Android ViewPager sliding background gradient, androidviewpager

Android ViewPager sliding background gradient, androidviewpager
Principle

The total layout is RelativeLayout or FrameLayout. Here we use RelativeLayout. First, set the background image. The width and height are both fill_parent. When setting viewpager, the background of viewpager should be transparent ~ In this way, the background image can be displayed on the page. Monitor the sliding of viewpager, fade out the current background by the sliding offset, and display the next background.

Layout

<RelativeLayout 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" Tools: context = ". MyActivity">   <Us. yydcdut. viewpagercolorchange. BackGroundImage Android: id = "@ + id/img" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent"/>   <Android. support. v4.view. ViewPager Android: id = "@ + id/viewPager" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent" /> </RelativeLayout>

There is a custom View, fade out, and other operations are performed in the Custom view.

Code

Public class MyActivity extends Activity { Private BackGroundImage mImg; Private ViewPager mViewPager; Private List <View> mViewLists; Private List <Drawable> mDrawableLists; Private static final int ALL = 5;   @ Override Protected void onCreate (Bundle savedInstanceState ){ Super. onCreate (savedInstanceState ); SetContentView (R. layout. activity_my ); InitViews (); MImg. setmDrawableLists (mDrawableLists ); MViewPager. setAdapter (new MyAdapter ()); MViewPager. setOnPageChangeListener (new ViewPager. OnPageChangeListener (){ @ Override Public void onPageScrolled (int I, float v, int i2 ){ MImg. setmDegree (v ); MImg. setmPosition (I ); MImg. invalidate (); // refresh }   @ Override Public void onPageSelected (int I ){   }   @ Override Public void onPageScrollStateChanged (int I ){   } }); }   Private void initViews (){ MImg = (BackGroundImage) findViewById (R. id. img ); MViewPager = (ViewPager) findViewById (R. id. viewPager ); MViewLists = new ArrayList <View> (); MDrawableLists = new ArrayList <Drawable> (); For (int I = 0; I <ALL; I ++ ){ View view = getLayoutInflater (). inflate (R. layout. vp, null ); MViewLists. add (view ); If (I % 2 = 0 ){ MDrawableLists. add (getResources (). getDrawable (R. drawable. bg_img1 )); } Else { MDrawableLists. add (getResources (). getDrawable (R. drawable. bg_img2 )); } } }     Class MyAdapter extends PagerAdapter {   @ Override Public int getCount (){ Return mViewLists. size (); }   @ Override Public boolean isViewFromObject (View view, Object o ){ Return view = o; }   @ Override Public void destroyItem (ViewGroup container, int position, Object object Object ){ (ViewPager) container). removeView (mViewLists. get (position )); // Super. destroyItem (container, position, object ); }   @ Override Public Object instantiateItem (ViewGroup container, int position ){ View v = mViewLists. get (position ); TextView textView = (TextView) v.findViewById(R.id.txt ); TextView. setText ("nth" + position + ""); (ViewPager) container). addView (v ); Return v; } } }

Public class BackGroundImage extends View { Private int mPosition; Private float mDegree; Private List <Drawable> mDrawableLists; Private int mPrePosition = 0; Private Drawable mNext;   Public void setmDrawableLists (List <Drawable> mDrawableLists ){ This. mDrawableLists = mDrawableLists; MNext = mDrawableLists. get (1); // set the drawable of the next background image }   Public void setmPosition (int mPosition ){ This. mPosition = mPosition; }   Public void setmDegree (float mDegree ){ This. mDegree = mDegree; }   Public BackGroundImage (Context context ){ Super (context ); // SetWillNotDraw (false ); }   Public BackGroundImage (Context context, AttributeSet attrs ){ Super (context, attrs ); // SetWillNotDraw (false ); }   Public BackGroundImage (Context context, AttributeSet attrs, int defStyleAttr ){ Super (context, attrs, defStyleAttr ); // SetWillNotDraw (false ); }   @ Override Protected void onDraw (Canvas canvas ){ Log. I ("111", "onDraw "); If (null = mDrawableLists ){ Return; } Int alpha1 = (int) (255-(mDegree * 255 )); Drawable fore = mDrawableLists. get (mPosition ); Fore. setBounds (0, 0, getWidth (), getHeight ()); MNext. setBounds (0, 0, getWidth (), getHeight ()); If (mPrePosition! = MPosition) {// boundary judgment If (mPosition! = MDrawableLists. size ()-1 ){ MNext = mDrawableLists. get (mPosition + 1 ); } Else { MNext = mDrawableLists. get (mPosition ); } } Fore. setAlpha (alpha1); // fade out MNext. setAlpha (255 ); MNext. draw (canvas ); Fore. draw (canvas ); MPrePosition = mPosition; Super. onDraw (canvas ); } }

I am the dividing line of tiantiao

 

 

 

 

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