内存的分配游标时 [英] Out of Memory when allocating cursors

问题描述

我有，我不能想出一个内存问题。我有一个类，做我的所有数据库中检索工作。我的错误是：

I have a memory problem that I can't figure out. I have one class that does all my database retrieving work. The error I have is the following:

android.database.CursorWindowAllocationException: Cursor window allocation of 2048 kb failed. # Open Cursors=733 (# cursors opened by this proc=733)

内存分配错误发生时，我这样做：

The memory allocation error occurs when I do this:

mDatabaseInterface.getGraphForLevel(level);

我知道这是一个泄漏，因为我粗略地调用这个方法每2.5秒，5或6首先调用通过轻松。现在，这里是我的DatabaseInterface类中的方法：

I know it's a leak because I call this method every 2.5 seconds roughly, and the 5 or 6 first calls go through easily. Now here are the methods in my DatabaseInterface class:

public Graph getGraphForLevel(Level level) {

    //get the nodes
    ArrayList<Node> nodes = new ArrayList<Node>(Arrays.asList(this.getNodesWithLevel(level)));
    //get the edges
    ArrayList<Edge> edges = new ArrayList<Edge>(Arrays.asList(this.getEdgesWithNodes(nodes)));

    return new Graph(nodes, edges);
}

public Node[] getNodesWithLevel(Level level) {

    List<Node> l = new ArrayList<Node>();

    Cursor cursor = mDatabase.query("nodes", null, 
            "level = " + wrapSql(String.valueOf(level.getId())), null, null, null, null);

    while (cursor.moveToNext()) {
        l.add(parseNodeFromCursor(cursor));
    }

    cursor.close();

    return l.toArray(new Node[l.size()]);       
}

private Node parseNodeFromCursor(Cursor cursor) {

    Level l = getLevelWithId(cursor.getInt(2));

    return new Node(cursor.getInt(0), cursor.getString(1), l, 
            cursor.getInt(4), cursor.getInt(5));
}

我有很多的相互调用的方法，但我知道这是不是一个递归问题，因为这类作品在另一个应用程序。我的主要问题是，为什么不 cursor.close（）解放光标？如果我是这样的：

I have a lot of methods that call each other but I know it's not a recursion problem because this class works in another app. My main question is why doesn't cursor.close() liberate the cursor? If I do something like:

cursor = mDatabase.query(...);
cursor.moveToNext();
Node node = new Node(cursor.getInt());
cursor.close();

时光标保留在这种情况下？

Is the cursor retained in that case?

在此先感谢。

推荐答案

到调用cursor.close（）应该在最后块中，以防你遍历它，当一个异常被抛出。

The call to cursor.close() should be in a finally block in case an exception is thrown while you're iterating over it.

Cursor cursor = mDatabase.query("nodes", null, 
        "level = " + wrapSql(String.valueOf(level.getId())), null, null, null, null);
try {
    while (cursor.moveToNext()) {
        l.add(parseNodeFromCursor(cursor));
    }
} finally {
    cursor.close();
}

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