Android app closes when checking if file exists

Question

I have a method:

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;
}

whatever I pass into fileName, the app just says "The app has stopped working" and closes. For example I'll pass in "test.txt" and even though it doesn't exist, it shouldn't crash the program. What am I doing wrong here?

EDIT: here is the log:

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)

Use LogCat to examine the Java stack trace associated with your crash: https://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this — CommonsWare, Oct 23 '15 at 21:56
if you set canOpen = false in every case of an Exception you could simply catch(Exception e) to catch all the Exceptions in one catch-block — Teddy, Feb 03 '16 at 13:39

score 0 · Answer 1 · answered Oct 23 '15 at 22:04

0

fileName is null, based on your stack trace, and based on the now-current implementation of makeFilename() in ContextImpl.

answered Oct 23 '15 at 22:04

CommonsWare

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score 0 · Accepted Answer · answered Oct 23 '15 at 22:05

0

You are catching FileNotFoundException and IOException, and your stack trace clearly says you're getting a NullPointerException.

You aren't catching that exception, so your app crashes.

answered Oct 23 '15 at 22:05

Moonbloom

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Android app closes when checking if file exists

2 Answers2