android，带有getApplicationContext（）的自定义类

Question

Im developing an app that uses a lot of network requests for data retrieval. The network request is currently a URLConnection , with HttpsURLConnection .

Issue I've got is that i call getApplicationContext() a couple of times. This has been fine prior when i declare the class inside of the activity class, however i wish to just have the AsyncTask declared in a separate class, to be imported to activity classes where needed. I'm assuming that i cannot getApplicationContext() from the custom class as it is not extending the activity. How would i resolve this? Can i pass the context as a parameter when i instantiate it?

---

would something like this work:

 Context contxt = getApplicationContext(); CustomClass custmClass = new CustomClass(); ArrayList<Object> parameters = new ArrayList<Object>(); parameters.add(contxt); ... custmClass.execute(parameters); 

Where CustomClass extends AsyncTask<ArrayList<Object>, Void, Boolean> ?

Answer 1

As told in the other answers, you should pass the context as a parameter to your AsyncTask. Still, you can got lots of problems doing this, if you close your activity for example while the AsyncTask is executing and using this reference this will cause an exception.

To prevent this, avoid having a strong reference to your activity as mentioned in the other posts and use weak references. Make sure you always check if the return value of your weak reference is null.

Example :

import com.example.MyActivity;

public class MyTask {

    private final WeakReference<MyActivity> myActivity;

    public MyTask(MyActivity myActivity) {
        this.myActivity = new WeakReference<MyActivity>(myActivity);
    }

    private AsyncTask<String, Integer, Integer> createAsyncTask() {
        return new AsyncTask<String, Integer, Integer>() {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                // prepare execution
            }

            @Override
            protected Integer doInBackground(String... params) {
                // code
                return 0;
            }

            @Override
            protected void onPostExecute(Integer result) {
                if (myActivity.get() != null && !myActivity.get().isFinishing()) {
                    // do something
                }
            }
        };
    }

}

Answer 2

in one of your activities (the main activity is better) declare this

public static Context context;

in your oncreate add this

 context=getApplicationContext();

and in other classes just use

MainActivity.context

this works for me

Answer 3

Can i pass the context as a parameter when i instantiate it?

Yes. You can pass current Context as parameter to your custom class.

1st Way:

Create single Argument Constructor in your Custom Classs

Context myCon;

public myClass(Context mCon){
 this.myCon=mCon;
}

And you can access in your Activity like

myClass mc=new myClass(Activity.this);

2nd Way:

By passing to Custom class method directly

public void getCount(Context mCon){
 //Directly used mCon here
}

Current Solution:

Context contxt = getApplicationContext();
CustomClass custmClass = new CustomClass(contxt);
ArrayList<Object> parameters = new ArrayList<Object>();
parameters.add(contxt);
...
custmClass.execute(parameters);