如何使用 CursorLoader 填充微调器？

Question

我正在尝试从 cursorloader 填充微调器。

我有一个用于微调器的 IndicatorFragment，我将把它包含到其他片段中（通过<include> 标签）。

---

首先我检查了数据是否在数据库（ContentProvider）中，一切正常。

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第二步是写一个xml文件：

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="3"
            android:text="@string/con_lbl_input_indicator"
            android:textSize="22sp"
            android:textStyle="bold"
            android:layout_marginTop="8dp"
            android:layout_marginLeft="5dp"/>

        <Spinner
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="2"
            android:id="@+id/indicators_spinner"
            android:layout_gravity="bottom"
            android:spinnerMode="dropdown" />
    </LinearLayout>
</merge>

然后我编写了 IndicatorFragment.class，我使用 SimpleCursorAdapter 和 Loader 从数据库中填充数据：

public class IndicatorsFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor>{

    private static final String LOG_TAG = IndicatorsFragment.class.getSimpleName();

    private static final int INDICATOR_LOADER_ID = 0;

    private Spinner spIndicator;
    private SimpleCursorAdapter spinAdapter;

    private static final String[] INDICATOR_PROJECTION = {
            ChemToolsContract.IndicatorsEntry._ID,
            ChemToolsContract.IndicatorsEntry.COLUMN_NAME
    };

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_indicators, container, false);

        spIndicator = (Spinner) rootView.findViewById(R.id.indicators_spinner);

        spinAdapter = new SimpleCursorAdapter(getActivity(),
                android.R.layout.simple_spinner_item, null,
                new String[]{ChemToolsContract.IndicatorsEntry.COLUMN_NAME},
                new int[] {android.R.id.text1}, 0);

        spinAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        spIndicator.setAdapter(spinAdapter);

        spIndicator.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            }
        });

        return rootView;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        getLoaderManager().initLoader(INDICATOR_LOADER_ID, null, this);
        spIndicator.setOnItemClickListener(null);
        super.onActivityCreated(savedInstanceState);
    }

    @Override
    public void onPause() {
        getLoaderManager().destroyLoader(INDICATOR_LOADER_ID);
        super.onPause();
    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        Uri baseUri = ChemToolsContract.IndicatorsEntry.CONTENT_URI;

        return new CursorLoader(getActivity(), baseUri, INDICATOR_PROJECTION, null, null, null);
    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        spinAdapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        spinAdapter.swapCursor(null);
    }
}

最后是 xml 文件，我在其中使用 <include> 属性添加了带有微调器的片段：

<include layout="@layout/fragment_indicators"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"/>

但我在启动应用程序时在微调器中看不到任何数据：

http://i.stack.imgur.com/bgi9R.png

---

所以我不知道我在做什么错：从数据库加载数据或将带有微调器的片段包含到另一个片段中？

Answer 1

您必须初始化 Loader，缺少这一行。我建议包括这一行：

getLoaderManager().initLoader(INDICATOR_LOADER_ID, null, this);

在 onCreateView 方法内部，就在return rootView; 行的上方。在这种情况下，方法应该是这样的：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_indicators, container, false);

    spIndicator = (Spinner) rootView.findViewById(R.id.indicators_spinner);

    spinAdapter = new SimpleCursorAdapter(getActivity(),
            android.R.layout.simple_spinner_item, null,
            new String[]{ChemToolsContract.IndicatorsEntry.COLUMN_NAME},
            new int[] {android.R.id.text1}, 0);

    spinAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    spIndicator.setAdapter(spinAdapter);

    spIndicator.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

        }
    });
    getLoaderManager().initLoader(INDICATOR_LOADER_ID, null, this);
    return rootView;
}

编码愉快！

Answer 2

很奇怪你没有遇到以下错误（因为我遇到了）。

java.lang.RuntimeException: setOnItemClickListener cannot be used with a spinner. 

尽管如此，@Reynel 的回答很好。只是我想做的一个轻微的编辑。而不是

spIndicator.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

    }
});

你写

spIndicator.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        // you code here
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // you code here
    }
});

取自post。