Java NullPointerException Logcat错误
LogCat NPE错误Java NullPointerException Logcat错误,java,android,eclipse,sqlite,nullpointerexception,Java,Android,Eclipse,Sqlite,Nullpointerexception,LogCat NPE错误 02-03 16:19:48.172: D/AndroidRuntime(959): Shutting down VM 02-03 16:19:48.182: W/dalvikvm(959): threadid=1: thread exiting with uncaught exception (group=0x41465700) 02-03 16:19:48.322: E/AndroidRuntime(959): FATAL EXCEPTION: main 0
02-03 16:19:48.172: D/AndroidRuntime(959): Shutting down VM
02-03 16:19:48.182: W/dalvikvm(959): threadid=1: thread exiting with uncaught exception (group=0x41465700)
02-03 16:19:48.322: E/AndroidRuntime(959): FATAL EXCEPTION: main
02-03 16:19:48.322: E/AndroidRuntime(959): java.lang.IllegalStateException: Could not execute method of the activity
02-03 16:19:48.322: E/AndroidRuntime(959): at android.view.View$1.onClick(View.java:3633)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.view.View.performClick(View.java:4240)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.view.View$PerformClick.run(View.java:17721)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.os.Handler.handleCallback(Handler.java:730)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.os.Handler.dispatchMessage(Handler.java:92)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.os.Looper.loop(Looper.java:137)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.app.ActivityThread.main(ActivityThread.java:5103)
02-03 16:19:48.322: E/AndroidRuntime(959): at java.lang.reflect.Method.invokeNative(Native Method)
02-03 16:19:48.322: E/AndroidRuntime(959): at java.lang.reflect.Method.invoke(Method.java:525)
02-03 16:19:48.322: E/AndroidRuntime(959): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-03 16:19:48.322: E/AndroidRuntime(959): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-03 16:19:48.322: E/AndroidRuntime(959): at dalvik.system.NativeStart.main(Native Method)
02-03 16:19:48.322: E/AndroidRuntime(959): Caused by: java.lang.reflect.InvocationTargetException
02-03 16:19:48.322: E/AndroidRuntime(959): at java.lang.reflect.Method.invokeNative(Native Method)
02-03 16:19:48.322: E/AndroidRuntime(959): at java.lang.reflect.Method.invoke(Method.java:525)
02-03 16:19:48.322: E/AndroidRuntime(959): at android.view.View$1.onClick(View.java:3628)
02-03 16:19:48.322: E/AndroidRuntime(959): ... 11 more
02-03 16:19:48.322: E/AndroidRuntime(959): Caused by: java.lang.NullPointerException
02-03 16:19:48.322: E/AndroidRuntime(959): at com.example.universitybudgetub.MainMenu.populateListViewFromDB(MainMenu.java:184)
02-03 16:19:48.322: E/AndroidRuntime(959): at com.example.universitybudgetub.MainMenu.addRecord(MainMenu.java:135)
02-03 16:19:48.322: E/AndroidRuntime(959): ... 14 more
这是我收到的错误消息,我似乎无法找到NPE错误在我的代码中的位置。我将在下面提供main menu.java和dbadpeter.java
main menu.java
package com.example.universitybudgetub;
import java.io.File;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
public class MainMenu extends FragmentActivity{
DBAdapter db = new DBAdapter(this); //Initiate DB class methods
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
//OnCreate
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_menu);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
public void onClick(View v){
String destPath = "/data/data/" + getPackageName() + "/databases/ExpensesDB";
@SuppressWarnings("unused")
File f = new File(destPath);
}
//OnCreateOptionsMenu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main_menu, menu);
return true;
}
//SectionsPagerAdapter Controls which Fragment is retrieved for each page
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment;
switch (position) {
case 0:
fragment = new Fragment1();
break;
case 1:
fragment = new Fragment2();
break;
case 2:
fragment = new Fragment3();
break;
case 3:
fragment = new Fragment4();
break;
case 4:
fragment = new Fragment5();
break;
default:
fragment = null;
break;
}
return fragment;
}
//Returns the amount of pages to display
@Override
public int getCount() {
// Show 3 total pages.
return 5;
}
//Page Title
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getString(R.string.title_section1);
case 1:
return getString(R.string.title_section2);
case 2:
return getString(R.string.title_section3);
case 3:
return getString(R.string.title_section4);
case 4:
return getString(R.string.title_section5);
}
return null;
}
}
//Add New Record
public void addRecord (View v){
//Get data from form
EditText foodTxt = (EditText)findViewById(R.id.editText_food);
EditText taxiTxt = (EditText)findViewById(R.id.editText_taxi);
EditText clothesTxt = (EditText)findViewById(R.id.editText_clothes);
EditText sportsTxt = (EditText)findViewById(R.id.editText_sports);
EditText supermarketTxt = (EditText)findViewById(R.id.editText_supermarket);
EditText clubs_barsTxt = (EditText)findViewById(R.id.editText_clubs);
EditText owed_moneyTxt = (EditText)findViewById(R.id.editText_owed_money);
EditText otherTxt = (EditText)findViewById(R.id.editText_other);
EditText electric_gasTxt = (EditText)findViewById(R.id.editText_electric_gas);
EditText waterbillTxt = (EditText)findViewById(R.id.editText_water);
EditText houseTxt = (EditText)findViewById(R.id.editText_house);
EditText rentTxt = (EditText)findViewById(R.id.editText_rent);
EditText internetTxt = (EditText)findViewById(R.id.editText_internet);
db.open();
@SuppressWarnings("unused")
long id = db.insertRecord(foodTxt.getText().toString(), clothesTxt.getText().toString(),
supermarketTxt.getText().toString(), taxiTxt.getText().toString(), sportsTxt.getText().toString(),
clubs_barsTxt.getText().toString(), owed_moneyTxt.getText().toString(), otherTxt.getText().toString(),
electric_gasTxt.getText().toString(), waterbillTxt.getText().toString(), rentTxt.getText().toString(),
houseTxt.getText().toString(), internetTxt.getText().toString());
populateListViewFromDB(); //Re-populate the list after new record is added
db.close();
//Set editText fields to empty
foodTxt.setText("");
taxiTxt.setText("");
clothesTxt.setText("");
sportsTxt.setText("");
supermarketTxt.setText("");
clubs_barsTxt.setText("");
owed_moneyTxt.setText("");
otherTxt.setText("");
electric_gasTxt.setText("");
waterbillTxt.setText("");
houseTxt.setText("");
rentTxt.setText("");
internetTxt.setText("");
Toast.makeText(MainMenu.this, "Expenses Added", Toast.LENGTH_LONG).show();
}
private void openDB(){
db = new DBAdapter(this);
db.open();
}
private void populateListViewFromDB() {
Cursor cursor = db.getAllRows();
//Allow activity to manage lifetime of the cursor
//DEPRECATED!
startManagingCursor(cursor);
//Setup mapping from cursor to view fields
String[] fromFieldNames = new String[]
{DBAdapter.KEY_ROWID, DBAdapter.KEY_FOOD, DBAdapter.KEY_CLOTHES, DBAdapter.KEY_SUPERMARKET, DBAdapter.KEY_TAXI, DBAdapter.KEY_SPORTS,
DBAdapter.KEY_CLUBS_BARS, DBAdapter.KEY_OWED_MONEY, DBAdapter.KEY_OTHER, DBAdapter.KEY_ELECTRIC_GAS, DBAdapter.KEY_WATERBILL,
DBAdapter.KEY_RENT, DBAdapter.KEY_HOUSE, DBAdapter.KEY_INTERNETBILL,};
int[] toViewIDs = new int[]
{R.id.textView_itemid, R.id.textView_itemfood, R.id.textView_itemclothes, R.id.textView_itemsupermarket, R.id.textView_itemtaxi, R.id.textView_itemsports,
R.id.textView_itemclubs, R.id.textView_itemowed, R.id.textView_itemother, R.id.textView_itemelectric, R.id.textView_itemwater,
R.id.textView_itemrent, R.id.textView_itemhouse, R.id.textView_iteminternet,};
//Create Adapter to map columns of the DB into elements in the UI
SimpleCursorAdapter myCursorAdapter = new SimpleCursorAdapter(
this, //Context
R.layout.history_expenses_layout, //Row layout template
cursor, //cursor (set of DB REcords to map)
fromFieldNames, //DB Column names
toViewIDs // View IDs to put information in
);
//Set the adapter for the list view
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setAdapter(myCursorAdapter);
}
}
package com.example.universitybudgetub;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DBAdapter {
public static final String KEY_ROWID = "_id";
public static final String KEY_FOOD = "food";
public static final String KEY_CLOTHES = "clothes";
public static final String KEY_SUPERMARKET = "supermarket";
public static final String KEY_TAXI= "taxi";
public static final String KEY_SPORTS = "sports";
public static final String KEY_CLUBS_BARS = "clubs_bars";
public static final String KEY_OWED_MONEY = "owed_money";
public static final String KEY_OTHER = "other";
public static final String KEY_ELECTRIC_GAS = "electric_gas";
public static final String KEY_WATERBILL = "waterbill";
public static final String KEY_RENT = "rent";
public static final String KEY_HOUSE = "house";
public static final String KEY_INTERNETBILL = "internetbill";
private static final String TAG = "DBAdapter";
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_FOOD, KEY_CLOTHES, KEY_SUPERMARKET, KEY_TAXI, KEY_SPORTS,
KEY_CLUBS_BARS, KEY_OWED_MONEY, KEY_OTHER, KEY_ELECTRIC_GAS, KEY_WATERBILL, KEY_RENT, KEY_HOUSE, KEY_INTERNETBILL};
private static String DATABASE_NAME = "ExpensesDB";
private static final String DATABASE_TABLE = "expenses";
private static final int DATABASE_VERSION = 4;
private static final String DATABASE_CREATE =
"create table if not exists expenses (_id integer primary key autoincrement, " +
"food VARCHAR, clothes VARCHAR, supermarket VARCHAR, taxi VARCHAR, sports VARCHAR, clubs_bars VARCHAR, owed_money VARCHAR, other VARCHAR, electric_gas VARCHAR, waterbill VARCHAR, rent VARCHAR, house VARCHAR, internetbill VARCHAR);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx){
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
//Instantiate's all the database methods
public 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();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
Log.w(TAG, "Upgrading data from version " + oldVersion + " to " + newVersion + " , which wll destroy all old data");
db.execSQL("DROP TABLE IF EXISTS contacts");
onCreate(db);
}
}
//Opens database
public DBAdapter open() throws SQLException{
db = DBHelper.getWritableDatabase();
return this;
}
//Close database
public void close(){
DBHelper.close();
}
//Insert record to database
public long insertRecord(String food, String clothes, String supermarket, String taxi, String sports, String clubs_bars,
String owed_money, String other, String electric_gas, String waterbill, String rent, String house, String internetbill){
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_FOOD, food);
initialValues.put(KEY_CLOTHES, clothes);
initialValues.put(KEY_SUPERMARKET, supermarket);
initialValues.put(KEY_TAXI, taxi);
initialValues.put(KEY_SPORTS, sports);
initialValues.put(KEY_CLUBS_BARS, clubs_bars);
initialValues.put(KEY_OWED_MONEY, owed_money);
initialValues.put(KEY_OTHER, other);
initialValues.put(KEY_ELECTRIC_GAS, electric_gas);
initialValues.put(KEY_WATERBILL, waterbill);
initialValues.put(KEY_RENT, rent);
initialValues.put(KEY_HOUSE, house);
initialValues.put(KEY_INTERNETBILL, internetbill);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//Delete particular record
public boolean deleteRecord(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//Retrieve particular record
public Cursor getRecord(long rowId) throws SQLException
{
Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_FOOD, KEY_CLOTHES, KEY_TAXI, KEY_SPORTS,
KEY_CLUBS_BARS, KEY_OWED_MONEY, KEY_OTHER, KEY_ELECTRIC_GAS, KEY_WATERBILL, KEY_RENT, KEY_HOUSE, KEY_INTERNETBILL},
KEY_ROWID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//Update particular record
public boolean updateRecord(long rowId, int food, int clothes, int taxi, int sports, int clubs_bars, int owed_money, int other,
int electric_gas, int waterbill, int rent, int house, int internetbill){
ContentValues args = new ContentValues();
args.put(KEY_FOOD, food);
args.put(KEY_CLOTHES, clothes);
args.put(KEY_TAXI, taxi);
args.put(KEY_SPORTS, sports);
args.put(KEY_CLUBS_BARS, clubs_bars);
args.put(KEY_OWED_MONEY, owed_money);
args.put(KEY_OTHER, other);
args.put(KEY_ELECTRIC_GAS, electric_gas);
args.put(KEY_WATERBILL, waterbill);
args.put(KEY_RENT, rent);
args.put(KEY_HOUSE, house);
args.put(KEY_INTERNETBILL, internetbill);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
}
DBAdapter.java
package com.example.universitybudgetub;
import java.io.File;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
public class MainMenu extends FragmentActivity{
DBAdapter db = new DBAdapter(this); //Initiate DB class methods
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
//OnCreate
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_menu);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
public void onClick(View v){
String destPath = "/data/data/" + getPackageName() + "/databases/ExpensesDB";
@SuppressWarnings("unused")
File f = new File(destPath);
}
//OnCreateOptionsMenu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main_menu, menu);
return true;
}
//SectionsPagerAdapter Controls which Fragment is retrieved for each page
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment;
switch (position) {
case 0:
fragment = new Fragment1();
break;
case 1:
fragment = new Fragment2();
break;
case 2:
fragment = new Fragment3();
break;
case 3:
fragment = new Fragment4();
break;
case 4:
fragment = new Fragment5();
break;
default:
fragment = null;
break;
}
return fragment;
}
//Returns the amount of pages to display
@Override
public int getCount() {
// Show 3 total pages.
return 5;
}
//Page Title
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getString(R.string.title_section1);
case 1:
return getString(R.string.title_section2);
case 2:
return getString(R.string.title_section3);
case 3:
return getString(R.string.title_section4);
case 4:
return getString(R.string.title_section5);
}
return null;
}
}
//Add New Record
public void addRecord (View v){
//Get data from form
EditText foodTxt = (EditText)findViewById(R.id.editText_food);
EditText taxiTxt = (EditText)findViewById(R.id.editText_taxi);
EditText clothesTxt = (EditText)findViewById(R.id.editText_clothes);
EditText sportsTxt = (EditText)findViewById(R.id.editText_sports);
EditText supermarketTxt = (EditText)findViewById(R.id.editText_supermarket);
EditText clubs_barsTxt = (EditText)findViewById(R.id.editText_clubs);
EditText owed_moneyTxt = (EditText)findViewById(R.id.editText_owed_money);
EditText otherTxt = (EditText)findViewById(R.id.editText_other);
EditText electric_gasTxt = (EditText)findViewById(R.id.editText_electric_gas);
EditText waterbillTxt = (EditText)findViewById(R.id.editText_water);
EditText houseTxt = (EditText)findViewById(R.id.editText_house);
EditText rentTxt = (EditText)findViewById(R.id.editText_rent);
EditText internetTxt = (EditText)findViewById(R.id.editText_internet);
db.open();
@SuppressWarnings("unused")
long id = db.insertRecord(foodTxt.getText().toString(), clothesTxt.getText().toString(),
supermarketTxt.getText().toString(), taxiTxt.getText().toString(), sportsTxt.getText().toString(),
clubs_barsTxt.getText().toString(), owed_moneyTxt.getText().toString(), otherTxt.getText().toString(),
electric_gasTxt.getText().toString(), waterbillTxt.getText().toString(), rentTxt.getText().toString(),
houseTxt.getText().toString(), internetTxt.getText().toString());
populateListViewFromDB(); //Re-populate the list after new record is added
db.close();
//Set editText fields to empty
foodTxt.setText("");
taxiTxt.setText("");
clothesTxt.setText("");
sportsTxt.setText("");
supermarketTxt.setText("");
clubs_barsTxt.setText("");
owed_moneyTxt.setText("");
otherTxt.setText("");
electric_gasTxt.setText("");
waterbillTxt.setText("");
houseTxt.setText("");
rentTxt.setText("");
internetTxt.setText("");
Toast.makeText(MainMenu.this, "Expenses Added", Toast.LENGTH_LONG).show();
}
private void openDB(){
db = new DBAdapter(this);
db.open();
}
private void populateListViewFromDB() {
Cursor cursor = db.getAllRows();
//Allow activity to manage lifetime of the cursor
//DEPRECATED!
startManagingCursor(cursor);
//Setup mapping from cursor to view fields
String[] fromFieldNames = new String[]
{DBAdapter.KEY_ROWID, DBAdapter.KEY_FOOD, DBAdapter.KEY_CLOTHES, DBAdapter.KEY_SUPERMARKET, DBAdapter.KEY_TAXI, DBAdapter.KEY_SPORTS,
DBAdapter.KEY_CLUBS_BARS, DBAdapter.KEY_OWED_MONEY, DBAdapter.KEY_OTHER, DBAdapter.KEY_ELECTRIC_GAS, DBAdapter.KEY_WATERBILL,
DBAdapter.KEY_RENT, DBAdapter.KEY_HOUSE, DBAdapter.KEY_INTERNETBILL,};
int[] toViewIDs = new int[]
{R.id.textView_itemid, R.id.textView_itemfood, R.id.textView_itemclothes, R.id.textView_itemsupermarket, R.id.textView_itemtaxi, R.id.textView_itemsports,
R.id.textView_itemclubs, R.id.textView_itemowed, R.id.textView_itemother, R.id.textView_itemelectric, R.id.textView_itemwater,
R.id.textView_itemrent, R.id.textView_itemhouse, R.id.textView_iteminternet,};
//Create Adapter to map columns of the DB into elements in the UI
SimpleCursorAdapter myCursorAdapter = new SimpleCursorAdapter(
this, //Context
R.layout.history_expenses_layout, //Row layout template
cursor, //cursor (set of DB REcords to map)
fromFieldNames, //DB Column names
toViewIDs // View IDs to put information in
);
//Set the adapter for the list view
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setAdapter(myCursorAdapter);
}
}
package com.example.universitybudgetub;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DBAdapter {
public static final String KEY_ROWID = "_id";
public static final String KEY_FOOD = "food";
public static final String KEY_CLOTHES = "clothes";
public static final String KEY_SUPERMARKET = "supermarket";
public static final String KEY_TAXI= "taxi";
public static final String KEY_SPORTS = "sports";
public static final String KEY_CLUBS_BARS = "clubs_bars";
public static final String KEY_OWED_MONEY = "owed_money";
public static final String KEY_OTHER = "other";
public static final String KEY_ELECTRIC_GAS = "electric_gas";
public static final String KEY_WATERBILL = "waterbill";
public static final String KEY_RENT = "rent";
public static final String KEY_HOUSE = "house";
public static final String KEY_INTERNETBILL = "internetbill";
private static final String TAG = "DBAdapter";
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_FOOD, KEY_CLOTHES, KEY_SUPERMARKET, KEY_TAXI, KEY_SPORTS,
KEY_CLUBS_BARS, KEY_OWED_MONEY, KEY_OTHER, KEY_ELECTRIC_GAS, KEY_WATERBILL, KEY_RENT, KEY_HOUSE, KEY_INTERNETBILL};
private static String DATABASE_NAME = "ExpensesDB";
private static final String DATABASE_TABLE = "expenses";
private static final int DATABASE_VERSION = 4;
private static final String DATABASE_CREATE =
"create table if not exists expenses (_id integer primary key autoincrement, " +
"food VARCHAR, clothes VARCHAR, supermarket VARCHAR, taxi VARCHAR, sports VARCHAR, clubs_bars VARCHAR, owed_money VARCHAR, other VARCHAR, electric_gas VARCHAR, waterbill VARCHAR, rent VARCHAR, house VARCHAR, internetbill VARCHAR);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx){
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
//Instantiate's all the database methods
public 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();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
Log.w(TAG, "Upgrading data from version " + oldVersion + " to " + newVersion + " , which wll destroy all old data");
db.execSQL("DROP TABLE IF EXISTS contacts");
onCreate(db);
}
}
//Opens database
public DBAdapter open() throws SQLException{
db = DBHelper.getWritableDatabase();
return this;
}
//Close database
public void close(){
DBHelper.close();
}
//Insert record to database
public long insertRecord(String food, String clothes, String supermarket, String taxi, String sports, String clubs_bars,
String owed_money, String other, String electric_gas, String waterbill, String rent, String house, String internetbill){
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_FOOD, food);
initialValues.put(KEY_CLOTHES, clothes);
initialValues.put(KEY_SUPERMARKET, supermarket);
initialValues.put(KEY_TAXI, taxi);
initialValues.put(KEY_SPORTS, sports);
initialValues.put(KEY_CLUBS_BARS, clubs_bars);
initialValues.put(KEY_OWED_MONEY, owed_money);
initialValues.put(KEY_OTHER, other);
initialValues.put(KEY_ELECTRIC_GAS, electric_gas);
initialValues.put(KEY_WATERBILL, waterbill);
initialValues.put(KEY_RENT, rent);
initialValues.put(KEY_HOUSE, house);
initialValues.put(KEY_INTERNETBILL, internetbill);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//Delete particular record
public boolean deleteRecord(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//Retrieve particular record
public Cursor getRecord(long rowId) throws SQLException
{
Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_FOOD, KEY_CLOTHES, KEY_TAXI, KEY_SPORTS,
KEY_CLUBS_BARS, KEY_OWED_MONEY, KEY_OTHER, KEY_ELECTRIC_GAS, KEY_WATERBILL, KEY_RENT, KEY_HOUSE, KEY_INTERNETBILL},
KEY_ROWID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//Update particular record
public boolean updateRecord(long rowId, int food, int clothes, int taxi, int sports, int clubs_bars, int owed_money, int other,
int electric_gas, int waterbill, int rent, int house, int internetbill){
ContentValues args = new ContentValues();
args.put(KEY_FOOD, food);
args.put(KEY_CLOTHES, clothes);
args.put(KEY_TAXI, taxi);
args.put(KEY_SPORTS, sports);
args.put(KEY_CLUBS_BARS, clubs_bars);
args.put(KEY_OWED_MONEY, owed_money);
args.put(KEY_OTHER, other);
args.put(KEY_ELECTRIC_GAS, electric_gas);
args.put(KEY_WATERBILL, waterbill);
args.put(KEY_RENT, rent);
args.put(KEY_HOUSE, house);
args.put(KEY_INTERNETBILL, internetbill);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
}
我将列表视图放在一个名为fragment5的java类中,并用id listViewFromDB将其命名。我要做的是在fragment5的列表中显示DB信息。我不确定是否有片段会影响MainMenu.java查找ListViewFromDB id的方式,因为这可能会导致NPE
任何帮助都会很好
private void openDB(){
db = new DBAdapter(this);
db.open();
}
此方法未被调用,因此当您尝试访问db
实例时,它会引发空指针异常
此方法未被调用,因此当您尝试访问
db
实例时,它会引发空指针异常。stacktrace中看到的第184行与以下行足够接近:
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setAdapter(myCursorAdapter);
确保
setContentView()
中的布局集实际上包含一个id为listViewFromDB
的listViewFromDB
行184,并且与这些行足够近:
ListView myList = (ListView) findViewById(R.id.listViewFromDB);
myList.setAdapter(myCursorAdapter);
确保在
setContentView()
中设置的布局实际上包含一个id为listViewFromDB
的listViewFromDB的addRecord
/populateListViewFromDB
错误。我看到的是你正在打开数据库,并试图用它做些什么。我看到它已初始化,但我认为不应该在onCreate之外添加新DBAdapter(this)
。你能把它放进去试试吗?似乎错误来自于数据库中的addRecord
/populateListViewFromDB
。我看到的是你正在打开数据库,并试图用它做些什么。我看到它已初始化,但我认为不应该在onCreate之外添加新DBAdapter(this)
。你能把它放进去试试吗?有一个(稍微不正确的)成员变量初始化:DBAdapter db=newdbadapter(这个)
没有注意到这是我的错误。我已经完全摆脱了方法openDB
,只是在我的onCreate
中调用了db.open()
,因为我注意到我已经启动了DBAdapter db=new DBAdapter(这个)代码>在开头。它仍然在给我一个NPErefer laalto的答案,似乎它无法从布局中获取listview。确保listViewFromDB中有一个列表视图。还要确保光标不为null。存在(稍微不正确的)成员变量初始化:DBAdapter db=new DBAdapter(this)
没有注意到这是我的错误。我已经完全摆脱了方法openDB
,只是在我的onCreate
中调用了db.open()
,因为我注意到我已经启动了DBAdapter db=new DBAdapter(这个)代码>在开头。它仍然在给我一个NPErefer laalto的答案,似乎它无法从布局中获取listview。确保listViewFromDB中有一个列表视图。还要确保光标不为空。我说的不是使用ListView
而是使用ListFragment
,对吗?由于我的应用程序将main menu
扩展到FragmentActivity
,因此它无法从数据库中找到idlistViewFromDB
,您可以在任何活动/片段中使用ListView
ListActivity
/ListFragment
只是预先打包了一个ListView
和使用它的帮助方法。嗯,然后我回到原点,它仍然会抛出一个NPE,即使我已经确保listViewFromDB
作为id存在。使用调试器单步执行时,NPE通常很容易确定。我通过调试器运行了它,在到达myList.setAdapter(myCursorAdapter)后它会出错
知道为什么会发生这种情况吗?我应该使用ListFragment
,而不是使用ListView
?由于我的应用程序将main menu
扩展到FragmentActivity
,因此它无法从数据库中找到idlistViewFromDB
,您可以在任何活动/片段中使用ListView
ListActivity
/ListFragment
只是预先打包了一个ListView
和使用它的帮助方法。嗯,然后我回到原点,即使我已经确保listViewFromDB
作为id存在,它仍然会抛出一个NPE。使用调试器单步执行时,NPE通常很容易确定。我通过调试器运行了它,在到达myList.setAdapter(myCursorAdapter)
后它会出错。你知道为什么会发生这种情况吗?