如何使用Spinner onItemSelected？

Question

编辑：Rooms从数据库中绘制其ArrayList。当我使用静态ArrayList时，我没有这个问题，但是在ArrayList中却没有这个问题，我是从数据库中提取的。我正在拉元素，但是单击时似乎为空。

我有一个微调器。我已将项目添加到此微调器。但是AdapterView.Onitemselectedlistener进程不能执行，该功能不起作用。我选择的数据不可读。如何读取微调器中选择的数据？此版本的代码不起作用，所选数据不会出现。问题出在哪里？

XML源：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
 xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#28B2C0"
android:elevation="4dp"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
    <Spinner
        android:id="@+id/spinnerMain"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:clickable="true"/>
</android.support.v7.widget.Toolbar>

源代码：

    public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener, AdapterView.OnItemSelectedListener, View.OnTouchListener {
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
    DatabaseReference ref = mDatabase.child("0").child("Rooms");
        private List<String> Rooms=new ArrayList<String>(10);

        private Spinner spinner;
      @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
     spinner = (Spinner)findViewById(R.id.spinnerMain);
            ArrayAdapter<String>adapterSpinner = new ArrayAdapter<String>(MainActivity.this,
                    android.R.layout.simple_spinner_item,Rooms);
            adapterSpinner.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(adapterSpinner);
            spinner.setOnItemSelectedListener(MainActivity.this);
            adapterSpinner.notifyDataSetChanged();



    ref.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                    for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                        String data = snapshot.getValue(String.class);
                        Rooms.add(data);

                    }
                }

            @Override
            public void onCancelled(DatabaseError databaseError) {

                Toast.makeText(getApplicationContext(), "AWW SNAP... Something is Wrong.", Toast.LENGTH_LONG).show();
            }
        });
 final AdapterView.OnItemSelectedListener listener = new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                switch (i) {
                    case 0:
                      Toast.makeText(MainActivity.this, "asdasdadsa", Toast.LENGTH_SHORT).show();
                       // break;
                    case 1:
                        Toast.makeText(MainActivity.this, "asdasdadsa", Toast.LENGTH_SHORT).show();
                      //  break;
                    case 2:
                        // Whatever you want to happen when the thrid item gets selected
                        break;

                }

                        }

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

            }
        };


        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                Toast.makeText(MainActivity.this, "Selected", Toast.LENGTH_SHORT).show();
                spinner.setOnItemSelectedListener(listener);

            }

            public void onNothingSelected(AdapterView<?> adapterView) {
                return;
            }
        });

Answer 1

试试这个：

  @Override
                public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                    if (Rooms.get(i).equals("Room 1"){
    Toast.makeText(MainActivity.this, "asdasdadsa", Toast.LENGTH_SHORT).show();
                       // break;
                    } else if (Rooms.get(i).equals("Room 2") {
 Toast.makeText(MainActivity.this, "asdasdadsa", Toast.LENGTH_SHORT).show();
}

Answer 2

您的代码有点混乱。您在spinner.setOnItemSelectedListener(listener);中使用了spinner.setOnItemSelectedListener(new ...)，并且spinner.setOnItemSelectedListener(MainActivity.this);也被用来设置监听器。

当我使用您的代码时，一旦打开MainActivity，就会显示“选定”吐司。然后，您的listener变量代替了Spinner的OnItemSelectedListener。

也许您的问题是您忘记了setContentView？

因此，请尝试以下代码：

public class MainActivity extends AppCompatActivity {

private Spinner spinner;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    spinner = (Spinner) findViewById(R.id.spinnerMain);

    List<String> Rooms = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        Rooms.add("room" + i);
    }
    ArrayAdapter<String> adapterSpinner = new ArrayAdapter<String>(MainActivity.this,
            android.R.layout.simple_spinner_item, Rooms);
    adapterSpinner.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapterSpinner);

    final AdapterView.OnItemSelectedListener listener = new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            switch (i) {
                case 0:
                    Toast.makeText(MainActivity.this, "select 0", Toast.LENGTH_SHORT).show();
                    break;
                case 1:
                    Toast.makeText(MainActivity.this, "select 1", Toast.LENGTH_SHORT).show();
                    break;
                default:
                    Toast.makeText(MainActivity.this, "select others", Toast.LENGTH_SHORT).show();
                    break;

            }

        }

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

        }
    };
    spinner.setOnItemSelectedListener(listener);
}
}

或：

public class MainActivity extends AppCompatActivity {

    private Spinner spinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        spinner = (Spinner) findViewById(R.id.spinnerMain);

        List<String> Rooms = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            Rooms.add("room" + i);
        }
        ArrayAdapter<String> adapterSpinner = new ArrayAdapter<String>(MainActivity.this,
                android.R.layout.simple_spinner_item, Rooms);
        adapterSpinner.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapterSpinner);

        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                switch (i) {
                    case 0:
                        Toast.makeText(MainActivity.this, "select 0", Toast.LENGTH_SHORT).show();
                        break;
                    case 1:
                        Toast.makeText(MainActivity.this, "select 1", Toast.LENGTH_SHORT).show();
                        break;
                    default:
                        Toast.makeText(MainActivity.this, "select others", Toast.LENGTH_SHORT).show();
                        break;

                }
            }

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

            }
        });
    }
}

或：

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

    private Spinner spinner;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        spinner = (Spinner) findViewById(R.id.spinnerMain);

        List<String> Rooms = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            Rooms.add("room" + i);
        }
        ArrayAdapter<String> adapterSpinner = new ArrayAdapter<String>(MainActivity.this,
                android.R.layout.simple_spinner_item, Rooms);
        adapterSpinner.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapterSpinner);

        spinner.setOnItemSelectedListener(this);
    }

    @Override
    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
        switch (i) {
            case 0:
                Toast.makeText(MainActivity.this, "select 0", Toast.LENGTH_SHORT).show();
                break;
            case 1:
                Toast.makeText(MainActivity.this, "select 1", Toast.LENGTH_SHORT).show();
                break;
            default:
                Toast.makeText(MainActivity.this, "select others", Toast.LENGTH_SHORT).show();
                break;

        }
    }

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

    }
}