Android change image in a ImageView? -

i have picture resource, need modify opencv, put new image in original imageview.

i tried way, :

public class verifianceactivity extends activity {     /** called when activity first created. */        private baseloadercallback mloadercallback = new baseloadercallback(this) {         @override         public void onmanagerconnected(int status) {             if (status == loadercallbackinterface.success ) {                 // can call opencv code !                  bitmap mbitmap = bitmapfactory.decoderesource(getresources(), r.drawable.cmc7);                 mat mymat = new mat();                 utils.bitmaptomat(mbitmap, mymat);                  imgproc.cvtcolor(mymat, mymat, imgproc.color_bgr2gray);                 utils.mattobitmap(mymat, mbitmap);                  imageview miv = (imageview) findviewbyid(r.id.imageview);                 miv.setimagebitmap(mbitmap);//npe                 //this line suppose work, app crashes.                 setcontentview(r.layout.main);              } else {                 super.onmanagerconnected(status);             }         }     };      @override     public void onresume() {;         super.onresume();         opencvloader.initasync(opencvloader.opencv_version_2_4_5,this, mloadercallback);         // may tempted, here, it's *async*, , may take time,         // opencv call here lead unresolved native errors.     } } 

any advice ? got nullpointerexception error

the problem need call

setcontentview(r.layout.main); 

before accessing views or null such as

 imageview miv = (imageview) findviewbyid(r.id.imageview); 

since views exist inside layout inflate setcontentview(), don't exist until inflate layout return null if try initialize them before inflating layout