Android 片段不会替换活动中的 UI



我目前正在构建一个使用导航抽屉的安卓应用程序。当用户从抽屉中选择项目时,将创建一个与所选项目对应的片段。例如,如果用户从导航抽屉中选择联系人项,则 UI 应从仪表板更改为联系人布局。

我已成功创建片段,但是片段保留了仪表板中的日历视图。

以下是仪表板布局:

这是仪表板布局

这是用户从导航抽屉中选择计时器后的布局在此处输入图像描述

问题是当片段充气时,日历视图仍然存在。理想情况下,它只是此片段中可见的"计时器碎片"按钮。

这是我的主要活动代码:

//Fragments will be inflated through this method.
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    Fragment fragment = null;
    // Handle navigation view item clicks here.
    int id = item.getItemId();
    if (id == R.id.nav_patient) {
        fragment = new Patient_Fragment();
        // Handle the camera action
    } else if (id == R.id.nav_timer) {
        fragment = new Timer_Fragment();
    } else if (id == R.id.nav_reminders) {
    } else if (id == R.id.nav_contacts) {
    } else if (id == R.id.nav_account) {
    } else if (id == R.id.nav_about) {
    }
    if(fragment !=null)
    {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.replace(R.id.dashboardArea, fragment);
        ft.commit();
    }
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

这是我的计时器片段:

public class Timer_Fragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
       return inflater.inflate(R.layout.fragment_timer, null);
    }
    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }
}

下面是片段 XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
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:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
    android:id="@+id/timerFrag"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:text="Timer Frag"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.181" />

这是仪表板 XML:

<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/dashboardArea"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.a517086.carefree.MainActivity"
tools:showIn="@layout/app_bar_main">
   <CalendarView
    android:id="@+id/calendarView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
   </FrameLayout>

问题是您要替换R.id.dashboardArea(位于CalendarView片段布局中(,但您需要替换MainActivity中将保存片段的View。对于这个例子,我称之为content_container

if(fragment !=null)
    {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.replace(R.id.content_container, fragment);
        ft.commit();
    }

例:
我使用DrawerLayout,但您可以使用任何布局。这是我的MainActivity布局。

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    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/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">
    <RelativeLayout
    android:id="@+id/content_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    </RelativeLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer"/>
</android.support.v4.widget.DrawerLayout>

当我想交换我的片段时,我只是得到我想要可见的片段对象并替换容器 - 在本例中为"content_container"。

您应该将 CalendarView 放在与日历片段相关的另一个 xml 片段中,就像您对计时器片段所做的那样:

fragment_calendar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
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:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
 <CalendarView
    android:id="@+id/calendarView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

日历片段.java

public class CalendarFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
       return inflater.inflate(R.layout.fragment_calendar, null);
    }
    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }
}

您的仪表板 xml 文件应为空,如下所示:

<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/dashboardArea"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.a517086.carefree.MainActivity"
tools:showIn="@layout/app_bar_main">
</FrameLayout>

然后,在您的主活动中初始化日历片段,就像这样:

FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.add(R.id.dashboardArea, CalendarFragment);
        ft.commit(); 

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