Android学习下载网络图片

public static Bitmap downloadBitmap(String imageUrl) {
        Log.d("try to download image","imageUrl:"+imageUrl);
        URL url = null;
        Bitmap bitmap = null;
        try {
            /* new URL对象将网址传入 */
            url = new URL(imageUrl);
        } catch (MalformedURLException e) {
            e.printStackTrace();
            return null;
        }
        try {
            /* 取得连接 */
            HttpURLConnection conn = (HttpURLConnection) url
                    .openConnection();
            conn.setConnectTimeout(5 * 1000);
            conn.connect();
            /* 取得返回的InputStream */
            InputStream is = conn.getInputStream();
            /* 将InputStream变成Bitmap */
            bitmap = BitmapFactory.decodeStream(is);
            /* 关闭InputStream */
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return bitmap;

    }

有时候，需要对下载下来的图片调整大小：

public static Drawable resizeImage(Bitmap bitmap, int w, int h) {

        Bitmap BitmapOrg = bitmap;

        int width = BitmapOrg.getWidth();
        int height = BitmapOrg.getHeight();
        int newWidth = w;
        int newHeight = h;

        // calculate the scale
        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float) newHeight) / height;

        // create a matrix for the manipulation
        Matrix matrix = new Matrix();
        // resize the Bitmap
        matrix.postScale(scaleWidth, scaleHeight);

        // recreate the new Bitmap
        Bitmap resizedBitmap = Bitmap.createBitmap(BitmapOrg, 0, 0, width,
                height, matrix, true);

        return new BitmapDrawable(resizedBitmap);

    }