AdapterView

尝试 Compose 方式

Jetpack Compose 是 Android 推荐的 UI 工具包。了解如何在 Compose 中使用布局。

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AdapterView 是一个 ViewGroup，它显示加载到适配器中的项目。最常见的适配器类型来自基于数组的数据源。

本指南展示了如何完成与设置适配器相关的几个关键步骤。

用数据填充布局

要将数据添加到您在应用的 UI 中创建的布局中，请添加类似于以下内容的代码

val PROJECTION = arrayOf(Contacts.People._ID, People.NAME)
...

// Get a Spinner and bind it to an ArrayAdapter that
// references a String array.
val spinner1: Spinner = findViewById(R.id.spinner1)
val adapter1 = ArrayAdapter.createFromResource(
        this, R.array.colors, android.R.layout.simple_spinner_item)
adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
spinner1.adapter = adapter1

// Load a Spinner and bind it to a data query.
val spinner2: Spinner = findViewById(R.id.spinner2)
val cursor: Cursor = managedQuery(People.CONTENT_URI, PROJECTION, null, null, null)
val adapter2 = SimpleCursorAdapter(this,
        // Use a template that displays a text view
        android.R.layout.simple_spinner_item,
        // Give the cursor to the list adapter
        cursor,
        // Map the NAME column in the people database to...
        arrayOf(People.NAME),
        // The "text1" view defined in the XML template
        intArrayOf(android.R.id.text1))
adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
spinner2.adapter = adapter2

// Get a Spinner and bind it to an ArrayAdapter that
// references a String array.
Spinner s1 = (Spinner) findViewById(R.id.spinner1);
ArrayAdapter adapter = ArrayAdapter.createFromResource(
    this, R.array.colors, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s1.setAdapter(adapter);

// Load a Spinner and bind it to a data query.
private static String[] PROJECTION = new String[] {
        People._ID, People.NAME
    };

Spinner s2 = (Spinner) findViewById(R.id.spinner2);
Cursor cur = managedQuery(People.CONTENT_URI, PROJECTION, null, null);

SimpleCursorAdapter adapter2 = new SimpleCursorAdapter(this,
    android.R.layout.simple_spinner_item, // Use a template
                                          // that displays a
                                          // text view
    cur, // Give the cursor to the list adapter
    new String[] {People.NAME}, // Map the NAME column in the
                                         // people database to...
    new int[] {android.R.id.text1}); // The "text1" view defined in
                                     // the XML template

adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s2.setAdapter(adapter2);

请注意，在使用 CursorAdapter 时，投影中必须包含 People._ID 列，否则您将收到异常。

如果在应用生命周期中，您更改了适配器读取的底层数据，则应调用 notifyDataSetChanged()。这将通知附加的视图数据已更改，它应该刷新自身。

注意：使用 Android Studio 3.6 及更高版本，视图绑定 功能可以替换 findViewById() 调用，并为与视图交互的代码提供编译时类型安全性。考虑使用视图绑定而不是 findViewById()。

处理用户选择

您可以通过将类的 AdapterView.OnItemClickListener 成员设置为侦听器并捕获选择更改来处理用户的选择。

val historyView: ListView = findViewById(R.id.history)
historyView.onItemClickListener = AdapterView.OnItemClickListener { parent, view, position, id ->
    Toast.makeText(context, "You've got an event", Toast.LENGTH_SHORT).show()
}

// Create a message handling object as an anonymous class.
private OnItemClickListener messageClickedHandler = new OnItemClickListener() {
    public void onItemClick(AdapterView parent, View v, int position, long id)
    {
        // Display a messagebox.
        Toast.makeText(context,"You've got an event",Toast.LENGTH_SHORT).show();
    }
};

// Now hook into our object and set its onItemClickListener member
// to our class handler object.
historyView = (ListView)findViewById(R.id.history);
historyView.setOnItemClickListener(messageClickedHandler);