关于Android实现文字上下滚动这个功能，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：
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);
}
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
@Override
public 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；
public void getTextData(final IdeaAutoTextview textView, Listlist, 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 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 autoTextReference;
public TimetaskHandler(IdeaAutoTextview autoText) {
this.autoTextReference = new WeakReference<>(autoText);
}
@Override
public void handleMessage(Message msg) {
IdeaAutoTextview autoText = autoTextReference.get();
if (autoText!=null)
{
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;
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();
}
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 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 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();
}
}
}
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();
}
public ViewPager getViewPager() {
return mVerticalViewPager;
}
public void setAdapter(PagerAdapter adapter){
mVerticalViewPager.setAdapter(adapter);
mAdapter = adapter;
dataChanged();
}
private void dataChanged(){
autoPlay();
}
}
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