Question

I am trying to work through an android example given on the developers’ page.
It gives 2 ways of drawing on a canvas. The first way is to use a class called CustomDrawableView, which looks like this:

public class CustomDrawableView extends View {
private ShapeDrawable mDrawable;

public CustomDrawableView(Context context) {
super(context);

int x = 10;
int y = 10;
int width = 300;
int height = 50;

mDrawable = new ShapeDrawable(new OvalShape());
mDrawable.getPaint().setColor(0xff74AC23);
mDrawable.setBounds(x, y, x + width, y + height);
}

protected void onDraw(Canvas canvas) {
mDrawable.draw(canvas);
}
}

This is then called by the main class:

CustomDrawableView mCustomDrawableView;
protected void onCreate(Bundle savedInstanceState) {    
super.onCreate(savedInstanceState);    
mCustomDrawableView = new CustomDrawableView(this);        
setContentView(mCustomDrawableView);
}

But then the tutorial says:

If you’d like to draw this custom drawable from the XML layout instead of from the Activity, then the CustomDrawable class must override the View(Context, AttributeSet) constructor, which is called when instantiating a View via inflation from XML. Then add a CustomDrawable element to the XML, like so:

<com.example.shapedrawable.CustomDrawableView
   android:layout_width="fill_parent"     
android:layout_height="wrap_content"     
/>

I have successfully got the first example to run but I do not know what my code should look like if I want to adopt the second option.
Presumably, I start with @Override View but then I am stuck.

The reason I want to do this is because I want to create a canvas that covers only part of the screen so I can fit buttons and text in the other part.

Answer 1

If the tutorial is correct then the only change you make is to add that constructor. You probably want to move the drawable init code to a separate method.

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

The xml

<com.example.shapedrawable.CustomDrawableView
   android:id="+id/custom_drawable_view"
   android:layout_width="fill_parent"     
    android:layout_height="wrap_content"     
/>

And you can obtain the view like this.

CustomDrawableView mCustomDrawableView;

protected void onCreate(Bundle savedInstanceState) {    
    super.onCreate(savedInstanceState);          
    setContentView(R.layout.main); // assuming your layout is named main.xml
    mCustomDrawableView = (CustomDrawableView) findViewById(R.id.custom_drawable_view);
}