文字上下滚动的效果

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关于这个功能，我目前有两种方法实现：
一个是在TextView 中加上翻转的动画效果，然后设置循环滚动；一种是改写ViewPager 的滚动方向，使它从下到上进行滚动，并设置循环滚动；

首先介绍第一种方法：
实现思路：自定义TextView，在TextView中加上从下到上滚动的动画效果，然后设置循环播放；

创建一个AutoTextVieW使之继承TextView,然后在onDraw方法中调用getHeight()方法获取textview当前的高度。
在接下来的动画翻转效果中，根据这个高度设置TextView上下滚动的距离。下面是动画实现的方法：

/** * 向上脱离屏幕的动画效果 */private void animationStart() {    ObjectAnimator translate = ObjectAnimator.ofFloat(this, "translationY", 0, -height);    ObjectAnimator alpha = ObjectAnimator.ofFloat(this, "alpha", 1f, 0f);    mAnimStart = new AnimatorSet();    mAnimStart.play(translate).with(alpha);    mAnimStart.setDuration(DURATION);    mAnimStart.addListener(this);}/** * 从屏幕下面向上的动画效果 */public void animationOver() {    ObjectAnimator translate = ObjectAnimator.ofFloat(this, "translationY", height, 0);    ObjectAnimator alpha = ObjectAnimator.ofFloat(this, "alpha", 0f, 1f);    mAnimOver = new AnimatorSet();    mAnimOver.play(translate).with(alpha);    mAnimOver.setDuration(DURATION);}

接下来实现ObjectAnimator的监听事件，在onAnimationEnd 调用setText方法，在动画没结束一次更新文字，并且继续执行动画效果

 @Overridepublic void onAnimationEnd(Animator animator) {    super.setText(mText);    if (mAnimOver == null) {       animationOver();    }    mAnimOver.start();}

然后调用一个可以设置循环滚动的类，这里可以使用ScheduledExecutorService，也可以使用 Timer几设置计时滚动，在更新UI的时候，调用Handler方法更新；
因为采用Timer执行定时任务时只创建一个线程，所以这里建议采用ScheduledExecutorService；

/** * 获取数据并设置滚动播放 * @param textView * @param list * @param autoPlayTime */public void getTextData(final IdeaAutoTextview textView, List<String> list, int autoPlayTime) {    this.textView = textView;    this.textList = list;    if (autoPlayTime != 0) {        scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();        scheduledExecutorService.scheduleWithFixedDelay(new WeakTimerTask(this), autoPlayTime, autoPlayTime, TimeUnit.SECONDS);    }}private TimeTaskHandler mHandler = new TimeTaskHandler(this);private static class WeakTimerTask extends TimerTask {    private WeakReference<IdeaAutoTextview> autoTextReference;    public WeakTimerTask(IdeaAutoTextview mautoText) {        this.autoTextReference = new WeakReference<>(mautoText);    }    @Override    public void run() {        IdeaAutoTextview autoText = autoTextReference.get();        if (autoText != null) {            if (autoText.isShown()) {                autoText.mHandler.sendEmptyMessage(0);            }        } else {            cancel();        }    }}

定时刷新频率较高，容易产生内存泄漏，这里采用弱引用避免这个情况发生

private final class TimeTaskHandler extends Handler {    private WeakReference<IdeaAutoTextview> autoTextReference;    public TimeTaskHandler(IdeaAutoTextview autoText) {        this.autoTextReference = new WeakReference<>(autoText);    }    @Override    public void handleMessage(Message msg) {        IdeaAutoTextview autoText = autoTextReference.get();        if (autoText!=null)        {            /**             * 设置当前文字             */            String text = textList.get(index);            index++;            if (index > textList.size() - 1) {                index = 0;            }            textView.setAutoText(text);        }    }}

到此第一种方法介绍完毕。

第二种方法实现的原理和轮播图的原理类似，轮播图一般是左右横向滚动，这里需要把ViewPager改成上下滑动，关于上下滑动的viewpager,可以在给github上找到；
其次轮播图中播放的是图片，把图片换成文字即可；
然后同样调用Timer或者ScheduledExecutorService使ViewPager自行滚动；
以下是代码：

package com.idea.idea.viewutils;import android.content.Context;import android.os.Handler;import android.os.Message;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.util.AttributeSet;import android.widget.RelativeLayout;import java.lang.ref.WeakReference;import java.util.TimerTask;import java.util.concurrent.Executors;import java.util.concurrent.ScheduledExecutorService;import java.util.concurrent.TimeUnit;/** * todo：修改ViewPager方法实现文字滚动 * * @author: Create by qjj * @email: gxuqjj@163.com */public class AutoViewpager extends RelativeLayout{    private VerticalViewPager mVerticalViewPager;    private PagerAdapter mAdapter;    private int autoPlayTime;    private ScheduledExecutorService scheduledExecutorService;    public AutoViewpager(Context context){        this(context,null);    }    public AutoViewpager(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public AutoViewpager(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        initView();    }    /**     * 初始化view     */    private void initView(){        if(mVerticalViewPager!=null){            removeView(mVerticalViewPager);        }        mVerticalViewPager = new VerticalViewPager(getContext());        mVerticalViewPager.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));        addView(mVerticalViewPager);    }    private final static class TimeTaskHandler extends Handler {        private WeakReference<AutoViewpager> mRollPagerViewWeakReference;        public TimeTaskHandler(AutoViewpager autoViewpager) {            this.mRollPagerViewWeakReference = new WeakReference<>(autoViewpager);        }        @Override        public void handleMessage(Message msg) {            AutoViewpager autoViewpager = mRollPagerViewWeakReference.get();            int cur = autoViewpager.getViewPager().getCurrentItem()+1;            if(cur>= autoViewpager.mAdapter.getCount()){                cur=0;            }            autoViewpager.getViewPager().setCurrentItem(cur);        }    }    private TimeTaskHandler mHandler = new TimeTaskHandler(this);    private static class WeakTimerTask extends TimerTask {        private WeakReference<AutoViewpager> mRollPagerViewWeakReference;        public WeakTimerTask(AutoViewpager mAutoViewpager) {            this.mRollPagerViewWeakReference = new WeakReference<>(mAutoViewpager);        }        @Override        public void run() {            AutoViewpager autoViewpager = mRollPagerViewWeakReference.get();            if (autoViewpager !=null){                if(autoViewpager.isShown()){                    autoViewpager.mHandler.sendEmptyMessage(0);                }            }else{                cancel();            }        }    }    /**     * 开始滚动     */    private void autoPlay(){        if(autoPlayTime<=0||mAdapter == null||mAdapter.getCount()<=1){            return;        }        scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();        scheduledExecutorService.scheduleWithFixedDelay(new WeakTimerTask(this), autoPlayTime, autoPlayTime, TimeUnit.SECONDS);    }    public void setAutoTime(int autoPlayTime){        this.autoPlayTime = autoPlayTime;        autoPlay();    }    /**     * viewpager     * @return     */    public ViewPager getViewPager() {        return mVerticalViewPager;    }    /**     * 设置Adapter     * @param adapter     */    public void setAdapter(PagerAdapter adapter){        mVerticalViewPager.setAdapter(adapter);        mAdapter = adapter;        dataChanged();    }    private void dataChanged(){        autoPlay();    }}

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