Hello I have a question about Android Activity.
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener (android.view.View$OnClickListener)' on a null object reference
what i want to make is a welcome page .
i have Main_welcome Page called
Activity_main. three page layout is welcome_layout1 welcome_layout2 and welcome_layout3.
i have only one Activity which is the following:
public class MainActivity extends AppCompatActivity {
private ViewPager myViewPager;
private View page1,page2,page3;
private List<View> pageList;
Button sign;
private MypageAdapter mypageAdapter;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
Button sign = (Button)this.findViewById(R.id.button_gotosign);
sign.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setContentView(R.layout.sign);
}
});
}
private void initView (){
myViewPager = (ViewPager) findViewById(R.id.welcome_viewpager);
LayoutInflater inflater = getLayoutInflater();
page1 = inflater.inflate(R.layout.welcome_layout1, null);
page2 = inflater.inflate(R.layout.welcome_layout2, null);
page3 = inflater.inflate(R.layout.welcome_layout3, null);
pageList = new ArrayList();
pageList.add(page1);
pageList.add(page2);
pageList.add(page3);
mypageAdapter = new MypageAdapter(pageList);
myViewPager.setAdapter(mypageAdapter);
}
}
i have a button called sign up at welcome_layout3
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/b3"
>
<Button
android:id="@+id/button_gotosign"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="sign"
android:textSize="@dimen/activity_vertical_margin"
android:textColor="#318C83"
android:background="#90000000"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="34dp">
</Button>
</RelativeLayout>
what i want to do is , when the user open this APP, he will Roll 3 pictures to the finally one , and there is a button he can click to sign.
how to make the button works?
