Android: can't find constructor for custom LinearLayout

Question

I'm trying to create a custom LinearLayout (on Android), but I keep getting compiler errors when trying to use it in my main Activity class. The extended LinearLayout needs a Context passed to it by the constructor, but I don't know where to get that Context. All the examples I see show the passing of the this pointer from the Activity. What am I doing wrong?

Compiler Error

MyApp.java:15: cannot find symbol symbol: constructor BoardLayout(com.test.program.MyApp) location: class com.test.program.BoardLayout BoardLayout board = new BoardLayout(this);

BoardLayout.java

public class BoardLayout extends LinearLayout { public void BoardLayout(Context context) { // initialisation code } public BoardLayout(Context context, AttributeSet attrs) { super(context, attrs); } }

MyApp.java

public class MyApp extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); BoardLayout board = new BoardLayout(this); // Doesn't work! setContentView(board); } }

Solution:

Looks like the problem was two issues.

Constructors don't have type void (careless mistake on my part).
Had to call "super(context)" as the first instruction in the constructor.

are you importing your BoardLayout class?

RoflcoptrException
– RoflcoptrException

2011-01-03 22:57:10 +00:00
Commented Jan 3, 2011 at 22:57 — RoflcoptrException
– RoflcoptrException, Commented Jan 3, 2011 at 22:57

RoflcoptrException · Accepted Answer · 2011-01-03 23:20:20Z

The problem is that you don't have a constructor that takes 1 argument in BoardLayout. As pointed out in the comments, the first isn0t a constructor but a method.

public class BoardLayout extends LinearLayout { public void BoardLayout(Context context) { // initialisation code } public BoardLayout(Context context, AttributeSet attrs) { super(context, attrs); } }

Keep in mind that Java implicitly calls super() with no arguments, if you don't explicitly call super. Since LinearLayout hasn't a constructor that takes no arguments you have to call super explicitly to avoid compilation errors.

The first one isn't actually a constructor as it has a return type and is therefore a method.
ah yes. sry i missed that. But then the problem is even clearer. There is no BoardLayout constructor that takes 1 argument ;)

dave.c · Accepted Answer · 2011-01-03 23:01:30Z

I'm not 100% sure, but the constructor you have defined requires two parameters:

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

However the constructor you are calling is only being passed one parameter:

BoardLayout board = new BoardLayout(this);

If you want to call your new constructor you need to pass in a value for the second parameter:

BoardLayout board = new BoardLayout(this,null);

I'm not familiar with extending a LinearLayout so I'm not sure how to get a proper value for the AttributeSet

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