return - kotlin function returning null -

-

i trying android development kotlin. in case want overwrite: contentprovider have overwrite function "query". "query" returns "cursor" type. however, when create cursor instance in function database.query "cursor?" type. can return cursor if not null, do if null?

this looks like:

override fun query(uri: uri, projection: array<out string>?, selection: string?, selectionargs: array<out string>?, sortorder: string?): cursor {      val cursor = querybuilder.query(db, projection, selection, selectionargs, null, null, sortorder)             // make sure potential listeners getting notified             cursor?.setnotificationuri(getcontext()?.getcontentresolver(), uri)              if(cursor != null)                 return cursor             else                 // here?

any ideas how solve that?

thanks, sven

update first of answers.

annotation seems not work in case can access compiled code , dont option annotate source. maybe missing here.

implementing own cursor seems overkill if have every time problem occurs.

so seems option return cursor!! dont know how it. code bit more complicated in example, missed when statement. updated version:

override fun query(uri: uri, projection: array<out string>?, selection: string?, selectionargs: array<out string>?, sortorder: string?): cursor {      val cursor = ??? //how initialize cursor somehow?     val db = database.getwritabledatabase()      if(db != null) {         val cursor = querybuilder.query(db, projection, selection, selectionargs, null, null, sortorder)                 // make sure potential listeners getting notified                 cursor?.setnotificationuri(getcontext()?.getcontentresolver(), uri)                  if(cursor != null)                     return cursor      }      // return here? cursor not exist }

do have implement own cursor , clutter code useless "throw unsupportedexceptions"?

your options are:

  • if cursor null, throw exception: return cursor!! (this ok in case sure cursor never null
  • if cursor null, return trivial cursor (e.g. own implementation of abstractcursor behaves empty result set
  • (as franck said in comment) annotate querybuilder.query() function @notnull: http://blog.jetbrains.com/kotlin/using-external-annotations/

Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more