数组适配器未填充列表视图

Question

我是 android 的新手，一直在关注 udacity 的视频讲座。列表视图没有被数组适配器填充，什么时候我运行手机上的应用程序只显示主要 activity 布局。

列表视图没有出现在手机屏幕上，谁能告诉我这里的错误是什么，是与框架布局有关还是有错误数组适配器。提前致谢

public class MainActivity extends AppCompatActivity {

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

}
public static class PlaceHolderFragment extends Fragment {
    private ArrayAdapter<String> mForecastAdapter;
    public PlaceHolderFragment(){}
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
       View rootview= inflater.inflate(R.layout.fragment_main, container, false);
        String[] forecastArray={
                "Today","Tommorow","wed","Thursday","Friday","Saturday","Sunday"
        };//creating some fake data to show in list view
        List<String> fore=new ArrayList<String>(Arrays.asList(forecastArray));
        mForecastAdapter=new ArrayAdapter<String>(getActivity(),R.layout.list_item_forecast,R.id.list_item_forecast_textview,fore);
        ListView listview= (ListView)rootview.findViewById(R.id.listview_forecast);
        listview.setAdapter(mForecastAdapter);
        return rootview;

    }
}
}

activity_main_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/container"
tools:context="com.saxenarc.jeetesh.layouts.MainActivity">
</FrameLayout>

list_item_forecast.xml

<?xml version="1.0" encoding="utf-8"?>

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

</TextView>

fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent"
android:layout_height="match_parent">

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

</FrameLayout>

发帖前检查了三次。

Answer 1

您的代码和列表运行良好，但您没有告诉列表在何处显示。您可以通过两种方式解决此问题。

第一

在主 activity 中添加片段，因为它不可见。

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

第二

停止使用片段并使用 Main 中的列表视图 activity

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent"
android:layout_height="match_parent">

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

</FrameLayout>

MainActivity.java

List<String> fore = new ArrayList<String>(Arrays.asList(forecastArray));
mForecastAdapter = new ArrayAdapter<String>(this,R.layout.list_item_forecast,R.id.list_item_forecast_textview,fore);
ListView listview= (ListView) findViewById(R.id.listview_forecast);
listview.setAdapter(mForecastAdapter);

数组适配器未填充列表视图

List view not getting populated by array adapter

android

android-arrayadapter