Spinner：当 ui(spinner) 包含在主 xml 文件中时，阵列适配器不起作用

Question

我有一个带有微调器的 UI 和一些使用 Arraydapter 的自定义字符串数组。

如果在activity_main中添加了微调项，一切正常。

但是，如果我在单独的布局中添加微调器并将其包含在 activity_main 中，则相同的代码不会填充微调器。

我使用 LayoutInflater 对视图进行了膨胀，并且在日志中没有发现异常。

谁能告诉我如何将 Arrayadapter 从 java 类添加到微调器到添加的 UI。

我试过了。

工作代码

MainActivity.java

        package com.abhiroop.simplespinnerappcustom;

   public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

// array of Strings
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);

    Spinner spino = findViewById(R.id.coursesspinner);
    spino.setOnItemSelectedListener(this);

    ArrayAdapter ad
            = new ArrayAdapter(
            this,
            android.R.layout.simple_spinner_item,
            courses);

    ad.setDropDownViewResource(
            android.R.layout
                    .simple_spinner_dropdown_item);
    spino.setAdapter(ad);
}


@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {

}

@Override
public void onNothingSelected(AdapterView<?> adapterView) {

}

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<!--Constraint layout which contain Spinner widget-->
 <androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<!--Spinner widget-->
<Spinner
    android:id="@+id/coursesspinner"
    android:layout_height="50dp"
    android:layout_width="160dp"
    android:layout_marginEnd="10dp"
    android:layout_marginStart="10dp"
    android:layout_marginBottom="10dp"
    android:layout_marginTop="10dp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>


</androidx.constraintlayout.widget.ConstraintLayout>

没有工作代码

MainActivity.java ''' 包 com.abhiroop.simplespinnerappcustom;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

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);

     View mainView = LayoutInflater.from(this).inflate(R.layout.activity_main, null);
    View view = LayoutInflater.from(this).inflate(R.layout.spinner_layout, (ViewGroup) mainView, true);
    Spinner spino = view.findViewById(R.id.coursesspinner);
    spino.setOnItemSelectedListener(this);

    
    ArrayAdapter ad
            = new ArrayAdapter(
            this,
            android.R.layout.simple_spinner_item,
            courses);

    ad.setDropDownViewResource(
            android.R.layout
                    .simple_spinner_dropdown_item);

    spino.setAdapter(ad);
}
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {

}

@Override
public void onNothingSelected(AdapterView<?> adapterView) {

}

} '''

activity_main.xml '''

<?xml version="1.0" encoding="utf-8"?>
    <!--Constraint layout which contain Spinner widget-->
        <androidx.constraintlayout.widget.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/main"
        android:layout_width="match_parent"
android:layout_height="match_parent">

<!--Spinner widget-->
<!--<Spinner
    android:id="@+id/coursesspinner"
    android:layout_height="50dp"
    android:layout_width="160dp"
    android:layout_marginEnd="10dp"
    android:layout_marginStart="10dp"
    android:layout_marginBottom="10dp"
    android:layout_marginTop="10dp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>-->

<include
    android:id="@+id/spinner_layout"
    layout="@layout/spinner_layout"/>

'''

spinner_layout.xml

<?xml version="1.0" encoding="utf-8"?>
    <Spinner xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/coursesspinner"
    android:layout_width="160dp"
    android:layout_height="50dp"
    android:layout_marginStart="10dp"
    android:layout_marginTop="10dp"
    android:layout_marginEnd="10dp"
    android:layout_marginBottom="10dp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

Answer 1

尝试更改不起作用的代码 spinner_layout.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<!--Spinner widget-->
<Spinner
    android:id="@+id/coursesspinner"
    android:layout_height="50dp"
    android:layout_width="160dp"
    android:layout_marginEnd="10dp"
    android:layout_marginStart="10dp"
    android:layout_marginBottom="10dp"
    android:layout_marginTop="10dp"
    />
</LinearLayout>