尝试保存约会信息时，应用程序不断崩溃

Question

我正在为理发店构建一个应用程序，我现在正在创建约会并保存该约会中的数据，但是当我去单击添加创建约会时，应用程序崩溃了，我离开了这个错误;

E/CursorWindow: Failed to read row 0, column -1 from a CursorWindow which has 2 rows, 3 columns.
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: ie.app.barbershop, PID: 31270
                  java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                      at android.database.CursorWindow.nativeGetString(Native Method)
                      at android.database.CursorWindow.getString(CursorWindow.java:438)
                      at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
                      at ie.app.barbershop.TableControllerAppointments.read(TableControllerAppointments.java:46)
                      at ie.app.barbershop.Landing.readRecords(Landing.java:47)
                      at ie.app.barbershop.OnClickListenerCreateAppointment$1.onClick(OnClickListenerCreateAppointment.java:38)
                      at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:162)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:135)
                      at android.app.ActivityThread.main(ActivityThread.java:5254)
                      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:903)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
I/Process: Sending signal. PID: 31270 SIG: 9
Application terminated.

这是我的TableControllerAppointments课程.java

package ie.app.barbershop;
import android.content.Context;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import java.util.ArrayList;
import java.util.List;
public class TableControllerAppointments extends DatabaseHandler {
    public TableControllerAppointments(Context context) {
        super(context);
    }
    public boolean create(ObjectAppointment objectAppointments) {
        ContentValues values = new ContentValues();
        values.put("fullname", objectAppointments.fullName);
        values.put("contactno", objectAppointments.contactNumber);
        SQLiteDatabase db = this.getWritableDatabase();
        boolean createSuccessful = db.insert("appointments", null, values) > 0;
        db.close();
        return createSuccessful;
    }

    public List<ObjectAppointment> read() {
        List<ObjectAppointment> recordsList = new ArrayList<>();
        String sql = "SELECT * FROM Appointments ORDER BY id DESC";
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(sql, null);
        if (cursor.moveToFirst()) {
            do {
                String fullName = cursor.getString(cursor.getColumnIndex("firstname"));
                int contactNumber = Integer.parseInt(cursor.getString(cursor.getColumnIndex("contactno")));
                ObjectAppointment objectAppointment = new ObjectAppointment();
                objectAppointment.fullName = fullName;
                objectAppointment.contactNumber = contactNumber;
                recordsList.add(objectAppointment);
            } while (cursor.moveToNext());
        }
        cursor.close();
        db.close();
        return recordsList;
    }
    public int count() {
        SQLiteDatabase db = this.getWritableDatabase();
        String sql = "SELECT * FROM appointments";
        int recordCount = db.rawQuery(sql, null).getCount();
        db.close();
        return recordCount;
    }
}

这是我的OnClickListenerCreateAppointment课程.java

package ie.app.barbershop;
import android.view.View;
import android.content.Context;
import android.view.LayoutInflater;
import android.widget.EditText;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.widget.Toast;
public class OnClickListenerCreateAppointment implements View.OnClickListener {
    public ObjectAppointment objectAppointment;
    @Override
    public void onClick(View view){
        final Context context = view.getRootView().getContext();
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        final View formElementsView = inflater.inflate(R.layout.appointment_input_form, null, false);
        final EditText editTextFullName = formElementsView.findViewById(R.id.editTextFullName);
        final EditText editTextContactNumber = formElementsView.findViewById(R.id.editTextContactNumber);
        ObjectAppointment objectAppointment = new ObjectAppointment();

        new AlertDialog.Builder(context)


                .setView(formElementsView)
                .setTitle("Create Appointment")
                .setPositiveButton("Add",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {

                                String fullname = editTextFullName.getText().toString();
                                String contactno = editTextContactNumber.getText().toString();
                                ((Landing) context).countRecords();
                                ((Landing) context).readRecords();
                                dialog.cancel();
                            }
                        }).show();
            boolean createSuccessful = new TableControllerAppointments(context).create(objectAppointment);
                if(createSuccessful){
                    Toast.makeText(context, "Appointment Information was saved.", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(context, "Unable to save appointment information", Toast.LENGTH_SHORT).show();
        }

    }
}

这是我的着陆.java课

package ie.app.barbershop;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.ScrollView;
import android.widget.TextView;
import java.util.List;

public class Landing extends AppCompatActivity{
    public Button buttonProducts;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.content_landing);
        countRecords();
        buttonProducts = findViewById(R.id.buttonProducts);
        Button buttonCreateAppointment = findViewById(R.id.buttonCreateAppointment);
        buttonCreateAppointment.setOnClickListener(new OnClickListenerCreateAppointment());
        buttonProducts.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(Landing.this, Products.class));
            }
        });

    }
    public void readRecords() {
        LinearLayout linearLayoutRecords = findViewById(R.id.linearLayoutRecords);
        linearLayoutRecords.removeAllViews();
        List<ObjectAppointment> appointments = new TableControllerAppointments(this).read();
        if (appointments.size() > 0) {
            for (ObjectAppointment obj : appointments) {

                String fullName = obj.fullName;
                int contactNumber = obj.contactNumber;
                String textViewContents = fullName + " - " + contactNumber;
                TextView textViewAppointmentItem= new TextView(this);
                textViewAppointmentItem.setPadding(0, 10, 0, 10);
                textViewAppointmentItem.setText(textViewContents);
                textViewAppointmentItem.setTag(Integer.toString(contactNumber));
                linearLayoutRecords.addView(textViewAppointmentItem);
            }
        }
        else {
            TextView locationItem = new TextView(this);
            locationItem.setPadding(8, 8, 8, 8);
            locationItem.setText("No records yet.");
            linearLayoutRecords.addView(locationItem);
        }
    }
    public void countRecords(){
        int recordCount = new TableControllerAppointments(this).count();
        TextView textViewRecordCount = findViewById(R.id.textViewRecordCount);
        textViewRecordCount.setText(recordCount + " records found.");
    }
}

数据库处理程序类

   package ie.app.barbershop;
import android.database.sqlite.SQLiteOpenHelper;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;

public class DatabaseHandler extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 1;
    protected static final String DATABASE_NAME = "AppointmentDatabase";
    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE appointments " +
                "( id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                "fullname TEXT, " +
                "contactno NUMBER ) ";
        db.execSQL(sql);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String sql = "DROP TABLE IF EXISTS students";
        db.execSQL(sql);
        onCreate(db);
    }
}

Answer 1

-1 是从 getColumnIndex 返回的，这意味着列的名字在下一行的光标中不存在。

 String fullName = cursor.getString(cursor.getColumnIndex("firstname"));

您可以使用 ：- 创建表

String sql = "CREATE TABLE appointments " +
                "( id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                "fullname TEXT, " +
                "contactno NUMBER ) ";

其中列是 id 全名和联系人号。

--

修复

要修复此更改以使用 ：-

String fullName = cursor.getString(cursor.getColumnIndex("fullname"));

<小时 />

附加

最好还是将列和表名称定义为常量，并始终引用它们。

例如

public class DatabaseHandler extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 1;
    protected static final String DATABASE_NAME = "AppointmentDatabase";
    public static final String TABLE_NAME = "appointments";
    public static final String COL_ID = "id";
    public static final String COl_FULLNAME = "fullname";
    public static final String COL_CONTACTNO = "contactno";
    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE " + TABLE_NAME +
                "( " + COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COL_FULLNAME + " TEXT, " +
                COL_CONTACTNO + " NUMBER ) ";
        db.execSQL(sql);
    }
    .... and so on

后来作为一个例子：-

    String fullName = cursor.getString(cursor.getColumnIndex(DatabaseHandler.COL_FULLNAME));