java - StrictMode 提示 InputStream 没有被关闭

Question

我收到了 StrictMode 报告的以下违规行为在 Android 中。

02-05 04:07:41.190: ERROR/StrictMode(15093): A resource was acquired at attached stack trace but never released. See java.io.Closeable for information on avoiding resource leaks. 02-05 04:07:41.190: ERROR/StrictMode(15093): java.lang.Throwable: Explicit termination method 'close' not called

关于没有正确关闭流的问题很糟糕。但是，关闭 in 不应该关闭底层流吗？标记错误的原因可能是什么？

    private ArrayList<Uri> loadPath() {
        ArrayList<Uri> uris = new ArrayList<Uri>();
        if (mFile.exists()) {
            ObjectInputStream in = null;
            try {
                in = new ObjectInputStream(new BufferedInputStream(
                         new FileInputStream(mFile), STREAM_BUFFER_SIZE));
                ArrayList<String> strings = new ArrayList<String>();
                strings.addAll((ArrayList<String>) in.readObject());
                for (String string : strings) {
                    uris.add(Uri.parse(string));
                }
            } catch (Exception e) {
                mFile.delete();
            } finally {
                IOUtils.closeQuietly(in);
            }
        }
        return uris;
     }

    public static void closeQuietly(InputStream input) {
        try {
            if (input != null) {
                input.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

Answer 1

查看源代码，ObjectInputStream 的构造函数和 BufferedInputStream可以抛出异常，导致在下一行分配 FileInputStream 对象，但 in 变量仍为空:

            in = new ObjectInputStream(
                    new BufferedInputStream(
                            new FileInputStream(mFile), 
                    STREAM_BUFFER_SIZE)
            );

因为当我们到达 finally block 时 in 为 null，打开的 FileInputStream 对象将不会被您的 closeQuietly 关闭() 方法，导致 StrictMode 最终报错 :)

我建议的最简单的修复方法是将该分配分成 3 个变量并在每个变量上调用 closeQuietly()，可能是这样的:

private ArrayList<Uri> loadPath() {
    final ArrayList<Uri> uris = new ArrayList<Uri>();
    if (mFile.exists()) {
        ObjectInputStream ois = null;
        FileInputStream fis = null;
        BufferedInputStream bis = null;
        try {
            fis = new FileInputStream(mFile);
            bis = new BufferedInputStream(fis, STREAM_BUFFER_SIZE);
            ois = new ObjectInputStream(bis);
            final ArrayList<String> strings = new ArrayList<String>();
            strings.addAll((ArrayList<String>) ois.readObject());
            for (final String string : strings) {
                uris.add(Uri.parse(string));
            }
        } catch (final Exception e) {
            mFile.delete();
        } finally {
            closeQuietly(fis);
            closeQuietly(bis);
            closeQuietly(ois);
        }
    }
    return uris;
}