仿淘宝-头条滚动

实现

1. 兼容动画
   compile 'com.nineoldandroids:library:2.4.0+'
2. 布局文件

3. UpDownTextView的具体实现

public class UpDownTextView extends TextView implements Animator.AnimatorListener {

    private static final String TAG = "UpDownTextView";

    private static final int ANIMATION_DURATION = 200;
    private float height;
    private AnimatorSet mAnimatorStartSet;
    private AnimatorSet mAnimatorEndSet;
    private String mText;

    public UpDownTextView(Context context) {
        super(context);
    }

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

    /**
     * 此方法就是获取view的高度
     *
     * @param canvas
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        height = getHeight();
    }

    /**
     * --- 初始化向上脱离屏幕的动画效果 ---
     */
    private void initStartAnimation() {
        ObjectAnimator translate = ObjectAnimator.ofFloat(this, "translationY", 0, -height);
        ObjectAnimator alpha = ObjectAnimator.ofFloat(this, "alpha", 1f, 0f);
        mAnimatorStartSet = new AnimatorSet();
        mAnimatorStartSet.play(translate).with(alpha);
        mAnimatorStartSet.setDuration(ANIMATION_DURATION);
        mAnimatorStartSet.addListener(this);
    }

    /**
     * --- 初始化从屏幕下面向上的动画效果 ---
     */
    private void initEndAnimation() {
        //translationY 属性肯定要归为0，不然显示的内容就有偏移了；alpha 也是一样
        ObjectAnimator translate = ObjectAnimator.ofFloat(this, "translationY", height, 0);
        ObjectAnimator alpha = ObjectAnimator.ofFloat(this, "alpha", 0f, 1f);
        mAnimatorEndSet = new AnimatorSet();
        mAnimatorEndSet.play(translate).with(alpha);
        mAnimatorEndSet.setDuration(ANIMATION_DURATION);
        mAnimatorStartSet.addListener(this);
    }

    /**
     * --- 设置内容 ---
     **/
    public void setText(String text) {
        if (TextUtils.isEmpty(text)) {
            Log.e(TAG, "--- 请确保text不为空 ---");
            return;
        }
        mText = text;
        if (null == mAnimatorStartSet) {
            initStartAnimation();
        }
        mAnimatorStartSet.start();
    }


    @Override
    public void onAnimationStart(Animator animator) {

    }

    @Override
    public void onAnimationEnd(Animator animator) {
        super.setText(mText);
        if (null == mAnimatorEndSet) {
            initEndAnimation();
        }
        mAnimatorEndSet.start();
    }

    @Override
    public void onAnimationCancel(Animator animator) {

    }

    @Override
    public void onAnimationRepeat(Animator animator) {

    }
}

说明：

• 这里用到了属性动画，应该依赖 nineoldandroids:library，以兼容3.0以下的机型。
• 对于 translationY 属性是表示内容的偏移。如果要显示内容，属性值肯定应该归为0 ，否则就会有偏移量。

项目地址

请戳我的github：UpMarqueerTextView-master