only one color is displayed in time

Question

I\'m developing paint app the problem is when i choose color and paint and then pick different color the whole paint color changes to the new color can any one tell why this is

Answer 1

Every time onDraw is called, the entire canvas is redraw. As you store only one paintColor in your custom class, only the last selected one is used.

You need to store the color together with the associated Point. Then when you loop throw your mTouches array, you change the color for the color of the current Point.

Btw the Paint object can be updated, so you don't need to create it every time as it's a bad practice to create new objects in onDraw.

EDIT

public class DrawView extends android.support.v7.widget.AppCompatImageView {
    private ArrayList<ColouredPoint> mTouches;
    // Current used colour
    private int mCurrColour;
    private Paint mPaint;

    public void setColor(int colour) {
        mCurrColour = colour;
    }

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

    // XML constructor
    public DrawView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        mTouches = new ArrayList<>();
        mPaint = new Paint();
        mPaint.setColor(mCurrColour);
        mPaint.setAntiAlias(true);
        mPaint.setStrokeWidth(5);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // Capture a reference to each touch for drawing
        float touchX = event.getX();
        float touchY = event.getY();
        mTouches.add(new ColouredPoint(Math.round(touchX), Math.round(touchY), mCurrColour));

        return super.onTouchEvent(event);
    }

    @Override
    protected void onDraw(Canvas c) {
        // Let the image be drawn first
        super.onDraw(c);
        // Draw your custom points here
        for (ColouredPoint p : mTouches) {
            mPaint.setColor(p.colour);
            c.drawCircle(p.x, p.y, 15, mPaint);
        }
    }

    /**
     * Class to store the coordinate and the colour of the point.
     */
    private class ColouredPoint {
        int x;
        int y;
        int colour;

        public ColouredPoint(int x, int y, int colour) {
            this.x = x;
            this.y = y;
            this.colour = colour;
        }
    }
}