Context - unable to create external files directory

I have a very strange problem with my app that appears when you start app on the Nexus 4.

I have following code in Application class:

public class MyApp extends Application {

@Override
public void onCreate() {
    super.onCreate();
    File dir = this.getExternalFilesDir(null);
    if (dir == null) {
        Log.e("App", "Problem with my dir!");
    }
}

In LogCat I saw message:

12-11 14:09:05.402 11739-11739/com.company.app W/ContextImpl: Unable to create external files directory
12-11 14:09:05.402 11739-11739/com.company.app E/App: Problem with my dir!

I already have <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> in my AndroidManifest.xml.

Also, this problem appears only when I re-install my application and don't reboot my device. If I reboot my Nexus, problem disappear.

What can be wrong in this simple code snippet?..

Thank you in advance for your reply.

I've finally found cause of this strange behaviour.

In my application, after some initialization in Application class, I've started logging process like this:

String[] cmd = new String[] {
    "logcat", "-f", myFileNameFromExternalDir, "-v", "time"
};
Runtime.getRuntime().exec(cmd);

And I didn't destroy this process anywhere. That's why after re-intalling my app, Android unable to create external files dir or cache dir.

Summary:

1. If you started some process, don't forget to destroy it, e.g:

   Process process = Runtime.getRuntime().exec(cmd); ... process.destroy();

2. To check, if there are some unusual processes running on your device, you can use adb shell. For example:

In Windows cmd

adb shell

In Android shell

ps - it will list all processes on your device.

If you found something interesting, you can check, does this process belong to your application with lsof command:

lsof -p process_name | grep app_package