c++ - edge detection opencv android -

i want use canny function on android used before on c++ write this

  public mat oncameraframe(cvcameraviewframe inputframe) {        mrgba = inputframe.gray();       imgproc.canny(mrgba, edge, 225, 250);        return edge;     } 

there no error on code when run on phone give me

unfortunately , nameproject preview has stopped 

and adb show

 07-20 23:03:01.568: e/opencv_for_tegra(6648): tegra version detected: 0     07-20 23:03:01.588: d/dalvikvm(6648): gc_for_alloc freed 150k, 10% free 9182k/10148k, paused 15ms, total 16ms     07-20 23:03:01.588: i/dalvikvm-heap(6648): grow heap (frag case) 11.226mb 1536016-byte allocation     07-20 23:03:01.598: d/dalvikvm(6648): gc_for_alloc freed 0k, 9% free 10682k/11652k, paused 12ms, total 12ms     07-20 23:03:01.608: d/javacameraview(6648): startpreview     07-20 23:03:01.658: e/dalvikvm(6648): adjustadaptivecoef max=4194304, min=1048576, ut=568     07-20 23:03:01.658: d/dalvikvm(6648): gc_concurrent freed 3k, 9% free 10681k/11652k, paused 3ms+2ms, total 62ms     07-20 23:03:02.149: d/javacameraview(6648): starting processing thread     07-20 23:03:02.469: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:02.529: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:02.639: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:02.739: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:02.839: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:02.939: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:03.000: w/dalvikvm(6648): threadid=11: thread exiting uncaught exception (group=0x40fb2930)     07-20 23:03:03.000: e/androidruntime(6648): fatal exception: thread-21050     07-20 23:03:03.000: e/androidruntime(6648): java.lang.nullpointerexception     07-20 23:03:03.000: e/androidruntime(6648):     @ org.opencv.imgproc.imgproc.canny(imgproc.java:448)     07-20 23:03:03.000: e/androidruntime(6648):     @ org.opencv.samples.tutorial1.tutorial1activity.oncameraframe(tutorial1activity.java:167)     07-20 23:03:03.000: e/androidruntime(6648):     @ org.opencv.android.camerabridgeviewbase.deliveranddrawframe(camerabridgeviewbase.java:387)     07-20 23:03:03.000: e/androidruntime(6648):     @ org.opencv.android.javacameraview$cameraworker.run(javacameraview.java:328)     07-20 23:03:03.000: e/androidruntime(6648):     @ java.lang.thread.run(thread.java:856)     07-20 23:03:03.040: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:03.150: d/javacameraview(6648): preview frame received. frame size: 576000     07-20 23:03:03.210: d/javacameraview(6648): disconnecting camera     07-20 23:03:03.210: d/javacameraview(6648): notify thread     07-20 23:03:03.210: d/javacameraview(6648): wating thread 

any idea ?

sorry cant comment must make this

public void oncameraviewstarted(int width, int height) { cany= new mat(height, width, cvtype.cv_8uc4); } 

see question here