Fehler in sqlite Datenbankkonnektivität

Question

bitte helfen Sie mir, den Fehler zu beheben. Ich erhalte diesen Fehler in Android Studio. Ich bin neu in der Android-Entwicklung. Problem mit Registrierung..nicht in der Lage Daten in die Datenbank einzufügen. Der Fehler ist:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.rawQuery(java.lang.String, java.lang.String[])' on a null object reference 

DB_Connectivity

package com.freedomkitchen.sonali.freedomkitchenAndroidApp; 
import android.annotation.SuppressLint; 
import android.content.Intent; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.os.Bundle; 
import android.support.v7.app.ActionBar; 
import android.support.v7.app.AppCompatActivity; 

import android.view.View; 
import android.widget.Toast; 
import com.freedomkitchen.sonali.freedomkitchenAndroidApp.NewUserWelcome; 
import java.util.logging.Handler; 
import java.util.logging.LogRecord; 


public class DB_Connectivity extends AppCompatActivity { 

    SQLiteDatabase myDB; 
    int user_ID; 

    private static final boolean AUTO_HIDE = true; 


    private static final int AUTO_HIDE_DELAY_MILLIS = 3000; 


    private static final int UI_ANIMATION_DELAY = 300; 
    private final Handler mHideHandler = new Handler() { 
     @Override 
     public void close() { 

     } 

     @Override 
     public void flush() { 

     } 

     @Override 
     public void publish(LogRecord record) { 

     } 
    }; 
    private View mContentView; 
    private final Runnable mHidePart2Runnable = new Runnable() { 
     @SuppressLint("InlinedApi") 
     @Override 
     public void run() { 

      mContentView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE 
        | View.SYSTEM_UI_FLAG_FULLSCREEN 
        | View.SYSTEM_UI_FLAG_LAYOUT_STABLE 
        | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY 
        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION 
        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION); 
     } 
    }; 
    private View mControlsView; 
    private final Runnable mShowPart2Runnable = new Runnable() { 
     @Override 
     public void run() { 
      // Delayed display of UI elements 
      ActionBar actionBar = getSupportActionBar(); 
      if (actionBar != null) { 
       actionBar.show(); 
      } 
      mControlsView.setVisibility(View.VISIBLE); 
     } 
    }; 
    private boolean mVisible; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 
     myDB = openOrCreateDatabase("FreedomKitchenDB.db", MODE_PRIVATE, null); 
     myDB.execSQL("CREATE TABLE IF NOT EXISTS User_Details(User_ID INTEGER PRIMARY KEY," + 
       "First_Name TEXT,Last_Name TEXT,Gender TEXT ,Age TEXT,Country TEXT);"); 
     myDB.execSQL("CREATE TABLE IF NOT EXISTS Login_Details(User_ID INTEGER," + 
       "Username TEXT,Password TEXT,FOREIGN KEY(User_ID) REFERENCES User_Details(User_ID));"); 

    } 


    @Override 
    protected void onPostCreate(Bundle savedInstanceState) { 
     super.onPostCreate(savedInstanceState); 

    } 

    public void UserLogin(String username,String password) { 

     myDB.execSQL("Select User_ID from Login_Details where Username=" + username + "and Password=" + password+");"); 

     Cursor cursor_one = myDB.rawQuery("Select * from User_Details", null); 
     int rows = cursor_one.getCount(); 
     cursor_one.moveToFirst(); 
     if (rows == 0) { 
      Toast.makeText(getApplicationContext(), "Incorrect Username or Password. Please try again.", Toast.LENGTH_SHORT).show(); 
     } else if (rows == 1) { 
      Intent i = new Intent(getApplicationContext(), FreedomKitchenMenu.class); 
      startActivity(i); 
     } 
    } 

    public void Registration(String first_name,String last_name,String age,String gender,String country,String username,String password){ 
     int user_ID=0; 
     Cursor cursor_one = myDB.rawQuery("Select * from User_Details", null); 
     int rows = cursor_one.getCount(); 
     cursor_one.moveToFirst(); 
     user_ID=rows+1; 
     myDB.execSQL("INSERT INTO User_Details(User_ID,User_FirstName,User_LastName,Gender,Age,Country)VALUES("+user_ID+"','"+first_name+"','" + last_name + "','" + gender + "','" + age + "','" + country + ");"); 
     myDB.execSQL("INSERT INTO Login_Details(User_ID,Username,Password)VALUES(" + user_ID + "','" + username+ "','" + password + ");"); 
     Intent i=new Intent(getApplicationContext(),NewUserWelcome.class); 
     startActivity(i); 

    } 

} 

Logcat

04-22 07:58:57.111 31243-31243/? E/Zygote: v2 
04-22 07:58:57.121 31243-31243/? E/SELinux: [DEBUG] get_category: variable seinfo: default sensitivity: NULL, cateogry: NULL 
04-22 07:59:08.501 31243-31243/com.freedomkitchen.sonali.freedomkitchen E/ViewRootImpl: sendUserActionEvent() mView == null 
04-22 07:59:12.971 31243-31243/com.freedomkitchen.sonali.freedomkitchen E/ViewRootImpl: sendUserActionEvent() mView == null 
04-22 07:59:33.221 31243-31243/com.freedomkitchen.sonali.freedomkitchen E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.freedomkitchen.sonali.freedomkitchen, PID: 31243 
java.lang.IllegalStateException: Could not execute method for android:onClick 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293) 
    at android.view.View.performClick(View.java:5076) 
    at android.view.View$PerformClick.run(View.java:20279) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:135) 
    at android.app.ActivityThread.main(ActivityThread.java:5910) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200) 
Caused by: java.lang.reflect.InvocationTargetException 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
    at android.view.View.performClick(View.java:5076)  
    at android.view.View$PerformClick.run(View.java:20279)  
    at android.os.Handler.handleCallback(Handler.java:739)  
    at android.os.Handler.dispatchMessage(Handler.java:95)  
    at android.os.Looper.loop(Looper.java:135)  
    at android.app.ActivityThread.main(ActivityThread.java:5910)  
    at java.lang.reflect.Method.invoke(Native Method)  
    at java.lang.reflect.Method.invoke(Method.java:372)  
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405)  
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)  
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.rawQuery(java.lang.String, java.lang.String[])' on a null object reference 
    at com.freedomkitchen.sonali.freedomkitchenAndroidApp.DB_Connectivity.Registration(DB_Connectivity.java:122) 
    at com.freedomkitchen.sonali.freedomkitchenAndroidApp.Registration.Reg(Registration.java:93) 
    at java.lang.reflect.Method.invoke(Native Method)  
    at java.lang.reflect.Method.invoke(Method.java:372)  
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)  
    at android.view.View.performClick(View.java:5076)  
    at android.view.View$PerformClick.run(View.java:20279)  
    at android.os.Handler.handleCallback(Handler.java:739)  
    at android.os.Handler.dispatchMessage(Handler.java:95)  
    at android.os.Looper.loop(Looper.java:135)  
    at android.app.ActivityThread.main(ActivityThread.java:5910)  
    at java.lang.reflect.Method.invoke(Native Method)  
    at java.lang.reflect.Method.invoke(Method.java:372)  
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405)  
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)  

auf Klick

public void Reg(View v){ 
    Spinner Gender,Country; 
    EditText FName,LName,Username,Password,Age; 
    FName = (EditText)findViewById(R.id.FirstName_et); 
    LName = (EditText)findViewById(R.id.LastName_et); 
    Gender=(Spinner)findViewById(R.id.spinnerGender); 
    Age=(EditText)findViewById(R.id.Age_et); 
    Country=(Spinner)findViewById(R.id.spinnerCountry); 
    Password =(EditText)findViewById(R.id.Password_et); 
    Username =(EditText)findViewById(R.id.Username_et); 
    first_name=FName.getText().toString(); 
    last_name=LName.getText().toString(); 
    age=Age.getText().toString(); 
    user_name=Username.getText().toString(); 
    pass_word=Password.getText().toString(); 
    gender=Gender.getSelectedItem().toString(); 
    country=Country.getSelectedItem().toString(); 
    DB_Connectivity mydb=new DB_Connectivity(); 
    mydb.Registration(first_name,last_name,age,gender,country,user_name,pass_word); 
} 

Answer 1

Sie haben wie zu kodieren unter

public class DBHelper extends SQLiteOpenHelper { 

public static final String DATABASE_NAME = "FreedomKitchenDB.db"; 
private static final int DATABASE_VERSION =1; 
//********** LOGIN TABLE COLUMNS ************* 

public static final String LOGIN_TABLE_NAME = "login_details"; 
public static final String LOGIN_COLUMN_ID = "user_id"; 
public static final String LOGIN_COLUMN_USERNAME = "username"; 
public static final String LOGIN_COLUMN_PASSWORD = "password"; 

//********** REGISTRATION TABLE COLUMNS ************* 

public static final String REG_TABLE_NAME = "user_details"; 
public static final String REG_COLUMN_ID = "user_id"; 
public static final String REG_COLUMN_FIRST_NAME = "first_name"; 
public static final String REG_COLUMN_LAST_NAME = "last_name"; 
public static final String REG_COLUMN_GENDER = "gender"; 
public static final String REG_COLUMN_AGE = "age"; 
public static final String REG_COLUMN_COUNTRY = "country"; 


public DBHelper(Context context) 
{ 
    super(context, DATABASE_NAME, null,DATABASE_VERSION); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    // TODO Auto-generated method stub 
    String CREATE_REG_TABLE="CREATE TABLE " +REG_TABLE_NAME+"("+REG_COLUMN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+REG_COLUMN_FIRST_NAME+" TEXT,"+REG_COLUMN_LAST_NAME+" TEXT,"+REG_COLUMN_GENDER+" TEXT,"+REG_COLUMN_AGE+" TEXT,"+REG_COLUMN_COUNTRY+" TEXT)"; 
    db.execSQL(CREATE_REG_TABLE); 
    String CREATE_LOGIN_TABLE="CREATE TABLE " + LOGIN_TABLE_NAME + "(" + LOGIN_COLUMN_ID + " INTEGER," + LOGIN_COLUMN_USERNAME + " TEXT," + LOGIN_COLUMN_PASSWORD + " TEXT,FOREIGN KEY(" + LOGIN_COLUMN_ID + ") REFERENCES " + REG_TABLE_NAME + "(" + REG_COLUMN_ID + "))"; 
    db.execSQL(CREATE_LOGIN_TABLE); 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    // TODO Auto-generated method stub 
    db.execSQL("DROP TABLE IF EXISTS contacts"); 
    onCreate(db); 
} 



public boolean insertUserDetail (String first_name,String last_name,String age,String gender,String country,String username,String password) 
{ 
    SQLiteDatabase db = this.getWritableDatabase(); 
    ContentValues contentValues = new ContentValues(); 
    contentValues.put(REG_COLUMN_FIRST_NAME, first_name); 
    contentValues.put(REG_COLUMN_LAST_NAME, last_name); 
    contentValues.put(REG_COLUMN_GENDER, gender); 
    contentValues.put(REG_COLUMN_AGE, age); 
    contentValues.put(REG_COLUMN_COUNTRY, country); 
    ContentValues mContentValues1=new ContentValues(); 
    mContentValues1.put(LOGIN_COLUMN_USERNAME,username); 
    mContentValues1.put(LOGIN_COLUMN_PASSWORD,password); 
    db.insert(LOGIN_TABLE_NAME, null, mContentValues1); 
    db.insert(REG_TABLE_NAME, null, contentValues); 
    return true; 
} 

public boolean Login(String username, String password) throws SQLException 
{ 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor mCursor = db.rawQuery("SELECT * FROM " + LOGIN_TABLE_NAME + " WHERE "+LOGIN_COLUMN_USERNAME+"=? AND "+LOGIN_COLUMN_PASSWORD+"=?", new String[]{username,password}); 
    if (mCursor != null) { 
     if(mCursor.getCount() > 0) 
     { 
      return true; 
     } 
    } 
    return false; 
}}