java - setText with onClick button and onCreate crashes app -


how text field change when application launches , how change again when click button?

mainactivity.java

protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      textview mytext=(textview)findviewbyid(r.id.myactivitytextview);     mytext.settext("launch text change");         }  public void mybuttonclicked(view v){     textview mytext=(textview)findviewbyid(r.id.myactivitytextview);     mytext.settext("button change text"); }

activity_main.xml

<textview android:text="@string/hello_world" android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:id="@+id/mytext" />  <button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="change text"     android:id="@+id/mybutton"     android:layout_below="@+id/mytext"     android:layout_alignparentleft="true"     android:layout_alignparentstart="true"     android:onclick="mybuttonclicked"/>

the textview have in xml has id of mytext. change lookup of 

textview mytext=(textview)findviewbyid(r.id.myactivitytextview);

to 

textview mytext=(textview)findviewbyid(r.id.mytext);

and should work.


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