Java 从游标创建数组

在以下两种方法中（均覆盖

long[]mArray

），首选哪种方法

第一个方法迭代

光标

，为每一行调用

ArrayList.add（）

，然后迭代

ArrayList

，将值复制到数组中

public void arrayFromCursor1(Cursor cursor) {

    // create a temp ArrayList to add to as we don't
    // know how many rows are in the cursor
    List<Long> list = new ArrayList<Long>();
    // iterate over the cursor
    if (cursor.moveToFirst()) {
        do {
            list.add(cursor.getLong(cursor.getColumnIndex("column_name")));
        } while (cursor.moveToNext());
        // create a long[] of appropriate length and copy values from the
        // ArrayList using a for loop
        final int size = list.size();
        mArray = new long[size];
        for (int i = 0; i < size; i++) {
            mArray[i] = list.get(i);
        }
    }
}

public void arrayFromCursor2(Cursor cursor) {

    // no need for a temp ArrayList this time
    // iterate over the cursor simply counting the rows
    if (cursor.moveToFirst()) {
        int size = 0;
        do {
            size++;
        } while (cursor.moveToNext());
        // create a long[] of appropriate length and iterate over the
        // cursor again, this time with a for loop copying values to the array
        mArray = new long[size];
        cursor.moveToFirst();
        for (int i = 0; i < size; i++) {
            mArray[i] = cursor.getLong(cursor.getColumnIndex("column_name"));
            cursor.moveToNext();
        }
    }
}

第二个方法在

光标上迭代两次。一次，每次调用
size++
对行进行计数，然后再次将值复制到数组中

public void arrayFromCursor1(Cursor cursor) {

    // create a temp ArrayList to add to as we don't
    // know how many rows are in the cursor
    List<Long> list = new ArrayList<Long>();
    // iterate over the cursor
    if (cursor.moveToFirst()) {
        do {
            list.add(cursor.getLong(cursor.getColumnIndex("column_name")));
        } while (cursor.moveToNext());
        // create a long[] of appropriate length and copy values from the
        // ArrayList using a for loop
        final int size = list.size();
        mArray = new long[size];
        for (int i = 0; i < size; i++) {
            mArray[i] = list.get(i);
        }
    }
}

public void arrayFromCursor2(Cursor cursor) {

    // no need for a temp ArrayList this time
    // iterate over the cursor simply counting the rows
    if (cursor.moveToFirst()) {
        int size = 0;
        do {
            size++;
        } while (cursor.moveToNext());
        // create a long[] of appropriate length and iterate over the
        // cursor again, this time with a for loop copying values to the array
        mArray = new long[size];
        cursor.moveToFirst();
        for (int i = 0; i < size; i++) {
            mArray[i] = cursor.getLong(cursor.getColumnIndex("column_name"));
            cursor.moveToNext();
        }
    }
}

public void arrayFromCursor1（游标）{
//创建要添加到的临时数组列表
//知道光标中有多少行
列表=新的ArrayList（）；
//在光标上迭代
if（cursor.moveToFirst（））{
做{
添加（cursor.getLong（cursor.getColumnIndex（“column_name”）））；
}while（cursor.moveToNext（））；
//创建适当长度的long[]，并从
//使用for循环的ArrayList
final int size=list.size（）；
mArray=新长[尺寸]；
对于（int i=0；i
我想出了一个干净、简单的解决方案，可以从光标创建数组。这在将数组存储在外键表中时非常有用，并且可以使用原语

public long[] arrayFromCursor(Cursor cursor) {

    int length = cursor.getCount();
    long[] array = new long[length];

    if (cursor.moveToFirst()) {
        for (int i = 0; i < length; i++) {
            array[i] = cursor.getLong(cursor.getColumnIndex("column_name"));
            cursor.moveToNext();
        }
    }
    return array;
}

public long[]数组自游标（游标游标）{
int length=cursor.getCount（）；
long[]数组=新的long[length]；
if（cursor.moveToFirst（））{
for（int i=0；i
您可以使用列表中的
toArray
方法
mArray=list.toArray（新的long[list.size（）]）
。我收回它，刚刚意识到这对基元类型的数组不起作用。。。