Android Dev - Using Built-In Classes in own class
<p>Im new in Android dev.
Here is my problem:
I have created my own class and can access the methods of this class in all Activities by created a new Instance of my class. 
But as soon as I want to use "Built-In"-Android Classes in my own class the app crashes.
For example when i try display Toast it crashes. When I try "getExternalStorageDirectory()" it crashes (in manifest-file permission is set). When I try to access String-Resources it crashes and so on.
At the moment my class extends Application (also tried extending Actitiy).
What do I have to do in order to use Build-In Android Classes in my own class?
Thanks in advance for Your help.</p>

<p>Regards
Enulien</p>
