Question

我在将参数传递给主要活动的片段时遇到问题。 getArguments方法返回null但同时片段显示我试图传递的参数但位于不同的位置。我确定它与我正在替换替换方法的容器有关。

我的主要活动：

public class MainActivity extends AppCompatActivity {

    private final String FRAGMENT_TAG = "fragment_tag";
    public static final String USER_NAME = "userName";
    public static final String USER_PASSWORD = "userPassword";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        User user = getIntent().getParcelableExtra(LoginActivityFragment.SERVER_MESSAGE);
        Bundle bundle = new Bundle();
        bundle.putString(USER_NAME, user.getUser_name());
        bundle.putString(USER_PASSWORD, user.getUser_password());

        if (user != null) {
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            MainActivityFragment fragment = (MainActivityFragment) getSupportFragmentManager()
                    .findFragmentByTag(FRAGMENT_TAG);
            if (fragment != null) {
                ft.replace(android.R.id.content, fragment);
                ft.commit();
            } else {
                MainActivityFragment newFragment = new MainActivityFragment();
                ft.replace(android.R.id.content, newFragment, FRAGMENT_TAG);
                newFragment.setArguments(bundle);
                ft.commit();
            }
        }
    }
}

我的MainActivityFragment：

public class MainActivityFragment extends Fragment {

    private final String ERROR = "Error";

    public MainActivityFragment() {
    }

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

        View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        TextView username = (TextView) rootView.findViewById(R.id.username_test);
        TextView password = (TextView) rootView.findViewById(R.id.pass_test);

        Bundle bundle = getArguments();
        try {
            username.setText(bundle.getString(MainActivity.USER_NAME));
            password.setText(bundle.getString(MainActivity.USER_PASSWORD));
        } catch (Exception e) {
            Log.e(ERROR, "Error: " + e.getMessage());
        }
        return rootView;
    }
}

MainActivity布局：

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.msc.ebla.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay">

            <SearchView
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

            </SearchView>

        </android.support.v7.widget.Toolbar>

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

</android.support.design.widget.CoordinatorLayout>

content_main布局

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/fragment"
    android:name="com.msc.ebla.MainActivityFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:layout="@layout/fragment_main" />

MainActivityFragment Layout

<LinearLayout 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:orientation="vertical"
    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="com.msc.ebla.MainActivityFragment"
    tools:showIn="@layout/activity_main">

    <TextView
        android:id="@+id/username_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="user"/>

    <TextView
        android:id="@+id/pass_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="pass"/>

    <ListView
        android:id="@android:id/list"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">

    </ListView>


</LinearLayout>

以下是我将testName和testPass作为参数传递时模拟器的屏幕截图：

Answer 1

看起来你正在加载两个Fragment s - 一个静态，一个动态。您在Fragment中声明的静态xml以及此getArguments()中的静态null将始终返回Fragment。但动态<fragment xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/fragment" android:name="com.msc.ebla.MainActivityFragment" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:layout="@layout/fragment_main" />不应该。

我建议你只使用动态片段。替换：

<FrameLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:layout="@layout/fragment_main" />

使用

MainActivity

在您的android.R.id.content中，将所有对R.id.fragment_container的引用替换为newInstance()

修改

顺便说一句，我建议使用Fragment方法将参数传递给MainActivityFragment，因为它更可靠。将此方法声明添加到public static MainActivityFragment newInstance(String userName, String userPassword) { Bundle args = new Bundle(); args.putString(USER_NAME_KEY, userName); args.putString(USER_PASSWORD_KEY, userPassword); MainActivityFragment frag = new MainActivityFragment(); frag.setArguments(args); return frag; }：

new MainActivityFragment()

而不是使用MainActivityFragment.newInstance("user_name", "user_password)创建新实例，而是使用selectOptions = [{id: 1, name: 'name1'}, {id: 2, name: 'name2'}, {id: 3, name: 'name3'}];。还有更多信息here

Answer 2

对于“getArgument（）”，返回null问题：

你应该设置参数 BEFORE 调用replace（）和commit（）。因此，将代码更改为以下内容：

MainActivityFragment newFragment = new MainActivityFragment();
newFragment.setArguments(bundle);
ft.replace(android.R.id.content, newFragment, FRAGMENT_TAG);
ft.commit();

布局问题：

您的content_main布局与AppBar布局处于同一级别。你必须把它放在AppBar布局中。**像这样：

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

  <android.support.design.widget.AppBarLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:popupTheme="@style/AppTheme.PopupOverlay">

      <SearchView
          android:layout_width="match_parent"
          android:layout_height="wrap_content">

      </SearchView>



    </android.support.v7.widget.Toolbar>

    <include layout="@layout/content_main" />

  </android.support.design.widget.AppBarLayout>

</android.support.design.widget.CoordinatorLayout>

Android FragmentTransaction替换方法

2 个答案:

对于“getArgument（）”，返回null问题：

布局问题：