将一个自定义视图的对象访问到另一个在Activty类上创建的Customview

Question

My actual problem: I have an array in CustomView1 class. And I want to access it in CustomView2 class. And when it will fill, I have to call view2.invalidate() .

This is my activity class:

public class TestApp extends Activity {

        CustomView1 view1;

        CustomView2 view2;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);

            view1 = (CustomView1) findViewbyId(R.id.CustomViewID1);
            view2 = (CustomView2) findViewbyID(R.id.CustomViewID2);

        }
    }

This is my first CustomView class . Here I want to call view2.invalidate() .

public class CustomView1 extends View {

    byte[] bytearray = new byte[200];

    public CustomView1(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @override
    onDraw() {
        view2.invalidate();
    }

}

And this is my second CustomView class. Here I want to access the same object of CustomView1 (ie view1 object ) class that I have created in Activity class.

public class CustomView2 extends View {

    public CustomView2(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
}

Is it possible to access like this? Any other idea how to do that?

Answer 1

You can just have a CustomView2 view2; member inside your CustomView1 class. At the layout time, just tell view1 what is its view2.

This may look like this:

view2 = (CustomView2)findViewById(R.id.view2);
view1 = (CustomView1)findViewById(R.id.view1);
view1.setView2(view2);

Answer 2

For this to work you need to have a reference of those views inside your custom views classes. Something like this in CustomView1 (same logic is applied for CustomView2 ):

public class CustomView1 extends View
{

    byte[] bytearray  = new byte[200];
    private CustomView2 view2;

    public CustomView1(Context context, AttributeSet attrs) 
    {
       super(context, attrs);  
    }

    public void setCustomView2(CustomView2 view2) 
    {
       this.view2 = view2;
    }

    @override 
    onDraw()
    {
       if(view2 != null) //If view2 is not already set, we do not want a null pointer exception to occur
       {
          view2.invalidate();
       }
    }

}

To use it, you need something like this:

public class TestApp extends Activity  
{ 

   CustomView1  view1 ;
   CustomView2  view2 ;


   @Override
   public void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.main); 

       view1   = (CustomView1) findViewbyId(R.id.CustomViewID1);
       view2   = (CustomView2) findViewbyID(R.id.CustomViewID2);

       view1.setCustomView2(view2);
       view2.setCustomView1(view1);

   }  
}

EDIT: You can create another custom constructor for your CustomView1 class in addition to the one you already have. Something like this:

public CustomView1(Context context) 
{
     super(context);  
}

This way you avoid passing a null AttributeSet to your view and you call your custom view like this: CustomView1 view1 = new CustomView1(context) .

The public CustomView1(Context context, AttributeSet attrs) constructor is used to handle the situation that you declare you custom view through a layout xml file and not programmatically. You will need to set the layout properties of your view programmatically that way. Check this for help in doing so.