Question

I have a simple class, BoundedView that extends View. I’m doing this primarily to mess with the onTouchEvent callback function.

Is there a way to draw a border around each instance of this view, from the class itself? If not, what is the easiest way to implement this?

Implementation:

public class BoundedView extends View
{
  public String cellName = "no name";

  // constructors are here.

  @Override
  public void onDraw( Canvas canvas )
  {
    // maybe here? Right now it's invisible, used only for touch detection
  }

  @Override
  public boolean onTouchEvent( MotionEvent event )
  {
    Intent i = new Intent( getContext(), TabCellDetails.class );
    i.putExtra( "cellName", this.cellName );
    getContext().startActivity( i );

    return false;
  }
}

Using:

<com.lifecoderdev.android.drawing1.BoundedView
        android:id="@+id/boundedView1"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="78dp"
        android:layout_marginRight="96dp" 
        android:tag="Smooth Endoplasmic Reticulum"/>

EDIT: This gets me close:

public void onDraw( Canvas canvas )
{
  int[] colors = { 0xFF000000, 0xCC000000 };
  float[] radii = { 5, 5, 5, 5, 5, 5, 5, 5 };
  GradientDrawable drawable = new GradientDrawable( GradientDrawable.Orientation.TOP_BOTTOM, colors );
  drawable.setCornerRadii( radii );
  drawable.setStroke( 1, 0xFF000000 );
  this.setBackgroundDrawable( drawable );
}

However, it is drawing a fully filled in black box, not a transparent one with a black border.

EDIT 2: Got it:

Paint paint = new Paint();

paint.setColor( Color.RED );
paint.setStrokeWidth( 1.0f );

canvas.drawRect( 0, 0, getWidth(), 1.0f, paint );
canvas.drawRect( 0, 0, 1.0f, getHeight(), paint );
canvas.drawRect( 0, getHeight()-1.0f, getWidth(), getHeight(), paint );
canvas.drawRect( getWidth()-1.0f, 0, getHeight(), getWidth(), paint );

EDIT 3: Andreas and Warren’s solution was much nicer:

@Override
public void onDraw( Canvas canvas )
{
  Paint paint = new Paint();
  paint.setColor( Color.RED );
  paint.setStrokeWidth( 1.5f );
  paint.setStyle( Style.STROKE );

  canvas.drawRect( 0, 0, getWidth(), getHeight(), paint );
}

Answer 1

Yes inside your onDraw() is the right place.

canvas.drawRect(0, 0, getWidth(), getHeight(), paint);

That should work. If you set the paint variable correctly (stroke width, color) you should see your border.