java - 如何在 Java - Android 的另一个类中调用我的数据库助手类的方法

标签 java android helper

类数据库助手

package br.com.mefti.simplefinance.sqlite;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Build;
import android.provider.BaseColumns;
import android.provider.ContactsContract;
import android.util.Log;

import java.util.ArrayList;

import br.com.mefti.simplefinance.sqlite.ContratoSF.*;
import br.com.mefti.simplefinance.modelo.*;
import br.com.mefti.simplefinance.ui.ExtratoDespesasCursorAdapter;


/**
 * Created by a_med on 13/10/2016.
 * clase que administra a conexao da base de dados e a estrutura
 */

public class BaseDadosSF extends SQLiteOpenHelper {
    public static final String NOME_BASE_DADOS = "BDSimpleFinance.db";
    private static final int VERSAO_ATUAL = 1;
    private final Context contexto;
    SQLiteDatabase db;

    interface Tabelas{
        String USUARIO = "usuario";
        String LANCAMENTO = "lancamento";
        String CATEGORIA = "categoria";
    }

    interface Referencias{
        String COD_USUARIO = String.format("REFERENCES %s(%s) ON DELETE CASCADE",Tabelas.USUARIO, Usuario.COD_USUARIO);
        String COD_LANCAMENTO = String.format("REFERENCES %s(%s)",Tabelas.LANCAMENTO, Lancamento.COD_LANCAMENTO);
        String COD_CATEGORIA = String.format("REFERENCES %s(%s)",Tabelas.CATEGORIA, Categoria.COD_CATEGORIA);
    }

    public BaseDadosSF(Context contexto){
        super(contexto, NOME_BASE_DADOS, null, VERSAO_ATUAL);
        this.contexto = contexto;
    }

    @Override
    public void onOpen(SQLiteDatabase db) {
        super.onOpen(db);
        if (!db.isReadOnly()){
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN){
                db.setForeignKeyConstraintsEnabled(true);
            }else {
                db.execSQL("PRAGMA foreign_keys=ON");
            }
        }
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {


        sqLiteDatabase.execSQL(String.format("CREATE TABLE %s ( %s INTEGER PRIMARY KEY AUTOINCREMENT," +
                        "%s TEXT NOT NULL UNIQUE,%s VARCHAR(50) NOT NULL,%s VARCHAR(20) NOT NULL,%s VARCHAR(30) NOT NULL UNIQUE, %s CHAR(1) NOT NULL )",
                Tabelas.USUARIO, BaseColumns._ID,
                Usuario.COD_USUARIO, Usuario.NOME, Usuario.SENHA, Usuario.EMAIL, Usuario.ESTADO
        ));

        sqLiteDatabase.execSQL(String.format("CREATE TABLE %s (%s INTEGER PRIMARY KEY AUTOINCREMENT," +
                "%s TEXT UNIQUE NOT NULL, %s TEXT NOT NULL %s, %s TEXT NOT NULL %s, %s CHAR(1) NOT NULL, " +
                "%s VARCHAR(100) NOT NULL, %s DOUBLE, %s DATETIME, %s CHAR(1) NOT NULL, %s DATETIME, " +
                "%s DOUBLE, %s VARCHAR(400))",
                Tabelas.LANCAMENTO, BaseColumns._ID,
                Lancamento.COD_LANCAMENTO, Lancamento.COD_USUARIO, Referencias.COD_USUARIO, Lancamento.COD_CATEGORIA, Referencias.COD_CATEGORIA, Lancamento.TP_LANCAMENTO,
                Lancamento.DESCRICAO, Lancamento.VALOR, Lancamento.DATA, Lancamento.REPETIR, Lancamento.PREVISAO_DATA,
                Lancamento.PREVISAO_VALOR, Lancamento.OBSERVACAO
        ));

        sqLiteDatabase.execSQL(String.format("CREATE TABLE %s (%s INTEGER PRIMARY KEY AUTOINCREMENT," +
                        "%s TEXT UNIQUE NOT NULL, %s TEXT NOT NULL %s, %s VARCHAR(20) NOT NULL, %s CHAR(1) NOT NULL)",
                Tabelas.CATEGORIA, BaseColumns._ID,
                Categoria.COD_CATEGORIA, Categoria.COD_USUARIO, Referencias.COD_USUARIO, Categoria.NOME, Categoria.TP_LANCAMENTO
        ));
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + Tabelas.USUARIO);
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + Tabelas.LANCAMENTO);
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + Tabelas.CATEGORIA);

        onCreate(sqLiteDatabase);
    }


    //Inicio Operacoes Categoria
    public Cursor ObterCategoriaPorCodCategoria(String cod_categoria){
        db = this. getReadableDatabase();
        String sql = String.format("SELECT * FROM %s WHERE %s=?",
                Tabelas.CATEGORIA, Categoria.COD_CATEGORIA);
        String[] selectionArgs = {cod_categoria};
        Cursor cursor = db.rawQuery(sql, selectionArgs);
        Log.d("Categoria", "Categoria");
        DatabaseUtils.dumpCursor(cursor);
        db.close();
        return cursor;
    }
}
调用类Database

方法的类 

package br.com.mefti.simplefinance.ui;

import android.content.Context;
import android.database.Cursor;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CursorAdapter;
import android.widget.TextView;


import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

import br.com.mefti.simplefinance.R;
import br.com.mefti.simplefinance.sqlite.BaseDadosSF;
import br.com.mefti.simplefinance.sqlite.ContratoSF;

/**
 * Created by a_med on 9/11/2016.
 */

public class ExtratoDespesasCursorAdapter extends CursorAdapter{
    public BaseDadosSF dados = new BaseDadosSF(this); ----> the error is here

    public ExtratoDespesasCursorAdapter(Context context, Cursor c) {
        super(context, c, 0);
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup viewGroup) {
        LayoutInflater inflater = LayoutInflater.from(cotext);
        return inflater.inflate(R.layout.list_item_extrato_despesas, viewGroup, false);
    }

    @Override
    public void bindView(View view, final Context context, Cursor cursor) {

        // Referencias UI.
        TextView descricaoText = (TextView) view.findViewById(R.id.descricao_despesa);
        TextView valorText = (TextView) view.findViewById(R.id.valor_despesa);
        TextView categoriaText = (TextView) view.findViewById(R.id.categoria_despesa);
        TextView dataText = (TextView) view.findViewById(R.id.data_despesa);
        //final ImageView avatarImage = (ImageView) view.findViewById(R.id.iv_avatar);

        // Get valores.
        String descricao = cursor.getString(cursor.getColumnIndex(ContratoSF.Lancamento.DESCRICAO));
        String valor = cursor.getString(cursor.getColumnIndex(ContratoSF.Lancamento.VALOR));
        String categoria = cursor.getString(cursor.getColumnIndex(ContratoSF.Lancamento.COD_CATEGORIA));
        String data = cursor.getString(cursor.getColumnIndex(ContratoSF.Lancamento.DATA));

        //Obtendo nome categorio pelo cod
        String nCategoria = "";
        Cursor cursor1 = dados.ObterCategoriaPorCodCategoria(categoria);
        if (cursor1.moveToFirst()){
            nCategoria = cursor.getString(3);
        }

        //Convertendo data
        SimpleDateFormat dateFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss Z yyyy");
        DateFormat targetFormat = new SimpleDateFormat("dd/MMM/yyyy");
        String formattedDate = null;
        Date convertedDate = new Date();
        try {
            convertedDate = dateFormat.parse(data);
            formattedDate = targetFormat.format(convertedDate);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(convertedDate);


        //String avatarUri = cursor.getString(cursor.getColumnIndex(LawyerEntry.AVATAR_URI));

        // Setup.
        descricaoText.setText(descricao);
        valorText.setText("Valor: R$ " + valor);
        categoriaText.setText("Categoria: " + nCategoria);
        dataText.setText("Data: " + formattedDate);
    }
}

错误:

E/AndroidRuntime: 致命异常: main 进程:br.com.mefti.simplefinance，PID:30549 java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“android.database.Cursor br.com.mefti.simplefinance.sqlite.BaseDadosSF.ObterCategoriaPorCodCategoria(java.lang.String)” 在 br.com.mefti.simplefinance.ui.ExtratoDespesasCursorAdapter.bindView(ExtratoDespesasCursorAdapter.java:56)

感谢帮助

最佳答案

替换这段代码

public class ExtratoDespesasCursorAdapter extends CursorAdapter{
  public BaseDadosSF dados = new BaseDadosSF(this); ----> the error is here

  public ExtratoDespesasCursorAdapter(Context context, Cursor c) {
    super(context, c, 0);
  }

有了这个

public class ExtratoDespesasCursorAdapter extends CursorAdapter{
  public BaseDadosSF dados;

  public ExtratoDespesasCursorAdapter(Context context, Cursor c) {
    super(context, c, 0);
    dados = new BaseDadosSF(context);
  }

需要传递你正在使用的context，抛出错误时的context还没有准备好。

另一点是 this 指的是 ExtratoDespesasCursorAdapter 而不是具有 context 的 activity。

关于java - 如何在 Java - Android 的另一个类中调用我的数据库助手类的方法，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40549000/

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