoom(float s) {
        if (dropZoomViewHeight <= 0 || dropZoomViewWidth <= 0) {
            return;
        }
        ViewGroup.LayoutParams lp = dropZoomView.getLayoutParams();
        lp.width = (int) (dropZoomViewWidth + s);
        lp.height = (int) (dropZoomViewHeight * ((dropZoomViewWidth + s) / dropZoomViewWidth));
        dropZoomView.setLayoutParams(lp);
    }
    /*
  该方法用来处理NestedScrollView是否拦截滑动事件
   */
    public void setNeedScroll(boolean isNeedScroll) {
        this.isNeedScroll = isNeedScroll;
    }
}