折叠展开动画

这篇目的一是记录下，二是将这个效果发布出来，网上虽然很多但是太模糊了。

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8多说先看效果

record_20190820161240530.gif

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上代码

import android.animation.ValueAnimator;
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;

import androidx.appcompat.widget.AppCompatImageView;

/**
 * Created by TU on 2019/3/14.
 * 具有折叠展开伸缩动画
 */
public class ExpandLayout extends RelativeLayout {

    private View layoutView;
    private int viewHeight;
    private boolean isExpand;
    private long animationDuration;
    private boolean lock;

    public ExpandLayout(Context context) {
        this(context, null);
    }

    public ExpandLayout(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ExpandLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView();
    }

    private void initView() {
        layoutView = this;
        isExpand = true;
        animationDuration = 300;
        setViewDimensions();
    }

    /**
     * @param isExpand 初始状态是否折叠
     */
    public void initExpand(boolean isExpand) {
        this.isExpand = isExpand;
        setViewDimensions();
    }

    /**
     * 设置动画时间
     *
     * @param animationDuration 动画时间
     */
    public void setAnimationDuration(long animationDuration) {
        this.animationDuration = animationDuration;
    }

    /**
     * 获取subView的总高度
     * View.post()的runnable对象中的方法会在View的measure、layout等事件后触发
     */
    private void setViewDimensions() {
        layoutView.post(new Runnable() {
            @Override
            public void run() {
                if (viewHeight <= 0) {
                    viewHeight = layoutView.getMeasuredHeight();
                }
                setViewHeight(layoutView, isExpand ? viewHeight : 0);
            }
        });
    }


    public static void setViewHeight(View view, int height) {
        final ViewGroup.LayoutParams params = view.getLayoutParams();
        params.height = height;
        view.requestLayout();
    }

    /**
     * 切换动画实现
     */
    private void animateToggle(long animationDuration) {
        ValueAnimator heightAnimation = isExpand ?
                ValueAnimator.ofFloat(0f, viewHeight) : ValueAnimator.ofFloat(viewHeight, 0f);
        heightAnimation.setDuration(animationDuration / 2);
        heightAnimation.setStartDelay(animationDuration / 2);

        heightAnimation.addUpdateListener(animation -> {
            int value = (int) (float) animation.getAnimatedValue();
            setViewHeight(layoutView, value);
            if (value == viewHeight || value == 0) {
                lock = false;
            }
        });

        heightAnimation.start();
        lock = true;
    }

    public boolean isExpand() {
        return isExpand;
    }

    /**
     * 折叠view
     */
    public void collapse() {
        isExpand = false;
        animateToggle(animationDuration);
    }

    /**
     * 展开view
     */
    public void expand() {
        isExpand = true;
        animateToggle(animationDuration);
    }

    /**
     * @param imageView 展开时旋转角标
     */
    public void toggleExpand(AppCompatImageView imageView) {
        if (lock) {
            return;
        }
        if (isExpand) {
            collapse();
            imageView.animate().rotation(0);
        } else {
            expand();
            imageView.animate().rotation(90);
        }
    }
}

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调用

 @BindView(R.id.expand)
 ExpandLayout expand;
 //oncreate()初始化
 expand.initExpand(false);
 //传入被执行动画的view
 expandPopular.toggleExpand(imgae);

soeasy，拿别人的轮子来改造了下，具体根据自己需求更改view代码。