无法从导航抽屉片段中的 sqlite 加载数据答案

【问题标题】：cannot load data from sqlite in navigation drawer fragment无法从导航抽屉片段中的 sqlite 加载数据
【发布时间】：2015-02-19 13:41:38
【问题描述】：

在我的应用程序中，我使用导航抽屉和 sqlite 数据库在片段中显示来自 sqlite 的数据。当我单击导航元素之一，即搜索医院时，它应该从数据库加载数据，但随后应用程序闪烁“不幸的是应用程序已关闭”。

下面是片段的代码，

public class SHospitals extends Fragment {

private hospitalDBadapter dbhelper;
private SimpleCursorAdapter dataAdapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    // TODO Auto-generated method stub
    View rootView = inflater.inflate(R.layout.shospitals, container, false);

    dbhelper = new hospitalDBadapter(getActivity());
    dbhelper.open();
    dbhelper.deleteallhospitals();
    dbhelper.insertsomehospitals();
    Cursor cursor = dbhelper.fetchallhospitals();

    String[] columns = new String[] { hospitalDBadapter.KEY_HOSP,
            hospitalDBadapter.KEY_ADD, hospitalDBadapter.KEY_CONT };

    int[] to = new int[] { R.id.hospital, R.id.address, R.id.contact, };

    dataAdapter = new SimpleCursorAdapter(getActivity(),
            R.layout.hospitalinfo, cursor, columns, to, 0);

    final ListView listview = (ListView) getView().findViewById(R.id.lv1);
    listview.setAdapter(dataAdapter);

    listview.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            // TODO Auto-generated method stub

            Cursor cursor = (Cursor) listview.getItemAtPosition(position);

            String hospital_name = cursor.getString(cursor
                    .getColumnIndexOrThrow("hosp_name"));
            Toast.makeText(getActivity(), hospital_name, Toast.LENGTH_SHORT)
                    .show();
        }
    });

    EditText myfilter = (EditText) getView().findViewById(R.id.filter);

    myfilter.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            // TODO Auto-generated method stub
            dataAdapter.getFilter().filter(s.toString());
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable s) {
            // TODO Auto-generated method stub

        }
    });

    dataAdapter.setFilterQueryProvider(new FilterQueryProvider() {

        @Override
        public Cursor runQuery(CharSequence constraint) {
            // TODO Auto-generated method stub
            return dbhelper.fetchhospitalsbyname(constraint.toString());
        }
    });
    return rootView;
}}

这是我的数据库助手类，

public class hospitalDBadapter {

public static final String KEY_ID = "_id";
public static final String KEY_HOSP = "hosp_name";
public static final String KEY_ADD = "hosp_Add";
public static final String KEY_CONT = "hosp_cont";

private static final String DATABASE_NAME = "hospitals_dbs";
private static final String SQLITE_TABLE = "hospitals_tables";
private static final int DATABASE_VERSION = 1;

public static final String TAG = "hospitalDBadapter";
public final Context ourcontext;
private DatabaseHelper mDBHelper;
private SQLiteDatabase mDB;

public static class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

        db.execSQL("CREATE TABLE " + SQLITE_TABLE + " (" + KEY_ID
                + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_HOSP
                + " TEXT NOT NULL, " + KEY_ADD + " TEXT NOT NULL, "
                + KEY_CONT + " TEXT NOT NULL);"

        );

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

        Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                + newVersion + ", which will destroy all old data");
        db.execSQL("DROP TABLE IF EXISTS " + SQLITE_TABLE);
        onCreate(db);

    }

}

public hospitalDBadapter(Context c) {
    ourcontext = c;
}

public hospitalDBadapter open() throws SQLException {
    mDBHelper = new DatabaseHelper(ourcontext);
    mDB = mDBHelper.getWritableDatabase();
    return this;
}

public void close() {
    if (mDBHelper != null) {
        mDBHelper.close();
    }
}

public boolean deleteallhospitals() {
    // TODO Auto-generated method stub

    int donedelete = 0;
    donedelete = mDB.delete(SQLITE_TABLE, null, null);
    Log.w(TAG, Integer.toString(donedelete));
    return donedelete > 0;
}

public void insertsomehospitals() {
    // TODO Auto-generated method stub

    createhospital("Lilavati Hospital", "Peddar Road", "6541324532");
    createhospital("Sion Hospital", "A B Road", "6451235478");
    createhospital("Dayaben Hospital", "S P Road", "4132456787");
    createhospital("ABC Hospital", "P D Road", "8451295421");
    createhospital("DEF Hospital", "D S Road", "9832151231");

}

private long createhospital(String hosp_name, String hosp_Add,
        String hosp_cont) {
    // TODO Auto-generated method stub

    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_HOSP, hosp_name);
    initialValues.put(KEY_ADD, hosp_Add);
    initialValues.put(KEY_CONT, hosp_cont);

    return mDB.insert(SQLITE_TABLE, null, initialValues);
}

public Cursor fetchallhospitals() {
    // TODO Auto-generated method stub

    Cursor mCursor = mDB.query(SQLITE_TABLE, new String[] { KEY_ID,
            KEY_HOSP, KEY_ADD, KEY_CONT }, null, null, null, null, null);

    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

public Cursor fetchhospitalsbyname(String string) throws SQLException {
    // TODO Auto-generated method stub

    Log.w(TAG, string);
    Cursor mCursor = null;
    if (string == null || string.length() == 0) {
        mCursor = mDB.query(SQLITE_TABLE, new String[] { KEY_ID, KEY_HOSP,
                KEY_ADD, KEY_CONT }, null, null, null, null, null);

    } else {
        mCursor = mDB.query(true, SQLITE_TABLE, new String[] { KEY_ID,
                KEY_HOSP, KEY_ADD, KEY_CONT }, KEY_HOSP + " like '%"
                + string + "%'", null, null, null, null, null);
    }
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

}

请帮帮我。

这是我的 LogCat

02-19 08:54:15.059: W/dalvikvm(2013): threadid=1: thread exiting with uncaught exception (group=0xb1aefba8)
02-19 08:54:15.069: E/AndroidRuntime(2013): FATAL EXCEPTION: main
02-19 08:54:15.069: E/AndroidRuntime(2013): Process:    com.beproject.pocketdoctor, PID: 2013
02-19 08:54:15.069: E/AndroidRuntime(2013): java.lang.NullPointerException
02-19 08:54:15.069: E/AndroidRuntime(2013):     at  com.beproject.pocketdoctor.SHospitals.onCreateView(SHospitals.java:45)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at  android.app.Fragment.performCreateView(Fragment.java:1700)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at  android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.BackStackRecord.run(BackStackRecord.java:684)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.BackStackRecord.run(BackStackRecord.java:684)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
02-19 08:54:15.069: E/AndroidRuntime(2013):     at dalvik.system.NativeStart.main(Native Method)

【问题讨论】：

你的应用会抛出异常吗（Logcat）？
不，它什么都不做。该应用程序只是崩溃了
是的，它会抛出 nullpointerException，@Christopher。
然后尝试修复 NPE 或附加您的日志。
附加日志@Christopher

标签： android sqlite android-fragments

【解决方案1】：

首先，这行看起来很奇怪，逗号作为数组中的最后一个条目：

int[] to = new int[] { R.id.hospital, R.id.address, R.id.contact, };

其次，我猜这不起作用：

final ListView listview = (ListView) getView().findViewById(R.id.lv1);

应该是

final ListView listview = (ListView) rootView.findViewById(R.id.lv1);

【讨论】：

this line looks strange with the comma as last entry in your array。不。这实际上是完全有效的，相当于省略了最后一个昏迷。
@Christopher ，它对我有用，非常感谢您在这方面为我提供的帮助。我没有使用 getView() ，而是使用了 rootVIew 。再次非常感谢:)
@njzk2 我知道这行代码是有效的。但我没有看到任何好处？你能给我一个用例吗？
@Christopher：当我有长数组（也适用于枚举）并且我正在编写/调试/烦躁值时，我通常会欣赏这个东西。我通常将一个值放在单独的行上，因此我可以注释或删除任何一行（包括最后一行）或在任何点（包括末尾）添加一行，而不必担心是否正确放置了逗号。