[英]OnClickListener throws NullPointerException
I'm trying to set onClick listener to a button from a ViewPager's page but when I try to run the app I get NullPointerException 我试图将onClick侦听器设置为ViewPager页面中的按钮,但是当我尝试运行应用程序时,我得到了NullPointerException
....
public class MainActivity extends Activity {
private ViewPager vPager;
private MyPagerAdapter pagerAdapter;
private TextView tv;
private MyViewPagerListener pagerListener;
private Button deleteAll;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv=(TextView) findViewById(R.id.page_state);
pagerListener = new MyViewPagerListener();
pagerAdapter = new MyPagerAdapter();
vPager = (ViewPager) findViewById(R.id.vPager);
vPager.setAdapter(pagerAdapter);
vPager.setCurrentItem(0);
vPager.setOnPageChangeListener(pagerListener);
//Here is the problem
ClickListener cl = new ClickListener();
deleteAll = (Button) vPager.findViewById(R.id.btnDelete);
deleteAll.setOnClickListener(cl);
}
.....
}
You should register a new OnClickListener object instead of a ClickListener. 您应该注册一个新的OnClickListener对象,而不是ClickListener。 Also, you have to provide an implementation for the onClick method like this: 另外,您还必须提供onClick方法的实现,如下所示:
new OnClickListener() {
public void onClick(View v) {
// do something when the button is clicked
}
};
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