简单轮播的实现

╰半橙微兮° 2022-06-17 23:10 186阅读 0赞

简单轮播的实现

1、适配器：BannerAdapter

【

public class BannerAdapter extends PagerAdapter \{  
  
private List<View> viewList ;  
  private int  size ;  
   
  public  BannerAdapter(List<View> viewList) \{  
this. viewList = viewList ;  
  size = viewList.size() ;  
 \}  
  
@Override  
  public void  destroyItem(ViewGroup container , int position , Object object) \{  
container.removeView( viewList.get(position% size)) ;  
 \}  
  
@Override  
  public Object instantiateItem(ViewGroup container , int position) \{  
container.addView( viewList.get(position% size)) ;  
  return  viewList.get(position% size) ;  
 \}  
  
@Override  
  public int  getCount() \{  
return Integer. *MAX\_VALUE* ;  
 \}  
  
@Override  
  public boolean  isViewFromObject(View view , Object object) \{  
return view == object ;  
 \}  
\}

】

2、BannerView

【

public class BannerView extends FrameLayout \{  
  
private static final int  *MSG\_LOOP* = 1000 ;  
  // 间隔时间  
  private static long  *LOOP\_INTERVAL* = 5000 ;  
  private LinearLayout mLinearPosition = null;  
  private ViewPager mViewPager = null;  
  private BannerHandler mBannerHandler = null;  
   
  // 真实显示的 banner view  集合  
  private List<View> viewList ;  
  // 真实显示的 banner view 个数  
  private int  viewSize ;  
   
  private static class BannerHandler extends Handler \{  
private WeakReference<BannerView> weakReference = null;  
   
  public  BannerHandler(BannerView bannerView) \{  
super(Looper. *getMainLooper*()) ;  
  this. weakReference = new WeakReference<BannerView>(bannerView) ;  
 \}  
  
@Override  
  public void  handleMessage(Message msg) \{  
super.handleMessage(msg) ;  
  if ( this. weakReference == null) \{  
return;  
 \}  
BannerView bannerView = this. weakReference.get() ;  
  if ( bannerView == null || bannerView. mViewPager == null || bannerView. mViewPager.getAdapter() == null || bannerView. mViewPager.getAdapter().getCount() <= 0) \{  
sendEmptyMessageDelayed( *MSG\_LOOP* ,  *LOOP\_INTERVAL*) ;  
  return;  
 \}  
int  curPos = bannerView. mViewPager.getCurrentItem() ;  
  curPos = ( curPos \+ 1) % bannerView. mViewPager.getAdapter().getCount() ;  
  bannerView. mViewPager.setCurrentItem( curPos) ;  
 sendEmptyMessageDelayed( *MSG\_LOOP* ,  *LOOP\_INTERVAL*) ;  
 \}  
\}  
  
public  BannerView(Context context) \{  
super(context) ;  
 init() ;  
 \}  
  
public  BannerView(Context context , AttributeSet attrs) \{  
super(context , attrs) ;  
 init() ;  
 \}  
  
public void  startLoop( boolean flag) \{  
if (flag) \{  
if ( mBannerHandler == null) \{  
mBannerHandler = new BannerHandler( this) ;  
 \}  
mBannerHandler.sendEmptyMessageDelayed( *MSG\_LOOP* ,  *LOOP\_INTERVAL*) ;  
 \} else \{  
if ( mBannerHandler != null) \{  
if ( mBannerHandler.hasMessages( *MSG\_LOOP*)) \{  
mBannerHandler.removeMessages( *MSG\_LOOP*) ;  
 \}  
\}  
\}  
\}  
  
private void  init() \{  
initViewPager() ;  
 initLinearPosition() ;  
  this.addView( mViewPager) ;  
  this.addView( mLinearPosition) ;  
 \}  
  
private void  initViewPager() \{  
mViewPager = new ViewPager(getContext()) ;  
 LayoutParams layoutParams = new LayoutParams(ViewGroup.LayoutParams. *WRAP\_CONTENT*  
  , ViewGroup.LayoutParams. *WRAP\_CONTENT*) ;  
  mViewPager.setLayoutParams( layoutParams) ;  
  mViewPager.addOnPageChangeListener( new ViewPager.OnPageChangeListener() \{  
@Override  
  public void  onPageScrolled( int position , float positionOffset , int positionOffsetPixels) \{  
Log. *d*( "dagger" , "position :"\+position+ " positionOffset :"\+positionOffset) ;  
 \}  
  
@Override  
  public void  onPageSelected( int position) \{  
Log. *d*( "dagger" , "onPageSelected :"\+position) ;  
 updateLinearPosition() ;  
 \}  
  
@Override  
  public void  onPageScrollStateChanged( int state) \{  
  
\}  
\}) ;  
  mViewPager.setOnTouchListener( new OnTouchListener() \{  
@Override  
  public boolean  onTouch(View v , MotionEvent event) \{  
switch (event.getAction())\{  
case MotionEvent. *ACTION\_DOWN*:  
if ( mBannerHandler != null) \{  
if ( mBannerHandler.hasMessages( *MSG\_LOOP*)) \{  
mBannerHandler.removeMessages( *MSG\_LOOP*) ;  
 \}  
\}  
break;  
  case MotionEvent. *ACTION\_UP*:  
if ( mBannerHandler != null) \{  
mBannerHandler.sendEmptyMessageDelayed( *MSG\_LOOP* ,  *LOOP\_INTERVAL*) ;  
 \}  
break;  
  default:  
break;  
 \}  
return false;  
 \}  
\}) ;  
 \}  
  
private void  initLinearPosition() \{  
mLinearPosition = new LinearLayout(getContext()) ;  
  mLinearPosition.setOrientation(LinearLayout. *HORIZONTAL*) ;  
 LayoutParams layoutParams = new LayoutParams(ViewGroup.LayoutParams. *WRAP\_CONTENT*  
  , ViewGroup.LayoutParams. *WRAP\_CONTENT*) ;  
  // 点在中间  
  layoutParams. gravity = Gravity. *CENTER\_HORIZONTAL* | Gravity. *BOTTOM* ;  
  layoutParams. bottomMargin = getResources().getDimensionPixelSize(R.dimen. *dimen\_9dp*) ;  
  mLinearPosition.setPadding(getResources().getDimensionPixelSize(R.dimen. *dimen\_9dp*) ,  0 ,  0 ,  0) ;  
  mLinearPosition.setLayoutParams( layoutParams) ;  
 \}  
  
public void  setAdapter(PagerAdapter adapter) \{  
mViewPager.setAdapter(adapter) ;  
 adapter.registerDataSetObserver( mDataObserver) ;  
 updateLinearPosition() ;  
 \}  
  
private DataSetObserver mDataObserver = new DataSetObserver() \{  
@Override  
  public void  onChanged() \{  
super.onChanged() ;  
 updateLinearPosition() ;  
 \}  
  
@Override  
  public void  onInvalidated() \{  
super.onInvalidated() ;  
 \}  
\} ;  
   
  private void  updateLinearPosition() \{  
if ( viewList != null && viewList.size() != 0) \{  
if ( mLinearPosition.getChildCount() != viewSize) \{  
int  diffCnt = mLinearPosition.getChildCount() - viewSize ;  
  boolean  needAdd = diffCnt < 0 ;  
  diffCnt = Math. *abs*( diffCnt) ;  
  for ( int  i = 0 ;  i < diffCnt ;  i\++) \{  
if ( needAdd) \{  
ImageView img = new ImageView(getContext()) ;  
 LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams. *WRAP\_CONTENT* , ViewGroup.LayoutParams. *WRAP\_CONTENT*) ;  
  layoutParams. rightMargin = getResources().getDimensionPixelOffset(R.dimen. *dimen\_9dp*) ;  
  img.setLayoutParams( layoutParams) ;  
  img.setBackgroundResource(R.drawable. *banner\_point*) ;  
  mLinearPosition.addView( img) ;  
 \} else \{  
mLinearPosition.removeViewAt( 0) ;  
 \}  
\}  
\}  
int  curPos = mViewPager.getCurrentItem() ;  
  for ( int  i = 0 ;  i < mLinearPosition.getChildCount() ;  i\++) \{  
if ( i == ( curPos % viewSize)) \{  
mLinearPosition.getChildAt( i).setBackgroundResource(R.drawable. *banner\_point\_select*) ;  
 \} else \{  
mLinearPosition.getChildAt( i).setBackgroundResource(R.drawable. *banner\_point*) ;  
 \}  
\}  
\}  
\}  
  
public void  setViewList(List<View> viewList) \{  
this. viewList = viewList ;  
  if (viewList != null && viewList.size() != 0) \{  
viewSize = viewList.size() ;  
 BannerAdapter bannerAdapter = new BannerAdapter(viewList) ;  
 setAdapter( bannerAdapter) ;  
 \}  
\}  
  
public void  setTransformAnim ( boolean flag)\{  
if (flag)\{  
*/\*\**  
  *\** *假设现在* *ViewPager* *在* *A* *页现在滑出* *B* *页，则* *:*  
  *A* *页的* *position* *变化就是* *( 0, -1\]*  
  *B* *页的* *position* *变化就是* *\[ 1 , 0 \]*  
  *\*/*  
  mViewPager.setPageTransformer( true, new ViewPager.PageTransformer() \{  
private static final float  *MIN\_SCALE* = 0.75f ;  
  @Override  
  public void  transformPage(View view , float position) \{  
int  pageWidth = view.getWidth() ;  
  if (position < - 1)  
\{ // \[-Infinity,-1)  
  // This page is way off-screen to the left.  
 view.setRotation( 0) ;  
   
 \} else if (position <= 1) // a 页滑动至 b 页 ；  a 页从  0.0 ~ -1  ； b 页从 1 ~ 0.0  
 \{ // \[-1,1\]  
  // Modify the default slide transition to shrink the page as well  
  if (position < 0)  
\{  
  
float  mRot = ( 20f \* position) ;  
 view.setPivotX(view.getMeasuredWidth() \* 0.5f) ;  
 view.setPivotY(view.getMeasuredHeight()) ;  
 view.setRotation( mRot) ;  
 \} else  
 \{  
  
float  mRot = ( 20f \* position) ;  
 view.setPivotX(view.getMeasuredWidth() \* 0.5f) ;  
 view.setPivotY(view.getMeasuredHeight()) ;  
 view.setRotation( mRot) ;  
 \}  
  
// Scale the page down (between MIN\_SCALE and 1)  
   
  // Fade the page relative to its size.  
   
 \} else  
 \{ // (1,+Infinity\]  
  // This page is way off-screen to the right.  
 view.setRotation( 0) ;  
 \}  
\}  
\}) ;  
 \}  
\}  
  
public static void  setLoopInterval( long loopInterval) \{  
*LOOP\_INTERVAL* = loopInterval ;  
 \}  
  
\}

】

3、布局

【

<? xml version= "1.0"  encoding= "utf-8" ?>  
 <LinearLayout  xmlns: android = "http://schemas.android.com/apk/res/android"  
  xmlns: tools = "http://schemas.android.com/tools"  
  android :layout\_width= "match\_parent"  
  android :layout\_height= "match\_parent"  
  android :orientation= "vertical"  
  tools :context= "com.blink.test.bannerview.MainActivity" >  
   
  <com.blink.test.bannerview.BannerView  
  android :layout\_width= "match\_parent"  
  android :layout\_height= "220dp"  
  android :id= "@+id/banner" />  
 </LinearLayout>

】

4、实例展示

【

public class MainActivity extends AppCompatActivity \{  
  
private int\[\] imgs = \{R.drawable. *a* ,R.drawable. *b* ,R.drawable. *c* ,R.drawable. *d*\} ;  
  private List<View> viewList ;  
 BannerView bannerView ;  
   
  @Override  
  protected void  onCreate(Bundle savedInstanceState) \{  
super.onCreate(savedInstanceState) ;  
 setContentView(R.layout. *activity\_main*) ;  
  viewList = new ArrayList<View>() ;  
  for ( int  i = 0 ;  i < imgs. length ;  i\++) \{  
ImageView image = new ImageView( this) ;  
  image.setLayoutParams( new ViewGroup.LayoutParams(ViewGroup.LayoutParams. *MATCH\_PARENT* , ViewGroup.LayoutParams. *MATCH\_PARENT*)) ;  
  // 设置显示格式  
  image.setScaleType(ImageView.ScaleType. *CENTER\_CROP*) ;  
  image.setImageResource( imgs\[ i\]) ;  
  viewList.add( image) ;  
 \}  
bannerView = (BannerView) findViewById(R.id. *banner*) ;  
  bannerView.setViewList( viewList) ;  
  bannerView.startLoop( true) ;  
 // bannerView.setTransformAnim(true);  
   
 \}  
\}

】