CODEWITHSUNDEEP
javaandroidandroid-contextcustom-view
SHAI
SHAI

Reputation: 859

Getting MainActivity context in CustomView class

I have 2 classes: MainActivity and CustomView. I have an XML layout with this CustomView.

I want to access all my MainActivity variables from my CustomView class and also to modify them, I tried to get the context but it didn't work.

MainActivity class:

 MyCustomView customV;
 int myVar;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.start_page);
    customV = (MyCustomView) findViewById(R.id.view2);
    myVar = 5;
    }

MyCustomView class:

public class MyCustomView extends TextView {

public MyCustomView(Context context) {
    super(context);
    init();
}

public MyCustomView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
}

public MyCustomView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
}

context.myVar = 7  //this is what I'm trying to do...

I also tried getContext which didn't work.

Upvotes: 4

Views: 1128

Answers (4)

Shia G
Shia G

Reputation: 1464

or make the variable static and use it like this.

 MainActivity.myVar=7;

or if you want to initialize in the custom view depend on a variable from the MainActivity then do it like that in the custom view.

private int myVar;
 public void init(int myVar) {
    this.myVar = myVar;
    invalidate();

in MainActivity.

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.start_page);
customV = (MyCustomView) findViewById(R.id.view2);
myVar = 5;
customV.init(myVar);
}

i hope this help you.

Upvotes: 1

LIProf
LIProf

Reputation: 436

If you don't care about the fact that you are tightly coupling your two classes, then the only thing you need to do is typecast your "context" variable to MainActivity. Something like:

((MainActivity) context).myVar = 5;

will work. But you really should consider an alternate design that only loosely couples your classes.

Upvotes: 1

Sazzad Hissain Khan
Sazzad Hissain Khan

Reputation: 40186

Best way to do so is,

public class MyCustomView extends TextView {
    private MainActivity mActivity;

    public void setActivity(MainActivity activity) {
        mActivity = activity;
    }

    public MyCustomView(Context context) {
        super(context);
        init();
    }

    public MyCustomView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MyCustomView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
}

Instantiate,

customView = (MyCustomView) findViewById(R.id.view2);
customView.setActivity(this);

Access variable inside functions in MyCustomView,

mActivity.myVar = 10;

Upvotes: 1

2Dee
2Dee

Reputation: 8627

By trying to access variables from your Activity directly in your TextView subclass, you introduce tight coupling between you subclass of Actity and your custom TextView, which essentially hinders the reusability of your custom TextView because it can then only be used in that type of Activity, using it in another layout would break everything. Basically, I would say it's bad design and would not recommend that approach.

You could simply add a method to your custom TextView, and use the variable there :

public class MyCustomView extends TextView {

    // your code

    public void setVariable(int myInt){
        //use the int here, either set a member variable 
        //or use directly in the method
    }
}

and in your Activity 

customV = (MyCustomView) findViewById(R.id.view2);
customV.setVariable(5);

Upvotes: 6

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