android - java.io.FileNotFoundException when writing to internal memory -

i've written functions making/editing files , worked fine. however, needed use these function in many activities, i've found guide on how globalize functions, , somehow did it. after put functions in separate class, stopped working. logcat not working, can't trycatch it, if could, don't think me.

here part of mainactivity.java:

myhelper myhelp = new myhelper(this); @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); myhelp.synchronizedb("filename"); } 

here part of myhelper.java:

public class myhelper extends actionbaractivity { context mcontext;  public myhelper(context context){     this.mcontext = context; } public void writefile(string fname, string fcontent) {         bufferedwriter bw = new bufferedwriter(new outputstreamwriter(openfileoutput(fname, mode_append)));         bw.write(fcontent);         bw.close(); }    public void synchronizedb(string filename) {     writefile(filename, "blabla"); } } 

you improperly making class not utilized activity subclass extend actionbaractivity. not workable call new subclass of activity, activity has been created system functional, , after oncreate() method has been called system.

likely hit upon making helper class sort of fake activity, in order able use methods inherited activity (and similar) such openfileoutput(). not workable.

a more workable solution drop "extends actionbaractivity" class name, , either utilize passed in context reference:

mcontext.openfileoutput(...) 

or, perhaps better, discovered internal storage location in constructor , save later use:

public class myhelper {   context mcontext;   file mdir;      public myhelper(context context){         this.mcontext = context;         this.mdir = context.getfilesdir();     }     public void writefile(string fname, string fcontent) {             bufferedwriter bw = new bufferedwriter(new outputstreamwriter(                new fileoutputstream(new file(mdir, fname), mode_append)));             bw.write(fcontent);             bw.close();     } 

further, because of rule activity class being functional after it's oncreate() called, must move creation of helper class or after utilizing activity's oncreate()

myhelper myhelp; //can't initialize our context not yet valid @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     myhelp = new myhelper(this); //now have working context pass     myhelp.synchronizedb("filename"); }