致命异常，Java lang空指针异常

Question

My following code shows no errors, yet does not execute.

package my.project.mil;

import android.content.Context;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class Cbdata extends MainActivity {

    public String str;

    public void onReceive(Context context, Intent intent) {
        //---get the CB message passed in---
        Bundle bundle = intent.getExtras();        
        SmsCbMessage[] msgs = null;
        str = "";            
        if (bundle != null)  {
            //---retrieve the SMS message received---
            Object[] pdus = (Object[]) bundle.get("pdus");
            msgs = new SmsCbMessage[pdus.length];            
            for (int i=0; i<msgs.length; i++) {
                msgs[i] = SmsCbMessage.createFromPdu((byte[])pdus[i]);                
                str += "CB " + msgs[i].getGeographicalScope() + msgs[i].getMessageCode() + msgs[i].getMessageIdentifier() + msgs[i].getUpdateNumber();                     
                str += " :";
                str += msgs[i].getMessageBody().toString();
                str += "\n";        
            }}
    }

    SQLiteDatabase cd = openOrCreateDatabase("MLIdb", MODE_WORLD_READABLE, null);



    Button submit;
Button viewdb;
EditText name;

@Override
    public void onCreate(Bundle savedInstanceState)
{
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.seventh);

    viewdb = (Button) findViewById(R.id.viewdb);
    submit = (Button) findViewById(R.id.submit);
    name = (EditText) findViewById(R.id.name);

    submit.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {

            String locname = name.getText().toString();
            if (locname.length()>0)
            {

                cd.execSQL("CREATE TABLE IF NOT EXITSTS MLITable (CblocationCode INT(10), CblocationName VARCHAR);");
                cd.execSQL("INSERT INTO MLITable VALUES (' ',' ');" +str +locname);
                Toast.makeText(getBaseContext(), "value successfully    entered.", Toast.LENGTH_LONG).show();
            }
            else
            {
                Toast.makeText(getBaseContext(), "Please enter the location name, for example 'Home'.", Toast.LENGTH_LONG).show();
            }

        }
    });

    cd.close();

    viewdb.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            // here comes the code for viewing the database


        }
    });
}

}

and my error log looks as follows, I've also checked my manifest and MainActivity files yet no luck.

My code is supposed to collect users cell tower area code and save that on a database with users choice of the name, that databases consists of two attributes one the name of the location which is collected from the user and second the cell broadcast tower information which is been obtained from the onReceive method, individually the onReceive method works fine.

This problem has occurred only when I've integrated database to my code.

Thank you.

Answer 1

SQLiteDatabase cd = openOrCreateDatabase("MLIdata", MODE_WORLD_WRITEABLE, null);

尝试将其替换为

SQLiteDatabase cd = openOrCreateDatabase("MLIdata", MODE_WORLD_WRITEABLE);

Answer 2

My Mistakes in the above code,

1. cd not all created, due to wrong method of connecting database.
2. EXISTS misspelled.
3. Wrong method for insert.

The final correct code is,

public class Cbdata extends MainActivity {

    public String str;

    public void onReceive(Context context, Intent intent) {
        //---get the CB message passed in---
        Bundle bundle = intent.getExtras();        
        SmsCbMessage[] msgs = null;
        str = "";            
        if (bundle != null)  {
            //---retrieve the SMS message received---
            Object[] pdus = (Object[]) bundle.get("pdus");
            msgs = new SmsCbMessage[pdus.length];            
            for (int i=0; i<msgs.length; i++) {
                msgs[i] = SmsCbMessage.createFromPdu((byte[])pdus[i]);                
                str += "CB " + msgs[i].getGeographicalScope() + msgs[i].getMessageCode() + msgs[i].getMessageIdentifier() + msgs[i].getUpdateNumber();                     
                str += " :";
                str += msgs[i].getMessageBody().toString();
                str += "\n";        
            }}
}

Button submit;
Button viewdb;
EditText name;

@Override
public void onCreate(Bundle savedInstanceState)
{
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.seventh);



    viewdb = (Button) findViewById(R.id.viewdb);
    submit = (Button) findViewById(R.id.submit);
    name = (EditText) findViewById(R.id.name);

    submit.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {

            String locname = name.getText().toString();
            if (locname.length()>0)
            {
                SQLiteDatabase cd = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null);
                cd.execSQL("CREATE TABLE IF NOT EXISTS MLITable (CblocationCode INT(10), CblocationName VARCHAR);");
                cd.execSQL("INSERT INTO MLITable VALUES ('"+str+ "','"+locname+ "');");
                Toast.makeText(getBaseContext(), "value successfully entered.", Toast.LENGTH_LONG).show();
                cd.close();
            }
            else
            {
                Toast.makeText(getBaseContext(), "Please enter the location name, for example 'Home'.", Toast.LENGTH_LONG).show();
            }

        }
    });



    viewdb.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            // here comes the code for viewing the database


        }
    });
}



}