如何在片段内膨胀视图

Question

如果我尝试在片段中膨胀视图，我会得到 NULL。例如：

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Here I will inflate my view using the layout ID & return.
    return view;
}

每当单击按钮时，我都需要创建一个动态视图，例如：按钮并添加到 LinearLayout。我想在我的片段类中执行这个操作，如下所示：

public void addPlaces() {    
    Button button = new Button(null);
    button.setText("button name");
    // e.g. like adding button to enter code here linear layout
    linearLayout.addView(button); 
}

所以，如果我在 onCreateView 中获得膨胀 LinearLayout 并在添加类中使用它，我会得到 NULL。如何实现？

Answer 1

将变量声明为实例变量，然后初始化线性布局

LinearLayout linearLayout;

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment1, container, false);
    linearLayout = (LinearLayout) rootView.findViewById(R.id.linearlayout);
    return rootView;
}

然后

public void addPlaces() {
    Button button = new Button(getActivity());
    // needs activity context
    // fragment hosted by a activity. use getActivity() to get the context of the hosting activity. 
    button.setText("button name");
    linearlayout.addView(button);
}

示例：根据您的要求修改以下内容。

fragment1.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" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Button" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:id="@+id/linearlayout"
        android:layout_height="fill_parent"
        android:layout_above="@+id/button1"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:orientation="vertical" >
    </LinearLayout>

</RelativeLayout>

Myfragment.java

public class Myfragment extends Fragment {

    LinearLayout linearLayout;
    View rootView;

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Button b = (Button) rootView.findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                addPlaces();
            }

        });
        linearLayout = (LinearLayout) rootView.findViewById(R.id.linearlayout);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.fragment1, container, false);
        return rootView;
    }

    public void addPlaces() {
        Button button = new Button(getActivity()); // needs activity context
        button.setText("button name");
        linearLayout.addView(button);
    }
}

我的模拟器快照

编辑：

activity-main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

     <fragment android:name="com.example.fragments.Myfragment"
            android:id="@+id/frag"
            android:layout_above="@+id/button1"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" />

      <Button
          android:id="@+id/button1"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignParentBottom="true"
          android:layout_centerHorizontal="true"
          android:text="Button" />

</RelativeLayout>

MainActivity.java

public class MainActivity extends FragmentActivity {
    Button b;
    Myfragment fragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragment = new Myfragment();
        fragmentTransaction.add(R.id.frag, fragment);
        fragmentTransaction.commit();
        b = (Button) findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                fragment.addPlaces();
            }

        });
    }
}

Myfragment.java

public class Myfragment extends Fragment {

    LinearLayout linearLayout;
    View rootView;

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        linearLayout = (LinearLayout) rootView.findViewById(R.id.linearlayout);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.fragment1, container, false);
        return rootView;
    }

    public void addPlaces() {
        Button button = new Button(getActivity()); // needs activity context
        button.setText("button name");
        linearLayout.addView(button);
    }
}