Android实现带指示器的自动轮播式ViewPager

//获取BannerViewPager实例
bannerViewPager = (BannerViewPager) findViewById(R.id.banner);
//实例化ViewPagerAdapter，第一个参数是View集合，第二个参数是页面点击监听器
mAdapter = new ViewPagerAdapter(mViews, new OnPageClickListener() {
 @Override
 public void onPageClick(View view, int position) {
 Log.d("cylog","position:"+position);
 }
});
//设置适配器
bannerViewPager.setAdapter(mAdapter);

public class BannerViewPager extends FrameLayout implements ViewPager.OnPageChangeListener {

 private ViewPager mViewPager;
 private ViewPagerIndicator mIndicator;
 private ViewPagerAdapter mAdapter;
 //...
 public BannerViewPager(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 this.mContext = context;
 initViews();
 }

 private void initViews() {
 //initialize the viewpager
 mViewPager = new ViewPager(mContext);
 ViewPager.LayoutParams lp = new ViewPager.LayoutParams();
 lp.width = ViewPager.LayoutParams.MATCH_PARENT;
 lp.height = ViewPager.LayoutParams.MATCH_PARENT;
 mViewPager.setLayoutParams(lp);

 //initialize the indicator
 mIndicator = new ViewPagerIndicator(mContext);
 FrameLayout.LayoutParams indicatorlp = new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
 indicatorlp.gravity = Gravity.BOTTOM | Gravity.CENTER;
 indicatorlp.bottomMargin = 20;
 mIndicator.setLayoutParams(indicatorlp);
 }
 //省略...
}

public interface OnPageChangeListener {
 //只要ViewPager进行了滑动，该方法就会回调
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);
 //当前页面被选定的时候，回调
 public void onPageSelected(int position);
 //ViewPager的状态发生改变的时候，回调
 public void onPageScrollStateChanged(int state);
}

 //保存当前的position值
 private int mCurrentPosition;
 //viewpager's rolling state
 private int mViewPagerScrollState;

 @Override
 public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 setIndicator(position,positionOffset); //下面会讲到
 }

 @Override
 public void onPageSelected(int position) {
 mCurrentPosition = position;
 }

 @Override
 public void onPageScrollStateChanged(int state) {
 if(state == ViewPager.SCROLL_STATE_DRAGGING){
  mViewPagerScrollState = ViewPager.SCROLL_STATE_DRAGGING;
 }else if(state == ViewPager.SCROLL_STATE_IDLE){
  mReleasingTime = (int) System.currentTimeMillis();
  mViewPagerScrollState = ViewPager.SCROLL_STATE_IDLE;
 }
 }

 private Handler mHandler = new Handler(){
 @Override
 public void handleMessage(Message msg) {
  switch (msg.what){
  case MESSAGE_AUTO_ROLLING:
   if(mCurrentPosition == mAdapter.getCount() - 1){
   mViewPager.setCurrentItem(0,true);
   }else {
   mViewPager.setCurrentItem(mCurrentPosition + 1,true);
   }
   postDelayed(mAutoRollingTask,mAutoRollingTime);
   break;
  case MESSAGE_AUTO_ROLLING_CANCEL:
   postDelayed(mAutoRollingTask,mAutoRollingTime);
   break;
  }
 }
 };
 /**
 * This runnable decides the viewpager should roll to next page or wait.
 */
 private Runnable mAutoRollingTask = new Runnable() {
 @Override
 public void run() {
  int now = (int) System.currentTimeMillis();
  int timediff = mAutoRollingTime;
  if(mReleasingTime != 0){
  timediff = now - mReleasingTime;
  }

  if(mViewPagerScrollState == ViewPager.SCROLL_STATE_IDLE){
  //if user's finger just left the screen,we should wait for a while.
  if(timediff >= mAutoRollingTime * 0.8){
   mHandler.sendEmptyMessage(MESSAGE_AUTO_ROLLING);
  }else {
   mHandler.sendEmptyMessage(MESSAGE_AUTO_ROLLING_CANCEL);
  }
  }else if(mViewPagerScrollState == ViewPager.SCROLL_STATE_DRAGGING){
  mHandler.sendEmptyMessage(MESSAGE_AUTO_ROLLING_CANCEL);
  }

 }
 };

public class ViewPagerIndicator extends LinearLayout {

 private Context mContext;
 private Paint mPaint;
 private View mMoveView; 
 //省略...

 public ViewPagerIndicator(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 this.mContext = context;
 init();
 }

 private void init() {
 //setOrientation(LinearLayout.HORIZONTAL);
 setWillNotDraw(false);
 mPaint = new Paint();
 mPaint.setAntiAlias(true);
 mPaint.setColor(Color.GRAY);

 mMoveView = new MoveView(mContext);
 addView(mMoveView);
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 setMeasuredDimension(mPadding + (mRadius*2 + mPadding) * mItemCount,2*mRadius + 2*mPadding);
 }

 @Override
 protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 for(int i = 0;i < mItemCount;i++){
  canvas.drawCircle(mRadius + mPadding + mRadius * i *2 + mPadding * i,
   mRadius + mPadding,mRadius,mPaint);
 }

 }

 //省略...

 private class MoveView extends View {
 private Paint mPaint;

 public MoveView(Context context) {
  super(context);
  mPaint = new Paint();
  mPaint.setAntiAlias(true);
  mPaint.setColor(Color.argb(255,255,176,93));
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  setMeasuredDimension(mRadius*2,mRadius*2);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  canvas.drawCircle(mRadius,mRadius,mRadius,mPaint);
 }
 }
}

public class ViewPagerIndicator extends LinearLayout {
 //以上省略..

 public void setPositionAndOffset(int position,float offset){
 this.mCurrentPosition = position;
 this.mPositionOffset =offset;
 requestLayout();
 }
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 super.onLayout(changed, l, t, r, b);
 mMoveView.layout(
  (int) (mPadding + mDistanceBtwItem * (mCurrentPosition + mPositionOffset) ),
  mPadding,
  (int) (mDistanceBtwItem * ( 1 + mCurrentPosition + mPositionOffset) ),
  mPadding+mRadius*2);
 }
}

public interface DataSetSubscriber { 
 void update(int count);
}


public interface DataSetSubject { 
 void registerSubscriber(DataSetSubscriber subscriber); 
 void removeSubscriber(DataSetSubscriber subscriber); 
 void notifySubscriber();
}

public class ViewPagerAdapter extends PagerAdapter implements DataSetSubject {

 private List mSubscribers = new ArrayList<>();
 private List<? extends View> mDataViews;
 private OnPageClickListener mOnPageClickListener;

 /**
 * 构造函数
 * @param mDataViews view列表
 */
 public ViewPagerAdapter(List<? extends View> mDataViews,OnPageClickListener listener) {
 this.mDataViews = mDataViews;
 this.mOnPageClickListener = listener;
 }

 //省略...

 @Override
 public void notifyDataSetChanged() {
 super.notifyDataSetChanged();
 notifySubscriber();
 }

 @Override
 public void registerSubscriber(DataSetSubscriber subscriber) {
 mSubscribers.add(subscriber);
 }

 @Override
 public void removeSubscriber(DataSetSubscriber subscriber) {
 mSubscribers.remove(subscriber);
 }

 @Override
 public void notifySubscriber() {
 for(DataSetSubscriber subscriber : mSubscribers){
  subscriber.update(getCount());
 }
 }
}```

```java
public void setAdapter(ViewPagerAdapter adapter){
 mViewPager.setAdapter(adapter);
 mViewPager.addOnPageChangeListener(this);

 mAdapter = adapter;
 mAdapter.registerSubscriber(new DataSetSubscriber() {
 @Override
 public void update(int count) {
  mIndicator.setItemCount(count);
 }
 });

 //add the viewpager and the indicator to the container.
 addView(mViewPager);
 addView(mIndicator);

 //start the auto-rolling task if needed
 if(isAutoRolling){
 postDelayed(mAutoRollingTask,mAutoRollingTime);
 }

}

public interface OnPageClickListener { 
 void onPageClick(View view,int position);
}

@Override
public View instantiateItem(ViewGroup container, int position) {
 View view = mDataViews.get(position);
 final int i = position;
 if(mOnPageClickListener != null){
 view.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
  mOnPageClickListener.onPageClick(v,i);
  }
 });
 }

 container.addView(view);
 return view;
}