在我的项目中，我有一个微调器来选择单位类型（长度，质量等），然后根据用户选择的内容选择两个旋转器。因此，如果用户从第一个微调器中选择Mass作为它们的单位，则第二个和第三个微调器应该更改它们显示的列表，显示克数，磅数等。
我正在尝试使用conversionAdapter的onItemSelectedListener（）来切换其他两个微调器显示的列表。我的尝试都没有奏效，因为这个内部类无法访问主要活动中的微调器。
public class MainActivity extends AppCompatActivity {
private ImageView equalSign;
private Spinner conversionSpinner, unitOneSpinner, unitTwoSpinner;
private EditText unitOneEditText, unitTwoEditText;
private List selectedList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
equalSign = (ImageView)findViewById(R.id.equal_sign);
equalSign.setImageResource(R.drawable.equal_sign_black_2);
unitOneEditText = (EditText)findViewById(R.id.unit_one);
unitTwoEditText = (EditText)findViewById(R.id.unit_two);
conversionSpinner = (Spinner)findViewById(R.id.conversion_spinner);
String[] conversion_list = {"Length", "Mass", "Time", "Temperature", "Volume"};
String[] length_list = {"Kilometer", "Meter", "Centimeter", "Millimeter", "Micrometer", "Nanometer", "Mile", "Yard", "Inch"};
String[] mass_list = {"Metric Ton", "Kilogram", "Gram", "Milligram", "Microgram", "Pound", "Ounce"};
String[] time_list = {"Nanosecond", "Microsecond", "Millisecond", "Second", "Minute", "Hour", "Day", "Year", "Decade", "Century"};
String[] temp_list = {"Fahrenheit", "Celsius", "Kelvin"};
String[] volume_list = {"US Liquid Gallon", "US Liquid Quart", "US Liquid Pint", "US Legal Cup", "US Fluid Ounce", "US Tablespoon", "US Teaspoon", "Liter", "Milliliter"};
List<String>conversion_types = new ArrayList<String>();
List<String>length = new ArrayList<String>();
List<String>mass = new ArrayList<String>();
List<String>time = new ArrayList<String>();
List<String>temp = new ArrayList<String>();
List<String>volume = new ArrayList<String>();
conversion_types = updateList(conversion_types, conversion_list);
length = updateList(length, length_list);
mass = updateList(mass, mass_list);
time = updateList(time, time_list);
temp = updateList(temp, temp_list);
volume = updateList(volume, volume_list);
selectedList = length;
ArrayAdapter<String> conversionAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, conversion_types);
conversionSpinner.setAdapter(conversionAdapter);
conversionSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
String unitType = (String)parent.getItemAtPosition(position);
switch(unitType){
case "length":
Toast.makeText(getApplicationContext(), "Length", Toast.LENGTH_SHORT).show();
break;
case "Mass":
Toast.makeText(getApplicationContext(), "Mass", Toast.LENGTH_SHORT).show();
break;
case "Time":
Toast.makeText(getApplicationContext(), "Time", Toast.LENGTH_SHORT).show();
break;
case "Temperature":
Toast.makeText(getApplicationContext(), "Temperature", Toast.LENGTH_SHORT).show();
break;
case "Volume":
Toast.makeText(getApplicationContext(), "Volume", Toast.LENGTH_SHORT).show();
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
unitOneSpinner = (Spinner)findViewById(R.id.unit_one_spinner);
ArrayAdapter<String> unitOneAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, selectedList);
unitOneSpinner.setAdapter(unitOneAdapter);
unitOneSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
unitTwoSpinner = (Spinner)findViewById(R.id.unit_two_spinner);
ArrayAdapter<String> unitTwoAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_dropdown_item, selectedList);
unitTwoSpinner.setAdapter(unitTwoAdapter);
unitTwoSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
unitOneAdapter.clear();
unitOneAdapter = updateList(unitOneAdapter, mass_list);
unitOneAdapter.notifyDataSetChanged();
}
public List<String> updateList(List<String> myArray, String[] list){
for(int i = 0; i < list.length; i++){
myArray.add(list[i]);
}
return myArray;
}
//Overloaded method used for ArrayAdapters
public ArrayAdapter<String> updateList(ArrayAdapter<String> myArray, String[] list){
for(int i = 0; i < list.length; i++){
myArray.add(list[i]);
}
return myArray;
}