改进版 bannerLayout(强烈建议使用此版本)：

设置一个接口得到想要的数据

public interface BannerInterface {

ViewPager getViewPager();

LinearLayout getLinearLayout();

BasePagerAdapter getBannerAdapter();

}

封装PagerAdapter这里对外提供两个方法，一个点击事件，一个获取数据的方法

public abstract class BasePagerAdapter extends PagerAdapter {

public List mDatas = null;

public BasePagerAdapter(List mDatas) {

this.mDatas = mDatas;

}

@Override

public int getCount() {

return Integer.MAX_VALUE;

}

@Override

public boolean isViewFromObject(View view, Object object) {

return view == object;

}

@Override

public void destroyItem(ViewGroup container, int position, Object object) {

container.removeView((View) object);

}

@Override

public Object instantiateItem(ViewGroup container, int position) {

position %= mDatas.size();

ImageView img = new ImageView(container.getContext());

img.setScaleType(ImageView.ScaleType.CENTER_CROP);

//这里是本地数据，如果是网络数据请使用Glide或者其他的加载工具实现

// Glide.with(context).load(url).placeholder(R.drawable.bili_default_image)

// .error(R.drawable.bili_default_image).centerCrop().into(imageView);

//用Glide举例，一般url是String类型,把displayImage改成String即可

img.setBackgroundResource(displayImage(position));

final int finalPosition = position;

img.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

onImageClick(finalPosition, mDatas.get(finalPosition));

}

});

container.addView(img);

return img;

}

protected abstract int displayImage(int position);

protected abstract void onImageClick(int finalPosition, T mDatas);

}

最重要的BannerHolder这里面实现了轮播以及小圆点，因为主要的控件以及数据已经通过接口取到了，所以这里只需要实现逻辑即可，这个类是通用的。

public class BannerHolder implements ViewPagerHandlerUtils.ViewPagerCurrent {

private int preEnablePosition = 0;

private ViewPager mViewPager;

private ViewPagerHandlerUtils mHandlerUtil;

private LinearLayout mLinearLayout;

public void setBanner(final List banner, BannerInterface bannerInterface) {

initHolder(banner.size(), bannerInterface);

mViewPager.setCurrentItem((Integer.MAX_VALUE / 2) - ((Integer.MAX_VALUE / 2) % banner.size()));

mHandlerUtil = new ViewPagerHandlerUtils(this, mViewPager.getCurrentItem());

//提供了setStart() 这个方法 如果想实现 在发送消息之前设置为false就行了

mHandlerUtil.sendEmptyMessage(ViewPagerHandlerUtils.MSG_START);

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {

@Override

public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

}

@Override

public void onPageSelected(int position) {

int newPosition = position % banner.size();

mLinearLayout.getChildAt(preEnablePosition).setEnabled(false);

mLinearLayout.getChildAt(newPosition).setEnabled(true);

preEnablePosition = newPosition;

mHandlerUtil.sendMessage(Message.obtain(mHandlerUtil, ViewPagerHandlerUtils.MSG_PAGE, mViewPager.getCurrentItem(), 0));

}

@Override

public void onPageScrollStateChanged(int state) {

switch (state) {

case ViewPager.SCROLL_STATE_DRAGGING:

mHandlerUtil.sendEmptyMessage(ViewPagerHandlerUtils.MSG_KEEP);

break;

case ViewPager.SCROLL_STATE_IDLE:

mHandlerUtil.sendEmptyMessageDelayed(ViewPagerHandlerUtils.MSG_UPDATE, ViewPagerHandlerUtils.MSG_DELAY);

break;

}

}

});

}

@Override

public void setCurrentItem(int page) {

mViewPager.setCurrentItem(page);

}

private void initHolder(int bannerCount, BannerInterface bannerInterface) {

mViewPager = bannerInterface.getViewPager();

mLinearLayout = bannerInterface.getLinearLayout();

mViewPager.setAdapter(bannerInterface.getBannerAdapter());

initRound(bannerCount);

}

private void initRound(int bannerCount) {

if (null != mLinearLayout) {

mLinearLayout.removeAllViews();

for (int i = 0; i < bannerCount; i++) {

View view = new View(mLinearLayout.getContext());

view.setBackgroundResource(R.drawable.point_background);

if (i == 0) {

view.setEnabled(true);

} else {

view.setEnabled(false);

}

LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(15, 15);

view.setLayoutParams(params);

params.leftMargin = 10;

mLinearLayout.addView(view);

}

}

}

}

Handler去实现轮播的效果

public class ViewPagerHandlerUtils extends Handler {

public static final int MSG_START = 0; //开始轮播

public static final int MSG_UPDATE = 1; //更新

public static final int MSG_KEEP = 2; //暂停

public static final int MSG_BREAK = 3; // 恢复

public static final int MSG_PAGE = 4; //最新的page

public static final long MSG_DELAY = 2000; //time

private ViewPagerCurrent mCurrent;

private int page = 0;

public boolean isStart() {

return isStart;

}

public void setStart(boolean start) {

isStart = start;

}

private boolean isStart = true;

public ViewPagerHandlerUtils(ViewPagerCurrent viewPager, int currentItem) {

this.page = currentItem;

this.mCurrent = viewPager;

}

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

if (hasMessages(MSG_UPDATE)) {

removeMessages(MSG_UPDATE);

}

if (null == mCurrent) {

return;

}

if (!isStart) {

return;

}

switch (msg.what) {

case MSG_START:

sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);

break;

case MSG_UPDATE:

mCurrent.setCurrentItem(++page);

sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);

break;

case MSG_PAGE:

page = msg.arg1;

break;

case MSG_KEEP:

break;

case MSG_BREAK:

sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);

break;

default:

sendEmptyMessageDelayed(MSG_UPDATE, MSG_DELAY);

break;

}

}

public interface ViewPagerCurrent {

void setCurrentItem(int page);

}

}

封装完成，在代码中实现adapter

public class PagerAdapter extends BasePagerAdapter {

public PagerAdapter(List mDatas) {

super(mDatas);

}

@Override

protected int displayImage(int position) {

return mDatas.get(position).getImageId();

}

@Override

protected void onImageClick(int finalPosition, PagerModel mDatas) {

}

}Activity

public class MainActivity extends AppCompatActivity implements BannerInterface {

private List mDatas = new ArrayList<>();

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

mDatas.add(new PagerModel(R.drawable.banner1));

mDatas.add(new PagerModel(R.drawable.banner2));

mDatas.add(new PagerModel(R.drawable.banner3));

mDatas.add(new PagerModel(R.drawable.banner4));

new BannerHolder().setBanner(mDatas, this);

}

@Override

public ViewPager getViewPager() {

return (ViewPager) findViewById(R.id.viewPager);

}

@Override

public LinearLayout getLinearLayout() {

return (LinearLayout) findViewById(R.id.ll_points);

}

@Override

public BasePagerAdapter getBannerAdapter() {

return new PagerAdapter(mDatas);

}

}

至此封装Banner完成，而且在项目中没有出现问题。以后使用起来不管是RecyclerView里面还是activity里面，只要几行简单的代码就可以实现Banner的轮播以及小圆点。

最后看下实际效果图