Question

我有一个方法：

private boolean canFileOpen(String fileName) {
    boolean canOpen = true;
    try {
            InputStream test = openFileInput(fileName);
        }
        catch(FileNotFoundException e)
        {
            canOpen = false;
        }
        catch (IOException e)
        {
            canOpen = false;
        }
    return canOpen;
}

无论我传入fileName，应用程序只是说＆＃34;应用程序已停止工作＆＃34;并关闭。例如，我将传入＆＃34; test.txt＆＃34;即使它不存在，它也不应该使程序崩溃。我在这里做错了什么？

编辑：这是日志：

10-23 17:57:22.564    1476-1476/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cloneeskimo.simplefile/com.cloneeskimo.simplefile.activity_fileeditor}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5103)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at android.app.ContextImpl.makeFilename(ContextImpl.java:2005)
            at android.app.ContextImpl.openFileInput(ContextImpl.java:709)
            at android.content.ContextWrapper.openFileInput(ContextWrapper.java:173)
            at com.cloneeskimo.simplefile.activity_fileeditor.canFileOpen(activity_fileeditor.java:49)
            at com.cloneeskimo.simplefile.activity_fileeditor.initSystems(activity_fileeditor.java:32)
            at com.cloneeskimo.simplefile.activity_fileeditor.onCreate(activity_fileeditor.java:41)
            at android.app.Activity.performCreate(Activity.java:5133)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5103)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

fileName为null，基于您的堆栈跟踪，并基于makeFilename() in ContextImpl的当前实施。

Answer 2

您正在捕获FileNotFoundException和IOException，并且您的堆栈跟踪清楚地表明您正在获取NullPointerException。

您没有捕获该异常，因此您的应用程序崩溃了。

检查文件是否存在时，Android应用会关闭

2 个答案: