在android上将画布图像保存到设备/图库

Bitmap bitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Bitmap.Config.ARGB_8888);
Canvas bitmapCanvas = new Canvas(bitmap);
canvas.drawBitmap(bitmap, 0, 0, null);

String galleryPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES).toString();

String fileName = "my_image.jpg";
File file = new File(galleryPath, fileName);
try {
    FileOutputStream fos = new FileOutputStream(file);
    bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
    fos.flush();
    fos.close();
    // 通知图库更新
    MediaScannerConnection.scanFile(context, new String[]{file.getAbsolutePath()}, null, null);
} catch (IOException e) {
    e.printStackTrace();
}