Question

我使用SQLite数据库来保存用户信息，例如用户名密码年龄性别高度等数据库似乎工作正常（调试时没有错误或异常）但是当我去检索单个用户和他/她的详细信息时，应用程序只是在单击按钮后停止。我有一个databasehandler java文件，其中包含用于单个用户检索的方法和一个带有setter和getter方法的Registerdetails文件。
该按钮的onclicklistner设置为名为Userinfo()的方法。用户界面有一个edittext框用于输入id，一个按钮和一个textview来显示结果我的问题是我的查询错误或是我的数据库？

RegisterDetails.java

public class Registerdetails {
int _id;
String _user_name;
String _password;
String _gender;
double _height;
int _age;

public Registerdetails(){}
public Registerdetails(int _id, String _user_name,String _password, String _gender, double _height, int _age){
    this._user_name = _user_name;
    this._password = _password;
    this._age = _age;
    this._gender = _gender;
    this._height = _height;
    this._id = _id;



}
public int getID(){
    return this._id;
}
public void setID(int id){
    this._id = id;
}
public String get_user_name(){
    return this._user_name;
}
public void set_user_name(String user_name){
    this._user_name = user_name;
}
public String get_password(){
    return this._password;
}
public void set_password(String password){
    this._password = password;
}
public String get_gender(){
    return this._gender;
}
public void set_gender(String gender){
    this._user_name = gender;
}
public int get_age(){
    return this._age;
}
public void set_age(int age){
    this._age = age;
}
public double get_height(){
    return this._height;
}
public void set_height(double height){
    this._height = height;
}

}

DatabaseHandler.java

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import com.example.john.databasetest.Product;
import com.example.john.databasetest.Registerdetails;

public class DatabaseHandler extends SQLiteOpenHelper {
    //DATABASE VERSION
    private static final int DATABASE_VERSION = 1;
    //DATABASE NAME
    private static final String DATABASE_NAME = "Appdatabase";
    //TABLE NAMES
    private static final String TABLE_REGISTER = "Register_Details";

    //REGISTER COLUMN NAMES
    private static final String KEY_USERID = "UserID";
    private static final String KEY_USERNAME = "Username";
    private static final String KEY_PASSWORD = "Password";
    private static final String KEY_AGE = "Age";
    private static final String KEY_GENDER = "Gender";
    private static final String KEY_HEIGHT = "Height";


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


    public void onCreate(SQLiteDatabase db){

        String CREATE_REGISTERDETAILS_TABLE = "CREATE TABLE " + TABLE_REGISTER + " ( "+ KEY_USERID + " INTEGER PRIMARY KEY , " + KEY_USERNAME + " TEXT, " +
                KEY_PASSWORD + " TEXT, " +
                KEY_GENDER + " TEXT, " +
                KEY_HEIGHT + " DOUBLE, " +
                KEY_AGE + " INTEGER, " +
                );";
        //CREATING REQUIRED TABLES
        db.execSQL(CREATE_REGISTERDETAILS_TABLE);


    }
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        //ON UPGRADE DROP THE OLDER TABLES
        db.execSQL("DROP TABLE IF EXISTS" + TABLE_REGISTER);
        onCreate(db);
    }
    //query for retrieving a single register
    Registerdetails get_userinfo (int id) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_REGISTER, new String[] { KEY_USERID,
                        KEY_USERNAME, KEY_PASSWORD }, KEY_USERID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);

        if(cursor != null)
            cursor.moveToFirst();
        Registerdetails user_info  = new Registerdetails(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2),cursor.getString(3), cursor.getDouble(4),
                cursor.getDouble(5));
        cursor.close();
        return user_info;

    }

}

Home.java

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ScrollView;
import android.widget.TextView;

import java.util.List;


public class Home extends ActionBarActivity {
    Button btn;
    TextView dbtxt;
    EditText idedit;
    int id;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        btn = (Button) findViewById(R.id.btndb);
        dbtxt = (TextView) findViewById(R.id.txtdb);

        DatabaseHandler db = new DatabaseHandler(this);
        Log.d("Inserting: ", "Inserting ..");
        db.addRegistered_user(new Registerdetails(0, "steve", "2345", "Male", 182.0, 21));
        db.addRegistered_user(new Registerdetails(1, "kevin", "1234","Male", 186.0,20));
        db.addRegistered_user(new Registerdetails(2, "paul", "5555","Male", 178.0, 86.0, 87.5, 1.5,20,0.0,0.0,0.0,0.0,0.0,0.0,0.0, 600.00));

    }

    public void Userinfo(){

        idedit = (EditText) findViewById(R.id.IDedit);
        id = Integer.parseInt(idedit.getText().toString());
        DatabaseHandler db = new DatabaseHandler(this);
        Registerdetails user = db.get_userinfo(id);
        String Log = "Id: " + user.getID() + "\nUsername: " + user.get_user_name() + "Password: " + user.get_password();
        dbtxt.setText(Log);

    }



    @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_home, 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);
    }
}

Main_activity.xml

<TextView
    android:layout_width="300dp"
    android:layout_height="80dp"
    android:id="@+id/txtdb"
    android:backgroundTint="#ff75ff2f"
    android:text="Results"
    android:layout_centerVertical="true"
    android:layout_centerHorizontal="true"
    android:textAlignment="center" />

<Button
    android:layout_width="100dp"
    android:layout_height="100dp"
    android:text="PRESS"
    android:id="@+id/btndb"
    android:onClick="Viewuserinfo"
    android:layout_below="@+id/txtdb"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="41dp" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:ems="10"
    android:id="@+id/IDedit"
    android:layout_above="@+id/txtdb"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="82dp" />

Answer 1

1 - 删除多余的逗号：

KEY_AGE + " INTEGER, " + );";

在创建表格时，您应该收到错误如果没有，则表示您更改了表结构，但仍然看到旧表。

这是因为您没有通知您的应用程序数据库已更新。

事实上，你的

private static final int DATABASE_VERSION = 1;

仍 1 。

为了使onUpgrade()方法触发，您必须增加该值即，将其更改为 2 ：

private static final int DATABASE_VERSION = 2;

2 - 您在此处插入了太多列值：

db.addRegistered_user(new Registerdetails(2, "paul", "5555","Male", 178.0, 86.0, 87.5, 1.5,20,0.0,0.0,0.0,0.0,0.0,0.0,0.0, 600.00));

您只能在表格中插入尽可能多的列。

Answer 2

尝试重用db DatabaseHandler

public class Home extends ActionBarActivity {
    Button btn;
    TextView dbtxt;
    EditText idedit;
    int id;
    DatabaseHandler db; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        db = new DatabaseHandler(this);

        btn = (Button) findViewById(R.id.btndb);
        dbtxt = (TextView) findViewById(R.id.txtdb);

        Log.d("Inserting: ", "Inserting ..");
        db.addRegistered_user(new Registerdetails(0, "steve", "2345", "Male", 182.0, 21));
        db.addRegistered_user(new Registerdetails(1, "kevin", "1234","Male", 186.0,20));
        db.addRegistered_user(new Registerdetails(2, "paul", "5555","Male", 178.0, 86.0, 87.5, 1.5,20,0.0,0.0,0.0,0.0,0.0,0.0,0.0, 600.00));

    }

    public void Userinfo(){

        idedit = (EditText) findViewById(R.id.IDedit);
        id = Integer.parseInt(idedit.getText().toString());
        // reuse the db object
        Registerdetails user = db.get_userinfo(id);
        String Log = "Id: " + user.getID() + "\nUsername: " + user.get_user_name() + "Password: " + user.get_password();
        dbtxt.setText(Log);

    }

Android SQLite查询问题

2 个答案: