CODEWITHSUNDEEP
javaandroidandroid-canvas
Groosha
Groosha

Reputation: 3067

Drawing on Canvas and refreshing

I'm new to Android programming and now I'm trying to make a simple Sea Battle game for one person. Ships are places, player hits the field and see whether the shot hit or not. Basically, the field looks like this:

the field

The code is: 

public void onDraw(Canvas canvas) {

    if (getWidth() > getHeight()) { 
         rebro = getHeight(); 
    } else {
        rebro = getWidth();  // the smaller size of screen is "rebro"
    }
    rebro_piece = rebro / 10; // divide the screen by 10 (to get 10x10 field)

    Paint background = new Paint();
    background.setColor(getResources().getColor(R.color.game_background));
    canvas.drawRect(0, 0, rebro, rebro, background);  // draw background

    Paint divider = new Paint();
    divider.setColor(getResources().getColor(R.color.divider_black));

    // drawing divider lines
    for (int i=0; i<11; i++) {
        canvas.drawLine(0, i*rebro_piece, rebro, i*rebro_piece, divider);  // horizontal
        canvas.drawLine(i*rebro_piece, 0, i*rebro_piece, rebro, divider);  // vertical
    }

canvas.drawLine(rebro-1, 0, rebro-1, rebro, divider);
}

That's how I make the "field."

In another class I have a method that collects numbers x and y of a 10×10 array that represents where the ships are placed. For debugging, I need to draw them on my field. Ship coordinates are retrieved in a cycle.

So I wrote a drawShip(int x, int y) method.

On Stack Overflow I've founded a question about "Why I can't paint outside onDraw()?" and I've changed my method to this:

public void drawShip(int x, int y) {
myX = x; //global
myY = y; //global
needToPaintShip = true; //boolean
invalidate(); // refreshing?
needToPaintShip = false;
}

Here needToPaintShip decides whether the redrawing of canvas is needed or not.

Also I've edited the onDraw(Canvas canvas) method:

if(needToPaintShip == true) {
        Paint ship = new Paint();
        ship.setColor(getResources().getColor(R.color.ship_color));
        Log.d(TAG, "onDraw(): rebro_piece = " + rebro_piece + " , myX = "+ myX + " , myY = " + myY); // I only get the last coordinates! 
        Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, myX*(rebro_piece+1), myY*(rebro_piece+1));
        canvas.drawRect(r, ship);
    }

but the result is awful:

the awful result

Guys, I'm desperate. How can I fix this and make "ships" be drawn on the field?

Upvotes: 1

Views: 304

Answers (1)

Sean Reilly
Sean Reilly

Reputation: 748

Why do you set needToPaintShip = false; after calling invalidate()? Don't you need to draw the ship again in subsequent frames?

Also, it seems like this item:

Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, myX*(rebro_piece+1), myY*(rebro_piece+1));

should probably be:

Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, (myX+1)*rebro_piece, (myY+1)*rebro_piece));

As for why the ship always appears in the bottom right corner, that depends on what you pass to drawShip(x,y), which isn't shown. Is it possible that you are passing pixel coordinates instead of something in the range [0-10)?

Upvotes: 1

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