NIOUtils.readableFileChannel的jcodec权限被拒绝

Question

我正在尝试使用JCodec从我的模拟器上的MP4中获取所有帧。我在清单中具有以下权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />

通过我的adb shell得到的文件如下所示：

root@generic_x86_64:/sdcard/Download # pwd
/sdcard/Download
root@generic_x86_64:/sdcard/Download # ls -la
-rwxrwx--x root     sdcard_rw 19967250 2015-10-12 16:39 Hummingbird.MP4

我试过做一个chmod777 Hummingbird.MP4，但由于某种原因，这并没有改变最后一组权限？

下面的代码产生了下面的异常。

String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
String fn = baseDir + "/Download/Hummingbird.MP4";
// test dir to make sure I'm in right place
String dir = baseDir + "/Download";
File fDir = new File(dir);
Log.i("TAG", "fDir.isDir()=" + fDir.isDirectory()); // this is true
fileMp4 = new File(fn);
try {
   ch = NIOUtils.readableFileChannel(fileMp4); // line 220 in trace below
} catch (FileNotFoundException e) {
   e.printStackTrace();
}

我还执行了一个fileMp4.exists()，它返回true。

异常

10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err: java.io.FileNotFoundException: /storage/1F1A-300C/Download/Hummingbird.MP4: open failed: EACCES (Permission denied)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at libcore.io.IoBridge.open(IoBridge.java:452)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at java.io.FileInputStream.<init>(FileInputStream.java:76)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at org.jcodec.common.NIOUtils.readableFileChannel(NIOUtils.java:336)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at medloh.com.mp4frames.MainActivity.onActivityResult(MainActivity.java:220)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.Activity.dispatchActivityResult(Activity.java:6428)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.ActivityThread.deliverResults(ActivityThread.java:3695)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3742)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.ActivityThread.-wrap16(ActivityThread.java)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1393)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.os.Looper.loop(Looper.java:148)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5417)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err: Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at libcore.io.Posix.open(Native Method)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     at libcore.io.IoBridge.open(IoBridge.java:438)
10-14 23:32:27.090 4595-4595/medloh.com.mp4frames W/System.err:     ... 14 more

看到这个代码/配置有什么问题了吗？

Answer 1

通过在/data/tmp/Hummingbird.MP4 (adb push)创建文件，我能够使'NIOUtils.readableFileChannel(fileMp4)‘语句工作。我不确定这是否与/sdcard及其符号链接有关，或者我只是需要确保所有目录和文件都归系统所有，而不是根目录。

不管怎样，我现在谈到了解码MP4的其他问题和问题，但那是另一回事了。