Android Studio 下拉框Spinner实例

功能

下拉框相当常见了，例如选择省、市、县；例如选择部门；选择员工。用处一般是多选一。

显示

下拉框一般有两种形式，一种是下拉显示可选项，一种是弹窗显示可选项。通过调整参数spinnerMode，dropdown/dialog分别代表两种下拉框。

注意下拉框的数据需要从资源中关联过来，资源文件res/values/arrays.xml代码如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="gradeArray">
        <item>初一</item>
        <item>初二</item>
        <item>初三</item>
    </string-array>
</resources>

Android布局文件如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="4dp">

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:entries="@array/gradeArray"
        android:spinnerMode="dropdown"></Spinner>

    <Spinner
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:entries="@array/gradeArray"
        android:spinnerMode="dialog"></Spinner>

    <Button
        android:id="@+id/buttonOk"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="确认" />
</LinearLayout>

效果如下：

动态设置选项

可以利用数组适配器ArrayAdapter动态设置下来框的选项，布局文件修改为:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="4dp">
    <Spinner
        android:id="@+id/spinnerGrade"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:spinnerMode="dropdown"></Spinner>
    <Button
        android:id="@+id/buttonOk"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="确认" />
</LinearLayout>

代码部分修改为：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
        //内容数组
        String[] gradeArray={"初一","初二","初三","初四"};
        //数组适配器
        ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
        spinnerGrade.setAdapter(gradeAdapter);
        //设置默认选中项
        spinnerGrade.setSelection(0);
    }
}

获取选中项

点击确认后获取选中项，并显示选中项内容。

public class MainActivity extends AppCompatActivity {
    //内容数组
    String[] gradeArray={"初一","初二","初三","初四"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
        //数组适配器
        ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
        spinnerGrade.setAdapter(gradeAdapter);
        //设置默认选中项
        spinnerGrade.setSelection(0);
        //获取按钮
        Button buttonOk = findViewById(R.id.buttonOk);
        //设置按钮点击监听器
        buttonOk.setOnClickListener(new MyOnClickListener());
    }
    //定义按钮点击监听器
    class MyOnClickListener implements View.OnClickListener {
        //按钮点击
        @Override
        public void onClick(View view) {
            if (view.getId() == R.id.buttonOk) {//被点击的是确认按钮
                //获取选中项
                Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
                //显示提示框
                Toast.makeText(MainActivity.this, gradeArray[spinnerGrade.getSelectedItemPosition()] , Toast.LENGTH_SHORT).show();
            }
        }
    }
}

监听下拉框选中项

当下拉框选中项发生改变时，弹窗显示新项目，代码如下：

public class MainActivity extends AppCompatActivity {
    //内容数组
    String[] gradeArray={"初一","初二","初三","初四"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
        //数组适配器
        ArrayAdapter<String> gradeAdapter=new ArrayAdapter<>(this,R.layout.support_simple_spinner_dropdown_item,gradeArray);
        spinnerGrade.setAdapter(gradeAdapter);
        //设置默认选中项
        spinnerGrade.setSelection(0);
        //获取按钮
        Button buttonOk = findViewById(R.id.buttonOk);
        //设置按钮点击监听器
        buttonOk.setOnClickListener(new MyOnClickListener());

        spinnerGrade.setOnItemSelectedListener(new MyOnItemSelectedListener());
    }

    //定义按钮点击监听器
    class MyOnClickListener implements View.OnClickListener {
        //按钮点击
        @Override
        public void onClick(View view) {
            if (view.getId() == R.id.buttonOk) {//被点击的是确认按钮
                //获取选中项
                Spinner spinnerGrade=findViewById(R.id.spinnerGrade);
                //显示提示框
                Toast.makeText(MainActivity.this, gradeArray[spinnerGrade.getSelectedItemPosition()] , Toast.LENGTH_SHORT).show();
            }
        }
    }

    class MyOnItemSelectedListener implements AdapterView.OnItemSelectedListener {
        //选择
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            Toast.makeText(MainActivity.this, gradeArray[i], Toast.LENGTH_SHORT).show();
        }
        //未选择
        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {
        }
    }
}