一個很常用的功能，一個ViewPager會自動滾動，并且有一排小圓點黑和白來指示當前的滾動進度

首先寫一個ViewPager的適配器，這里這個適配器為了方便里面的元素全都是ImageView

import android.content.Context;import android.os.Handler;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.view.View;import android.view.ViewGroup;import android.view.animation.Interpolator;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.Scroller; /** * Created by Administrator on 2016/2/24. */public class HomeHomeBannerAdapter extends PagerAdapter{ private Context context; private ImageView[] eventImageViews; private String[] eventUrls; int destWidth,destHeight; public HomeHomeBannerAdapter(Context context, String[] eventUrls,int destWidth,int destHeight) {this.context = context;this.eventUrls = eventUrls;this.destHeight = destHeight;this.destWidth = destWidth;initImageViews(); } /** * 初始化viewPager里的幾張圖 */ private void initImageViews(){if(eventUrls==null)return;eventImageViews = new ImageView[eventUrls.length];for (int i=0;i<eventUrls.length;i++) { eventImageViews[i] = new ImageView(context); eventImageViews[i].setLayoutParams(new LinearLayout.LayoutParams(destWidth, destHeight)); eventImageViews[i].setPadding(0, 0, 0, 0); eventImageViews[i].setScaleType(ImageView.ScaleType.FIT_XY); JImageUtils.loadImageFromServerByUrl(context,eventImageViews[i],eventUrls[i]);}//顯示圖片 } @Override public void destroyItem(ViewGroup container, int position, Object object) {if (eventImageViews != null && eventImageViews.length > position && position >= 0) container.removeView(eventImageViews[position]); } @Override public Object instantiateItem(ViewGroup container, int position) {container.addView(eventImageViews[position], 0);return eventImageViews[position]; } @Override public int getCount() {return eventUrls==null?0:eventUrls.length;} @Override public boolean isViewFromObject(View arg0, Object arg1) {return arg0 == arg1; }//ViewPager監聽器集成到內部類去 static public class EventViewPagerChangeListener implements ViewPager.OnPageChangeListener {LinearLayout llGuideGroup;int oldEventPosition;int currentItem; public EventViewPagerChangeListener(LinearLayout llGuideGroup){ this.llGuideGroup = llGuideGroup;} @Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {} /** * 控制小點的白色還是黑色的顯示 * @param position */public void onPageSelected(int position) { llGuideGroup.getChildAt(oldEventPosition).setBackgroundResource(R.drawable.dot_normal);//黑色點 llGuideGroup.getChildAt(position).setBackgroundResource(R.drawable.dot_focused);//白色點 oldEventPosition = position; currentItem = position;} @Overridepublic void onPageScrollStateChanged(int state) { } } /** * 控制viewpager自動滑動的定時任務 */ public static class ScrollTask implements Runnable {EventViewPagerChangeListener listener;ViewPager vpEvent;int eventSize;Handler handler;public ScrollTask(EventViewPagerChangeListener listener,final ViewPager vpEvent, int eventSize){ this.listener = listener; this.vpEvent = vpEvent; this.eventSize = eventSize; handler = new Handler();}public void run() { if(listener==null||vpEvent==null||eventSize==0)return; listener.currentItem = (listener.currentItem + 1) % eventSize; Log.i('Alex','currentItem是'+listener.currentItem); handler.post(new Runnable() {@Overridepublic void run() { vpEvent.setCurrentItem(listener.currentItem); // 通過Handler切換圖片} });} } public static class FixedSpeedScroller extends Scroller {private static final int mDuration = 400;private int eventCount; public FixedSpeedScroller(Context context, Interpolator interpolator,int eventCount) { super(context, interpolator); this.eventCount = eventCount;} @Overridepublic void startScroll(int startX, int startY, int dx, int dy, int duration) { if (duration % 100 == 0 && duration > 0) {//'現在是自動劃'if (duration / 100 == eventCount) super.startScroll(startX, startY, dx, dy, 1);//如果是最后一張else super.startScroll(startX, startY, dx, dy, mDuration); } else {// '現在是手動劃'super.startScroll(startX, startY, dx, dy, 80); }} }}

在上面適配器的內部類有一個監聽器，這個監聽器里有一個成員LinearLayout llGuideGroup，這個線性布局里面裝有幾個小點，下面是這個布局的定義：

<RelativeLayoutandroid: android:layout_width='match_parent'android:layout_height='200dp'android:visibility='gone'> <android.support.v4.view.ViewPager android: android:layout_width='match_parent' android:layout_height='200dp' android:background='@color/black666666' /> <LinearLayout android: android:layout_width='match_parent' android:layout_height='10dp' android:layout_alignParentBottom='true' android:layout_marginBottom='10dp' android:layout_centerHorizontal='true' android:gravity='center' android:orientation='horizontal' > </LinearLayout></RelativeLayout>

設置小圓點的數量并初始化監聽器

/** * 向一個線性布局里添加小圓點，具體的控制邏輯在listener里 * @param llGuideGroup * @param count 要添加多少個小圓點 */ public EventViewPagerChangeListener addViewPagerDots(LinearLayout llGuideGroup,ViewPager vpEvents,int count){if(llGuideGroup==null||vpEvents==null||count<1)return null;LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(15, 15);lp.leftMargin = 5;lp.rightMargin = 5;for(int i=0;i<count;i++){ ImageView imageView = new ImageView(llGuideGroup.getContext()); imageView.setLayoutParams(lp); imageView.setBackgroundResource(i==0?R.drawable.dot_focused:R.drawable.dot_normal); llGuideGroup.addView(imageView);}//控制小圓點顯示的監聽器EventViewPagerChangeListener listener = new EventViewPagerChangeListener(llGuideGroup);vpEvents.addOnPageChangeListener(listener);return listener; }

通過多線程實現定時切換頁面

HomeHomeBannerAdapter.EventViewPagerChangeListener listener = producer.addViewPagerDots(holder.llGuideGroup,holder.viewPager,eventUrls.length);//添加用于指示的小圓點 // 當Activity顯示出來后，每3秒鐘切換一次圖片顯示 ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(); scheduledExecutorService.scheduleAtFixedRate(new HomeHomeBannerAdapter.ScrollTask(listener,holder.viewPager,eventUrls.length), 3, 3, TimeUnit.SECONDS);

設置自定義滾動器降低viewPager的切換速度

/** * 給ViewPager設置自定義的滾動器，降低默認的滾動速度 * @param vpEvent */ public void setViewPagerScroller(ViewPager vpEvent){if(vpEvent==null)return;Field mField;Scroller mScroller;try { mField = ViewPager.class.getDeclaredField('mScroller'); mField.setAccessible(true); mScroller = new HomeHomeBannerAdapter.FixedSpeedScroller(vpEvent.getContext(), new AccelerateInterpolator(),vpEvent.getChildCount()); try {mField.set(vpEvent, mScroller); } catch (IllegalAccessException e) {e.printStackTrace(); }} catch (NoSuchFieldException e) { e.printStackTrace();} }

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好吧啦網。