一个简单的自定义RecyclerView适配器（五）——动画

一、开启动画

在BaseRecyclerViewAdapter中

/**
 * 渐显动画，使用 {@link #openLoadAnimation}
 */
public static final int ALPHAIN = 0x00000001;
/**
 * 缩放动画，使用 {@link #openLoadAnimation}
 */
public static final int SCALEIN = 0x00000002;
/**
 * 从下到上动画，使用 {@link #openLoadAnimation}
 */
public static final int SLIDEIN_BOTTOM = 0x00000003;
/**
 * 从左到右动画，使用 {@link #openLoadAnimation}
 */
public static final int SLIDEIN_LEFT = 0x00000004;
/**
 * 从右到左动画，使用 {@link #openLoadAnimation}
 */
public static final int SLIDEIN_RIGHT = 0x00000005;

/**
 * 五种默认动画类型
 */
@IntDef({ALPHAIN, SCALEIN, SLIDEIN_BOTTOM, SLIDEIN_LEFT, SLIDEIN_RIGHT})
@Retention(RetentionPolicy.SOURCE)
private  @interface AnimationType {
}

/**
 * 是否开启动画标志，默认不打开
 */
private boolean mOpenAnimationEnable = false;

/**
 * 设置是否开启动画
 * @param mOpenAnimationEnable true为开启
 */
public void isOpenAnimationEnable(boolean mOpenAnimationEnable){
    this.mOpenAnimationEnable = mOpenAnimationEnable;
}

/**
 * 自定义动画基类
 */
private BaseAnimation mCustomAnimation;
public interface BaseAnimation {
    Animator[] getAnimators(View view);
}

/**
 * 自定义的默认动画
 */
private BaseAnimation mSelectAnimation;

/**
 * 使用默认的五种动画
 * 1.开启动画，2.使用自定义的默认动画，3.根据animationType选中动画类型
 * @param animationType ALPHAIN, SCALEIN, SLIDEIN_BOTTOM, SLIDEIN_LEFT, SLIDEIN_RIGHT
 */
public void openLoadAnimation(@AnimationType int animationType) {
    this.mOpenAnimationEnable = true;
    mCustomAnimation = null;
    switch (animationType) {
        case ALPHAIN:
            mSelectAnimation = new AlphaInAnimation();
            break;
        case SCALEIN:
            mSelectAnimation = new ScaleInAnimation();
            break;
        case SLIDEIN_BOTTOM:
            mSelectAnimation = new SlideInBottomAnimation();
            break;
        case SLIDEIN_LEFT:
            mSelectAnimation = new SlideInLeftAnimation();
            break;
        case SLIDEIN_RIGHT:
            mSelectAnimation = new SlideInRightAnimation();
            break;
        default:
            break;
    }
}

/**
 * 使用自定义动画
 *
 * @param animation 自定义动画
 */
public void openLoadAnimation(BaseAnimation animation) {
    this.mOpenAnimationEnable = true;
    this.mCustomAnimation = animation;
}

使用

默认提供5种方法（渐显、缩放、从下到上，从左到右、从右到左）

mAdapter.openLoadAnimation(BaseRecyclerViewAdapter.ALPHAIN)

也可以自己自定义动画

mAdapter.openLoadAnimation(BaseRecyclerViewAdapter.BaseAnimation {
    arrayOf(ObjectAnimator.ofFloat(it, "scaleY", 1.0f, 1.1f, 1.0f), ObjectAnimator.ofFloat(it, "scaleX", 1.0f, 1.1f, 1.0f))
})

二、显示动画

在BaseRecyclerViewAdapter中

/**
 * 当列表项出现到可视界面的时候调用
 * @param holder holder
 */
@Override
public void onViewAttachedToWindow(@NonNull K holder) {
    super.onViewAttachedToWindow(holder);
    //显示动画
    addAnimation(holder);
}

/**
 * true只在加载数据时显示动画,false每次都显示动画
 */
private boolean mFirstOnlyEnable = true;
public void isFirstOnly(boolean firstOnly) {
    this.mFirstOnlyEnable = firstOnly;
}

/**
 * 统计有多少个动画
 */
private int mLastPosition = -1;

/**
 * 显示动画，默认只在加载数据时显示动画
 *
 * @param holder
 */
private void addAnimation(RecyclerView.ViewHolder holder) {
    if (mOpenAnimationEnable) {
        if (!mFirstOnlyEnable || holder.getLayoutPosition() > mLastPosition) {
            BaseAnimation animation;
            if (mCustomAnimation != null) {
                animation = mCustomAnimation;
            } else {
                animation = mSelectAnimation;
            }
            for (Animator anim : animation.getAnimators(holder.itemView)) {
                startAnim(anim, holder.getLayoutPosition());
            }
            mLastPosition = holder.getLayoutPosition();
        }
    }
}

/**
 * 动画时间
 */
private int mDuration = 1000;
public void setDuration(int duration) {
    mDuration = duration;
}

/**
 * 插值器,默认速率恒定
 */
private Interpolator mInterpolator = new LinearInterpolator();
public void setInterpolator(Interpolator mInterpolator){
    this.mInterpolator = mInterpolator;
}

/**
 * 设置动画时间，设置插值器，开启动画
 *
 * @param anim
 * @param position
 */
private void startAnim(Animator anim, int position) {
    anim.setDuration(mDuration).start();
    anim.setInterpolator(mInterpolator);
}

使用

//加载数据时是否显示动画，false为总是显示，默认为true
mAdapter.isFirstOnly(false)

//设置动画时间
mAdapter.setDuration(1000)
//设置插值器
mAdapter.setInterpolator(BounceInterpolator())

三、五种默认动画

public class AlphaInAnimation implements BaseRecyclerViewAdapter.BaseAnimation {
    private static final float DEFAULT_ALPHA_FROM = 0f;
    private final float mFrom;

    public AlphaInAnimation() {
        this(DEFAULT_ALPHA_FROM);
    }

    public AlphaInAnimation(float from) {
        mFrom = from;
    }

    @Override
    public Animator[] getAnimators(View view) {
        return new Animator[]{ObjectAnimator.ofFloat(view, "alpha", mFrom, 1f)};
    }
}

缩放动画

public class ScaleInAnimation implements BaseRecyclerViewAdapter.BaseAnimation {
    private static final float DEFAULT_SCALE_FROM = .5f;
    private final float mFrom;

    public ScaleInAnimation() {
        this(DEFAULT_SCALE_FROM);
    }

    public ScaleInAnimation(float from) {
        mFrom = from;
    }

    @Override
    public Animator[] getAnimators(View view) {
        ObjectAnimator scaleX = ObjectAnimator.ofFloat(view, "scaleX", mFrom, 1f);
        ObjectAnimator scaleY = ObjectAnimator.ofFloat(view, "scaleY", mFrom, 1f);
        return new ObjectAnimator[]{scaleX, scaleY};
    }
}

从下到上动画

public class SlideInBottomAnimation implements BaseRecyclerViewAdapter.BaseAnimation {
    @Override
    public Animator[] getAnimators(View view) {
        return new Animator[]{
                ObjectAnimator.ofFloat(view, "translationY", view.getMeasuredHeight(), 0)
        };
    }
}

从左到右动画

public class SlideInLeftAnimation implements BaseRecyclerViewAdapter.BaseAnimation {
    @Override
    public Animator[] getAnimators(View view) {
        return new Animator[]{
                ObjectAnimator.ofFloat(view, "translationX", -view.getRootView().getWidth(), 0)
        };
    }
}

从右到左动画

public class SlideInRightAnimation implements BaseRecyclerViewAdapter.BaseAnimation {
    @Override
    public Animator[] getAnimators(View view) {
        return new Animator[]{
                ObjectAnimator.ofFloat(view, "translationX", view.getRootView().getWidth(), 0)
        };
    }
}