Cant create folder using mkdir to sd card for android tablet

im having this problem of mkdir keep returning false even though i have done all the necessary the following are my active codes.

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    File folder = new File(Environment.getExternalStorageDirectory().toString() + "/myappfolder" );

    boolean maked = folder.mkdir();
    System.out.println("the folder is maked or not? "+maked);

    setContentView(R.layout.activity_main);


    }

folder.mkdir() returns me false.

yes i have:

include

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

in my manifest.

i have also maked sure the folder does not exist in my sd card.
and in one of my project it display

06-22 01:23:58.130: W/ActivityManager(143): No content provider found for permission revoke: file:///data/local/tmp/simulation.apk

i even tried unplugging it from my computer in case sd card is mounted to my desktop.
i had also tried in sumsung galaxy s3

im mainly using acer A100 ICS factory data reset tablet. i suspect something is blocking my tablet for allowing me to write on the sd card

i would really appreciate if someone can come out with a solution

The followings are my logcat

06-22 04:33:55.850: D/AndroidRuntime(18556): >>>>>> AndroidRuntime START        com.android.internal.os.RuntimeInit <<<<<<
06-22 04:33:55.850: D/AndroidRuntime(18556): CheckJNI is OFF
06-22 04:33:56.030: D/AndroidRuntime(18556): Calling main entry com.android.commands.pm.Pm
06-22 04:33:56.030: D/AndroidRuntime(18556): Shutting down VM
06-22 04:33:56.040: D/dalvikvm(18556): GC_CONCURRENT freed 100K, 83% free 454K/2560K, paused 0ms+0ms
06-22 04:33:56.040: D/dalvikvm(18556): Debugger has detached; object registry had 1 entries
06-22 04:33:56.590: D/AndroidRuntime(18570): >>>>>> AndroidRuntime START com.android.internal.os.RuntimeInit <<<<<<
06-22 04:33:56.590: D/AndroidRuntime(18570): CheckJNI is OFF
06-22 04:33:56.760: D/AndroidRuntime(18570): Calling main entry com.android.commands.pm.Pm
06-22 04:33:56.770: W/ActivityManager(143): No content provider found for permission revoke: file:///data/local/tmp/myapp.apk
06-22 04:33:56.780: W/ActivityManager(143): No content provider found for permission revoke: file:///data/local/tmp/myapp.apk
06-22 04:33:56.850: I/PackageManager(143): Running dexopt on: com.android.myapp
06-22 04:33:57.150: D/dalvikvm(18581): DexOpt: load 41ms, verify+opt 183ms
06-22 04:33:57.230: I/ActivityManager(143): Force stopping package com.android.myapp uid=10071
06-22 04:33:57.320: D/PackageManager(143): New package installed in /data/app/com.android.myapp-1.apk
06-22 04:33:57.320: W/PackageManager(143): Unknown permission android.permission.READ_EXTERNAL_STORAGE in package com.android.myapp
06-22 04:33:57.440: D/PackageManager(143): generateServicesMap(android.accounts.AccountAuthenticator): 3 services unchanged
06-22 04:33:57.450: I/Launcher(1776): setLoadOnResume
06-22 04:33:57.470: D/dalvikvm(18159): GC_FOR_ALLOC freed 227K, 8% free 6680K/7239K, paused 17ms
06-22 04:33:57.490: D/SyncManager(143): setIsSyncable: Account {[email protected], type=com.google}, provider com.google.android.gallery3d.GooglePhotoProvider -> 0
06-22 04:33:57.490: D/SyncManager(143): setIsSyncable: already set to 0, doing nothing
06-22 04:33:57.520: D/PackageManager(143): generateServicesMap(android.content.SyncAdapter): 18 services unchanged
06-22 04:33:57.570: D/BackupManagerService(143): Received broadcast Intent { act=android.intent.action.PACKAGE_ADDED dat=package:com.android.myapp flg=0x10000010 (has extras) }
06-22 04:33:57.570: V/BackupManagerService(143): addPackageParticipantsLocked: com.android.myapp
06-22 04:33:57.660: D/dalvikvm(143): GC_EXPLICIT freed 1056K, 24% free 11640K/15239K, paused 6ms+7ms
06-22 04:33:57.670: D/AndroidRuntime(18570): Shutting down VM
06-22 04:33:57.680: D/dalvikvm(18570): GC_CONCURRENT freed 101K, 83% free 459K/2560K, paused 0ms+0ms
06-22 04:33:57.680: D/jdwp(18570): Got wake-up signal, bailing out of select
06-22 04:33:57.680: D/dalvikvm(18570): Debugger has detached; object registry had 1 entries
06-22 04:33:57.680: I/AndroidRuntime(18570): NOTE: attach of thread 'Binder Thread #3' failed
06-22 04:33:57.830: D/dalvikvm(1776): GC_CONCURRENT freed 2458K, 47% free 10173K/19079K, paused 2ms+6ms
06-22 04:33:57.840: D/dalvikvm(17407): GC_CONCURRENT freed 276K, 6% free 7177K/7559K, paused 16ms+3ms
06-22 04:33:57.930: D/dalvikvm(1776): GC_FOR_ALLOC freed 994K, 47% free 10233K/19079K, paused 32ms
06-22 04:33:58.020: D/dalvikvm(1776): GC_FOR_ALLOC freed 769K, 45% free 10581K/19079K, paused 21ms
06-22 04:33:58.080: D/AndroidRuntime(18593): >>>>>> AndroidRuntime START com.android.internal.os.RuntimeInit <<<<<<
06-22 04:33:58.080: D/AndroidRuntime(18593): CheckJNI is OFF
06-22 04:33:58.090: D/dalvikvm(1776): GC_CONCURRENT freed 5K, 38% free 11836K/19079K, paused 2ms+3ms
06-22 04:33:58.180: D/dalvikvm(1776): GC_CONCURRENT freed 1398K, 37% free 12143K/19079K, paused 1ms+4ms
06-22 04:33:58.290: D/dalvikvm(1776): GC_FOR_ALLOC freed 2316K, 42% free 11191K/19079K, paused 25ms
06-22 04:33:58.370: D/AndroidRuntime(18593): Calling main entry com.android.commands.am.Am
06-22 04:33:58.370: I/ActivityManager(143): START {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.android.myapp/.MainActivity} from pid 18593
06-22 04:33:58.420: D/AndroidRuntime(18593): Shutting down VM
06-22 04:33:58.420: I/AndroidRuntime(18593): NOTE: attach of thread 'Binder Thread #3' failed
06-22 04:33:58.420: D/dalvikvm(18593): GC_CONCURRENT freed 102K, 81% free 489K/2560K, paused 0ms+1ms
06-22 04:33:58.430: D/jdwp(18593): Got wake-up signal, bailing out of select
06-22 04:33:58.430: D/dalvikvm(18593): Debugger has detached; object registry had 1 entries
06-22 04:33:58.470: D/dalvikvm(18604): Late-enabling CheckJNI
06-22 04:33:58.490: I/ActivityManager(143): Start proc com.android.myapp for activity com.android.myapp/.MainActivity: pid=18604 uid=10071 gids={1015}
06-22 04:33:58.570: D/OpenGLRenderer(18507): Flushing caches (mode 1)
06-22 04:33:58.580: D/OpenGLRenderer(18507): Flushing caches (mode 0)
06-22 04:33:58.660: I/System.out(18604): folder newed going to make folder
06-22 04:33:58.660: I/System.out(18604): here/mnt/sdcard/myappfolder
06-22 04:33:58.660: I/System.out(18604): the folder is maked or not? false
06-22 04:33:58.680: D/dalvikvm(1776): GC_CONCURRENT freed 2487K, 47% free 10154K/19079K, paused 2ms+47ms
06-22 04:33:58.710: D/dalvikvm(18239): GC_CONCURRENT freed 339K, 6% free 6935K/7367K, paused 3ms+4ms
06-22 04:33:58.760: D/libEGL(18604): loaded /system/lib/egl/libEGL_tegra.so
06-22 04:33:58.780: D/libEGL(18604): loaded /system/lib/egl/libGLESv1_CM_tegra.so
6-22 04:33:58.810: D/dalvikvm(1776): GC_FOR_ALLOC freed 675K, 46% free 10318K/19079K, paused 35ms
06-22 04:33:58.830: D/libEGL(18604): loaded /system/lib/egl/libGLESv2_tegra.so
06-22 04:33:58.870: D/OpenGLRenderer(1776): Flushing caches (mode 1)
06-22 04:33:58.870: D/OpenGLRenderer(18604): Enabling debug mode 0
06-22 04:33:58.910: D/dalvikvm(1776): GC_FOR_ALLOC freed 642K, 46% free 10474K/19079K, paused 46ms
06-22 04:33:58.940: D/OpenGLRenderer(1776): Flushing caches (mode 0)
06-22 04:33:58.970: I/ActivityManager(143): Displayed com.android.myapp/.MainActivity: +516ms
06-22 04:33:59.000: D/dalvikvm(1776): GC_FOR_ALLOC freed 941K, 47% free 10204K/19079K, paused 41ms
06-22 04:33:59.010: I/dalvikvm-heap(1776): Grow heap (frag case) to 11.236MB for 1286224-byte allocation
06-22 04:33:59.050: D/dalvikvm(1776): GC_CONCURRENT freed 31K, 41% free 11429K/19079K, paused 2ms+4ms
06-22 04:34:00.210: E/DigitalAppWidgetUpdateService(17962): onReceive():948: screen mode = ORIENTATION_PORTRAIT
06-22 04:34:00.250: D/dalvikvm(17962): GC_CONCURRENT freed 321K, 8% free 6809K/7367K, paused 1ms+2ms

Solution

Two things.

Your code reads

File folder = new File(Environment.getExternalStorageDirectory().toString() + "/myappfolder" );

and you'd be better off using this syntax

File folder = new File(Environment.getExternalStorageDirectory().toString() , "myappfolder" );

If you're debugging your code, it's possible that the external SD Card has been dismounted. Go to Setting->Storage and verify that your SD Card is accessible to apps on your device.

After seeing your logcat, one thing seems to be causing you trouble. Your logcat has this line in it:

06-22 04:33:57.320: W/PackageManager(143): Unknown permission  
 android.permission.READ_EXTERNAL_STORAGE in package com.android.myapp

which means you're actually having trouble with your manifest (you're targetting an Android version which didn't have that permission implemented yet. I also suspect that if you remove that permission, your troubles will cease). According to the permission's description you don't need it anyway, since you're already granting WRITE_EXTERNAL_STORAGE.