關于Android實現(xiàn)文字上下滾動這個功能，我目前有兩種方法實現(xiàn)：
一個是在TextView 中加上翻轉的動畫效果，然后設置循環(huán)滾動；一種是改寫ViewPager 的滾動方向，使它從下到上進行滾動，并設置循環(huán)滾動；
首先介紹第一種方法：
實現(xiàn)思路：自定義TextView，在TextView中加上從下到上滾動的動畫效果，然后設置循環(huán)播放；
創(chuàng)建一個AutoTextVieW使之繼承TextView,然后在onDraw方法中調用getHeight()方法獲取textview當前的高度。
在接下來的動畫翻轉效果中，根據(jù)這個高度設置TextView上下滾動的距離。下面是動畫實現(xiàn)的方法：
/** * 向上脫離屏幕的動畫效果 */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);}/** * 從屏幕下面向上的動畫效果 */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);}接下來實現(xiàn)ObjectAnimator的監(jiān)聽事件，在onAnimationEnd 調用setText方法，在動畫沒結束一次更新文字，并且繼續(xù)執(zhí)行動畫效果
@Overridepublic void onAnimationEnd(Animator animator) { super.setText(mText); if (mAnimOver == null) { animationOver(); } mAnimOver.start();}然后調用一個可以設置循環(huán)滾動的類，這里可以使用ScheduledExecutorService，也可以使用 Timer幾設置計時滾動，在更新UI的時候，調用Handler方法更新；
因為采用Timer執(zhí)行定時任務時只創(chuàng)建一個線程，所以這里建議采用ScheduledExecutorService；
/** * 獲取數(shù)據(jù)并設置滾動播放 * @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(); } }}定時刷新頻率較高，容易產生內存泄漏，這里采用弱引用避免這個情況發(fā)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) { /** * 設置當前文字 */ String text = textList.get(index); index++; if (index > textList.size() - 1) { index = 0; } textView.setAutoText(text); } }}到此第一種方法介紹完畢。
第二種方法實現(xiàn)的原理和輪播圖的原理類似，輪播圖一般是左右橫向滾動，這里需要把ViewPager改成上下滑動，關于上下滑動的viewpager,可以在給github上找到；
其次輪播圖中播放的是圖片，把圖片換成文字即可；
然后同樣調用Timer或者ScheduledExecutorService使ViewPager自行滾動；
以下是代碼：
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方法實現(xiàn)文字滾動 * * @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(); } } } /** * 開始滾動 */ 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; } /** * 設置Adapter * @param adapter */ public void setAdapter(PagerAdapter adapter){ mVerticalViewPager.setAdapter(adapter); mAdapter = adapter; dataChanged(); } private void dataChanged(){ autoPlay(); }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。
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