ListView in fragment 列表視圖的使用

Use ListView in fragment:

1 Create a list view in fragment.xml (You must create the id for it):
在fragment的xml文件中創建一個<ListView>，賦上id

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

while the fragment must have the <FrameLayout> to be the root view:
fragment的根視圖要是<FrameLayout>

<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"
    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.example.android.sunshine.MainActivityFragment"
    tools:showIn="@layout/activity_main">
    <ListView
        android:id="@+id/listview_forecast"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </ListView>
</FrameLayout>

2 Create a new xml file (Such as：list_item_forecast) to contain the textview (show the data).
It will offer a space to adapter in order to generate listview automatically.
For example(You must create the id for it):
創建一個新的xml文件（比如 list_item_forecast） 包含 <TextView>(賦id)

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

3 Create a arraylist to contain the data.
創建一個數組列表ArrayList

     String [] forecastArray = {
                "Today-Sunny-88/63",
                "Tomorrow-Foggy-70/46",
                "Weds-Cloudy-72/63",
                "Thurs-Rainy-64/51",
                "Fri-Foggy-70/46",
                "Sat-Sunny-76/68"
        };
        // Assign to the ArrayList
        List<String> weekForecast = new ArrayList<String>(Arrays.asList(forecastArray));

**4 Initialize the adapter.
設定轉換器**

     // Create the ArrayAdapter to set the parameter
        // It will take data from the resource and populate the ListView
        ArrayAdapter<String> mForecaseAdapter =
                new ArrayAdapter <String> (
                        getActivity(),
                        R.layout.list_item_forecast,
                        R.id.list_item_forecast_textiew,
                        weekForecast
                );

5 Set the adapter to listview.
將轉換器配給ListView

   /*
    * Calling findViewById() on the Activity object will only work if
    * the current Activity layout is set by setContentView().
    * You need a View object of the layout to call the findViewById() in not MainActivity
    */
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        ListView weather = (ListView) rootView.findViewById(R.id.listview_forecast);
        weather.setAdapter(mForecaseAdapter);

So, in the public onCreateView(), the return statement becomes: return rootView.

findViewById()這個方法在非MainActivity裏面不能調用，只有當前佈局中設置了setContentView()的纔可以調用。所以我們需要一個視圖對象來調用
然後把返回值直接改成rootView就好了。

關於轉換器（不知道中文書翻譯是什麼樣，我自己叫它轉換器）：
原始數據需要先傳給轉換器，轉換器會將原始數據進行排列，當listview發出相應請求時，再合適的放置在listview裏面。如圖

設定轉換器：
它有四個參數 （parameters）：
1. 環境 （context）
2. 列表項佈局的id (ID of list item layout)
3. 文本視圖的id (ID of text view)
4. 一列數據 (list of data)
如圖：

Reference: https://www.udacity.com/course/viewer#!/c-ud853/l-1395568821/e-1395668598/m-1402878728