Code example for Canvas

Methods: drawCircle, drawColor, restore, save, translate

0
        /* 
         * Draw a wireframe cube by drawing 12 3 dimensional lines between 
         * adjacent corners of the cube 
         */ 
        void drawCube(Canvas c) {
            c.save();
            c.translate(mCenterX, mCenterY);
            c.drawColor(0xff000000);
            drawLine(c, -400, -400, -400,  400, -400, -400);
            drawLine(c,  400, -400, -400,  400,  400, -400);
            drawLine(c,  400,  400, -400, -400,  400, -400);
            drawLine(c, -400,  400, -400, -400, -400, -400);
 
            drawLine(c, -400, -400,  400,  400, -400,  400);
            drawLine(c,  400, -400,  400,  400,  400,  400);
            drawLine(c,  400,  400,  400, -400,  400,  400);
            drawLine(c, -400,  400,  400, -400, -400,  400);
 
            drawLine(c, -400, -400,  400, -400, -400, -400);
            drawLine(c,  400, -400,  400,  400, -400, -400);
            drawLine(c,  400,  400,  400,  400,  400, -400);
            drawLine(c, -400,  400,  400, -400,  400, -400);
            c.restore();
        } 
 
        /* 
         * Draw a 3 dimensional line on to the screen 
         */ 
        void drawLine(Canvas c, int x1, int y1, int z1, int x2, int y2, int z2) {
            long now = SystemClock.elapsedRealtime();
            float xrot = ((float)(now - mStartTime)) / 1000;
            float yrot = (0.5f - mOffset) * 2.0f;
            float zrot = 0;
 
            // 3D transformations 
 
            // rotation around X-axis 
            float newy1 = (float)(Math.sin(xrot) * z1 + Math.cos(xrot) * y1);
            float newy2 = (float)(Math.sin(xrot) * z2 + Math.cos(xrot) * y2);
            float newz1 = (float)(Math.cos(xrot) * z1 - Math.sin(xrot) * y1);
            float newz2 = (float)(Math.cos(xrot) * z2 - Math.sin(xrot) * y2);
 
            // rotation around Y-axis 
            float newx1 = (float)(Math.sin(yrot) * newz1 + Math.cos(yrot) * x1);
            float newx2 = (float)(Math.sin(yrot) * newz2 + Math.cos(yrot) * x2);
            newz1 = (float)(Math.cos(yrot) * newz1 - Math.sin(yrot) * x1);
            newz2 = (float)(Math.cos(yrot) * newz2 - Math.sin(yrot) * x2);
 
            // 3D-to-2D projection 
            float startX = newx1 / (4 - newz1 / 400);
            float startY = newy1 / (4 - newz1 / 400);
            float stopX =  newx2 / (4 - newz2 / 400);
            float stopY =  newy2 / (4 - newz2 / 400);
 
            c.drawLine(startX, startY, stopX, stopY, mPaint);
        } 
 
        /* 
         * Draw a circle around the current touch point, if any. 
         */ 
        void drawTouchPoint(Canvas c) {
            if (mTouchX >=0 && mTouchY >= 0) {
                c.drawCircle(mTouchX, mTouchY, 80, mPaint);
            } 
        } 
 
    } 
}