Android NULL pointer Exception when trying to add a view

Question

I am 2 days old to Android Programming. I may be comitting a mistake at the core level. If this is the case, pardon.

I am trying to add a text box to a Relative Layout. When a button is clicked. The method is bound to the button by the attribute android:onClick="method"

By doing the below.

public method (View view){
    RelativeLayout vRL = (RelativeLayout)findViewById(R.layout.rLayout);
    TextView vET = new TextView(this);
    vET.setText("Text added to view.");
    vET.setId(1);
    vRL.addView(vET);
    setContentView(R.layout.rLayout);
}

But I am getting a null pointer exception at vRL.addView(vET);

what is it that I am doing wrong? -OR-
Am I not adding the TextView element properly?

@SamirMangroliya it is set to rLayoutHome. How to proceed the same with inflating a layout and adding an element.? — user1203914
– user1203914, Commented Sep 11, 2012 at 11:02

Sankar · Accepted Answer · 2012-09-11 10:49:59Z

1

in below line

RelativeLayout vRL = (RelativeLayout)findViewById(R.layout.rLayout);

change the R.layout.rLayout to R.id.rLayout

answered Sep 11, 2012 at 10:49

Sankar

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2 Comments

user1203914 Over a year ago

yup it results in null but Why?

user370305 Over a year ago

Because there is no any setContenView() in your Activity before accessing this RelativeLayout and findViewById() only works in there is any View inflated to Activity. Or you can inflated a View and access RelativeLayout by reference of this view...

user370305 · Accepted Answer · 2012-09-11 10:50:19Z

0

setContentView(R.layout.rLayout);

put this line in onCreate() of Activity..

and this line from method()

RelativeLayout vRL = (RelativeLayout)findViewById(R.id.rLayout);

answered Sep 11, 2012 at 10:50

user370305

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2 Comments

user1203914 Over a year ago

I am trying to change the contentview from one layout to another from an activity. I do not want to setthe view to setContentView(R.layout.rLayout); at the beginning.

user370305 Over a year ago

Then you can not find R.id.rLayout RelativeLayout in your activity without setContentVIew() before. It always be null.

Shachilies · Accepted Answer · 2012-09-11 10:50:13Z

0

Replace below line with

`RelativeLayout vRL = (RelativeLayout)findViewById(R.id."id name of relative layout");`

answered Sep 11, 2012 at 10:50

Shachilies

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Comments

user1357696 · Accepted Answer · 2012-09-11 10:52:11Z

0

Change like this:

public method (View view){
    RelativeLayout vRL = (RelativeLayout)findViewById(R.id.rLayout);
    TextView vET = new TextView(this);
    vET.setText("Text added to view.");
    vET.setId(1);
    vRL.addView(vET);
    setContentView(R.layout.rLayout);
}

answered Sep 11, 2012 at 10:52

user1357696

Comments

Ankitkumar Makwana · Accepted Answer · 2012-09-11 11:05:08Z

0

change the R.layout.rLayout to R.id.rLayoutR.layout.rLayout);

answered Sep 11, 2012 at 11:05

Ankitkumar Makwana

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