Question

我在我的应用中做了以下事情：

我有一个名为FragmentOne的片段，其布局为list_view_details。
我在我的片段中使用ViewPager。
我在ViewPager中生成了一个名为details的布局。我在详细信息布局中有一个带有id android:id="@+id/page"和其他小部件的textview。

我想将android:id="@+id/page"中标识为details.xml的textview设置为值＆＃34; hii＆＃34;编程。我尝试进行以下编码，但它在第103行给了我nullpointerexception，即tv.setText（＆＃34; hiii＆＃34;）;我发布了我的代码和错误日志。我是这个概念的新手，所以请一步一步指导我。

FragmentOne extends Fragment类如下：

 public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.list_view_details, container,
            false);
        final int imageArra[] = { R.drawable.leftbar_logo ,R.drawable.leftbar_logo};
        ViewPagerAdapter adapter = new ViewPagerAdapter(getActivity(),imageArra);
        ViewPager myPager = (ViewPager)view.findViewById(R.id.pagers2);

       myPager.setAdapter(adapter);
      TextView tv=(TextView)myPager.findViewById(R.id.page);
      tv.setText("hiii");
      myPager.setCurrentItem(0);    

    return view;
}

ViewPagerAdapter扩展PagerAdapter类如下

         public Object instantiateItem(View collection, int position) {

    LayoutInflater inflater = (LayoutInflater) collection.getContext()
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    int resId = 0,textviews;
    switch (position) {
    case 0:
        resId = R.layout.details;

        break;
    case 1:
        resId = R.layout.activity_main__load;
        break;
    case 2:
        resId = R.layout.feedback_email;
        break;
    case 3:
        resId = R.layout.feedback_email;
        break;
    case 4:
        resId = R.layout.menulist;
        break;
    }

    View view = inflater.inflate(resId, null);

    ((ViewPager) collection).addView(view, 0);

    return view;
}

错误日志

    E/AndroidRuntime(12230): FATAL EXCEPTION: main
    E/AndroidRuntime(12230): Process: com.alrimal, PID: 12230
    E/AndroidRuntime(12230): java.lang.NullPointerException
    E/AndroidRuntime(12230):    at com.alrimal.FragmentOne.onCreateView(FragmentOne.java:103)
    : E/AndroidRuntime(12230):  at android.app.Fragment.performCreateView(Fragment.java:1700)
     E/AndroidRuntime(12230):   at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
     E/AndroidRuntime(12230):   at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
     E/AndroidRuntime(12230):   at android.app.BackStackRecord.run(BackStackRecord.java:684)
     E/AndroidRuntime(12230):   at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
     E/AndroidRuntime(12230):   at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
     E/AndroidRuntime(12230):   at android.os.Handler.handleCallback(Handler.java:733)
     E/AndroidRuntime(12230):   at android.os.Handler.dispatchMessage(Handler.java:95)
     E/AndroidRuntime(12230):   at android.os.Looper.loop(Looper.java:136)
     E/AndroidRuntime(12230):   at android.app.ActivityThread.main(ActivityThread.java:5001)
     E/AndroidRuntime(12230):   at java.lang.reflect.Method.invokeNative(Native Method)
     E/AndroidRuntime(12230):   at java.lang.reflect.Method.invoke(Method.java:515)
    E/AndroidRuntime(12230):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
     E/AndroidRuntime(12230):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
    E/AndroidRuntime(12230):    at dalvik.system.NativeStart.main(Native Method)

第103行是tv.setText("hiii");。

list_view_details.xml

 <?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:background="@drawable/category_bg"

>

<HorizontalScrollView
    android:id="@+id/horizontalScrollView1"
    android:layout_width="fill_parent"
    android:layout_height="70dp"
    android:layout_alignParentLeft="true"
    android:background="@android:color/white"
    android:layout_alignParentTop="true" >

    <LinearLayout
         android:id="@+id/linear"
        android:layout_width="fill_parent"
        android:layout_height="50dp"

        android:orientation="horizontal" >
    </LinearLayout>
</HorizontalScrollView>

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/horizontalScrollView1" >
 <android.support.v4.view.ViewPager
    android:id="@+id/pagers2"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
 </RelativeLayout>

</RelativeLayout>

details.xml

  <?xml version="1.0" encoding="utf-8"?>
      <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
       >

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="250dp"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:background="@drawable/categoryitem_bg" >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/textView1"
        android:layout_marginLeft="23dp"
        android:layout_marginTop="18dp"
        android:src="@drawable/alrimal_logo" />

    <TextView
        android:id="@+id/page"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/imageView1"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="18dp"
        android:layout_marginRight="28dp"
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge" />

     </RelativeLayout>

    </RelativeLayout>

Answer 1

更改

TextView tv=(TextView)myPager.findViewById(R.id.page);

到

TextView tv=(TextView)view.findViewById(R.id.page);

Answer 2

您正在使用viewpager作为视图来引用视图。使用viewpager引用类似textview的视图可能是问题所在。

在ViewPager中将值设置为TextView会强制关闭

2 个答案: