插入值到SQLite數據庫？ java.lang.NullPointerException

Question

我想插入一些值到我的數據庫。 但我的代碼給「java.lang.NullPointerException」錯誤。 我是新來的android和我無法修復這個錯誤。任何人都可以幫忙嗎？下面

是我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

是我的數據庫處理器類

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; 
} 
} 

這是我的聯繫類

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;} 

} 

它顯示的錯誤是在這裏

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視圖CLSS

公共類contact_view延伸活動{

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); 
    } 
} 
    } 

Answer 1

需要初始化dbHandler。

在onCreate

dbHandler = new DatabaseHandler(this); 

編輯1：

你不必在一個循環中設置適配器。設置適配器一次並添加項目以循環列出li。循環完成後，請致電dataAdapter.notifyDataSetChanged()刷新Gridview。

編輯2：

我還沒有看到，你已經初始化contactsAdapter。您只有dataAdapter已在onCreate中聲明和初始化。錯誤太多了。

Answer 2

你應該首先初始化你的dbHandler變量。
你可以在你的onCreate方法或插入方法的開始行執行它。

Answer 3

試試這個.....

  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; 
} 
} 

在活動創建對象和的onCreate（）

 SQLiteDatabase sql_lite_db_obj; 
    ContentValues values ; 
     AndroidContexte.setContext(this);  
     sql_lite_db_obj = DatabaseHelpere.getInstance().getDb(); 

通話插入方法初始化

insertData(edt_txt_nickname_var.getText().toString().trim(), edt_txt_class.getText().toString().trim() , random_number , ih.getBitmapAsByteArray(R.drawable.index1)); 

最後

  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); 

}