java - 如何添加 fragment 以使我的应用程序不会在屏幕上显示为空白

Question

我正在制作 Udacity Sunshine 应用程序。因为以前使用的android studio版本是0.5.8，现在我使用的是android studio 3.0.1。因此，这两者中使用的编码技术之间存在很大差距。 因此，在这里我在空 Activity 中使用了 fragment ，并且通过阅读developer.android.com上有关 fragment 的文章来实现它，我得到了关于它的抽象想法，但其中很多内容仍然不清楚。 所以我完成了添加 fragment 并向 ListView 添加假数据以填充它。 但是当我在设备上运行该应用程序时，它仍然显示空白屏幕，并且没有我在代码中添加的 TextView :

布局/activity_main.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
tools:ignore="MergeRootFrame" />

布局/fragment_layout.xml

    <FrameLayout 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"
    tools:context=".ArticleFragment"
    tools:showIn="@layout/activity_main">

    <ListView
        android:id="@+id/listview_forecast"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</FrameLayout>

布局/list_of_item_forecast.xml

 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:minHeight="?android:attr/listPreferredItemHeight"
    android:gravity="center_vertical"
    android:id="@+id/list_item_forecast_textview"
    tools:layout="@layout/fragment_layout"/>

包/MainActivity.java

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

public class MainActivity extends FragmentActivity {

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

包/ArticleFragment.java

import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ArrayAdapter;
    import android.widget.ListView;
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;

    public class ArticleFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    // Create some dummy data for the ListView.  Here's a sample weekly forecast
    String[] data = {
            "Mon 6/23 - Sunny - 31/17",
            "Tue 6/24 - Foggy - 21/8",
            "Wed 6/25 - Cloudy - 22/17",
            "Thurs 6/26 - Rainy - 18/11",
            "Fri 6/27 - Foggy - 21/10",
            "Sat 6/28 - TRAPPED IN WEATHERSTATION - 23/18",
            "Sun 6/29 - Sunny - 20/7"
    };
    List<String> weekForecast = new ArrayList<String>(Arrays.asList(data));

    // Now that we have some dummy forecast data, create an ArrayAdapter.
    // The ArrayAdapter will take data from a source (like our dummy forecast) and
    // use it to populate the ListView it's attached to.
    ArrayAdapter<String> mForecastAdapter =
            new ArrayAdapter<String>(
                    getActivity(), // The current context (this activity)
                    R.layout.list_item_forecast, // The name of the layout ID.
                    R.id.list_item_forecast_textview, // The ID of the textview to populate.
                    weekForecast);
    View rootView = inflater.inflate(R.layout.fragment_layout, container, false);

    // Get a reference to the ListView, and attach this adapter to it.
    ListView listview = (ListView) rootView.findViewById(
            R.id.listview_forecast);
    listview.setAdapter(mForecastAdapter);
    // Inflate the layout for this fragment
    return rootView;
}
}

Answer 1

您的代码的问题是您没有实例化您创建的 Fragment 类。您需要实例化它并将其传递给 FragmentManager，并在主 Activity 中更改 setContentView(R.layout.fragment_layout)。

只需将您的 MainActivity.java 类更改为此即可解决您的问题。无需更改布局文件。

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.container, new ArticleFragment())
                .commit();
    }
}