Question

我正在制作一个可以存储3个数据收入，ExpenseName和ExpenseCost的应用程序。我正在尝试仅获取txt_incomeview的收入，而忽略其他2个数据，但我不知道ExpenseName和ExpenseCost的用法和相同之处。在数据库中，我将收入保存在同一张表中，但ExpenseName和ExpenseCost的值为空。

收入

例如nullnull100

与ExpenseName和ExpenseCost相同

Ex.name100null

就像我将其保存在SQL数据库中

MainActivity：

package com.example.back4app.userregistrationexample.Classes;

import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.example.back4app.userregistrationexample.Data.DatabaseHelper;
import com.example.back4app.userregistrationexample.R;

public class MainActivity extends AppCompatActivity {

DatabaseHelper mDatabaseHelper;
private TextView nameview, costview, income;


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

    income = (TextView) findViewById(R.id.txt_incomeview);
    mDatabaseHelper = new DatabaseHelper(this);

    Cursor cursor = mDatabaseHelper.getData();

    if(cursor.getCount()==0){
        Toast.makeText(getApplicationContext(), "No Data", Toast.LENGTH_SHORT).show();
    }
    else{
        while (cursor.moveToNext()){

        }
    }



    final Button btn_income = findViewById(R.id.btn_Income);
    btn_income.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, IncomeActivity.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(intent);
            }
        });
    final Button btn_expense = findViewById(R.id.btn_Expense);
    btn_expense.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, ExpenseActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
            startActivity(intent);
        }
    });
}
}

DatabaseHelper：

package com.example.back4app.userregistrationexample.Data;

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


public class DatabaseHelper extends SQLiteOpenHelper {

private static final String TAG = "DatabaseHelper";
private static final String TABLE_NAME = "Financial";
private static final String COL1 = "ID";
private static final String COL2 = "item";
private static final String COL3 = "cost";
private static final String COL4 = "income";



public DatabaseHelper(Context context) {
    super(context, TABLE_NAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
   String createTable = "CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COL2  + " TEXT, " +
           COL3 + " INTEGER, " +
           COL4 + " INTEGER);";
    db.execSQL(createTable);
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

public boolean addData(String item, String cost, String income) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COL2, item);
    contentValues.put(COL3, cost);
    contentValues.put(COL4, income);

    Log.d(TAG, "addData: Adding " + item  + cost + income + " to " + TABLE_NAME);

    long result = db.insert(TABLE_NAME, null, contentValues);

    //if date as inserted incorrectly it will return -1
    if (result == -1) {
        return false;
    } else {
        return true;
    }
}

/**
 * Returns all the data from database
 * @return
 */
public Cursor getData(){
    SQLiteDatabase db = this.getWritableDatabase();
    String query = "SELECT * FROM " + TABLE_NAME;
    Cursor data = db.rawQuery(query, null);
    return data;
}

/**
 * Returns only the ID that matches the name passed in
 * @param name
 * @return
 */
public Cursor getItemID(String name){
    SQLiteDatabase db = this.getWritableDatabase();
    String query = "SELECT " + COL1 + " FROM " + TABLE_NAME +
            " WHERE " + COL2 + " = '" + name + "'";
    Cursor data = db.rawQuery(query, null);
    return data;
}

/**
 * Updates the name field
 * @param newName
 * @param id
 * @param oldName
 */
public void updateName(String newName, int id, String oldName){
    SQLiteDatabase db = this.getWritableDatabase();
    String query = "UPDATE " + TABLE_NAME + " SET " + COL2 +
            " = '" + newName + "' WHERE " + COL1 + " = '" + id + "'" +
            " AND " + COL2 + " = '" + oldName + "'";
    Log.d(TAG, "updateName: query: " + query);
    Log.d(TAG, "updateName: Setting name to " + newName);
    db.execSQL(query);
}

/**
 * Delete from database
 * @param id
 * @param name
 */
public void deleteName(int id, String name){
    SQLiteDatabase db = this.getWritableDatabase();
    String query = "DELETE FROM " + TABLE_NAME + " WHERE "
            + COL1 + " = '" + id + "'" +
            " AND " + COL2 + " = '" + name + "'";
    Log.d(TAG, "deleteName: query: " + query);
    Log.d(TAG, "deleteName: Deleting " + name + " from database.");
    db.execSQL(query);
}

}

我尝试使用

    ArrayList<String> listData = new ArrayList<>();

但是我在youtube上看到的这种方法仅在ListView上显示1列，但我希望在textview中查看它

如何在忽略SQLite中的其他列的同时从特定列获取特定数据？

0 个答案: