BitmapFactory.decodeStream返回null值 ，InputStream 被调用两次，第一次调用流被关闭清空了！！！

 
　　InputStream inputstrem =getContentResolver().openInputStream(图片Uri);
　　//解码获取图片的宽高
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;//只读取图片,不加载到内存中
    BitmapFactory.decodeStream(inputstrem ,null,options);
　//通过图片的宽高压缩图片，解决OOM~
    options.inSampleSize = calculateInSampleSize(options,300,300);
    options.inJustDecodeBounds = false;//加载到内存中
    options.inPreferredConfig = Bitmap.Config.RGB_565;
    options.inDither = true;//采用抖动解码
     //InputStream 被调用两次，第一次调用流被关闭清空了！！！因此需要重新打开流
    inputstrem=getContentResolver().openInputStream(图片Uri); //关键代码，重新打开图片流，不加这一行代码 BitmapFactory.decodeStream返回的就是空null
    Bitmap bmp = BitmapFactory.decodeStream(inputstrem , null, options);

    /***绑定ImageView**/
    Imageview1.setImageBitmap(bmp);

　　///calculateInSampleSize方法

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;
    if (height > reqHeight || width > reqWidth) {
        final int halfHeight = height / 2;
        final int halfWidth = width / 2;
        while ((halfHeight / inSampleSize) >= reqHeight
                && (halfWidth / inSampleSize) >= reqWidth) {
            inSampleSize *= 2;
        }
    }
    return inSampleSize;
}