Can not create array of buttons programatically without an error

Question

This block of code does not work for me. I debugged and I think the error is coming from the setlayoutparams but it doesn't make sense because if I take out the for loop and create just 1 button (not an array of buttons) then it'll work.

   Button btn[] = new Button[oNumber];
    for (int i=0;i<oNumber;i++){
        btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT));
        btn[i].setText(oName[i]);
        System.out.println("making b's");
        layout.addView(btn[i]);
    }

This is the error I get. I do have the activity correctly written in the manifest.

    08-14 12:45:56.482: E/AndroidRuntime(4060): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rcontrol/com.example.rcontrol.ViewTarget}: java.lang.NullPointerException

follow the steps of azgolfer. It solves your problem

G_S
– G_S

2012-08-14 17:59:04 +00:00
Commented Aug 14, 2012 at 17:59 — G_S
– G_S, Commented Aug 14, 2012 at 17:59

azgolfer · Accepted Answer · 2012-08-14 17:52:02Z

10

You created the array of buttons but did not initialize it:

Button btn[] = new Button[oNumber];
for (int i=0;i<oNumber;i++){
    btn[i] = new Button(this); // initialize it
    btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT));
    btn[i].setText(oName[i]);
    System.out.println("making b's");
    layout.addView(btn[i]);
}

answered Aug 14, 2012 at 17:52

azgolfer

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UmAnusorn · Accepted Answer · 2013-04-25 03:06:06Z

1

for more Detail.

int oNumber = 4;

    String oName[] = {"x","2","3","4"};
    Button btn[] = new Button[oNumber];
     LinearLayout layout = (LinearLayout) findViewById(R.id.layout1);

    for (int i=0;i<oNumber;i++){
        btn[i] = new Button(this); // initialize it
        btn[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.WRAP_CONTENT));
        btn[i].setText(oName[i]);
        btn[i].setOnClickListener(this);
        System.out.println("making b's");
        layout.addView(btn[i]);
    }

answered Apr 25, 2013 at 3:06

UmAnusorn

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