import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private EditText myTextEdit;
    private myImageView myImage;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myTextEdit = (EditText) findViewById(R.id.textFieldForNum);
        myImage = (myImageView) findViewById(R.id.imageView);
    }

    public void drawMethod(View view) {
        myImage.enableDrawing(Integer.parseInt(myTextEdit.getText().toString()));
        myImage.invalidate();

    }
}

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.widget.ImageView;

public class myImageView extends ImageView {

    private Paint myPaint;
    private int pointX;
    private int pointY;
    private int length;
    private boolean toDraw;

    public myImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        toDraw=false;
        myPaint = new Paint();
        pointX = 700;
        pointY = 900;
    }

    @Override
    protected void onDraw(Canvas canvas){
        super.onDraw(canvas);
        if(toDraw) {
            drawRecursiveSideCross(canvas,pointX, pointY, length);
        }
    }

    public void enableDrawing(int length){
        this.length=length;
        toDraw=true;
    }

    public void drawRecursiveSideCross(Canvas canvas,int pointX, int pointY, int length){
        myPaint.setColor(Color.RED);
        myPaint.setStrokeWidth(5);
        if(length>=50) {
            canvas.drawLine(pointX, pointY, pointX, pointY - length, myPaint);
            canvas.drawLine(pointX, pointY, pointX-3*length/4, pointY+length, myPaint);
            canvas.drawLine(pointX, pointY, pointX+3*length/4, pointY+length, myPaint);
            drawRecursiveStraightCross(canvas, pointX, pointY - length, length/2);
            drawRecursiveStraightCross(canvas, pointX-3*length/4, pointY+length, length/2);
            drawRecursiveStraightCross(canvas, pointX+3*length/4, pointY+length, length/2);
        } else return;
    }

    public void drawRecursiveStraightCross(Canvas canvas, int pointX, int pointY, int length){
        myPaint.setColor(Color.BLUE);
        myPaint.setStrokeWidth(5);
        if(length>=50){
            canvas.drawLine(pointX, pointY, pointX, pointY-length, myPaint);
            canvas.drawLine(pointX, pointY, pointX, pointY+length, myPaint);
            canvas.drawLine(pointX, pointY, pointX-length, pointY, myPaint);
            canvas.drawLine(pointX, pointY, pointX+length, pointY, myPaint);
            drawRecursiveSideCross(canvas, pointX, pointY-length, length/2);
            drawRecursiveSideCross(canvas, pointX, pointY+length, length/2);
            drawRecursiveSideCross(canvas, pointX-length, pointY, length/2);
            drawRecursiveSideCross(canvas, pointX+length, pointY, length/2);
        } else return;
    }

}