android - 无法保存微调器状态android

Question

我尝试了一个教程，但我无法保存微调器的状态。

这是我的代码:

        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Firebase.setAndroidContext(this);

        setContentView(R.layout.activity_main);         
    //language selection list   
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
            this, R.array.language_list, android.R.layout.simple_spinner_item);

    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);

    spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {

           // storing string resources into Array
            lang_list = getResources().getStringArray(R.array.language_list);

            Toast.makeText(getBaseContext(), "You have selected : " + lang_list[index], 
                    Toast.LENGTH_SHORT).show();

           choice =  spinner.getSelectedItem().toString();
           spinnerPos = arg2;

            final ImageView country_flag = (ImageView)findViewById(R.id.country);
            String s=((TextView)arg1).getText().toString();
            if(s.equals("English"))
                country_flag.setImageDrawable(getResources().getDrawable(R.drawable.eng_spinner));
            if(s.equals("German"))
                country_flag.setImageDrawable(getResources().getDrawable(R.drawable.german_spinner));
            if(s.equals("French"))
                country_flag.setImageDrawable(getResources().getDrawable(R.drawable.french_spinner));
            if(s.equals("Spanish"))
                country_flag.setImageDrawable(getResources().getDrawable(R.drawable.spanish_spinner));
        }

        /*private int getPersistedItem() { 
            String keyName = makePersistedItemKeyName();
             return PreferenceManager.getDefaultSharedPreferences(MainActivity.this).getInt(keyName, 0); 
            }
            protected void setPersistedItem(int position) {
             String keyName = makePersistedItemKeyName();
             PreferenceManager.getDefaultSharedPreferences(MainActivity.this).edit().putInt(keyName, position).commit();
             }
            private String makePersistedItemKeyName() {
             return currentUserName + "_your_key"; 
            }*/


        public void onNothingSelected(AdapterView<?> arg0) {

            // do nothing               
        } 

    });
}

要保存状态(这些在 oncreate 之后):

 protected void onResume(){
    super.onResume();
    spinner.setSelection(spinnerPos);
}

protected void onSaveInstanceState(Bundle outState){
    super.onSaveInstanceState(outState);
    outState.putInt("spinnerIndex", spinnerPos);
    Log.d("SpinnerState", "Spinner at position " + spinnerPos + " was saved");
}
protected void onRestoreInstanceState(Bundle savedInstanceState){
    super.onRestoreInstanceState(savedInstanceState);
    savedInstanceState.getInt("spinnerIndex");
    Log.d("SpinnerState", "Spinner at position " + spinnerPos + " was restored");
}

我正在尝试保存微调器状态，即使应用已关闭或 Activity 已停止。有人可以解释为什么它不起作用。

Answer 1

我使用共享首选项让它工作，

1. 我得到微调器的位置:

   spinnerPos = arg2;

2. 我在 onCreate 中创建了设置/初始化共享首选项:

   SharedPreferences spinnersaving = getSharedPreferences("spinnerstate",0);

3. 将 onStop 方法用于带有微调器位置的共享首选项:

   protected void onStop(){
   super.onStop();
   SharedPreferences spinnersaving = getSharedPreferences("spinnerstate",0);
   
   SharedPreferences.Editor editor = spinnersaving.edit();
   editor.putInt("spinnerPos", spinnerPos);
   editor.commit();
   }  
   

4. 在微调器点击监听器函数之前，我从 sharepreferences 获取微调器位置并将其设置到微调器上:

   spinner.setSelection(spinnersaving.getInt("spinnerPos", 0));

然后就成功了。 :)