Question

The documentation about this is really confusing. I simply need to add rectangels to a View I defined in my main.xml layout file. It will be a small part of the layout.

What I want to achieve is, I want to add shelves to a room but since the room shape and shelves change, I need to add them programmatically.

Below is a little part of my main.xml file, you can see the View I defined:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    android:id="@+id/relativeLayout2"
    android:layout_width="600dp"
    android:layout_height="650dp"
    android:layout_marginTop="70dp"
    android:layout_marginLeft="30dp"
    android:layout_toRightOf="@+id/relativeLayout1" >

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="@string/getDirections"
        android:textSize="20dp"
        android:textStyle="bold" />

    <View
        android:id="@+id/roomplan"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
            android:layout_below="@+id/textView3"
        android:layout_marginTop="40dp"
        android:background="@android:color/white" />

</RelativeLayout>

This is the custom View class I created to handle dynamic changes:

public class CustomView extends View {
    ShapeDrawable roomFrame;
    ArrayList<ShapeDrawable> shelfFrames;

    public CustomView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }

    @Override
    protected void onDraw(Canvas canvas){
        super.onDraw(canvas);
        roomFrame.draw(canvas);
        for (ShapeDrawable shelfFrame : shelfFrames){
            shelfFrame.draw(canvas);
        }
    }

    public void setRoom(Stage stage){
        roomFrame = new ShapeDrawable(new RectShape());
        roomFrame.getPaint().setColor(0xff74AC23);   
        roomFrame.setBounds(10, 10, stage.getWidth(), stage.getHeight());
    }

    public void setShelves(ArrayList<Shelf> shelves){
        shelfFrames = new ArrayList<ShapeDrawable>();
        for(int i = 0; i<shelves.size(); i++){
            ShapeDrawable shelfFrame = new ShapeDrawable(new RectShape());
            shelfFrame.getPaint().setColor(0xff74AC23);
            shelfFrame.setBounds(shelves.get(i).getXPosition(), shelves.get(i).getYPosition(), shelves.get(i).getWidth(), shelves.get(i).getHeight());
            shelfFrames.add(shelfFrame);
        }
    }
}

Now simply, when a new room plan is asked I am trying to assign this class to the View object in the xml layout:

public void loadRoomPlan(Room room, ArrayList<Shelf> shelves){
    CustomView asdsView = (CustomView)findViewById(R.id.roomplan);
    asdsView.setRoom(room);
    asdsView.setShelves(shelves);
    asdsView.invalidate();
}

I always get

Caused by: java.lang.ClassCastException: android.view.View cannot be cast to org.example.myproject.CustomView

error.

Probably I am doing this very very wrong, am I not?

Answer 1

The error seems to be in this line:

CustomView asdsView = (CustomView)findViewById(R.id.shopplan);

What is shopplan? In case it is a mistake and you meant R.id.roomplan try to subtitute the View in your layout for your Custom view:

<org.example.myproject.CustomView
    android:id="@+id/roomplan"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView3"
    android:layout_marginTop="40dp"
    android:background="@android:color/white" />

UPDATE:

Try adding the other two constructors to your CustomView class:

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

public CustomView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

When you use a custom view in an xml layout, your view has to deal with the layout attributes (the constructor AttributeSet param).