Question

我已经尝试过创建一个注册数据库，仅用于知识目的。但是，我的数据库似乎无法捕获任何数据。我已经对我的代码进行了三次检查，但无济于事。任何帮助将不胜感激。

DatabaseHelper.java

public class DatabaseHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "contacts.db";
public static final String TABLE_NAME = "contacts";
public static final String COLUMN_ID = "id";
public static final String COL_1 = "Name";
public static final String COL_2 = "Pass";
public static final String COL_3 = "email";
SQLiteDatabase db;

private static final String TABLE_CREATE = "create table contacts (id integer primary key not null , " +
        "name text not null, pass text not null, email text not null);";


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

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(TABLE_CREATE);
    this.db = db;

}

public void insertContact(Contact c)
{
    db = this.getWritableDatabase();
    ContentValues values = new ContentValues();

    String query = "select * from contacts";
    Cursor cursor = db.rawQuery(query , null);
    int count = cursor.getCount();

    values.put(COLUMN_ID , count);
    values.put(COL_1 , c.getName());
    values.put(COL_2 , c.getPass());
    values.put(COL_3 , c.getEmail());

    db.insert(TABLE_NAME , null , values);
    db.close();
}

public String searchPass(String name)
{
    db = this.getReadableDatabase();
    String query = "select Name, Pass from " + TABLE_NAME;
    Cursor cursor = db.rawQuery(query , null);
    String a, b;
    b = "not found";

    if(cursor.moveToFirst())
    {
        do {
            a = cursor.getString(0);


            if(a.equals(name))
            {
                b = cursor.getString(1);
                break;
            }
        }
        while (cursor.moveToNext());
    }

    return b;

}




@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    String query = "DROP TABLE IF EXISTS " + TABLE_NAME;
    db.execSQL(query);
    this.onCreate(db);

}
}

Register.java

public class Register extends AppCompatActivity {

DatabaseHelper helper = new DatabaseHelper(this);

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

public void onRegisterClick(View v)
{
 if (v.getId()== R.id.button17){
     EditText name = (EditText)findViewById(R.id.editText8);
     EditText email = (EditText)findViewById(R.id.editText9);
     EditText pass1 = (EditText)findViewById(R.id.editText10);
     EditText pass2 = (EditText)findViewById(R.id.editText11);

     String namestr = name.getText().toString();
     String emailstr = email.getText().toString();
     String pass1str = pass1.getText().toString();
     String pass2str = pass2.getText().toString();

     if (!pass1str.equals(pass2str))
     {
         Toast pass = Toast.makeText(Register.this , "Password don't match" , Toast.LENGTH_SHORT);
         pass.show();
     }
     else
     {
         Contact c = new Contact();
         c.setName(namestr);
         c.setPass(pass1str);
         c.setEmail(emailstr);

         helper.insertContact(c);
     }


 }
 }

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

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

Contacts.java

public class Contact {
String name,pass,email;

public void setName(String name)
{

    this.name = name;
}

public String getName()
{

    return this.name;
}

public void setPass(String pass)
{
    this.pass = pass;
}

public String getPass()
{

    return this.pass;
}

public void setEmail(String email)
{
    this.email = email;
}

public String getEmail()
{

    return this.email;
}
}

Answer 1

您没有在数据库中插入正确的数据。您的方法应如下所示：

public void insertContact(Contact c)
{
   db = this.getWritableDatabase();
   ContentValues values = new ContentValues();

   values.put(COL_1 , c.getName());
   values.put(COL_2 , c.getPass());
   values.put(COL_3 , c.getEmail());

   db.insert(TABLE_NAME , null , values);
   db.close();
}

要编辑联系人，请添加以下方法：

public void updateContact(Contact c, int id)
{
   db = this.getWritableDatabase();
   ContentValues values = new ContentValues();

   values.put(COL_1 , c.getName());
   values.put(COL_2 , c.getPass());
   values.put(COL_3 , c.getEmail());

   db.update(TABLE_NAME, values, "id = ? ", new String[]{Integer.toString(id)});
   db.close();
}

其中＆＃34; id＆＃34;是您要更改它的项目的唯一ID。

无法将数据放入SQLite

1 个答案: