java - 如何设置 Spinner Initial Text "SELECT ONE"？

Question

我想将 Spinner 初始文本设置为 SELECT ONE？怎么可能？

public class MainActivity extends AppCompatActivity {

RecyclerView recyclerView;
Adapter adapter;
ArrayList<ModelClass> arrayList;
RecyclerView.LayoutManager layoutManager;
EditText edit_name, edit_desc;
Spinner spinner;
Button btm_save, btn_delete;
String Name, Description, Spinner;
SqliteHelper sqliteHelper;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    edit_name = findViewById(R.id.edit_name);
    edit_desc = findViewById(R.id.edit_desc);
    btm_save = findViewById(R.id.btn_save);
    btn_delete = findViewById(R.id.btn_view);
    spinner = findViewById(R.id.spinner);
    sqliteHelper = new SqliteHelper(this);


    ArrayAdapter<CharSequence> arrayAdapter = ArrayAdapter.createFromResource(this, R.array.Options, android.R.layout.simple_spinner_item);
    arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(arrayAdapter);


    recyclerView = findViewById(R.id.recylerView);
    arrayList = new ArrayList<>();
    adapter = new Adapter(this, arrayList);
    recyclerView.setAdapter(adapter);
    layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);

    edit_name.addTextChangedListener(textWatcher);
    edit_desc.addTextChangedListener(textWatcher);
    btm_save.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Name = edit_name.getText().toString();
            Description = edit_desc.getText().toString();
            Spinner = spinner.getSelectedItem().toString();
            if (!ValidateUser(Name)) {
                if (!TextUtils.isEmpty(Spinner)) {
                    ModelClass modelClass = new ModelClass(Name, Spinner, Description);
                    arrayList.add(modelClass);
                    adapter.notifyItemInserted(arrayList.size());
                    InsertData();
                } else {
                    Toast.makeText(MainActivity.this, "Please Select Experience", Toast.LENGTH_SHORT).show();
                }
            }else
            {
                Toast.makeText(MainActivity.this, "User name Already Exits", Toast.LENGTH_SHORT).show();
            }


        }
    });

    btn_delete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            /*RetriveData();*/
           Integer deletedRows = sqliteHelper.deleteData(edit_name.getText().toString());
           if (deletedRows > 0 )
           {
               Toast.makeText(MainActivity.this, "Record Deleted", Toast.LENGTH_SHORT).show();
           } else {
               Toast.makeText(MainActivity.this, "Record Not Found", Toast.LENGTH_SHORT).show();
           }
        }
    });




}

private void InsertData() {

        boolean InsertSuccessfully = sqliteHelper.InsertData(Name, Description, Spinner);
    if (InsertSuccessfully) {
        Toast.makeText(this, "Record Inserted", Toast.LENGTH_SHORT).show();
    } else {
        Toast.makeText(this, "Record Not Inserted", Toast.LENGTH_SHORT).show();
    }
}

private TextWatcher  textWatcher = new TextWatcher() {
  @Override
  public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

  }

  @Override
  public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
      Name = edit_name.getText().toString();
      Description = edit_desc.getText().toString();
      btm_save.setEnabled(!Name.isEmpty() && !Description.isEmpty());
  }

  @Override
  public void afterTextChanged(Editable editable) {
  }
};

public boolean ValidateUser(String name)
{
  SQLiteDatabase database = sqliteHelper.getWritableDatabase();
    Cursor cursor = database.query(SqliteHelper.TABLE_NAME, null, SqliteHelper.COL_2 + "=?", new String[]{name},
            null, null, null);
    int i = cursor.getCount();
    if (i>0)
    {
        return true;
    }else
        {
            return false;
        }

  }

}

Answer 1

final ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this,R.layout.spinner_item,plantsList){
        @Override
        public boolean isEnabled(int position){
            if(position == 0)
            {
                // Disable the first item from Spinner
                // First item will be use for hint
                return false;
            }
            else
            {
                return true;
            }
        }
        @Override
        public View getDropDownView(int position, View convertView,
                                    ViewGroup parent) {
            View view = super.getDropDownView(position, convertView, parent);
            TextView tv = (TextView) view;
            if(position == 0){
                // Set the hint text color gray
                tv.setTextColor(Color.GRAY);
            }
            else {
                tv.setTextColor(Color.BLACK);
            }
            return view;
        }
    };

将提示消息添加为微调器数组中的第一个元素。像这样添加创建 ArrayAdapter。这将使初始元素不可选择并以灰色显示。