android 線性梯度

Bitmap類

       private static class SampleView extends View {

        private Bitmap mBitmap;

        private Bitmap mBitmap2;

        private Bitmap mBitmap3;

        private Shader mShader;

        private static void drawIntoBitmap(Bitmap bm) {

            float x = bm.getWidth();

            float y = bm.getHeight();

            Canvas c = new Canvas(bm);

            Paint p = new Paint();

            p.setAntiAlias(true);

            p.setAlpha(0x80);//設定顔色透明度為十六進制80

            c.drawCircle(x/2, y/2, x/2, p);

            p.setAlpha(0x30);

     p.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));

            p.setTextSize(60);

            p.setTextAlign(Paint.Align.CENTER);

            Paint.FontMetrics fm = p.getFontMetrics();

            c.drawText("Alpha", x/2, (y-fm.ascent)/2, p);

        }

        public SampleView(Context context) {

            super(context);

            setFocusable(true);

            InputStream is = context.getResources()

          .openRawResource(R.drawable.app_sample_code);

            mBitmap = BitmapFactory.decodeStream(is);

            mBitmap2 = mBitmap.extractAlpha();

 mBitmap3 = Bitmap.createBitmap(200, 200, Bitmap.Config.ALPHA_8);

            drawIntoBitmap(mBitmap3);

 mShader = new LinearGradient(0, 0, 100, 70,

new int[] {Color.RED, Color.GREEN, Color.BLUE },

                null, Shader.TileMode.MIRROR);

  }

        @Override protected void onDraw(Canvas canvas) {

            canvas.drawColor(Color.WHITE);

            Paint p = new Paint();

            float y = 10;

            p.setColor(Color.RED);

            canvas.drawBitmap(mBitmap, 10, y, p);

            y += mBitmap.getHeight() + 10;

            canvas.drawBitmap(mBitmap2, 10, y, p);

            y += mBitmap2.getHeight() + 10;

            p.setShader(mShader);

            canvas.drawBitmap(mBitmap3, 10, y, p);

            Path path = new Path();

            path.moveTo(0, 0);

            path.lineTo(100,70);

            p.setColor(Color.RED);

            p.setStyle(Paint.Style.STROKE);

            canvas.drawPath(path, p);

        }

    }

}