Implementing a customized drawable in Android

Question

Hi ,

I was trying to get hold of 2D graphics in Android. As a example i want to implement a custom drawable and show it in my Activity

I have defined a customized drawable by extending from Android drawable as mentioned below

myDrawable extends Drawable {

 private static final String TAG = myDrawable.class.getSimpleName();
 private ColorFilter cf;
 @Override
 public void draw(Canvas canvas) {


  //First you define a colour for the outline of your rectangle

  Paint rectanglePaint = new Paint();
  rectanglePaint.setARGB(255, 255, 0, 0);
  rectanglePaint.setStrokeWidth(2);
  rectanglePaint.setStyle(Style.FILL);

  //Then create yourself a Rectangle
  RectF rectangle = new RectF(15.0f, 50.0f, 55.0f, 75.0f); //in pixels


  Log.d(TAG,"On Draw method");
  // TODO Auto-generated method stub
  Paint paintHandl = new Paint();
//  paintHandl.setColor(0xaabbcc);
  paintHandl.setARGB(125, 234, 213, 34 );
  RectF rectObj = new RectF(5,5,25,25);
  canvas.drawRoundRect(rectangle, 0.5f, 0.5f, rectanglePaint);

 }

 @Override
 public int getOpacity() {
  // TODO Auto-generated method stub
  return 100;
 }

 @Override
 public void setAlpha(int alpha) {
  // TODO Auto-generated method stub

 }

 @Override
 public void setColorFilter(ColorFilter cf) {
  // TODO Auto-generated method stub
  this.cf = cf;

 }


}

I am trying to get this displayed in my activity, as shown below

public class custDrawable extends Activity {
/** Called when the activity is first created. */


 LinearLayout layObj = null;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        layObj = (LinearLayout) findViewById(R.id.parentLay);
        ImageView imageView = (ImageView) findViewById(R.id.icon2);
        myDrawable myDrawObj = new myDrawable();
        imageView.setImageDrawable(myDrawObj);
        imageView.invalidate();
//  layObj.addView(myDrawObj, params);

    }
}

But when i run the app i see no rectangle on the activity, can anyone help me out? Where am i going wrong?

Answer 1

Your problem is in the getOpacity() method. 100 is not a valid value. You should use a PixelFormat value. Also, you should create your RectF and Paint in the constructor and then just adjust the values in draw() so you don't create so many objects that need garbage collected. Like this:

public class Square extends Drawable
{
    private final Paint mPaint;
    private final RectF mRect;

    public Square()
    {
        mPaint = new Paint();
        mRect = new RectF();
    }

    @Override
    public void draw(Canvas canvas)
    {
        // Set the correct values in the Paint
        mPaint.setARGB(255, 255, 0, 0);
        mPaint.setStrokeWidth(2);
        mPaint.setStyle(Style.FILL);

        // Adjust the rect
        mRect.left = 15.0f;
        mRect.top = 50.0f;
        mRect.right = 55.0f;
        mRect.bottom = 75.0f;

        // Draw it
        canvas.drawRoundRect(mRect, 0.5f, 0.5f, mPaint);
    }

    @Override
    public int getOpacity()
    {
        return PixelFormat.OPAQUE;
    }

    @Override
    public void setAlpha(int arg0)
    {
    }

    @Override
    public void setColorFilter(ColorFilter arg0)
    {
    }
}

Answer 2

Could you please provide an example, where in i can embed an image, with in a Traingle?