How to drag and draw a line?

Question

I'm new to android programming and I created an app to draw a rectangle and a circle. Now I want to draw ellipses and lines. I know drawLine takes starting point x, starting point y, end point x and end point y.

This is what I tried in mycustomView.java but I can only drag the line from top left to bottom right and bottom right to top left ? How to make it work for all directions?

 protected void onDraw(Canvas canvas) {
    this.canvas = canvas;

    canvas.drawColor(Color.WHITE);

    for (int i = 0; i < numberShapes; i++) {
        paint.setColor(Color.parseColor("#" + Integer.toHexString(Integer.parseInt(shapes[i].getColor())).substring(2))); //avoids alpha
        paint.setStrokeWidth(shapes[i].getBorder());
         //some code here....

                    else if(shapes[i].getShapeType().equals("Ellipse")){
            RectF rect= new RectF(shapes[i].getX(),shapes[i].getY(),shapes[i].getX() + shapes[i].getWidth(),shapes[i].getY() + shapes[i].getHeight());
            canvas.drawOval(rect,paint);

        }
        else if(shapes[i].getShapeType().equals("StraightLine")){
           canvas.drawLine(shapes[i].getX(),shapes[i].getY(),shapes[i].getX() + shapes[i].getWidth(),shapes[i].getY() + shapes[i].getWidth(),paint);
        }
    }

}
}

This is my viewShapes.java with my motion events

public boolean onTouch(View v, MotionEvent ev) {
            //Circle is the default shape if can't find the key
            String selectedShapeDrawing = getActivity().getSharedPreferences("settings", Context.MODE_PRIVATE).getString("selectedShapeDrawing", "Circle");
            int x = (int) ev.getX(); int y = (int) ev.getY();
            int dX, dY;

            int action = MotionEventCompat.getActionMasked(ev);
            switch (action){
                case MotionEvent.ACTION_DOWN:
                    mLastTouchX = x; mLastTouchY = y;
                    break;
                case MotionEvent.ACTION_MOVE:


                        break;
                case MotionEvent.ACTION_UP:
                    if ((selectedShapeDrawing.equals("Rectangle")) || selectedShapeDrawing.equals("Circle") || selectedShapeDrawing.equals("Ellipse")) {
                        //some code here...                        }
                   if(selectedShapeDrawing.equals("StraightLine")){
                        if((x>mLastTouchX) && (y>mLastTouchY)) {

                            storeShape(selectedShapeDrawing, mLastTouchX, mLastTouchY, x, y);
                        }

                        else if((x<mLastTouchX) && (y<mLastTouchY)) {

                            storeShape(selectedShapeDrawing, x, y, mLastTouchX, mLastTouchY);
                        }
                        else if((x>mLastTouchX) && (y<mLastTouchY)) {

                            storeShape(selectedShapeDrawing,mLastTouchX, y,x,mLastTouchY);
                        }

                        else if((x<mLastTouchX) && (y>mLastTouchY)) {

                            storeShape(selectedShapeDrawing, x,mLastTouchY,mLastTouchX, y);
                        }

Any help will be appreciated!

EDIT:This is my store shape

 private void storeShape(String shape, int x, int y, int deltaX, int deltaY) 
{
    int selectedColor = getActivity().getSharedPreferences("settings", Context.MODE_PRIVATE).getInt("selectColor", 0);

    ContentValues contentValues = new ContentValues();
    contentValues.put(SchemeShapes.Shape.SHAPE_TYPE, shape);
    contentValues.put(SchemeShapes.Shape.SHAPE_X, x);
    contentValues.put(SchemeShapes.Shape.SHAPE_Y, y);

    contentValues.put(SchemeShapes.Shape.SHAPE_RADIUS, Math.max(deltaX, deltaY));



    contentValues.put(SchemeShapes.Shape.SHAPE_WIDTH, deltaX);
    contentValues.put(SchemeShapes.Shape.SHAPE_HEIGHT, deltaY);
    contentValues.put(SchemeShapes.Shape.SHAPE_BORDER_THICKNESS, 10);
    contentValues.put(SchemeShapes.Shape.SHAPE_COLOR, selectedColor);

    resolver.insert(SchemeShapes.Shape.CONTENT_URI, contentValues);
}

refer : https://stackoverflow.com/questions/3616676/how-to-draw-a-line-in-android — Sahil, May 14 '18 at 08:35

score 1 · Answer 1 · edited May 14 '18 at 13:33

Okay I over-complicated this a bit in my canvas.drawLine I shold do this:

else if(shapes[i].getShapeType().equals("StraightLine")){
    canvas.drawLine(shapes[i].getX(), shapes[i].getY(), shapes[i].getWidth(), shapes[i].getHeight(), paint);
}

and in my Action_Up I should do this:

if ((selectedShapeDrawing.equals("StraightLine"))) {
    storeShape(selectedShapeDrawing,mLastTouchX,mLastTouchY,x,y); 
}

score 0 · Answer 2 · answered May 14 '18 at 10:59

Here is something you can try :

public boolean onTouch(View v, MotionEvent event) {
        switch(event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startX = event.getRawX();
                startY = event.getRawY();
                break;

            case MotionEvent.ACTION_UP:
                Paint paint = new Paint(); 
                paint.setStrokeWidth(10f);
                paint.setColor(getResources().getColor(R.color.text_red));
                canvas.drawLine(startX, startY, event.getRawX(), event.getRawY(), paint);
                break;
        }
    }

How to drag and draw a line?

2 Answers2