Is Use of getApplicationContext() considered Harmful?

Question

Yesterday I read that using getApplicationContext() was potentially hazardous. Thus, code like this:

Toast.makeText(getApplicationContext(), "You mashed the button, dude.", Toast.LENGTH_SHORT).show();

...should be this instead:

Toast.makeText(MainActivity.this, "You mashed the button, dude.", Toast.LENGTH_SHORT).show();

(where "MainActivity" is the name of the class in which the code lives).

Yet I see many code snippets that include getApplicationContext(), such as:

button.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        _initTask = new InitTask();
        _initTask.execute( getApplicationContext() );
    }
});

...from here. Is it really preferable to use <className>.this over getApplicationContext()?

UPDATE

I've obviously still not understanding the niceties (or meanities) of this; with this code:

Toast.makeText(GetVendorsTask.this, s[0], Toast.LENGTH_SHORT).show();

I get this compilation err msg:

Error:(156, 18) error: no suitable method found for makeText(MainActivity.GetVendorsTask,String,int) method Toast.makeText(Context,CharSequence,int) is not applicable (argument mismatch; MainActivity.GetVendorsTask cannot be converted to Context) method Toast.makeText(Context,int,int) is not applicable (argument mismatch; MainActivity.GetVendorsTask cannot be converted to Context)

So I changed the complained-about line of code to:

Toast.makeText(MainActivity.this, s[0], Toast.LENGTH_SHORT).show();

...and it works (compiles). MainActivity is the outermost class in the .java file (named MainActivity.java, that is); but GetVendorsTask is the most proximate class (that line of code is within the GetVendorsTask class). To be clear, the code is:

public class MainActivity extends ActionBarActivity {

    . . .

    class GetVendorsTask extends AsyncTask<Context, String, SearchResponse>
    {
    . . .
        @Override
        protected void onProgressUpdate(String... s)
        {
            super.onProgressUpdate(s);
            //Toast.makeText(getApplicationContext(), s[0], Toast.LENGTH_SHORT).show(); <= "getApplicationContext()" might be null
            //Toast.makeText(GetVendorsTask.this, s[0], Toast.LENGTH_SHORT).show();
            Toast.makeText(MainActivity.this, s[0], Toast.LENGTH_SHORT).show();
        }

So replacing "GetVendorsTask" with "MainActivity" appeases the beast, but is it the best way to do it?

UPDATE 2

This sample code uses simply "this" in place of the other possibilities.

Hey Clay, what were the reasons given for application context being hazardous? Do you have a link to an article? — Justin Pollard, Apr 03 '14 at 18:22
[I think the docs do a pretty good job of describing when to use it](http://bit.ly/1kvxajO) — adneal, Apr 03 '14 at 18:24

score 5 · Accepted Answer · edited May 23 '17 at 12:09

The Application Context is a singleton class that will always return the same Context instance no matter where you are in your Application. In other words, the Application Context will persist for as long as your Application is running.

In the other hand, using an Activity for Context will be specific to that Activity and it is different than the Application Context. For example, you can use the Activity Context to show a Dialog, but not the Application Context.

Here is an answer that explains it in more detail.

Also, I cannot recommend this post enough; it clarified the topic for me quite a bit when I read it.

score 1 · Answer 2 · answered Apr 03 '14 at 18:22

1

It is best to pass in the minimum required Context for whatever you're doing. Treating the application context as a kind of god object can temporarily hide problems arising from misuse of lifecycle methods.

answered Apr 03 '14 at 18:22

Collin Flynn

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Is Use of getApplicationContext() considered Harmful?

UPDATE

UPDATE 2

2 Answers2