android - Set ImageView from Bitmap (null pointer exception) -

so app has actiondialog contains blank canvas interface simple cancel , save buttons. happening best demonstrated in brief illustration

screen layout before

-(textview)-(imageview)-(button)-

then when user presses button actiondialog pops requesting sign. once sign captured drawing saved. drawing accessed via memory , placed original imageview bitmap. ends happening

screen layout after

----------nothing--------------

they disappear , error in logcat:

05-14 19:06:27.004: e/error(25274): java.io.filenotfoundexception: /storage/emulated/0signature.png: open failed: eacces (permission denied) 05-14 19:06:27.004: e/bitmapfactory(25274): unable decode stream: java.io.filenotfoundexception: /storage/emulated/0signature.png: open failed: enoent (no such file or directory) 

java.io.filenotfoundexception: /storage/emulated/0signature.png: open failed: enoent (no such file or directory)

it not crash program though. anyways here code files

action dialog

public class capturesignature extends dialogfragment { sign sign; view view;  public dialog oncreatedialog(bundle savedinstancestate) {      alertdialog.builder capsig = new alertdialog.builder(getactivity());      capsig.setview(sign = new sign(this.getactivity(), null))             .setmessage(r.string.store_question)             .setpositivebutton(r.string.save,                     new dialoginterface.onclicklistener() {                         public void onclick(dialoginterface dialog, int id) {                             try {                                 sign.setdrawingcacheenabled(true);                                 sign.getdrawingcache()                                         .compress(                                                 bitmap.compressformat.png,                                                 10,                                                 new fileoutputstream(                                                         new file(                                                                 getactivity()                                                                         .getexternalfilesdir(                                                                                 "img"),                                                                 "signature.png")));                             } catch (exception e) {                                 log.e("error ", e.tostring());                             }                             file mysig = new file(getactivity()                                     .getexternalfilesdir("img"),                                     "signature.png");                             imageview sig = (imageview) getactivity()                                     .findviewbyid(r.id.sig_image);                             bitmap bmp = bitmapfactory.decodefile(mysig                                     .getabsolutepath());                             sig.setimagebitmap(bmp);                          }                     })              .setnegativebutton(r.string.cancel,                     new dialoginterface.onclicklistener() {                         public void onclick(dialoginterface dialog, int id) {                         }                     });      // create dialog object , return     return capsig.create(); } } 

so i've messed somewhere. if has insight grateful. thanks!

i think either saving wrong or i'm not correctly declaring sign, in call don't give value, drawing cache not being accessed.

edit have declared in manifest

<uses-permission android:name="android.permission.write_external_storage" /> <uses-permission android:name="android.permission.read_external_storage" /> 

2nd edit

showing new code , logcat, error has changed

final edit

thank matt giles , jrowan, driving me insane. works , above code final version.

the problem line:

new file(environment.getexternalstoragedirectory().getpath() + "signature.png" 

the call getpath() returns path doesn't have trailing '/'. hence file path in error message, /storage/emulated/0signature.png instead of /storage/emulated/0/signature.png.

it better use application-specific storage, instead of putting files in sdcard root directory. instead of new file(...) call have now, use:

new file(getactivity().getexternalfilesdir("img"), "signature.png") 

getexternalfilesdir(name) creates folder called "name" that's dedicated application. prevents app cluttering sdcard root directory.