我想知道为什么我不能打开我的应用程序。另外，我正在尝试从SQLite数据库中检索数据并插入到微调器中。
LogCat说：
08-06 09:37:41.262: I/dalvikvm(532): threadid=3: reacting to signal 3
08-06 09:37:41.343: I/dalvikvm(532): Wrote stack traces to '/data/anr/traces.txt'
08-06 09:37:41.643: D/gralloc_goldfish(532): Emulator without GPU emulation detected.
08-06 09:37:41.773: I/dalvikvm(532): threadid=3: reacting to signal 3
08-06 09:37:41.793: I/dalvikvm(532): Wrote stack traces to '/data/anr/traces.txt'
08-06 09:37:43.293: D/AndroidRuntime(532): Shutting down VM
08-06 09:37:43.303: W/dalvikvm(532): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
08-06 09:37:43.312: E/AndroidRuntime(532): FATAL EXCEPTION: main
08-06 09:37:43.312: E/AndroidRuntime(532): java.lang.RuntimeException: Unable to start activity ComponentInfo{main.page/main.page.PersonalInfo}: java.lang.NullPointerException
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread.access$600(ActivityThread.java:123)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.os.Handler.dispatchMessage(Handler.java:99)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.os.Looper.loop(Looper.java:137)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread.main(ActivityThread.java:4424)
08-06 09:37:43.312: E/AndroidRuntime(532): at java.lang.reflect.Method.invokeNative(Native Method)
08-06 09:37:43.312: E/AndroidRuntime(532): at java.lang.reflect.Method.invoke(Method.java:511)
08-06 09:37:43.312: E/AndroidRuntime(532): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-06 09:37:43.312: E/AndroidRuntime(532): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-06 09:37:43.312: E/AndroidRuntime(532): at dalvik.system.NativeStart.main(Native Method)
08-06 09:37:43.312: E/AndroidRuntime(532): Caused by: java.lang.NullPointerException
08-06 09:37:43.312: E/AndroidRuntime(532): at main.page.InfoDBAdapter.getAllContacts(InfoDBAdapter.java:113)
08-06 09:37:43.312: E/AndroidRuntime(532): at main.page.PersonalInfo.onCreate(PersonalInfo.java:41)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.Activity.performCreate(Activity.java:4465)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
08-06 09:37:43.312: E/AndroidRuntime(532): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
08-06 09:37:43.312: E/AndroidRuntime(532): ... 11 more
08-06 09:37:43.694: I/dalvikvm(532): threadid=3: reacting to signal 3
08-06 09:37:43.713: I/dalvikvm(532): Wrote stack traces to '/data/anr/traces.txt'
08-06 09:37:43.923: I/dalvikvm(532): threadid=3: reacting to signal 3
08-06 09:37:43.933: I/dalvikvm(532): Wrote stack traces to '/data/anr/traces.txt'
以下是从数据库中检索数据并放入微调器的代码。
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.info);
Cursor c = infoDB.getAllContacts();
startManagingCursor(c);
//Create an array to specify which fields want to display
String[] from = new String[] {"name"};
//Create an array of the display item want to bind our data to
int[] to = new int[] {R.id.fName};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, android.R.layout.simple_spinner_item, c, from, to);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
nameSpinner.setAdapter(adapter);
nameSpinner = (Spinner) findViewById(R.id.nameSpinner);
哦，是的，在我输入代码（上面的代码）之前，我可以打开应用程序。但在我输入代码后，我无法打开应用程序。我不确定这是否与代码有关。
以下是DBAdapter类：
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_DATE = "date";
public static final String KEY_TYPE = "type";
public static final String KEY_LIKES = "likes";
public static final String KEY_DISLIKES = "dislikes";
private static final String TAG = "InfoDBAdapter";
private static final String DATABASE_NAME = "friendsDB";
private static final String DATABASE_TABLE = "friends_info";
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE = "create table friends_info(name_id integer primary key autoincrement, "
+ "name text not null, date text not null, type text not null, likes text not null, dislikes text not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public InfoDBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
try
{
db.execSQL(DATABASE_CREATE);
} catch (SQLException e)
{
e.printStackTrace();
}
}// end onCreate()
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS friends_info");
onCreate(db);
}// end onUpgrade()
}// end DatabaseHelper
public InfoDBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}// end open()
public void close()
{
DBHelper.close();
}// end close()
public long insertContact(String name, String date, String type, String likes, String dislikes)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_DATE, date);
initialValues.put(KEY_TYPE, type);
initialValues.put(KEY_LIKES, likes);
initialValues.put(KEY_DISLIKES, dislikes);
return db.insert(DATABASE_TABLE, null, initialValues);
}// end insertContact()
public boolean deleteContact(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}// end deleteContact()
public Cursor getAllContacts()
{
return db.query(DATABASE_TABLE, new String[]
{ KEY_ROWID, KEY_NAME, KEY_DATE, KEY_TYPE, KEY_LIKES, KEY_DISLIKES }, null, null, null, null, null);
}// end getAllContacts()
public Cursor getContact(long rowId) throws SQLException
{
Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {
KEY_ROWID, KEY_NAME, KEY_DATE, KEY_TYPE, KEY_LIKES, KEY_DISLIKES }, KEY_ROWID + "=" + rowId,
null, null, null, null, null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}// end getContact()
public boolean updateContact(long rowId, String name, String date, String type, String likes, String dislikes)
{
ContentValues args = new ContentValues();
args.put(KEY_NAME, name);
args.put(KEY_DATE, date);
args.put(KEY_TYPE, type);
args.put(KEY_LIKES, likes);
args.put(KEY_DISLIKES, dislikes);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}// end updateContact()
感谢您提供的任何帮助。哦，如果有人知道从数据库中检索数据的其他方法并放入微调器，我将非常感谢帮助 谢谢=）
答案 0 :(得分：0)
您似乎忘记打开DataBase进行操作，db reference为null并投掷NullPointerException。尝试调用以下行 -
infoDB = new InfoDBAdapter(mContext);
infoDB.open();
Cursor c = infoDB.getAllContacts();
答案 1 :(得分：0)
InfoDb似乎是null。你是如何初始化它的？
您需要open()数据库才能使用它。