Question

我想创建数据库，我有这个错误

package it.unimi.di.simplephone;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DBhelper extends SQLiteOpenHelper
{
  public static final String DBNAME="BILLBOOK";

public DBhelper(Context context) {
    super(context, DBNAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db)  
{
    db= SQLiteDatabase.openDatabase("Log", null, Context.MODE_PRIVATE);
    String q="CREATE TABLE "+DatabaseStrings.TBL_NAME+
            " ( _id INTEGER PRIMARY KEY AUTOINCREMENT," +
                DatabaseStrings.FIELD_NOME+" TEXT," +
                DatabaseStrings.FIELD_NUMERO+" TEXT)";
    db.execSQL(q);
}



@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
{  }

}

这是我的DBhelper课程。

这是我的活动课

package it.unimi.di.simplephone;

import android.app.ListActivity;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract.CommonDataKinds;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

public class MainActivity extends ListActivity{

   private ListAdapter mAdapter = null;

//database
private DBhelper dbhelper;
private Context ctx;
private SQLiteDatabase db;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //DATABASE
     dbhelper=new DBhelper(ctx);
     dbhelper.onCreate(db);

    Cursor c = getContentResolver().query(
            CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);

    String[] columns = new String[] { CommonDataKinds.Phone.DISPLAY_NAME };
    int[] names = new int[] { R.id.contact_name };

    mAdapter = new SimpleCursorAdapter(this, R.layout.row_layout, c,
            columns, names,
            SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);

    setListAdapter(mAdapter);

    Button button = (Button) findViewById(R.id.BtnComponi);
    button.setOnClickListener(new View.OnClickListener(){

        public void onClick(View v){
            Intent it=new Intent(MainActivity.this,componi.class);
            startActivity(it);

        }
    });

    Button log = (Button) findViewById(R.id.LastCall);
    log.setOnClickListener(new View.OnClickListener(){

        public void onClick(View v){
            Intent itlog=new Intent(MainActivity.this,log.class);
            startActivity(itlog);

        }
    });

}
@Override
protected void onStart() {
    super .onStart();
    Cursor c = getContentResolver().query(
            CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);

    String[] columns = new String[] { CommonDataKinds.Phone.DISPLAY_NAME };
    int[] names = new int[] { R.id.contact_name };

    mAdapter = new SimpleCursorAdapter(this, R.layout.row_layout, c,
            columns, names,
            SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);

    setListAdapter(mAdapter);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

    Cursor c = (Cursor) mAdapter.getItem(position);
    String phone = c.getString(c
            .getColumnIndex(CommonDataKinds.Phone.NUMBER));
    //database
    String nome= c.getString(c.getColumnIndex(CommonDataKinds.Phone.DISPLAY_NAME));

    //database

    db=dbhelper.getWritableDatabase();
    ContentValues cv=new ContentValues();
    cv.put("nome", nome);
    cv.put("numero", phone);
    try
    {
        db.insert(DatabaseStrings.TBL_NAME, null,cv);
    }
    catch (SQLiteException sqle)
    {

    }

    Intent i = new Intent(Intent.ACTION_CALL);
    i.setData(Uri.parse("tel:" + phone));
    startActivity(i);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);



    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}



}

错误是无法打开数据库..但是使用类助手中的函数opendatabase我创建数据库（如果不存在）..

感谢

Answer 1

我注意到的一些事情：

dbhelper=new DBhelper(ctx);
dbhelper.onCreate(db);

您不应该致电onCreate()课程的SQLiteOpenHelper。 Android在第一次创建此数据库时调用此方法。此外，您的崩溃可能是NullPointerException，因为您正在将null对象传递给此方法;成员字段db从未初始化。

@Override
public void onCreate(SQLiteDatabase db)  
{
    db= SQLiteDatabase.openDatabase("Log", null, Context.MODE_PRIVATE);
    String q="CREATE TABLE "+DatabaseStrings.TBL_NAME+
            " ( _id INTEGER PRIMARY KEY AUTOINCREMENT," +
                DatabaseStrings.FIELD_NOME+" TEXT," +
                DatabaseStrings.FIELD_NUMERO+" TEXT)";
    db.execSQL(q);
}

您已在此处打开第二个数据库文件，并为其添加了一个表格。但是你永远不会在当前数据库中创建一个表。这是故意的吗？如果没有，您应该使用在执行SQL时传递给您的db参数，因为那是SQLiteOpenHelper为您打开的参数。

如果第二个数据库文件是故意的，那么值得注意的是，因为你没有SQLiteOpenHelper来记录＆＃34; Log＆＃34;数据库，您只能使用SQLiteDatabase.openDatabase打开它，并且不会自动获取onCreate和onUpgrade个钩子。如果您只需要一个表，那么我可能会建议您在主数据库中使用该表。

错误数据库Sqlite无法打开数据库

1 个答案: