Question

我正在为Android编写一些代码，问题是，当我调用findViewById时它返回null，我无法理解为什么！从昨天起我一直在浪费我的大脑，但我无法找到解决方案。目标是将布局设置为listView的标题。这是我的代码，分别是我的标题和我的页面：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/header"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="5dp">

    <TextView
        android:text="@string/bydistance"
        android:layout_gravity="left"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:textSize="13dp"
        android:gravity="center_horizontal"/>

    <TextView
        android:text="@string/byactivity"
        android:layout_gravity="right"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content"
        android:textSize="13dp"
        android:gravity="center_horizontal"/>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:background="#ff0000"
    >

    <ListView
        android:id="@+id/parkList"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:divider="@android:color/transparent"
        android:dividerHeight="5.0dp">
    </ListView>

</LinearLayout>

这里是我调用addheaderView的代码：

public class NearMeFragment extends Fragment implements View.OnClickListener{

private FragmentManager fragmentManager;

@Override
public void onCreate(Bundle savedBundle){
    super.onCreate(savedBundle);
}

@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedBundle) {
    View v = inflater.inflate(R.layout.park_list, container, false);

    //TODO remove
    make_test(v, container);

    return v;
}

public void openTest(View view){
    new LiveComment().show(getChildFragmentManager(), "dialog");
}

public void onClick(View view){
    if (fragmentManager == null)
        fragmentManager = getChildFragmentManager();
    //if (view.getId() == R.id.test){
        fragmentManager.beginTransaction().add(new LiveComment(), "livecomment").commit();
}

private void make_test(View v, ViewGroup container) {

    ListView listView = (ListView) v.findViewById(R.id.parkList);
    Park[] list = new Park[3];
    list[0] = new Park("parco a", "acquasparta", false, false, 1, 2, 3);
    list[1]=new Park("parco b", "perugia", false, false, 1, 2, 3);
    list[2]=new Park("parco b", "perugia", false, false, 1, 2, 3);
    ParkListAdapter adapter = new ParkListAdapter(v.getContext(), R.layout.small_park_container,list);
    LinearLayout header = (LinearLayout) container.findViewById(R.id.header);
    listView.addHeaderView(header);
    listView.setAdapter(adapter);

}
}

错误在

处给出

listView.addHeaderView(header)

Answer 1

R.id.header位于v内，不在container内。

更改

LinearLayout header = (LinearLayout) container.findViewById(R.id.header);

与

LinearLayout header = (LinearLayout) v.findViewById(R.id.header);

关于docGroup的ViewGroup容器说：

如果为非null，则这是片段的UI应该是父视图附属于。片段不应该添加视图本身，但这可以用于生成视图的LayoutParams。

编辑：由于您的标题视图位于另一个布局中，您也必须对其进行充气：

@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedBundle) {
    View v = inflater.inflate(R.layout.park_list, container, false);
    View header = inflater.inflate(R.layout.headerlayout, null);
    //TODO remove
    make_test(v, header);

    return v;
}

和

private void make_test(View v, View header) {

     // your code  

    // you  have to remove LinearLayout header = (LinearLayout) container.findViewById(R.id.header);
    listView.addHeaderView(header);
    listView.setAdapter(adapter);

}

Android，findViewById返回null

1 个答案: