Android Viewpager Sliding background gradient

Principle

The overall layout is relativelayout or framelayout, and here we use Relativelayout. First set the background image, width and height are fill_parent, set Viewpager,viewpager background to be transparent yo ~ so background picture can be displayed on the page. Slide monitoring of the Viewpager, fade the current background by sliding the 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>

A custom view, fade out, and so on, is done in a 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) { ((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 ("first" + position + "one"); ((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 next background picture of the drawable } 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); } }

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Android Viewpager Sliding background gradient