java - 从外部循环中获取值在内部循环中接收

Question

如何在循环外接收循环内创建的数据/值？
我确实在很多网站、博客和此处进行了搜索，但没有找到答案。

像这样:

public  ArrayList<Dicionario> retornaArray() {
    controlaBanco = new controlaBanco(this);//the classe with methods to manipule the data in a database
    List<String> str = new ArrayList<>();
    cursor = controlaBanco.carregaDados(); //this will give me the cursor with some data from a database(sqlite)
    arr = new ArrayList<Dicionario>(); //an arraylist formated to hand my data and then put it in a personalized listview

    int count = 0; //an number to control the data flow(it's 3000 linea of data and I guess my application might get slow by this

    while (!cursor.isAfterLast() && count <= 1000) {

//here I take the data from  columns separately
        str.add(cursor.getString(0));
        str.add(cursor.getString(1));
        str.add(cursor.getString(2));
        str.add(cursor.getString(3));

//here I take that data to formating this in my class
        dicionario = new Dicionario(str.get(0), str.get(1), str.get(2), str.get(3));

//here I put my formated data into my formated array
        arr.add(dicionario);

        count++; //the count is upping...
    }
//now I receive the array and returning this to my personalized adapter
    return arr;
}

但它不起作用，因为它只会获取并返回第一行 :(

Answer 1

发生的事情是 str 为每次迭代添加了 4 个元素。然而，您从元素 0-4 中获取值(即第一行)。

有各种修复方法，您可以使用:-

dicionario = new Dicionario(str.get(0 + (count * 4)), str.get(1 + (count * 4)), str.get(2 + (count * 4)), str.get(3 + (count * 4)));

• str 最后会包含 4 * 行元素

如果在将值分配给 str 之前可以使用 str.clear(); 之后不想使用 str，例如:-

//here I take the data from  columns separately
        str.clear();
        str.add(cursor.getString(0));
        str.add(cursor.getString(1));
        str.add(cursor.getString(2));
        str.add(cursor.getString(3));

• 在这种情况下，str
中只会有 4 个元素

或者您可以取消 str 并使用 :-

直接应用当前行的值

public  ArrayList<Dicionario> retornaArray() {
    controlaBanco = new controlaBanco(this);//the classe with methods to manipule the data in a database
    //List<String> str = new ArrayList<>(); //<<< not needed
    cursor = controlaBanco.carregaDados(); //this will give me the cursor with some data from a database(sqlite)
    arr = new ArrayList<Dicionario>(); //an arraylist formated to hand my data and then put it in a personalized listview

    int count = 0; //an number to control the data flow(it's 3000 linea of data and I guess my application might get slow by this

    while (!cursor.isAfterLast() && count <= 1000) {


//here I take that data to formating this in my class
        dicionario = new Dicionario(
            cursor.getString(0), 
            cursor.getString(1), 
            cursor.getString(2), 
            cursor.getString(3)
        );

//here I put my formated data into my formated array
        arr.add(dicionario);

        count++; //the count is upping...
    }
//now I receive the array and returning this to my personalized adapter
    return arr;
}

我个人会使用:-

public  ArrayList<Dicionario> retornaArray() {
    controlaBanco = new controlaBanco(this);//the classe with methods to manipule the data in a database
    cursor = controlaBanco.carregaDados(); //this will give me the cursor with some data from a database(sqlite)
    arr = new ArrayList<Dicionario>(); //an arraylist formated to hand my data and then put it in a personalized listview

    while (cursor.moveToNext() && cursor.getPosition() < 1000) {

       //here I take that data to formating this in my class
       arr.add(new Dicionario(
            cursor.getString(0), 
            cursor.getString(1), 
            cursor.getString(2), 
            cursor.getString(3)
        ));

    }
//now I receive the array and returning this to my personalized adapter
    return arr;
}