android.app.Application cannot be cast to android.app.Activity

Bitmap myBitmap = BitmapFactory.decodeResource(getResources(),R.drawable.my_image)
.copy(Bitmap.Config.ARGB_8888, true);
Canvas c = new Canvas(myBitmap);
// etc.  ....... 

EditText hEditText;

// TextChanged in onCreate

hEditText = (EditText)findViewById(R.id.idEditText);

hEditText.addTextChangedListener(new TextWatcher() {

	public void afterTextChanged(Editable str) {

	}



	public void beforeTextChanged(CharSequence s, int start, int count,

			int after) {

	}



	public void onTextChanged(CharSequence sq, int start, int before,

			int count) {

	}

});

public class MainActivity extends Activity {
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(new SampleView(this));
	}

	private static Bitmap codec(Bitmap src, Bitmap.CompressFormat format,
			int quality) {
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		src.compress(format, quality, os);

		byte[] array = os.toByteArray();
		return BitmapFactory.decodeByteArray(array, 0, array.length);
	}

	private static class SampleView extends View {

		// CONSTRUCTOR
		public SampleView(Context context) {
			super(context);
			setFocusable(true);

		}
		@Override
		protected void onDraw(Canvas canvas) {
			Paint paint = new Paint();
			
			canvas.drawColor(Color.YELLOW);
            
        
			Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.flower_blue);
             
			Bitmap bPNGcompress = codec(bmp, Bitmap.CompressFormat.PNG, 0);

		   int h = bmp.getHeight();
           
           canvas.drawBitmap(bmp, 10,10, paint);
           canvas.drawBitmap(bPNGcompress, 10,10 + h + 10, paint);
           
		}

	}
}

android:textColorHint="@color/grey"

 <TextView
        android:id="@+id/first_element_id"
        .........
 />
    <TextView
        android:id="@+id/second_element_id"
        android:layout_below="@id/first_element_id"
        ..........
 />