Android 中的 Spinner 示例

Android Spinner 是一个类似于下拉列表的视图，用于从选项列表中选择一个选项。它提供了一种从项目列表中选择一个项目的简单方法，当我们单击它时，它会显示所有值的下拉列表。 android spinner 的默认值将是当前选择的值，通过使用Adapter ，我们可以轻松地将项目绑定到 spinner 对象。通常，我们通过在 Kotlin 文件中使用ArrayAdapter来使用项目列表填充 Spinner 控件。

Spinner 小部件的不同属性

XML attributes	Description
android:id	Used to specify the id of the view.
android:textAlignment	Used to the text alignment in the dropdown list.
android:background	Used to set the background of the view.
android:padding	Used to set the padding of the view.
android:visibility	Used to set the visibility of the view.
android:gravity	Used to specify the gravity of the view like center, top, bottom, etc

演示 Spinner 的示例

这是一个显示 GFG 课程列表的 Android 应用程序示例。使用 ArrayAdapter 存储课程列表。创建一个包含微调器的 MainActivity 并单击任何具有该课程名称的微调器 Toast 项目。

创建活动：将有一个活动，因此 MainActivity 将有一个 XML 文件。 activity_main.xml ：第一个活动的 XML 文件由带有微调器小部件的约束布局组成。以下是活动 XML 文件的代码：

创建Java和 Kotlin 文件：有一个活动，因此 MainActivity 文件有一个Java/Kotlin 文件。 Main Activity 的Java/Kotlin 文件，其中Array Adapter用于将数据绑定到微调器。我们将在字符串数组中填充数据并将该数据绑定到微调器。这是代码：

Java

import android.support.v7.app.AppCompatActivity;
import android.widget.AdapterView;
import android.view.View;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.os.Bundle;
 
// Main Activity implements Adapter view
public class MainActivity
    extends AppCompatActivity
    implements AdapterView.OnItemSelectedListener {
 
    // create array of Strings
    // and store name of courses
    String[] courses = { "C", "Data structures",
                        "Interview prep", "Algorithms",
                        "DSA with java", "OS" };
 
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        // Take the instance of Spinner and
        // apply OnItemSelectedListener on it which
        // tells which item of spinner is clicked
        Spinner spino = findViewById(R.id.coursesspinner);
        spin.setOnItemSelectedListener(this);
 
        // Create the instance of ArrayAdapter
        // having the list of courses
        ArrayAdapter ad
            = new ArrayAdapter(
                this,
                android.R.layout.simple_spinner_item,
                courses);
 
        // set simple layout resource file
        // for each item of spinner
        ad.setDropDownViewResource(
            android.R.layout
                .simple_spinner_dropdown_item);
 
        // Set the ArrayAdapter (ad) data on the
        // Spinner which binds data to spinner
        spino.setAdapter(ad);
    }
 
    // Performing action when ItemSelected
    // from spinner, Overriding onItemSelected method
    @Override
    public void onItemSelected(AdapterView<*> arg0,
                            View arg1,
                            int position,
                            long id)
    {
 
        // make toastof name of course
        // which is selected in spinner
        Toast.makeText(getApplicationContext(),
                    courses[position],
                    Toast.LENGTH_LONG)
            .show();
    }
 
    @Override
    public void onNothingSelected(AdapterView<*> arg0)
    {
        // Auto-generated method stub
    }
}

科特林

import android.os.Bundle
import android.view.View
import android.widget.AdapterView
import android.widget.AdapterView.OnItemSelectedListener
import android.widget.ArrayAdapter
import android.widget.Spinner
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
class MainActivity : AppCompatActivity(), OnItemSelectedListener {
    // create array of Strings
    // and store name of courses
    var courses = arrayOf("C", "Data structures",
            "Interview prep", "Algorithms",
            "DSA with java", "OS")
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
 
        // Take the instance of Spinner and
        // apply OnItemSelectedListener on it which
        // tells which item of spinner is clicked
        val spin = findViewById(R.id.coursesspinner)
        spin.onItemSelectedListener = this
 
        // Create the instance of ArrayAdapter
        // having the list of courses
        val ad: ArrayAdapter<*> = ArrayAdapter(
                this,
                android.R.layout.simple_spinner_item,
                courses)
 
        // set simple layout resource file
        // for each item of spinner
        ad.setDropDownViewResource(
                android.R.layout.simple_spinner_dropdown_item)
 
        // Set the ArrayAdapter (ad) data on the
        // Spinner which binds data to spinner
        spin.adapter = ad
    }
 
    override fun onItemSelected(parent: AdapterView<*>?,
                                view: View, position: Int,
                                id: Long) {
        // make toastof name of course
        // which is selected in spinner
        Toast.makeText(applicationContext,
                courses[position],
                Toast.LENGTH_LONG)
                .show()
    }
 
    override fun onNothingSelected(parent: AdapterView<*>?) {}
}

输出：