java - FileInputStream 在 .close() NPE 上崩溃

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为什么我的应用程序崩溃了？它在 fis.close(); 上崩溃线。这是在 doInBackground 中AsyncTask的方法.

    String collected = null;
    FileInputStream fis = null;
    try {
        fis = openFileInput(FILENAME);
        byte[] dataArray = new byte[fis.available()];
        while (fis.read(dataArray) != -1) {
            collected = new String(dataArray);
        }
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        try {
            fis.close();
            return collected;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    return null;
}

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12-10 14:12:47.431: E/AndroidRuntime(701): FATAL EXCEPTION: AsyncTask #1
12-10 14:12:47.431: E/AndroidRuntime(701): java.lang.RuntimeException: An error occured while executing doInBackground()
12-10 14:12:47.431: E/AndroidRuntime(701):  at android.os.AsyncTask$3.done(AsyncTask.java:299)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)
12-10 14:12:47.431: E/AndroidRuntime(701):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.lang.Thread.run(Thread.java:856)
12-10 14:12:47.431: E/AndroidRuntime(701): Caused by: java.lang.NullPointerException
12-10 14:12:47.431: E/AndroidRuntime(701):  at com.ollygrov.doughpro.CustomRecipe$loadDatas.doInBackground(CustomRecipe.java:471)
12-10 14:12:47.431: E/AndroidRuntime(701):  at com.ollygrov.doughpro.CustomRecipe$loadDatas.doInBackground(CustomRecipe.java:1)
12-10 14:12:47.431: E/AndroidRuntime(701):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-10 14:12:47.431: E/AndroidRuntime(701):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)

Answer 1

openFileInput有可能返回null吗？在这种情况下，NullPointerException 将在 byte[] dataArray = new byte[fis.available()]; 行被默默吞掉。

然后执行将跳转到 finally block ，从这里抛出异常，因为它没有在任何 catch block 中处理。