Android - setAdapter ViewPager 上的 NullPointerException

Question

我有个小问题。我正在尝试使用 fragment 创建布局，但是当我调用 setAdapter 方法时出现 Java NullPointerException，但我找不到错误。 谢谢大家!

类代码

public class Agenda extends FragmentActivity{

PagerAdapter mPagerAdapter;

ViewPager mViewPager;

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.agenda_sw);

    mPagerAdapter = new PagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.agendaPager);

    mViewPager.setAdapter(mPagerAdapter); //Line 32, the error is on this line.

}

xml代码

<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/agenda_sw"
android:layout_width="match_parent"
android:layout_height="match_parent" 
/>

日志

03-04 11:06:14.686: E/AndroidRuntime(1356): FATAL EXCEPTION: main
03-04 11:06:14.686: E/AndroidRuntime(1356): java.lang.RuntimeException: Unable to start activity ComponentInfo{conf.main/conf.main.Agenda}: java.lang.NullPointerException
...
03-04 11:06:14.686: E/AndroidRuntime(1356): Caused by: java.lang.NullPointerException
03-04 11:06:14.686: E/AndroidRuntime(1356): at conf.main.Agenda.onCreate(Agenda.java:32)

Answer 1

错误的 viewpager id。你用 xml 写的:

android:id="@+id/agenda_sw"

但在代码中，您可以找到 R.id.agendaPager 并且应该找到 R.id.agenda_sw。