更改设备方向后如何保存 ArrayList 数据并在 AutoCompleteTextView 中使用

Question

我有 tride saveInstanceState 它实际上有助于保存数据但是 AutoCompleteTextView 没有看到任何数据（在日志中我看到数据存在并且它们是正确的）然后我第二次改变方向，在日志中看到 ArrayList = null; 这里有一些代码

  ...
    public class AddDayActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor> 
    ...
    ArrayAdapter<String> adapter;
    private AutoCompleteTextView edit_day_name; 
    private ArrayList<String> autoCompleteList;
    private ArrayList<Integer> autoCompleteListPrice;
    ...
     protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.add_pay_day);
             autoCompleteList = new ArrayList<String>(); //Array list witch need to save 
             autoCompleteListPrice = new ArrayList<Integer>();//Array list witch need to save 

    ...
        edit_day_name = findViewById(R.id.edit_day_name); //AutoCompleteTextView
    ...
    if (savedInstanceState != null) {
            autoCompleteList.addAll(Objects.requireNonNull(savedInstanceState.getStringArrayList("BundleAutoCompleteList")));
            autoCompleteListPrice.addAll(Objects.requireNonNull(savedInstanceState.getIntegerArrayList("BundleAutoCompleteListPrice")));
            Log.d(UtilContract.LOG_KEY, " onRestoreInstanceState Working " + savedInstanceState.getIntegerArrayList("BundleAutoCompleteList")
                    + "\n" +
                    savedInstanceState.getIntegerArrayList("BundleAutoCompleteListPrice")
                    + "\n" + autoCompleteList + "\n" + autoCompleteListPrice);


        } 
            adapter = new ArrayAdapter<String>(this,
                    R.layout.dropdown_menu_popup_item, autoCompleteList);
            Log.d(UtilContract.LOG_KEY, ".." + autoCompleteList);
            edit_day_name.setAdapter(adapter);

        ...
         LoaderManager.getInstance(this).initLoader(NAME_UNIC_LOADER, null, this);
        ...
         @Override
        protected void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        //Save data in  Bundle
        outState.putStringArrayList("BundleAutoCompleteList", autoCompleteList);
        outState.putIntegerArrayList("BundleAutoCompleteListPrice", autoCompleteListPrice);
        Log.d(UtilContract.LOG_KEY, " savedInstanceState Save " + autoCompleteListPrice + "\n" + autoCompleteList);
    }

从 SQL 数据库

填充数组的加载程序

 @NonNull
    @Override
    public Loader<Cursor> onCreateLoader(int id, @Nullable Bundle args) {
        String[] projection = {
                UtilContract.KEY_ID,
                KEY_NAME_DETAIL,
                KEY_PRICE_OF_DETAIL
        };

        CursorLoader cursorLoader = new CursorLoader(this,
                UtilContract.DetailTable.CONTENT_URI,
                projection,
                null,
                null,
                KEY_NAME_DETAIL
        );
        Log.d(LOG_KEY, " CursorLoader  DetailTable " + cursorLoader);
        return cursorLoader;
    }
      @Override
    public void onLoadFinished(@NonNull Loader<Cursor> loader, Cursor data) {
        int count = data.getCount();
        if (autoCompleteList.isEmpty() || autoCompleteListPrice.isEmpty()) {
            //
            while (data.moveToNext()) {
                autoCompleteList.add(data.getString(data.getColumnIndexOrThrow(KEY_NAME_DETAIL)));
                autoCompleteListPrice.add(data.getInt(data.getColumnIndexOrThrow(KEY_PRICE_OF_DETAIL)));
            }
        } else {
            //
            autoCompleteList.clear();
            autoCompleteListPrice.clear();
            // 
            while (data.moveToNext()) {
                autoCompleteList.add(data.getString(data.getColumnIndexOrThrow(KEY_NAME_DETAIL)));                autoCompleteListPrice.add(data.getInt(data.getColumnIndexOrThrow(KEY_PRICE_OF_DETAIL)));
            }
        }
        Log.d(LOG_KEY, " Cursor  DetailTable " + data + " count " + count);
    }

    @Override
    public void onLoaderReset(@NonNull Loader<Cursor> loader) {
 adapter.clear();
    }

在这种情况下如何正确保存 AutoComplateView 的数据？

PS: 我用 "androidx" 和 " .material:1.1.0-alpha09" 来自 AutoComplateView "ExposedDropdownMenu"

Answer 1

代码量太少，无法确定，但据我所知，问题可能出在 Loader 实现及其与其余代码的同步上。

Loaded 异步加载数据。这意味着在您旋转设备后，您的代码执行良好，但加载程序开始再次加载。在实际开始加载之前，它会调用 onLoaderReset，其中包含 adapter.clear() 调用。因此，来自适配器的所有数据都消失了，因此 AutocompleteTextView 没有任何显示。

我还可以在 onLoadFinished 方法中看到您检索数据但没有将其设置到适配器中 - 因此适配器是空的。

再来一次 - 我不确定是不是这个原因，因为代码不完整，但我希望它能以某种方式帮助你。

更改设备方向后如何保存 ArrayList 数据并在 AutoCompleteTextView 中使用

How to save ArrayList data and use in AutoCompleteTextView , after change device orientation

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