java.lang.RuntimeException: 无法启动活动 ComponentInfo {...}: java.lang.NullPointerException [英] java.lang.RuntimeException: Unable to start activity ComponentInfo {...}: java.lang.NullPointerException
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问题描述
当您点击从一项活动转到另一项活动时，出现错误:
when you click to go from one activity to another, I have an error:
java.lang.RuntimeException: 无法启动活动 ComponentInfo {...}: java.lang.NullPointerException
我缺少一些方法?请帮助我理解我做错了什么，这就是您看到此错误的原因?
I am missing some method? Please help me to understand what I did wrong, which is why you see this error?
我的活动:Zaselenie.java
My activity: Zaselenie.java
import java.util.ArrayList;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
public class Zaselenie extends Activity {
ContactDBmoy cqh;
KvartDB kdb;
SQLiteDatabase sdb;
private Long rowId;
Spinner spZaselenie;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.zaselenie);
spZaselenie = (Spinner)findViewById(R.id.spZaselenie);
// Инициализируем наш класс-обёртку
cqh = new ContactDBmoy(Zaselenie.this);
kdb = new KvartDB(Zaselenie.this);
// База нам нужна для записи и чтения
sdb = cqh.getWritableDatabase();
sdb = kdb.getWritableDatabase();
Bundle extras = getIntent().getExtras();
rowId = extras.getLong(ContactMain.rowId);
Cursor cursorKvart = sdb.query(KvartDB.TABLE_NAME, new String[] {
KvartDB._ID, KvartDB.NAME_COLUMN }, null, // The
// columns
// for the
// WHERE
// clause
null, // The values for the WHERE clause
null, // don't group the rows
null, // don't filter by row groups
null // The sort order
);
ArrayList<String> labels = new ArrayList<String>();
while (cursorKvart.moveToNext()) {
// GET COLUMN INDICES + VALUES OF THOSE COLUMNS
int idKvart = cursorKvart.getInt(cursorKvart.getColumnIndex(KvartDB._ID));
String nameKvart = cursorKvart.getString(cursorKvart.getColumnIndex(KvartDB.NAME_COLUMN));
Log.i("LOG_TAG", "ROW " + idKvart + " HAS NAME " + nameKvart);
labels.add(nameKvart);
// Creating adapter for spinner
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, labels);
// Drop down layout style - list view with radio button
dataAdapter
.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
dataAdapter.notifyDataSetChanged();
// attaching data adapter to spinner
spZaselenie.setAdapter(dataAdapter);
}
cursorKvart.close();
}
public Zaselenie() {
// TODO Auto-generated constructor stub
}
@Override
protected void onResume() {
super.onResume();
}
@Override
protected void onStop() {
super.onStop();
// закрываем соединения с базой данных
sdb.close();
kdb.close();
}
}
Logcat 错误:
03-06 12:04:43.802: E/AndroidRuntime(20861): FATAL EXCEPTION: main
03-06 12:04:43.802: E/AndroidRuntime(20861): java.lang.RuntimeException: Unable to start activity ComponentInfo{ru.zloyel.manager_sutochnoy_arendy_1/ru.zloyel.manager_sutochnoy_arendy_1.Zaselenie}: java.lang.NullPointerException
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread.access$600(ActivityThread.java:130)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.os.Handler.dispatchMessage(Handler.java:99)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.os.Looper.loop(Looper.java:137)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread.main(ActivityThread.java:4745)
03-06 12:04:43.802: E/AndroidRuntime(20861): at java.lang.reflect.Method.invokeNative(Native Method)
03-06 12:04:43.802: E/AndroidRuntime(20861): at java.lang.reflect.Method.invoke(Method.java:511)
03-06 12:04:43.802: E/AndroidRuntime(20861): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-06 12:04:43.802: E/AndroidRuntime(20861): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-06 12:04:43.802: E/AndroidRuntime(20861): at dalvik.system.NativeStart.main(Native Method)
03-06 12:04:43.802: E/AndroidRuntime(20861): Caused by: java.lang.NullPointerException
03-06 12:04:43.802: E/AndroidRuntime(20861): at ru.zloyel.manager_sutochnoy_arendy_1.Zaselenie.onCreate(Zaselenie.java:39)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.Activity.performCreate(Activity.java:5008)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
03-06 12:04:43.802: E/AndroidRuntime(20861): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
03-06 12:04:43.802: E/AndroidRuntime(20861): ... 11 more
推荐答案
检查 extras 不是 null 如下...
Check that extras isn't null as below...
if(extras != null) {
rowId = extras.getLong(ContactMain.rowId);
}
还要检查您的 Cursor 对象是否为空，如下所示...
Also check that your Cursor object isn't null as below...
if(cursorKvart != null && cursorKvart.getCount() > 0) {
while (cursorKvart.moveToNext()) {
......
}
}
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