An IllegalStateException is thrown in Java when a method is invoked at an inappropriate time or in an inappropriate way. In the case of the error message you mentioned (you must either set a text or a view), it typically means that you are trying to set the content of a view without actually providing any content.
Example:
Suppose you have a TextView in your XML layout file:
<TextView
android:id="@+id/myTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
In your Java code, you may have something like this:
TextView textView = findViewById(R.id.myTextView);
textView.setText(""); // Or textView.setText(null);
When you call setText() with an empty string or null, the IllegalStateException may occur because you are not providing any valid content for the TextView.
To fix this issue, make sure to set the text of the TextView to a non-empty string or provide valid content (such as a drawable) in order to display something:
TextView textView = findViewById(R.id.myTextView);
textView.setText("Hello, World!");
Alternatively, you can set the text in the XML layout itself:
<TextView
android:id="@+id/myTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello, World!"
/>
By providing valid content for the TextView, you will prevent the IllegalStateException: you must either set a text or a view.