java是否可以使用setWeightSum（float）以编程方式更改weightSum值？

Question

我试图从片段控制线性布局的权重和。我想知道是否可以使用setWeightSum（float）方法来实现这一点。 我试图在id为header\u Linear的线性布局中控制权重和

<LinearLayout
安卓:id="@+id/header_Linear"
xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
安卓:layout_width="match_parent"
安卓:layout_height="?安卓:attr/actionBarSize"
安卓:orientation="horizontal"
安卓:weightSum="8">

        <TextView
            安卓:id="@+id/table_0.0"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.1"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:textAlignment="center"
            安卓:gravity="center"
            安卓:text="M"
            安卓:textColor="@color/colorTableItem"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.2"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="T"
            安卓:textColor="@color/colorTableItem"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.3"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="W"
            安卓:textColor="@color/colorTableItem"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.4"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="T"
            安卓:visibility="visible"
            安卓:textColor="@color/colorTableItem"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.5"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="F"
            安卓:visibility="visible"
            安卓:textColor="@color/colorTableItem"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.6"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="S"
            安卓:textColor="@color/colorTableItem"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>

        <TextView
            安卓:id="@+id/table_0.7"
            安卓:layout_width="0dp"
            安卓:layout_height="match_parent"
            安卓:layout_weight="1"
            安卓:gravity="center"
            安卓:text="S"
            安卓:textColor="@color/sunday_text_color"
            安卓:visibility="visible"
            安卓:background="@drawable/header_bg"/>
</LinearLayout>

这是我使用setWeightSum的片段

public class TimeTableFragment extends Fragment {

public View onCreateView(@NonNull LayoutInflater inflater,
                         ViewGroup container, Bundle savedInstanceState) {

    View root = inflater.inflate(R.layout.fragment_timetable, container, false);

    LinearLayout linearLayout = root.findViewById(R.id.header_Linear);

    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(Objects.requireNonNull(getContext()));
    String header_value = sharedPreferences.getString("Header","0");
    Toast.makeText(getContext(),""+header_value,Toast.LENGTH_LONG).show();

    if (header_value.equals("0")){
        linearLayout.setWeightSum(6);
    }

    return root;
}

当我启动应用程序时，它崩溃了。我想知道是否有可能控制weightSum而不出错。 多谢各位

Upate

The reason why I got nullPointException even though I declared Linear Layout using findViewById was due to xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"in Layout.

The View that contains xmlns:安卓="http://schemas.安卓.com/apk/res/安卓" would return null after using findViewById in this situation

Answer 1

        public class TimeTableFragment extends Fragment {

        public View onCreateView(@NonNull LayoutInflater inflater,
                                 ViewGroup container, Bundle savedInstanceState) {

            View root = inflater.inflate(R.layout.fragment_timetable, container, false);

            return root;
        }

        @Override
        public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);

            LinearLayout linearLayout = view.findViewById(R.id.header_Linear);

            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(Objects.requireNonNull(getContext()));
            String header_value = sharedPreferences.getString("Header","0");
            Toast.makeText(getContext(),""+header_value,Toast.LENGTH_LONG).show();

            if (header_value.equals("0")){
                linearLayout.setWeightSum(6);
            }

    }
}