Android：微调器和 setOnItemSelectedListener 和 getSharedPreferencesString

Question

1) 在我的活动中，我有两个微调器：countrySpinner、citySpinner。第二个微调器取决于第一个 - 如果用户从 countrySpinner 中选择项目 A，则第二个 citySpinner 中的值也会更新，例如如果用户从第一个中选择俄罗斯，则在第二个微调器中，他将获得俄罗斯城市...

2) 在我的活动中，我有一个按钮，用于保存用户在微调器中提供的信息。信息存储在共享应用首选项中。我没有在代码示例中包含它，因为它不相关。

3.在活动的 onCreate 方法中，我读取了以前保存的值 -> checkIfLocalSettingExists()) 并将保存的值分配给“countryStr”和“cityStr”变量。

4.然后我想更新一开始有默认值的微调器。我有存储在共享首选项中的字符串，因此为了获得正确的元素，我使用了 getIndex 函数，它返回我应该设置的元素的 id。

5.在我得到需要在两个微调器上设置的元素后，我可以设置它们。我将检索到的 id 分配给微调器，但是 setOnItemSelectedListener 执行了两次不知道为什么，可能是它不起作用的原因！。

代码：

public class Settings extends ActionBarActivity{
public Spinner countrySpinner;
public Spinner citySpinner;
public String cityStr;
public String countryStr;    

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_chat_settings);
    countrySpinner = (Spinner) findViewById(R.id.kraje_spinner);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.Countries, R.layout.spinner_layout);
    countrySpinner.setAdapter(adapter);

    citySpinner = (Spinner) findViewById(R.id.przejscie_spinner);
    ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(this, R.array.CitiesRussia, R.layout.spinner_layout);
    citySpinner.setAdapter(adapter2);


    if (checkIfLocalSettingExists())
    {           
        System.out.println("Gathered following values from settings");
        System.out.println("Country: " + countryStr);
        System.out.println("City: " + cityStr);
        System.out.println("----");
        System.out.println("Setting the spinners...");
        System.out.println("Country spinner:");
        // I found the ID of saved country, I can set it in countrySpinner
        countrySpinner.setSelection(getIndex(countrySpinner, countryStr));
        System.out.println("City spinner:");

        //without this it didn't work at all, don't know why            
        if (kraj.toLowerCase().equals("russia"))
            adapter2 = ArrayAdapter.createFromResource(this, R.array.CitiesRussia, R.layout.spinner_layout);
        else if (kraj.toLowerCase().equals("ukraine"))
            adapter2 = ArrayAdapter.createFromResource(this, R.array.CitiesUkraine, R.layout.spinner_layout);
        else {
            adapter2 = ArrayAdapter.createFromResource(this, R.array.CitiesBelarus, R.layout.spinner_layout);
        }
        citySpinner.setAdapter(adapter2);

        // I found the ID of saved city, I can set it in citySpinner
        citySpinner.setSelection(getIndex(citySpinner, cityStr));       
    }   


    countrySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long arg3) {               
            if (position == 0) {
                System.out.println("SELECTED RUSSIA");
                ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(Settings.this,
                        R.array.CitiesRussia, R.layout.spinner_layout);                    
                adapter2.setDropDownViewResource(R.layout.spinner_layout);
                citySpinner.setAdapter(adapter2);
            }
            //
            else if (position == 1) {
                System.out.println("SELECTED UKRAINE");
                ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(Settings.this,
                        R.array.CitiesUkraine, R.layout.spinner_layout);
                adapter2.setDropDownViewResource(R.layout.spinner_layout);
                citySpinner.setAdapter(adapter2);
            } else {
                System.out.println("SELECTED BELARUS");
                ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(Settings.this,
                        R.array.CitiesRussia, R.layout.spinner_layout);
                adapter2.setDropDownViewResource(R.layout.spinner_layout);
                citySpinner.setAdapter(adapter2);
            }              
        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {

        }
    });
   }
private int getIndex(Spinner spin, String myString){
    int index = 0;
    String tmp = "";
    System.out.println("Im in get index function!");
    System.out.println("Seraching for: " + myString);
    for (int i=0;i<spin.getCount();i++){
        tmp = spin.getItemAtPosition(i).toString();
        System.out.println("checking if " + tmp.toLowerCase() + " equals " + myString.toLowerCase());
        if (tmp.toLowerCase().equals(myString.toLowerCase())){
            System.out.println("FOUND IT --> " +tmp + " ---->" + i +", its: " + myString);
            index = i;
            break;
        }
        else
            System.out.println("NOT FOUND IT --> " +tmp + "-->" + i +", its NOT: " + myString);

    }
    return index;
}

代码输出：

03-16 15:51:12.590  I/System.out: Gathered following values from settings
03-16 15:51:12.590  I/System.out: Country: Belarus
03-16 15:51:12.590  I/System.out: City: Terespol
03-16 15:51:12.590  I/System.out: ----
03-16 15:51:12.590  I/System.out: Setting the spinners...
03-16 15:51:12.590  I/System.out: Country spinner:
03-16 15:51:12.590  I/System.out: Im in get index function!
03-16 15:51:12.590  I/System.out: Seraching for: Belarus
03-16 15:51:12.590  I/System.out: checking if russia equals belarus
03-16 15:51:12.590  I/System.out: NOT FOUND IT --> russia -->0, its NOT: Belarus
03-16 15:51:12.590  I/System.out: checking if ukraine equals belarus
03-16 15:51:12.590  I/System.out: NOT FOUND IT --> ukraine-->1, its NOT: Belarus
03-16 15:51:12.590  I/System.out: checking if belarus equals belarus
03-16 15:51:12.590  I/System.out: FOUND IT --> Belarus ---->2, its: Belarus
03-16 15:51:12.590  I/System.out: City spinner:
03-16 15:51:12.590  I/System.out: Im in get index function!
03-16 15:51:12.590  I/System.out: Seraching for: Terespol
03-16 15:51:12.590  I/System.out: checking if cityA equals terespol
03-16 15:51:12.590  I/System.out: NOT FOUND IT --> cityA -->0, its NOT: Terespol
03-16 15:51:12.590  I/System.out: checking if cityB equals terespol
03-16 15:51:12.590  I/System.out: NOT FOUND IT --> cityB -->1, its NOT: Terespol
03-16 15:51:12.590  I/System.out: checking if cityC equals terespol
03-16 15:51:12.594  I/System.out: NOT FOUND IT --> cityC -->2, its NOT: Terespol
03-16 15:51:12.594  I/System.out: checking if cityD equals terespol
03-16 15:51:12.594  I/System.out: NOT FOUND IT --> cityD -->3, its NOT: Terespol
03-16 15:51:12.594  I/System.out: checking if cityE equals terespol
03-16 15:51:12.594  I/System.out: NOT FOUND IT --> cityE -->4, its NOT: Terespol
03-16 15:51:12.594  I/System.out: checking if terespol equals terespol
03-16 15:51:12.594  I/System.out: FOUND IT --> Terespol ---->5, its: Terespol
03-16 15:51:12.594  I/System.out: 5
03-16 15:51:12.642  I/System.out: SELECTED BELARUS

所以白俄罗斯的代码是 2，它由 getIndex 函数正确返回，然后将 spinner 设置为有效值（BELARUS）。 Terespol 的返回码是 5，它由 getIndex 函数正确返回，然后由于 setOnItemSelectedListener 再次为 countrySpinner 执行而未正确设置微调器..（检查输出的最后一行）。为什么？我只为 countrySpinner 设置了侦听器，而不为 citySpinner 设置了侦听器？！结果 citySpinner 被设置为第 1 个而不是第 5 个元素。为什么在世界上它不起作用！？

Answer 1

每当您从微调器中手动选择任何项目或像这样调用setSelection() 时-

countrySpinner.setSelection(getIndex(countrySpinner, countryStr));

它肯定会调用onItemSelected() 并且在onItemSelected() 中，您正在加载您的城市微调器值，尽管您之前选择了特定项目，但它会重置您的选择。

要解决此问题，您必须跟踪您是否已从 checkIfLocalSettingExists() 加载国家微调器值，在这种情况下，您不必在 onItemSelected() 中设置城市微调器适配器，因为您是已经这样做了。

Answer 2

我设法通过设置额外的侦听器来做到这一点，在该侦听器中我将 allowModification 标志设置为 true。仍然不知道为什么以前它不起作用以及为什么最后总是执行侦听器（错误？）

 citySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long arg3) {
            allowModification = true;

        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {

        }
    });