Attempt to invoke virtual method '...TextView.setText(java.lang.CharSequence)' on a null object reference
Simple problem and even simpler fix. You are accessing a view prior to inflating layout. Your code needs to instead by rearranged this way:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView( R.layout.activity);
TextView t= (TextView)findViewById(R.id.startofweek);
t.setText("05.09.2016");
}
In your xml file, you used "example" as the id of your TextView. But, inside the code, you are looking for "R.id.startofweek" when you are initializing your TextView.
PS: You also called "setContentView( R.layout.activities);" after the variable initialization. It has to be done before you initialize the TextView.
You can use the following code:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView( R.layout.activities);
TextView t= (TextView)findViewById(R.id.example);
t.setText("05.09.2016");
}