即使文件存在，Drawable createFromPath也返回null

Question

d = Drawable.createFromPath(Environment.getExternalStorageDirectory().toString()+"/"+filenameString);
System.err.println(Environment.getExternalStorageDirectory().toString()+"/"+filenameString+"  -  "+d);
image.setImageDrawable(d);

以上是我用于获取drawable且低于Logcat的代码：

04-09 15:34:44.005: I/System.out(20814): Not a DRM File, opening notmally
04-09 15:34:44.010: I/System.out(20814): buffer returned 
04-09 15:34:44.010: D/skia(20814): --- SkImageDecoder::Factory returned null
04-09 15:34:44.010: W/System.err(20814): /storage/sdcard0/1396850896.482724.png
04-09 15:34:44.010: W/System.err(20814):   -  null

我检查过，文件存在。

我设置了 WRITE_EXTERNAL_STORAGE 和 READ_EXTERNAL_STORAGE 。