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AdapterView

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

本指南介绍了如何完成与设置适配器相关的一些关键步骤。

使用数据填充布局

要将数据添加到您在应用的界面内创建的布局中,请添加类似于以下内容的代码:

Kotlin

    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
    

Java

    // 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,必须将投影中的 People._ID 列与 CursorAdapter 结合使用,否则将会出现异常。

如果您在应用的生命周期内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被更改,它应该自行进行刷新。

处理用户选择

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

Kotlin

    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()
    }
    

Java

    // 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);
    

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