JNI ERROR (app bug): local reference table overflow (max=512)

[tshirtman]

Loading some classes on android simply break because of the limit of jni reference table, would be great to find a way around this.

Exemple found just now, that crashes kivy-remote-shell on its own.

>>> from jnius import autoclass
>>> WebView = autoclass('android.webkit.WebView')

Connection to 192.168.0.10 closed by remote host.

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[jitendranair]

Same here, I am using the android java contacts api and the app crashes due to this error

JNI ERROR (app bug): local reference table overflow (max=512)
W/dalvikvm(27097): JNI local reference table (0x57901190) dump:
W/dalvikvm(27097):   Last 10 entries (of 512):
W/dalvikvm(27097):       511: 0x41e5e950 android.os.Parcel
W/dalvikvm(27097):       510: 0x41e594f0 android.os.BinderProxy
W/dalvikvm(27097):       509: 0x41e53f80 java.lang.String "552"
W/dalvikvm(27097):       508: 0x41eb0018 java.lang.String[] (1 elements)
W/dalvikvm(27097):       507: 0x41f083a8 java.lang.String "551"
W/dalvikvm(27097):       506: 0x41e53f30 java.lang.String "contact_id = ?"
W/dalvikvm(27097):       505: 0x41f07230 java.lang.String "545"
W/dalvikvm(27097):       504: 0x416c70e0 java.lang.Class<java.lang.String>
W/dalvikvm(27097):       503: 0x41edbdf0 java.lang.String "1730"
W/dalvikvm(27097):       502: 0x416c70e0 java.lang.Class<java.lang.String>
W/dalvikvm(27097):   Summary:
W/dalvikvm(27097):       267 of java.lang.Class (18 unique instances)
W/dalvikvm(27097):       242 of java.lang.String (242 unique instances)
W/dalvikvm(27097):         1 of java.lang.String[] (1 elements)
W/dalvikvm(27097):         1 of android.os.Parcel
W/dalvikvm(27097):         1 of android.os.BinderProxy
E/dalvikvm(27097): Failed adding to JNI local ref table (has 512 entries)

[KeyWeeUsr]

@tshirtman ref this answer and #371. I'm not sure we would be able to somehow overcome this. If the table has that limitation, we can only make sure we remove our references right after we don't need them. We might try to store the refs on the Python side, but I don't think JNI would be happy about that and it'd just collect the objects or just return segfault, no?

However we might switch to PushLocalFrame()/PopLocalFrame() in places where we create our local refs to be really sure the refs are gone, though it might cause more harm due to us not being able to track the refs and we might end up with prematurely collected refs.

Minor sidenote: I've been able to autoclass('android.webkit.WebView') just fine and I don't think my JNI table size has been altered, so I'd say #371 did a good job for fixing this issue and I'd close it.

[KeyWeeUsr]

In Android versions prior to Android 8.0, the number of local references is capped at a version-specific limit. Beginning in Android 8.0, Android supports unlimited local references.

ref Android JNI docs