Fragment中的findViewById返回Null

Question

I've tried both getActivity().findViewById() and getView() . This is the code in my fragment. They all return null..

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.edit_viewer, container, false);

    Bundle bundle = getArguments();
    id = bundle.getLong("VIEWER_ID");

    DatabaseHelper dbHelper = new DatabaseHelper(getActivity());

    username = (EditText)getView().findViewById(R.id.username);
    password = (EditText)getView().findViewById(R.id.entry);
    hostUrl = (EditText)getView().findViewById(R.id.hostUrl);
    webApp = (EditText)getView().findViewById(R.id.webApp);
    modelId = (EditText)getView().findViewById(R.id.modelId);
    properties = (EditText)getView().findViewById(R.id.properties);

Code from Activity

public class EditViewerActivity extends ActionBarActivity {
    private Long id;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_edit_viewer);

        Intent intent = getIntent();
        Long id = intent.getLongExtra("VIEWER_ID", 0);

        ViewerEditFragment newFragment = new ViewerEditFragment();
        Bundle bundle = new Bundle();
        bundle.putLong("VIEWER_ID", id);
        newFragment.setArguments(bundle);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, newFragment)
                    .commit();
        }

    }

edit_viewer.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/edit_viewer"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">

    <TextView
        style="?android:attr/listSeparatorTextViewStyle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="sfn Credentials"/>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/username"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/username"
            android:hint="Admin"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/password"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/entry"
            android:inputType="textPassword"
            android:hint="Password"
            android:minWidth="100dip"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

    <TextView
        style="?android:attr/listSeparatorTextViewStyle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Host Settings"/>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/host_url"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/hostUrl"
            android:hint="http://www.mysfn.com"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/web_app"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/webApp"
            android:hint="sfn"
            android:minWidth="100dip"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/model_id"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/modelId"
            android:hint="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/properties"
            android:paddingLeft="10dp" />
        <EditText
            android:id="@+id/properties"
            android:hint="dv=icon"
            android:minWidth="100dip"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

    <Button android:id="@+id/close"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:text="Save" />
</LinearLayout>

Answer 1

Change this

 username = (EditText)getView().findViewById(R.id.username);

to

 username = (EditText)rootView.findViewById(R.id.username);

and do the same for all other Views

Answer 2

getView returns the view you inflated in onCreateView , and before onCreateView returns it is not available. You should use the inflated view to retrieve your component or override onViewCreated that takes the inflated View as parameter, and use it to retrieve your component. Here you can find the documentation for onViewCreated

Called immediately after onCreateView(LayoutInflater, ViewGroup, Bundle) has returned, but before any saved state has been restored in to the view. This gives subclasses a chance to initialize themselves once they know their view hierarchy has been completely created.

Answer 3

您应该这样呼叫：

username = (EditText) rootView.findViewById(R.id.username);