java - 将值添加到 DataPoint 数组中导致应用程序在运行时崩溃

Question

我正在使用包含DataPoint[]数组的GraphView库代码。我的代码还包含一个名为olddb 的数据库，我用它在下面的代码中插入数组长度。前 2 个 for 循环用于将数据库中的值添加到数组中，第三个 for 循环用于从数组 arrayWeight 和 arrayId 中获取值并将它们添加到 DataPoint[] 数组中。

虽然似乎出了问题，但在我运行程序后它就崩溃了，任何人都可以找出导致应用程序崩溃的原因吗？

private DataPoint[] getDataPoint() {
        if (olddb.check()) {
            List<oldDetails> details = olddb.getDetails();
            double[] arrayWeight = new double[olddb.getDetailsCount()];
            int[] arrayId = new int[olddb.getDetailsCount()];
            for (oldDetails cn : details) { //Adding weights and id of all time to an array.
                double num = cn.getWeight();
                int id = cn.getId();
                for (int i = arrayWeight.length; i > 0; i--) {
                    arrayWeight[i] = num;
                    arrayId[i] = id;
                }
            }
            DataPoint[] dp = new DataPoint[olddb.getDetailsCount()];
            for (int i = 0; i < arrayId.length; i++) {
                for (int j = 0; j < arrayWeight.length; j++)
                    dp[i] = new DataPoint(i, arrayWeight[j]);
            }

            return dp;
        }
        else {
            DataPoint[] dp = new DataPoint[]{
                    new DataPoint(0, 0)
            };
            return dp;
        }
    }

以下是 DataPoint 数组的工作代码示例:

private DataPoint[] getDataPoint(){
    DataPoint[] dp = new DataPoint[]{
                new DataPoint(0,1),
                new DataPoint(2,5),
                new DataPoint(5,5),
                new DataPoint(7,4)
    };
    return dp;
}

编辑:这是错误消息:

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.none.myapplication, PID: 3881
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.none.myapplication/com.none.myapplication.MainActivity}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteQuery: SELECT  * FROM oldDetails

Database

Answer 1

您可以通过将所有 3 次调用替换为 olddb.getDetailsCount() 来修复此问题

与

int count = olddb.getDetailsCount();

然后:

double[] arrayWeight = new double[count];
int[] arrayId = new int[count];
DataPoint[] dp = new DataPoint[count];

但是您需要了解这个问题:

java.lang.IllegalStateException:尝试重新打开已关闭的对象:SQLiteQuery:SELECT * FROM oldDetails 是错误，发生在 DatabaseHandlerOld.getDetailsCount 第 141 行内

Android SQLite DB When to Close