我想在我的数据库中插入一些值。 但我的代码给出了＆＃34; java.lang.NullPointerException＆＃34;错误。 我是Android的新手，我无法修复此错误。任何人都可以帮忙吗？
下面的是我的Add_new calss
public class Add_new extends Activity {
EditText nameText, phoneText, emailText, addressText;
ImageView contactImageImgView;
List<Contact> Contacts = new ArrayList<Contact>();
//Uri imageUri = Uri.parse("android.resource://com.kmks.no_user_image.png");
DatabaseHandler dbHandler;
ArrayAdapter<Contact> contactAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_contact_details);
nameText = (EditText) findViewById(R.id.contactName);
phoneText = (EditText) findViewById(R.id.editPhone);
emailText = (EditText) findViewById(R.id.editEmail);
addressText = (EditText) findViewById(R.id.editAdd);
contactImageImgView = (ImageView) findViewById(R.id.imgContactView);
}
public void insert(){
Contact contact = new Contact(dbHandler.getContactsCount(),
String.valueOf(nameText.getText()),
String.valueOf(phoneText.getText()),
String.valueOf(emailText.getText()),
String.valueOf(addressText.getText()), imageUri);
if (!contactExists(contact)) {
dbHandler.createContact(contact);
Contacts.add(contact);
contactAdapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), String.valueOf(nameText.getText()) + " has been added to your Contacts!", Toast.LENGTH_SHORT).show();
return;
}
Toast.makeText(getApplicationContext(), String.valueOf(nameText.getText()) + " already exists. Please use a different name.", Toast.LENGTH_SHORT).show();
}
private boolean contactExists(Contact contact) {
String name = contact.getName();
int contactCount = Contacts.size();
for (int i = 0; i < contactCount; i++) {
if (name.compareToIgnoreCase(Contacts.get(i).getName()) == 0)
return true;
}
return false;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.my_add, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (id) {
case R.id.action_search:
insert();
return true;
case R.id.action_done:
insert();
return true;
case R.id.action_cancel:
add_new();
// Toast.makeText(getApplicationContext(), "Search Clicked", Toast.LENGTH_SHORT).show();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void add_new(){
Intent intent = new Intent(this,contact_view.class);
startActivity(intent);
}
}
下面是我的databasehandler类
public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "contactManager",
TABLE_CONTACTS = "contacts",
KEY_ID = "id",
KEY_NAME = "name",
KEY_PHONE = "phone",
KEY_EMAIL = "email",
KEY_ADDRESS = "address",
KEY_IMAGEURI = "image";
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE " + TABLE_CONTACTS + "(" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_NAME + " TEXT," + KEY_PHONE + " TEXT," + KEY_EMAIL + " TEXT," + KEY_ADDRESS + " TEXT," + KEY_IMAGEURI + " TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
onCreate(db);
}
public void createContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, contact.getName());
values.put(KEY_PHONE, contact.getPhone());
values.put(KEY_EMAIL, contact.getEmail());
values.put(KEY_ADDRESS, contact.getAddress());
values.put(KEY_IMAGEURI, contact.get_imageURI().toString());
db.insert(TABLE_CONTACTS, null, values);
db.close();
}
public Contact getContact(int id) {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID, KEY_NAME, KEY_PHONE, KEY_EMAIL, KEY_ADDRESS, KEY_IMAGEURI }, KEY_ID + "=?", new String[] { String.valueOf(id) }, null, null, null, null );
if (cursor != null)
cursor.moveToFirst();
Contact contact = new Contact(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), Uri.parse(cursor.getString(5)));
db.close();
cursor.close();
return contact;
}
public void deleteContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
db.delete(TABLE_CONTACTS, KEY_ID + "=?", new String[] { String.valueOf(contact.getId()) });
db.close();
}
public int getContactsCount() {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CONTACTS, null);
int count = cursor.getCount();
db.close();
cursor.close();
return count;
}
public int updateContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, contact.getName());
values.put(KEY_PHONE, contact.getPhone());
values.put(KEY_EMAIL, contact.getEmail());
values.put(KEY_ADDRESS, contact.getAddress());
values.put(KEY_IMAGEURI, contact.get_imageURI().toString());
int rowsAffected = db.update(TABLE_CONTACTS, values, KEY_ID + "=?", new String[] { String.valueOf(contact.getId()) });
db.close();
return rowsAffected;
}
public List<Contact> getAllContacts() {
List<Contact> contacts = new ArrayList<Contact>();
SQLiteDatabase db = getWritableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CONTACTS, null);
if (cursor.moveToFirst()) {
do {
contacts.add(new Contact(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), Uri.parse(cursor.getString(5))));
}
while (cursor.moveToNext());
}
cursor.close();
db.close();
return contacts;
}
}
这是我的联系班级
public class Contact {
private String _name, _phone, _email, _address;
private Uri _imageURI;
private int _id;
public Contact(int id, String name, String phone, String email, String address, Uri imageURI){
_id = id;
_name = name;
_phone = phone;
_email = email;
_address = address;
_imageURI = imageURI;
}
public int getId() { return _id;}
public String getName(){
return _name;
}
public String getPhone(){
return _phone;
}
public String getEmail(){
return _email;
}
public String getAddress(){
return _address;
}
public Uri get_imageURI() { return _imageURI;}
}
它显示错误在这里
public void insert(){
Contact contact = new Contact(dbHandler.getContactsCount(),
String.valueOf(nameText.getText()),
String.valueOf(phoneText.getText()),
String.valueOf(emailText.getText()),
String.valueOf(addressText.getText()), imageUri);
if (!contactExists(contact)) {
dbHandler.createContact(contact);
Contacts.add(contact);
contactAdapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), String.valueOf(nameText.getText()) + " has been added to your Contacts!", Toast.LENGTH_SHORT).show();
return;
}
Toast.makeText(getApplicationContext(), String.valueOf(nameText.getText()) + " already exists. Please use a different name.", Toast.LENGTH_SHORT).show();
}
logcat的
07-23 04:08:24.267 2332-2332/codes.MUDALIapps.sameera.contact E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: codes.MUDALIapps.sameera.contact, PID: 2332
java.lang.NullPointerException
at codes.MUDALIapps.sameera.contact.Add_new.insert(Add_new.java:58)
at codes.MUDALIapps.sameera.contact.Add_new.onOptionsItemSelected(Add_new.java:91)
at android.app.Activity.onMenuItemSelected(Activity.java:2600)
at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1012)
at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
at com.android.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:546)
at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:115)
at android.view.View.performClick(View.java:4438)
at android.view.View$PerformClick.run(View.java:18422)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
07-23 04:08:26.823 2356-2356/codes.MUDALIapps.sameera.contact E/OpenGLRenderer﹕ Getting MAX_TEXTURE_SIZE from GradienCache
07-23 04:08:26.823 2356-2356/codes.MUDALIapps.sameera.contact E/OpenGLRenderer﹕ MAX_TEXTURE_SIZE: 16384
07-23 04:08:26.831 2356-2356/codes.MUDALIapps.sameera.contact E/OpenGLRenderer﹕ Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
07-23 04:08:26.831 2356-2356/codes.MUDALIapps.sameera.contact E/OpenGLRenderer﹕ MAX_TEXTURE_SIZE: 16384
Gride view clss
public class contact_view extends Activity {
DatabaseHandler mydb;
GridView data;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gride_view);
data = (GridView) findViewById(R.id.grid);
List<String> li = new ArrayList<String>();
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_spinner_item, li);
dataAdapter.setDropDownViewResource(R.layout.gride_view);
try{
// mydb = openOrCreateDatabase("contactManager.db",MODE_PRIVATE,null);
// Cursor cr = mydb.rawQuery("SELECT * FROM contacts",null);
Cursor cr = (Cursor) mydb.getAllContacts();
if(cr != null ){
if(cr.moveToFirst()) {
do {
String id = cr.getString(cr.getColumnIndex("id"));
String name = cr.getString(cr.getColumnIndex("name"));
li.add(id);
li.add(name);
data.setAdapter(dataAdapter);
} while (cr.moveToNext());
}
else {
Toast.makeText(getApplicationContext(),"There is no data",Toast.LENGTH_LONG).show();
}
}
cr.close();
mydb.close();
}catch (Exception e){
Toast.makeText(getApplicationContext(),"Error:"+ e.getMessage(),Toast.LENGTH_LONG).show();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.my_add, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (id) {
case R.id.action_search:
return true;
case R.id.action_call:
return true;
case R.id.action_send:
return true;
case R.id.action_mail:
return true;
case R.id.action_edit:
return true;
case R.id.action_delete:
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
答案 0 :(得分：2)
您需要初始化dbHandler。
在onCreate
dbHandler = new DatabaseHandler(this);
编辑1：
您不必在循环中设置适配器。设置适配器一次，并将项目添加到循环列表li中。循环完成后，调用dataAdapter.notifyDataSetChanged()以刷新Gridview。
编辑2：
我仍然没有看到您初始化contactsAdapter的位置。您只在dataAdapter中声明并初始化了onCreate。错误太多了。
答案 1 :(得分：0)
你应该首先初始化你的dbHandler变量 你可以在onCreate方法或插入方法的开头行完成。
答案 2 :(得分：0)
试试这个......
public class DatabaseHelpere extends SQLiteOpenHelper {
private static DatabaseHelpere o_instance = null;
public static final String DATABASE_NAME = "test_table";
public static final int DATABASE_VERSION = 1;
public SQLiteDatabase o_db = null;
public static final String Table1 = "parent_table1";
public static final String Table2 = "child_table2";
public DatabaseHelpere() {
super(AndroidContexte.getContext(), DATABASE_NAME, null,
DATABASE_VERSION);
o_db = getWritableDatabase();
}
public static DatabaseHelpere getInstance() {
if (o_instance == null) {
o_instance = new DatabaseHelpere();
}
return o_instance;
}
@Override
public void onCreate(SQLiteDatabase db) {
final String[] creatStatments = new String[] {
"create table "
+ Table1
+ " (_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,name TEXT ,nick_name TEXT , ran_no INTEGER , img_clm BLOB)",
"create table "
+ Table2
+ " (_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,name TEXT ,stander TEXT , roll INTEGER , ran_no_forn_k INTEGER , FOREIGN KEY (ran_no_forn_k) REFERENCES "+Table1+" (ran_no));)",
};
for (String sStmt : creatStatments) {
db.execSQL(sStmt);
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + Table1);
onCreate(db);
}
public SQLiteDatabase getDb() {
return o_db;
}
}
and then
public class AndroidContexte {
private static Context s_oContext;
/**
* Sets the Android context used for file access. Should be set
* at application startup, before the log is used.
* @param oContext Application context
*/
public static synchronized void setContext( Context oContext )
{
s_oContext = oContext;
}
/**
* Sets the Android context used for file access. Should be set
* at application startup, before the log is used.
* @param oContext Application context
*/
public static synchronized Context getContext()
{
return s_oContext;
}
}
在Activity中创建对象并在onCreate（）
中初始化 SQLiteDatabase sql_lite_db_obj;
ContentValues values ;
AndroidContexte.setContext(this);
sql_lite_db_obj = DatabaseHelpere.getInstance().getDb();
调用插入方法
insertData(edt_txt_nickname_var.getText().toString().trim(), edt_txt_class.getText().toString().trim() , random_number , ih.getBitmapAsByteArray(R.drawable.index1));
最后
private void insertData(String name , String class_s , int ran_num , byte[] img) {
if (values != null) {
values.clear();
}
if (sql_lite_db_obj == null) {
sql_lite_db_obj = DatabaseHelpere.getInstance().getDb();
}
values.put("name", name);
//values.put("nick_name", nikname);
values.put("nick_name", class_s);
values.put("ran_no", ran_num);
values.put("img_clm", img);
sql_lite_db_obj.insert(DatabaseHelpere.Table1, null, values);
}