android - 如何实现两级 DrawerLayout

Question

我正在尝试实现两级 DrawerLayout。作为基准，我使用来自 http://developer.android.com/training/implementing-navigation/nav-drawer.html 的 Google 星球示例.所以我想扩展这个例子，从行星列表中选择一个行星，用该行星上的城市列表替换行星列表(除地球外大部分是空白的——我仍在充实我的数据:- ))。

我认为我可以采取三种方法:-

1. 替换 ListView
2. 保留 ListView，但替换其 ArrayAdapter
3. 保留 ListView 和 ArrayAdapter，但替换适配器的数据

所以尝试选项 3(这是最好的方法吗？)，在我的 DrawerItemClickListener 中我执行以下操作......

arrayAdapter.clear(); 
arrayAdapter.addAll(arrayListOfCities);
arrayAdapter.notifyDataSetChanged(); 
mDrawerList.invalidateViews();
mDrawerList.forceLayout();
mDrawerList.refreshDrawableState();

但它似乎不起作用，即行星列表没有被城市列表替换。

我的方法是否正确？如果正确，我该如何刷新列表？

Answer 1

Replace the ListView

真的没有这个必要。

---

Keep the ListView, but replace its ArrayAdapter

这将是最容易实现的。首先，将以下字符串数组(城市名称)添加到 res/values/strings.xml:

<string-array name="mercury_array">
    <item>Undiscovered City 1 (Mercury)</item>
    <item>Undiscovered City 2 (Mercury)</item>
    <item>Undiscovered City 3 (Mercury)</item>
    <item>Undiscovered City 4 (Mercury)</item>
</string-array>
<string-array name="venus_array">
    <item>Undiscovered City 1 (Venus)</item>
    <item>Undiscovered City 2 (Venus)</item>
    <item>Undiscovered City 3 (Venus)</item>
    <item>Undiscovered City 4 (Venus)</item>
</string-array>
<string-array name="earth_array">
    <item>New York</item>
    <item>Hong Kong</item>
    <item>New Delhi</item>
    <item>London</item>
</string-array>
<string-array name="mars_array">
    <item>Undiscovered City 1 (Mars)</item>
    <item>Undiscovered City 2 (Mars)</item>
    <item>Undiscovered City 3 (Mars)</item>
    <item>Undiscovered City 4 (Mars)</item>
</string-array>
<string-array name="jupiter_array">
    <item>Undiscovered City 1 (Jupiter)</item>
    <item>Undiscovered City 2 (Jupiter)</item>
    <item>Undiscovered City 3 (Jupiter)</item>
    <item>Undiscovered City 4 (Jupiter)</item>
</string-array>
<string-array name="saturn_array">
    <item>Undiscovered City 1 (Saturn)</item>
    <item>Undiscovered City 2 (Saturn)</item>
    <item>Undiscovered City 3 (Saturn)</item>
    <item>Undiscovered City 4 (Saturn)</item>
</string-array>
<string-array name="uranus_array">
    <item>Undiscovered City 1 (Uranus)</item>
    <item>Undiscovered City 2 (Uranus)</item>
    <item>Undiscovered City 3 (Uranus)</item>
    <item>Undiscovered City 4 (Uranus)</item>
</string-array>
<string-array name="neptune_array">
    <item>Undiscovered City 1 (Neptune)</item>
    <item>Undiscovered City 2 (Neptune)</item>
    <item>Undiscovered City 3 (Neptune)</item>
    <item>Undiscovered City 4 (Neptune)</item>
</string-array>

在 MainActivity 中创建方法 loadContentList(int)。这是将在主列表的项目点击时调用的方法:

private void loadContentList(int position) {

    setTitle(mPlanetTitles[position]);

    String[] content;

    switch(position) {
    case 0:
            content = getResources().getStringArray(R.array.mercury_array);
            break;
    case 1:
            content = getResources().getStringArray(R.array.venus_array);
            break;
    case 2:
            content = getResources().getStringArray(R.array.earth_array);
            break;
    case 3:
            content = getResources().getStringArray(R.array.mars_array);
            break;
    case 4:
            content = getResources().getStringArray(R.array.jupiter_array);
            break;
    case 5:
            content = getResources().getStringArray(R.array.saturn_array);
            break;
    case 6:
            content = getResources().getStringArray(R.array.uranus_array);
            break;
    case 7:
            content = getResources().getStringArray(R.array.neptune_array);
            break;
    default:
            content = getResources().getStringArray(R.array.neptune_array);     
}

    // Change ListView's adapter    
    mDrawerList.setAdapter(new ArrayAdapter<String>(this,
            R.layout.drawer_list_item, content));

    // Change OnItemClickListener // CityItemClickListener is defined below
    mDrawerList.setOnItemClickListener(new CityItemClickListener());
}

由于我们希望在点击行星项目时更新 ListView，因此我们将更改 DrawerItemClickListener 的方法体并调用新添加的 loadContentList(int):

/* The click listner for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        //selectItem(position);
        loadContentList(position);
    }
}

我们将需要另一个 OnItemClickListener 来在单击城市时更改 fragment 。 :

private class CityItemClickListener implements ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

        // This is the method that was being called on planet click 
        // in the original example. Implementation of it is up to you
        selectItem(position);
    }
}

---

Keep the ListView and the ArrayAdapter, but replace the adapter's data

定义 ArrayAdapter:

private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;    
---------> private ArrayAdapter<String> mAdapter;     

在 MainActivity 的 onCreate(Bundle) 中:

ArrayList<String> planetList = new ArrayList<String>();

planetList.addAll(Arrays.asList(mPlanetTitles));

mAdapter = new ArrayAdapter<String>(this,
            R.layout.drawer_list_item, planetList);

// set up the drawer's list view with items
mDrawerList.setAdapter(mAdapter);      

调用 mAdapter.clear() 时，我们必须传递一个 ArrayList 以避免 UnsupportedOperationException。

将 loadContentList(int) 更改为以下内容:

private void loadContentList2(int position) {

    setTitle(mPlanetTitles[position]);

    String[] content;

    switch(position) {

        ....
        ....
    }

    ArrayList<String> cityList = new ArrayList<String>();

    cityList.addAll(Arrays.asList(content));

    mAdapter.clear();

    mAdapter.addAll(cityList);

    // update
    mAdapter.notifyDataSetChanged();        

    // Change on item click listener
    mDrawerList.setOnItemClickListener(new CityItemClickListener());

}

CityItemClickListener 和 DrawerItemClickListener 将与以前保持一致。唯一的变化是:我们不会在行星列表项点击时创建新的 ArrayAdapter。

您需要想出一种方法(也许是一个按钮)让用户从城市 View 返回到行星列表。

我还建议您查看 ExpandableListView。它可能会更优雅地解决您的问题。