Java 在android中获取数据库信息时出现NullPointerException
我想用htis方法和stor在对象中获取数据库记录:Java 在android中获取数据库信息时出现NullPointerException,java,android,database,android-cursoradapter,Java,Android,Database,Android Cursoradapter,我想用htis方法和stor在对象中获取数据库记录: SQLiteDatabase db = openOrCreateDatabase("lingodb",MODE_PRIVATE, null); Cursor cur; cur = db.rawQuery("Select * from lingo where stage='1'", null); cur.moveToFirst(); int n=0; while (!cur.is
SQLiteDatabase db = openOrCreateDatabase("lingodb",MODE_PRIVATE, null);
Cursor cur;
cur = db.rawQuery("Select * from lingo where stage='1'", null);
cur.moveToFirst();
int n=0;
while (!cur.isAfterLast()) {
words_array[n].word = cur.getString(cur.getColumnIndex("word"));
words_array[n].pack = cur.getInt(cur.getColumnIndex("stage"));
words_array[n].id = cur.getInt(cur.getColumnIndex("pack_id"));
n=n+1;
cur.moveToNext();
}
cur.close();
db.close();
我在db中的信息有效,但此代码提供以下错误:
04-26 23:15:52.090: E/AndroidRuntime(22002): FATAL EXCEPTION: main
04-26 23:15:52.090: E/AndroidRuntime(22002): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.english.game/com.english.game.MainActivity}: java.lang.NullPointerException
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.os.Handler.dispatchMessage(Handler.java:99)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.os.Looper.loop(Looper.java:137)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-26 23:15:52.090: E/AndroidRuntime(22002): at java.lang.reflect.Method.invokeNative(Native Method)
04-26 23:15:52.090: E/AndroidRuntime(22002): at java.lang.reflect.Method.invoke(Method.java:511)
04-26 23:15:52.090: E/AndroidRuntime(22002): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-26 23:15:52.090: E/AndroidRuntime(22002): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-26 23:15:52.090: E/AndroidRuntime(22002): at dalvik.system.NativeStart.main(Native Method)
04-26 23:15:52.090: E/AndroidRuntime(22002): Caused by: java.lang.NullPointerException
04-26 23:15:52.090: E/AndroidRuntime(22002): at com.english.game.MainActivity.onCreate(MainActivity.java:75)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.Activity.performCreate(Activity.java:5104)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-26 23:15:52.090: E/AndroidRuntime(22002): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
为什么会发生这种情况?您是否为
单词数组分配了空间
在代码段中,您提供的words\u array
和cur
都可以为空。请确保为正在填充的阵列分配空间。因为stacktrace引用了行
words_array[n].word = cur.getString(cur.getColumnIndex("word"))
和cur
不能为空,只有words\u array
可以为空MainActivity类的第75行是什么?@rciovati:此行:words\u array[n].word=cur.getString(cur.getColumnIndex(“word”);是的,我做到了。我想我的问题是从数据库中获取信息哇,你做到了。我忘了为单词数组分配空间,事实上。。。谢谢你,我的朋友