java.io.FileNotFoundException: xxx: open failed: EROFS (Read

pond2539

　　12-21 17:21:13.672: W/System.err(1583): java.io.FileNotFoundException: /downloadedMusic.mp3: open failed: EROFS (Read-only file system)
12-21 17:21:13.672: W/System.err(1583): at libcore.io.IoBridge.open(IoBridge.java:416)
12-21 17:21:13.672: W/System.err(1583): at java.io.FileOutputStream.(FileOutputStream.java:88)
12-21 17:21:13.672: W/System.err(1583): at java.io.FileOutputStream.(FileOutputStream.java:73)
12-21 17:21:13.672: W/System.err(1583): at crifan.com.crifanLib.downlodFile(crifanLib.java:197)
12-21 17:21:13.672: W/System.err(1583): at crifan.com.crifanLibSongtaste.stDownloadFromUrl(crifanLibSongtaste.java:204)
12-21 17:21:13.672: W/System.err(1583): at crifan.com.downloadsongtastemusic.MainActivity.preformDownload(MainActivity.java:74)
12-21 17:21:13.672: W/System.err(1583): at java.lang.reflect.Method.invokeNative(Native Method)
12-21 17:21:13.672: W/System.err(1583): at java.lang.reflect.Method.invoke(Method.java:511)
12-21 17:21:13.672: W/System.err(1583): at android.view.View$1.onClick(View.java:3586)
12-21 17:21:13.672: W/System.err(1583): at android.view.View.performClick(View.java:4084)
12-21 17:21:13.672: W/System.err(1583): at android.view.View$PerformClick.run(View.java:16966)
12-21 17:21:13.672: W/System.err(1583): at android.os.Handler.handleCallback(Handler.java:615)
12-21 17:21:13.672: W/System.err(1583): at android.os.Handler.dispatchMessage(Handler.java:92)
12-21 17:21:13.672: W/System.err(1583): at android.os.Looper.loop(Looper.java:137)
12-21 17:21:13.672: W/System.err(1583): at android.app.ActivityThread.main(ActivityThread.java:4745)
12-21 17:21:13.672: W/System.err(1583): at java.lang.reflect.Method.invokeNative(Native Method)
12-21 17:21:13.672: W/System.err(1583): at java.lang.reflect.Method.invoke(Method.java:511)
12-21 17:21:13.672: W/System.err(1583): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-21 17:21:13.672: W/System.err(1583): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-21 17:21:13.672: W/System.err(1583): at dalvik.system.NativeStart.main(Native Method)
12-21 17:21:13.672: W/System.err(1583): Caused by: libcore.io.ErrnoException: open failed: EROFS (Read-only file system)
12-21 17:21:13.672: W/System.err(1583): at libcore.io.Posix.open(Native Method)
12-21 17:21:13.689: W/System.err(1583): at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
12-21 17:21:13.689: W/System.err(1583): at libcore.io.IoBridge.open(IoBridge.java:400)
12-21 17:21:13.689: W/System.err(1583): … 19 more
　　

很明显，是没有权限去访问对应的位置：
/downloadedMusic.mp3
所以，接着就是去，想办法，如何将下载的东西，存储到Android中的，某个位置，程序有权限访问的位置。
　　去AndroidManifest.xml中添加了：

　　
然后继续添加代码。
结果代码：
File extDir = Environment.getExternalStorageDirectory();
String filename = "downloadedMusic.mp3";
File fullFilename =new File(extDir.getAbsolutePath() + extDir.pathSeparatorChar + filename);
try {
    fullFilename.createNewFile();
    fullFilename.setWritable(Boolean.TRUE);
    songtaste.stDownloadFromUrl(strSongUrl, fullFilename);
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}　　就出错了：
　　

12-21 17:45:48.298: W/System.err(1547): java.io.IOException: open failed: EROFS (Read-only file system)
12-21 17:45:48.298: W/System.err(1547):     at java.io.File.createNewFile(File.java:940)
12-21 17:45:48.298: W/System.err(1547):     at crifan.com.downloadsongtastemusic.MainActivity.preformDownload(MainActivity.java:83)
12-21 17:45:48.298: W/System.err(1547):     at java.lang.reflect.Method.invokeNative(Native Method)
12-21 17:45:48.298: W/System.err(1547):     at java.lang.reflect.Method.invoke(Method.java:511)
12-21 17:45:48.298: W/System.err(1547):     at android.view.View$1.onClick(View.java:3586)
12-21 17:45:48.298: W/System.err(1547):     at android.view.View.performClick(View.java:4084)
12-21 17:45:48.298: W/System.err(1547):     at android.view.View$PerformClick.run(View.java:16966)
12-21 17:45:48.298: W/System.err(1547):     at android.os.Handler.handleCallback(Handler.java:615)
12-21 17:45:48.298: W/System.err(1547):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-21 17:45:48.298: W/System.err(1547):     at android.os.Looper.loop(Looper.java:137)
12-21 17:45:48.298: W/System.err(1547):     at android.app.ActivityThread.main(ActivityThread.java:4745)
12-21 17:45:48.298: W/System.err(1547):     at java.lang.reflect.Method.invokeNative(Native Method)
12-21 17:45:48.298: W/System.err(1547):     at java.lang.reflect.Method.invoke(Method.java:511)
12-21 17:45:48.298: W/System.err(1547):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
12-21 17:45:48.298: W/System.err(1547):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-21 17:45:48.298: W/System.err(1547):     at dalvik.system.NativeStart.main(Native Method)
12-21 17:45:48.298: W/System.err(1547): Caused by: libcore.io.ErrnoException: open failed: EROFS (Read-only file system)
12-21 17:45:48.309: W/System.err(1547):     at libcore.io.Posix.open(Native Method)
12-21 17:45:48.309: W/System.err(1547):     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
12-21 17:45:48.309: W/System.err(1547):     at java.io.File.createNewFile(File.java:933)
12-21 17:45:48.309: W/System.err(1547):     … 15 more
　　再去改为：
File extDir = Environment.getExternalStorageDirectory();
String filename = "downloadedMusic.mp3";
File fullFilename = new File(extDir, filename);
try {
    fullFilename.createNewFile();
    fullFilename.setWritable(Boolean.TRUE);
    songtaste.stDownloadFromUrl(strSongUrl, fullFilename);
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}　　
结果是，可以正常新建文件：
/mnt/sdcard/downloadedMusic.mp3
看来之前就是由于：
/mnt/sdcard:downloadedMusic.mp3
而导致无法创建的。