java - android 中的 SQL 数据库，请求索引 -1，大小为 0

Question

我一直在开发一个 Android 应用程序，它需要从 SQL 数据库检索一些信息。最初我试图在databaseHelper1类中形成一个名为getRemainingAmount()的函数来做到这一点，但这导致了错误

FATAL EXCEPTION: main Process: com.carrot.wallet, PID: 30591 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.carrot.wallet/com.carrot.wallet.MainActivity}: android.view.InflateException: Binary XML file line #10 in com.carrot.wallet:layout/activity_main: Binary XML file line #10 in com.carrot.wallet:layout/activity_main: Error inflating class fragment at

之后，当我尝试从 addTransaction 类获取数据时，我开始收到以下错误:

2020-05-30 09:25:12.946 11239-11239/com.carrot.wallet E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.carrot.wallet, PID: 11239
    android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0
        at android.database.AbstractCursor.checkPosition(AbstractCursor.java:468)
        at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
        at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
        at com.carrot.wallet.AddTransaction$4.onClick(AddTransaction.java:102)
        at android.view.View.performClick(View.java:6294)
        at android.view.View$PerformClick.run(View.java:24770)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

这是我的databaseHeleper1类，其中包含函数getRemainingAmount()

package com.carrot.wallet.Database;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

import androidx.annotation.Nullable;

public class DatabaseHelper1 extends SQLiteOpenHelper {

    private static final int version = 3;
    private static final String name = "YEAR_DETAILS";
    private static final String COL0 = "YEAR";
    private static final String COL1 = "MONTH";
    private static final String COL2 = "SPENT";
    private static final String COL3 = "REMAINING";
    private static final String TAG = "Database Helper 1";

    public DatabaseHelper1(@Nullable Context context) {
        super(context, name, null, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.d(TAG , "Database 1 is being created");
        String create_table = "CREATE TABLE "+name+"("+
                COL0+" INTEGER, "+
                COL1+" TEXT, "+
                COL2+" DOUBLE, "+
                COL3+" DOUBLE);";
        db.execSQL(create_table);
    }

    @Override
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS "+name);
        onCreate(db);
    }

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

    private boolean createMonth(String month , String year){
        Log.d(TAG , "month row is being created");
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COL0 , year);
        contentValues.put(COL1 , month);
        contentValues.put(COL2 , 0.0);
        contentValues.put(COL3 , 0.0);
        long result = db.insert(name,null , contentValues);
        return result != -1;
    }

    public boolean spentChange(String month , String year , Double newAmount){
        Log.d(TAG , "spent amount is being changed");
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COL2 , newAmount);
        long result = db.update(name, values , "MONTH = ? AND YEAR = ?", new String[]{month , year});
        return  result != -1;
    }

    public boolean remainingChange(String month ,String year, Double newAmount){
        Log.d(TAG , "Remaining amount is being changed");
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues =new ContentValues();
        contentValues.put(COL3 , newAmount);
        long result = db.update(name , contentValues , "MONTH = ? AND YEAR = ?" , new String[]{month , year});
        return result != -1;
    }


    public void checkExistance(String month, String year){
        Log.d(TAG , "Checking if month already exits");
        SQLiteDatabase database = this.getWritableDatabase();
        Cursor cur =  database.query(name , null , "MONTH = ? AND YEAR = ?" , new String[]{month , year} , null , null , null);
        System.out.println(cur);
        if(cur.getCount() <= 0) {
            boolean b = createMonth(month , year);
            if(b)
                Log.d(TAG , "checkExistance: failed to create month");
            else
                Log.d(TAG, "checkExistance: month created successfully");
        }
    }

    public Cursor getdata(){
        SQLiteDatabase db = this.getReadableDatabase();
        String query = "SELECT * FROM YEAR_DETAILS;";
        return db.rawQuery(query , null);
    }

    public Cursor getSpentAmount(String month , String year){
        SQLiteDatabase db = this.getWritableDatabase();
        String query = "SELECT * FROM YEAR_DETAILS WHERE MONTH = " + month+ " AND YEAR = "+year;
        return db.rawQuery(query , null);
    }

    public Cursor getRemainingAmount(String month , String year){
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cur =  db.query(name , new String[]{COL3} , "MONTH = ? AND YEAR = ?" , new String[]{month , year} , null , null , null);
        return cur;
    }


}

AddTransaction 类(我在其中检索数据)

package com.carrot.wallet;

import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;

import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;


import com.carrot.wallet.ArrayListClasses.add_transaction_data;
import com.carrot.wallet.Database.DatabaseHelper1;
import com.carrot.wallet.Database.DatabaseHelper2;
import com.carrot.wallet.recyclerview.at_btn_adapter;

import java.util.ArrayList;
import java.util.Calendar;

import com.carrot.wallet.recyclerview.onClickRecyclerButtion;

public class AddTransaction extends AppCompatActivity {


    int type1 ;
    int type2;
    double amount;
    ArrayList<add_transaction_data> data;
    Context context;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_transaction);
        ActionBar actionBar = getSupportActionBar();
        assert actionBar != null;
        actionBar.hide();
        populateList();

        final ImageButton cancel = findViewById(R.id.at_btn_cancel);
        final EditText EditAmount = findViewById(R.id.at_enter_amount);
        ImageButton save = findViewById(R.id.at_btn_save);
        ImageButton income = findViewById(R.id.at_btn_income);
        ImageButton loan = findViewById(R.id.at_btn_loan);
        RecyclerView recyclerView = findViewById(R.id.at_btn_recyclerview);

        recyclerView.setLayoutManager(new GridLayoutManager(this , 5));
        recyclerView.setAdapter(new at_btn_adapter(data, new onClickRecyclerButtion() {
            @Override
            public void onPositionClicked(int position) {
                type1 = 2;
                type2 = position;

            }
        }));


        income.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                type1 = 1;
                type2 = -1;
            }
        });

        loan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                type1 = 1;
                type2 = -2;
            }
        });

        context = this;
        save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                System.out.println("it is  all cool here");
                DatabaseHelper1 databaseHelper1 = new DatabaseHelper1(getBaseContext());
                DatabaseHelper2 databaseHelper2 = new DatabaseHelper2(getBaseContext());
                double amount = Double.parseDouble(EditAmount.getText().toString());
                System.out.println(amount);
                Calendar c = Calendar.getInstance();
                int year = c.get(Calendar.YEAR);
                int month = c.get(Calendar.MONTH);
                String m = changeString(month);
                System.out.println(type1);
                String mRamount = "ds";
                if(type1 == 1){

                    SQLiteDatabase database = databaseHelper1.getReadableDatabase();
                    String ca = "SELECT * FROM YEAR_DETAILS WHERE MONTH = " + month+ " AND YEAR = "+year;
                    Cursor cursor = database.rawQuery(ca , null);
                    mRamount = cursor.getString(1);
                    System.out.println(mRamount);//printing amount.
                }
                startActivity(new Intent(AddTransaction.this , MainActivity.class));
            }
        });

        cancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(AddTransaction.this , MainActivity.class));
            }
        });


    }


    void populateList(){
        data = new ArrayList<>();
        data.add(new add_transaction_data("Add" , R.drawable.ic_add_black_24dp));
        data.add(new add_transaction_data("Shopping" , R.drawable.at_ic_shopping));
        data.add(new add_transaction_data("Food" , R.drawable.at_ic_food));
        data.add(new add_transaction_data("Traveling" , R.drawable.at_ic_travel));
        data.add(new add_transaction_data("Education" , R.drawable.at_ic_education));
        data.add(new add_transaction_data("Energy" , R.drawable.at_ic_energy));
        data.add(new add_transaction_data("House" , R.drawable.at_ic_home));
        data.add(new add_transaction_data("Fitness" , R.drawable.at_ic_sports));
        data.add(new add_transaction_data("Personal" , R.drawable.at_ic_personal));
        data.add(new add_transaction_data("Other" , R.drawable.at_ic_other));
    }

    String changeString(int month){
        String m;
        switch (month){
            case 0:
                m = "January";
                break;
            case 1:
                m = "Feburary";
                break;
            case 2:
                m = "March";
                break;
            case 3:
                m = "April";
                break;
            case 4:
                m = "May";
                break;
            case 5:
                m = "June";
                break;
            case 6:
                m = "July";
                break;
            case 7:
                m = "August";
                break;
            case 8:
                m = "September";
                break;
            case 9:
                m = "October";
                break;
            case 10:
                m = "November";
                break;
            case 11:
                m = "December";
                break;
            default:
                m = " ";

        }
        return m;
    }

}

activity_main xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <fragment
        android:id="@+id/fragNavHost"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/mobile_navigation" />


    <me.ibrahimsn.lib.SmoothBottomBar
        android:elevation="30dp"
        android:id="@+id/bottom_nav"
        android:layout_width="match_parent"
        app:iconTint="@color/colorPrimary"
        app:indicatorColor="#EFEFEF"
        app:iconTintActive="@color/colorPrimaryDark"
        app:textColor="@color/colorPrimaryDark"
        android:layout_height="70dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/bottom_navigation_bar"/>

</androidx.constraintlayout.widget.ConstraintLayout>

有人可以帮助我了解导致这两个错误的原因吗？

Answer 1

在 getData() 方法中，有两个分号

String query = "SELECT * FROM YEAR_DETAILS;";

尝试将其更改为

String query = "SELECT * FROM YEAR_DETAILS"

我建议您迁移到 Room 库