recyclerview 弹性滑动 + 中间元素放大

最新推荐文章于 2023-09-07 13:54:51 发布

转载最新推荐文章于 2023-09-07 13:54:51 发布 · 1.3k 阅读

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CC 4.0 BY-SA版权

原文链接：https://juejin.im/post/5c8754f5f265da2de52dc6dc

文章标签：

#移动开发 #ui

本文介绍了一种自定义RecyclerView的实现方式，通过继承RecyclerView并覆盖其onScrollStateChanged和onScrolled方法，实现了特殊的滚动效果。文章详细展示了如何通过计算当前可见视图的位置和高度来平滑滚动，并调整视图的缩放比例。

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import android.animation.ValueAnimator;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;

/**
 * Created by Bruce .
 */

public class TempRecyclerView extends RecyclerView {
    public TempRecyclerView(@NonNull Context context) {
        this(context,null);
    }

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

    private void init() {

    }
    LinearLayoutManager linearLayoutManager;
    @Override
    public void setLayoutManager(LayoutManager layout) {
        super.setLayoutManager(layout);
        linearLayoutManager = (LinearLayoutManager) layout;
    }

    int viewHeight = 0;
    @Override
    public void onScrollStateChanged(int state) {
        Log.d("bruce","state:"+state);
        super.onScrollStateChanged(state);
        if(state == 0){
            int postion = linearLayoutManager.findFirstVisibleItemPosition();
            View view = linearLayoutManager.findViewByPosition(postion);
            int top = view.getTop();
            int offset = 0;
            if(viewHeight == 0){
                viewHeight = view.getHeight();
            }
            if(top == 0){
                return;
            }
            else if(-top < viewHeight/2){
                offset = top;
            }
            else {
                offset = viewHeight+top;
            }
            smoothScrollBy(0, offset);
        }
    }

    int offsetY = 0;


    @Override
    public void onScrolled(int dx, int dy) {
        super.onScrolled(dx, dy);
        offsetY+=dy;

        int first = linearLayoutManager.findFirstCompletelyVisibleItemPosition();
        int last = linearLayoutManager.findLastCompletelyVisibleItemPosition();
        View firstview = linearLayoutManager.findViewByPosition(first);
        if(viewHeight == 0){
            viewHeight = firstview.getHeight();
        }
            int offseta = firstview.getTop();
        float sx = 1f+(float) offseta/viewHeight;
        if(offsetY == 0){
            View view = linearLayoutManager.findViewByPosition(first+1);
            view.setScaleX(2);
        }

        firstview.setScaleX(sx);
        View lastview = linearLayoutManager.findViewByPosition(last);
        offseta = getHeight()-lastview.getBottom();
        sx = 1f+(float) offseta/viewHeight;
        lastview.setScaleX(sx);
    }


}
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