在没有Activity的另一个类文件中使用Toast扩展了Android

Question

I've 2 files: Core (extends Activity) and DwCore. I'm using AsyncTask in a Core subclass and I want to use Toast in DwCore subclass but I can't get properly the Core Context.

Core

class DwFiles extends AsyncTask<Void, Void, Long> {
    protected Long doInBackground(Void... parms) {
        long totalSize = 0;
        dwCore.mainCounter(Core.this);
        return totalSize;
    }
}

DwCore subclass

public void mainCounter(Context c){
    Integer count = 0;
    for(int i=0;i<count;i++){
        Toast.makeText(c, count.toString(), Toast.LENGTH_SHORT).show();
    }
}

Answer 1

You can't do anything that affects the UI from worker threads - that includes showing toasts.

class DwFiles extends AsyncTask<Void, Void, Long> {
protected Long doInBackground(Void... parms) {
    long totalSize = 0;
     publishProgress(check_point);
    return totalSize;
}
}

protected void onProgressUpdate(Integer integers) {
   dwCore.mainCounter(Core.this);
}

Answer 2

public void mainCounter(Context c){
Integer count = 0;
     for(int i=0;i<count;i++){
         Toast.makeText(getActivity(), count.toString(), Toast.LENGTH_SHORT).show();
    }
}

You can use getActivity() function or this.getActivity().
getActivity() can be used in a Fragment for getting the parent Activity of the Fragment (basically the Activity that displayed the Fragment).

Answer 3

can't be done as doInBackGround runs on a background thread which cant access the ui thread. What you can do is ,Create an Custom interface implement it on your activity then push the ui related update from the onProgressUpdate().

    Interface ProgUpdate{
void uiUpdate(int update)
}

BackGround theread :
ProgUpdate listener;

onProgressUpdate(Int i){
listener.uiUpdate(i)
}