Set up a layout with a custom view

Question

I have a custom view class (a canvas for drawing). When I want it to take up the whole screen, I instantiate the class and call setContentView like so:

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        drawingPanel = new DrawingPanel(this);
        setContentView(drawingPanel);
}

However, when I want the screen to be base on an xml layout (activity_make.xml) with say 2 elements, one button and a placeholder for the drawing canvas, how do 'stick' my custom view into the view placeholder?

public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_make); // the layout which has a button and a placeholder view
      drawingPanel = new DrawingPanel(this); // instantiating my canvas
      View drawPanelPlaceholder = (View) findViewById(R.id.drawingview);
      // how do i stick the drawingPanel into the drawPanelPlaceholder?
}

Or is there a better way to approach this? Links to documentation regarding this are also appreciated!

Answer 1

You can instanciate your custom view directly in your XML layout.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content">
  <com.mypackage.DrawingPanel 
      android:id="@+id/drawin_panel"
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" />
</LinearLayout>

Some doc about custom components on the developer's guide

Answer 2

If your DrawingPanel class extends View you can do something like this,

In your xml declare this custom component with its package name,

<com.myview.DrawingPanel android:id="@+id/drawingview" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" >

Please note that, com.myview.DrawingPanel is just a name that I have used to demonstrate. But make sure you use the same package name in which you have your DrawingPanel.class.

And now in your onCreate,

public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_make); 
      drawingPanel = (DrawingPanel) findViewById(R.id.drawingview);

}

Answer 3

If you want to add your drawingPanel to drawPanelPlaceholder, drawPanlePlaceholder should extend ViewGroup. So it can be ViewGroup, RelativeLayout, LinearLayout or other. Then you just simply do this

drawPanelPlaceholder.addView(drawingPanel);
drawPanelPlaceholder.invalidate();