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How to make an invisible button in runtime

Hi Experts,

I am trying to make a button invisible when the application starts (android), but my code does not work.

      Button b3;      
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);        
        login = (EditText) findViewById(R.id.editText1);
        senha = (EditText) findViewById(R.id.editText2);
        b3 = (Button) findViewById(R.id.button3);
        b3.setVisibility(View.GONE);   <-- code Crash here

How to do this code works ?

Thanks
Alexandre
0
alpires
Asked:
alpires
1 Solution
 
alexey_gusevCommented:
set it to "gone" in xml resource.

besides, are you sure your b3 object is not null?
0
 
AlanJayWeinerCommented:
There are three visibility states for Views, controls, etc - anything subclassed from View:

VISIBLE which means just that; the item is visible, takes up space in the layout, etc

INVISIBLE which means the item takes up space in the layout, but the item itself is not visible.  (think of three buttons in a row; the middle one is INVISIBLE, so it won't be drawn, but there will be space for it between the other two buttons)

GONE which means the item is not drawn, and doesn't take up space in the layout.  if the middle button of the three-button example were GONE, then the other two buttons would be positioned as if the middle button wasn't even defined at all; they would likely be close together.


Just offhand, try checking that b3 isn't null:

    b3 = (Button) findViewById(R.id.button3);
    if (b3 != null) {
        b3.setVisibility(View.GONE);   <-- code Crash here
    } else {
        Log.i("b3 is null");
    }

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You can also set a breakpoint at the setVisibility line and use the debugger.

Check that whatever is named 'button3' really is a button.  (there must be something otherwise the compiler would complain that R.id.button3 doesn't exist.  it's interesting that it does crash; anything subclassed from View has setVisibility() so I wouldn't expect it to crash...)

To make it invisible right from the start, set the "android:visibility" property to GONE right in the XML file:

    <Button
	android:id="@+id/clearMessage"
	android:layout_height="wrap_content"
	android:layout_width="wrap_content"
	android:text="Clear Message"
	android:visibility="gone">
    </Button>

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