import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

public class AimView extends View {

    private Paint mPaint;

    public AimView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public AimView(Context context) {
        super(context);
        init();
    }

    private void init(){
        mPaint = new Paint();
        mPaint.setColor(Color.BLACK);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(10);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        int w = getWidth();
        int h = getHeight();

        float left   = w*3.f/10;
        float top    = h*3.f/10;
        float right  = w*7.f/10;
        float bottom = h*7.f/10;

        canvas.drawRect(left, top, right, bottom, mPaint); //todo smth like this
    }
}