我正在尝试使用我已保存在资产中的数据库填充列表视图。在运行应用程序时，我已经检查了数据库是否正在创建（它是）。我目前的问题是试图弄清楚如何获取列并在列表视图中显示它们。我的列是名称，位置和部门，以防您看到一段您不理解的代码。我一直在尝试使用http://saigeethamn.blogspot.com/2011/02/listview-of-data-from-sqlitedatabase.html中的代码 如果有人能够帮助我，我会非常感激，谢谢你的进步。
编辑：当代码运行时，它给我一个空指针异常
public class Favorites extends ListActivity {
public static String tableName = "fac";
private ListView lv;
SQLiteDatabase newDB;
private ArrayList<String> results = new ArrayList<String>();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.favorites);
openAndQueryDatabase();
displayResultList();
}
private void displayResultList() {
TextView tView = new TextView(this);
tView.setText("This data is retrieved from the database and only 4 "
+ "of the results are displayed");
getListView().addHeaderView(tView);
setListAdapter(new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, results));
getListView().setTextFilterEnabled(true);
}
private void openAndQueryDatabase() {
try {
DataBaseHelper dbHelper = new DataBaseHelper(
this.getApplicationContext());
newDB = dbHelper.getWritableDatabase();
Cursor c = newDB.rawQuery("SELECT name, position FROM " + tableName
+ "where ", null);
if (c != null) {
if (c.moveToFirst()) {
do {
String name = c.getString(c.getColumnIndex("name"));
String position = c.getString(c
.getColumnIndex("position"));
results.add("name: " + name + ",Position " + position);
} while (c.moveToNext());
}
}
} catch (SQLiteException se) {
} finally {
if (newDB != null)
{
newDB.execSQL("DELETE FROM " + tableName);
newDB.close();
}}
}
}
logcat的：
04-24 04:43:19.064: E/AndroidRuntime(1644): FATAL EXCEPTION: main
04-24 04:43:19.064: E/AndroidRuntime(1644): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cerealBarApps/com.cerealBarApps.Faculty_tab}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cerealBarApps/com.cerealBarApps.Favorites}: java.lang.NullPointerException
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.access$1500(ActivityThread.java:132)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.os.Handler.dispatchMessage(Handler.java:99)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.os.Looper.loop(Looper.java:143)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.main(ActivityThread.java:4196)
04-24 04:43:19.064: E/AndroidRuntime(1644): at java.lang.reflect.Method.invokeNative(Native Method)
04-24 04:43:19.064: E/AndroidRuntime(1644): at java.lang.reflect.Method.invoke(Method.java:507)
04-24 04:43:19.064: E/AndroidRuntime(1644): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-24 04:43:19.064: E/AndroidRuntime(1644): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-24 04:43:19.064: E/AndroidRuntime(1644): at dalvik.system.NativeStart.main(Native Method)
04-24 04:43:19.064: E/AndroidRuntime(1644): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cerealBarApps/com.cerealBarApps.Favorites}: java.lang.NullPointerException
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.startActivityNow(ActivityThread.java:1651)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:656)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.widget.TabHost.setCurrentTab(TabHost.java:326)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.widget.TabHost.addTab(TabHost.java:216)
04-24 04:43:19.064: E/AndroidRuntime(1644): at com.cerealBarApps.Faculty_tab.onCreate(Faculty_tab.java:55)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
04-24 04:43:19.064: E/AndroidRuntime(1644): ... 11 more
04-24 04:43:19.064: E/AndroidRuntime(1644): Caused by: java.lang.NullPointerException
04-24 04:43:19.064: E/AndroidRuntime(1644): at com.cerealBarApps.Favorites.openAndQueryDatabase(Favorites.java:63)
04-24 04:43:19.064: E/AndroidRuntime(1644): at com.cerealBarApps.Favorites.onCreate(Favorites.java:25)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
04-24 04:43:19.064: E/AndroidRuntime(1644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
抱歉
答案 0 :(得分：0)
试试这个PLZ .. 在下面的语句中，请将''before'放在'keyword'。
旧
Cursor c = newDB.rawQuery("SELECT name, position FROM " + tableName + "where ", null);
新
Cursor c = newDB.rawQuery("SELECT name, position FROM " + tableName + " where ", null);