java - Spinner onItemSelectedListener 不起作用？

Question

我使用 Android 4.4，并且在实现微调器时遇到问题。问题:从列表中选择项目时，微调器未设置所选项目。

根据this我尝试过的数百个其他帖子似乎没有解决方案对我有用，我是否错过了一些我没有意识到的非常重要的事情？。

程序应该做什么:我确实想扫描 wifi 网络，并希望用户从微调器中选择 wifi 连接并进行设置。

现在情况如何:微调器显示可用的 wifi 网络，但当我单击一个网络时，它未被选中。

public class SetupActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener
{

    private WifiManager wifiManager;
    private ListView listView;
    private Button buttonScan;
    private int size = 0;
    private List<ScanResult> results;
    private ArrayList<String> arrayList = new ArrayList<>();
    private ArrayAdapter adapter;
    private Spinner spinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate( savedInstanceState );
        setContentView( R.layout.activity_setup );
        buttonScan = findViewById(R.id.btnScan);
        buttonScan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                scanWifi();
            }
        });
        spinner = findViewById(R.id.spinnerSSID);
        listView = findViewById(R.id.wifiList);
        wifiManager = (WifiManager) getApplicationContext().getSystemService( Context.WIFI_SERVICE);

        if (!wifiManager.isWifiEnabled()) {
            Toast.makeText(this, "WiFi is disabled ... We need to enable it", Toast.LENGTH_LONG).show();
            wifiManager.setWifiEnabled(true);
        }

        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, arrayList);
        listView.setAdapter(adapter);
        scanWifi();
        ArrayAdapter<String> adp = new ArrayAdapter<String>(SetupActivity.this,
                android.R.layout.simple_spinner_item, arrayList );
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adp);
        spinner.setOnItemSelectedListener(this);
    }

    private void scanWifi() {
        arrayList.clear();
        registerReceiver(wifiReceiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
        wifiManager.startScan();
        Toast.makeText(this, "Scanning WiFi ...", Toast.LENGTH_SHORT).show();
    }

    BroadcastReceiver wifiReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            results = wifiManager.getScanResults();
            unregisterReceiver(this);

            for (ScanResult scanResult : results) {
                arrayList.add(scanResult.SSID + " - " + scanResult.capabilities);
                adapter.notifyDataSetChanged();
            }
        }
    };

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        parent.getItemAtPosition(position);
        Toast.makeText(parent.getContext(),
                "OnItemSelectedListener : " + parent.getItemAtPosition(position).toString(),
                Toast.LENGTH_SHORT).show();
    }

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

    }
}

这里是布局中的 xml:

<?xml version="1.0" encoding="utf-8"?>

<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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:tint="?attr/colorControlNormal"
    tools:context=".SetupActivity">

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="DeviceID: 1234abcd"
        app:layout_constraintBottom_toTopOf="@+id/textView4"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="Setup"
        android:textSize="36sp"
        app:layout_constraintBottom_toTopOf="@+id/textView2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="No Content Installed!"
        app:layout_constraintBottom_toTopOf="@+id/textView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Choose  which Setup"
        android:textSize="30sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView3" />

    <TextView
        android:id="@+id/textView11"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="240dp"
        android:layout_marginTop="196dp"
        android:text="Local"
        android:textSize="24sp"
        android:textStyle="bold"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView12"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="196dp"
        android:layout_marginEnd="240dp"
        android:text="Online"
        android:textSize="24sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView6"
        android:layout_width="432dp"
        android:layout_height="297dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="24dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView11"
        app:srcCompat="@drawable/usbstick" />

    <ImageView
        android:id="@+id/imageView8"
        android:layout_width="11dp"
        android:layout_height="252dp"
        android:layout_marginTop="150dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView4"
        app:srcCompat="@color/colorPrimary" />

    <EditText
        android:id="@+id/etxtContentId"
        android:layout_width="445dp"
        android:layout_height="44dp"
        android:layout_marginTop="63dp"
        android:layout_marginEnd="3dp"
        android:ems="10"
        android:hint="Content ID"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/imageView6"
        app:layout_constraintTop_toBottomOf="@+id/textView12" />

    <EditText
        android:id="@+id/etxtWifiPassword"
        android:layout_width="445dp"
        android:layout_height="44dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="3dp"
        android:ems="10"
        android:hint="Wifi Password"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toEndOf="@+id/imageView6"
        app:layout_constraintTop_toBottomOf="@+id/spinnerSSID" />

    <Spinner
        android:id="@+id/spinnerSSID"
        android:layout_width="447dp"
        android:layout_height="44dp"
        android:layout_marginStart="1dp"
        android:layout_marginTop="38dp"
        android:spinnerMode="dropdown"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/imageView6"
        app:layout_constraintTop_toBottomOf="@+id/etxtContentId" />

    <Button
        android:id="@+id/btnTestConnection"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="20dp"
        android:layout_marginTop="24dp"
        android:text="Test Connection"
        app:layout_constraintStart_toEndOf="@+id/imageView6"
        app:layout_constraintTop_toBottomOf="@+id/etxtWifiPassword" />

    <Button
        android:id="@+id/btnWifiConnect"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginTop="24dp"
        android:text="Connect"
        app:layout_constraintStart_toEndOf="@+id/btnTestConnection"
        app:layout_constraintTop_toBottomOf="@+id/etxtWifiPassword" />

    <Button
        android:id="@+id/btnFinish"
        android:layout_width="392dp"
        android:layout_height="45dp"
        android:layout_marginStart="13dp"
        android:layout_marginTop="9dp"
        android:layout_marginEnd="43dp"
        android:text="Finish and perform online update"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/imageView6"
        app:layout_constraintTop_toBottomOf="@+id/btnTestConnection" />

    <Button
        android:id="@+id/btnScan"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="27dp"
        android:layout_marginTop="25dp"
        android:text="Scan"
        app:layout_constraintStart_toEndOf="@+id/btnWifiConnect"
        app:layout_constraintTop_toBottomOf="@+id/etxtWifiPassword" />

    <ListView
        android:id="@+id/wifiList"
        android:layout_width="412dp"
        android:layout_height="99dp"
        android:layout_marginTop="1dp"
        android:layout_marginEnd="2dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

重要的部分在activity和layout.xml中

private Spinner spinner;
...
spinner = findViewById(R.id.spinnerSSID);
...
ArrayAdapter<String> adp = new ArrayAdapter<String>(SetupActivity.this,
            android.R.layout.simple_spinner_item, arrayList );
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adp);
    spinner.setOnItemSelectedListener( new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            parent.getItemAtPosition(position);
            Toast.makeText(parent.getContext(),
                    "OnItemSelectedListener : " + parent.getItemAtPosition(position).toString(),
                    Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            parent.getItemAtPosition(0);
            Toast.makeText(parent.getContext(),
                    "OnItemSelectedListener : " + parent.getItemAtPosition(0).toString(),
                    Toast.LENGTH_SHORT).show();
        }
    } );

在 XML 中:

<Spinner
android:id="@+id/spinnerSSID"
android:layout_width="447dp"
android:layout_height="44dp"
android:layout_marginStart="1dp"
android:layout_marginTop="38dp"
android:spinnerMode="dropdown"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/imageView6"
app:layout_constraintTop_toBottomOf="@+id/etxtContentId" />

感谢您提前提供的任何帮助!

编辑:我在控制台中注意到此错误:

E/dalvikvm: Could not find class 'android.widget.ThemedSpinnerAdapter', referenced from method androidx.appcompat.widget.AppCompatSpinner$DropDownAdapter.<init>

还在调试器中我注意到监听器没有被调用...

Answer 1

使用

 spinner.setAdapter(adapter);

当您将适配器设置为微调器时。我查过了。

注意 - 您的适配器“adp”有问题。我不知道你为什么使用它。