实现无限循环
使用取模，获取到当前图片所在的位置。
private class MyPagerAdapter extends PagerAdapter { private Context context; List<ImageView> list; public MyPagerAdapter(Context context, List<ImageView> list) { this.context = context; this.list = list; } @Override public int getCount() { //使用Integer的最大值，这样基本上就不需要滑动到最后了 //除非用户很蛋疼 return Integer.MAX_VALUE; } @Override public Object instantiateItem(ViewGroup container, int position) { //当前位置模上总数等于图片在数组中的位置 position %= list.size(); if (position < 0) { position = list.size() + position; } ImageView imageView = list.get(position); //设置轮播点击事件 final int finalPosition = position; imageView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(getApplicationContext(), BannerActivity.class); intent.putExtra("position", finalPosition); startActivity(intent); } }); ViewGroup parent = (ViewGroup) imageView.getParent(); if (parent != null) { parent.removeView(imageView); } container.addView(imageView); return list.get(position); } @Override public boolean isViewFromObject(View view, Object object) { return object == view; } @Override public void destroyItem(ViewGroup container, int position, Object object) { //注意这里不要使用 //container.removeView(list.get(position)); } }
自动循环实现
使用Handler每隔5秒一次消息，接收到轮播的动作就继续发一次消息，实现自动轮播的效果。
private class MyHandler extends Handler { private Context context; //使用弱引用，避免handler造成内存泄露 private WeakReference<MainActivity> weakReference; public MyHandler(WeakReference<MainActivity> weakReference) { this.weakReference = weakReference; } @Override public void handleMessage(Message msg) { MainActivity activity = weakReference.get(); //Activity不存在了，就不需要再处理了 if (activity == null) { return; } //如果已经有消息了，先移除消息 if (activity.handler.hasMessages(BANNER_NEXT)) { activity.handler.removeMessages(BANNER_NEXT); } switch (msg.what) { case BANNER_NEXT: //跳到下一页， int currentItem = vpBanner.getCurrentItem(); activity.vpBanner.setCurrentItem(++currentItem); //5秒后继续轮播 activity.handler.sendEmptyMessageDelayed(BANNER_NEXT, 5000); break; case BANNER_PAUSE: //暂停,不需要做任务操作 break; case BANNER_RESUME: //继续轮播 activity.handler.sendEmptyMessageDelayed(BANNER_NEXT, 5000); break; } } }
在Activity中使用
//这里放了3张图片，使用Gilde加载 ImageView imageView1 = new ImageView(this); ImageView imageView2 = new ImageView(this); ImageView imageView3 = new ImageView(this); RequestManager requestManager = Glide.with(this); requestManager.load("http://img1.imgtn.bdimg.com/it/u=3251910782,1174316217&fm=21&gp=0.jpg").into(imageView1); requestManager.load("http://pic2.ooopic.com/10/78/50/34b1OOOPICf0.jpg").into(imageView2); requestManager.load("http://www.swkweike.com/data/uploads/2015/08/18/193226787255d2dbd711a33.jpg").into(imageView3); List<ImageView> list = new ArrayList<>(); list.add(imageView1); list.add(imageView2); list.add(imageView3); MyPagerAdapter adapter = new MyPagerAdapter(this, list); vpBanner = (ViewPager) findViewById(R.id.vpBanner); vpBanner.setAdapter(adapter); //将起始位置设置在中间，让用户看不到边界 vpBanner.setCurrentItem(Integer.MAX_VALUE / 2); //开始轮播 handler.sendEmptyMessageDelayed(BANNER_NEXT, 5000);
用户滑动时停止轮播,松开时继续轮播
使用ViewPager的滑动监听事件，判断用户是否正在滑动
vpBanner.addOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { } @Override public void onPageScrollStateChanged(int state) { switch (state) { case ViewPager.SCROLL_STATE_DRAGGING: //用户正在滑动，暂停轮播 handler.sendEmptyMessage(BANNER_PAUSE); break; case ViewPager.SCROLL_STATE_IDLE: //滑动结束，继续轮播 handler.sendEmptyMessageDelayed(BANNER_NEXT, 5000); break; } } });
