Mixing
Returning HashMap from native method
0
I need to return a HashMap from Android native implementation. On Running the app I am getting following crash:
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Below are implementation details.
Method signature on Java side:
private native HashMap<String, Double> testBitmapJNI(Bitmap bitmap);
in C++ code:
static const JNINativeMethod g_NativeMethods = {
....
{"testBitmapJNI", "(Landroid/graphics/Bitmap;)Ljava/util/HashMap;",
(void*)testBitmapJNI},
....
};
jobject testBitmapJNI(JNIEnv* env, jobject instance, jobject bitmap){
jobject myHashMap= ...
/* every thing is working good here */
return myHashMap;
}
If I change the signature of testBitmapJNI to return void, it no longer crashes. I believe the signature in mapping table is not correct. It will be great if someone can suggest the correct signature to use in the table or another approach to fix / implement the same.
android jni asked Nov 20 '18 at 10:50
user1155172user1155172
284
add a comment |
0
I need to return a HashMap from Android native implementation. On Running the app I am getting following crash:
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Below are implementation details.
Method signature on Java side:
private native HashMap<String, Double> testBitmapJNI(Bitmap bitmap);
in C++ code:
static const JNINativeMethod g_NativeMethods = {
....
{"testBitmapJNI", "(Landroid/graphics/Bitmap;)Ljava/util/HashMap;",
(void*)testBitmapJNI},
....
};
jobject testBitmapJNI(JNIEnv* env, jobject instance, jobject bitmap){
jobject myHashMap= ...
/* every thing is working good here */
return myHashMap;
}
If I change the signature of testBitmapJNI to return void, it no longer crashes. I believe the signature in mapping table is not correct. It will be great if someone can suggest the correct signature to use in the table or another approach to fix / implement the same.
android jni asked Nov 20 '18 at 10:50
user1155172user1155172
284
1
jobject myHashMap= ...and/* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.
– Andrew Henle
Nov 20 '18 at 10:53
How do you create the myHashMap object? Is it really aHashMap<String, Double>?
– Alex Cohn
Nov 20 '18 at 12:06
One problem could be that you don't create (boxing)Doublevalue. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.
– Alex Cohn
Nov 20 '18 at 12:13
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16
add a comment |
0
0
0
I need to return a HashMap from Android native implementation. On Running the app I am getting following crash:
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Below are implementation details.
Method signature on Java side:
private native HashMap<String, Double> testBitmapJNI(Bitmap bitmap);
in C++ code:
static const JNINativeMethod g_NativeMethods = {
....
{"testBitmapJNI", "(Landroid/graphics/Bitmap;)Ljava/util/HashMap;",
(void*)testBitmapJNI},
....
};
jobject testBitmapJNI(JNIEnv* env, jobject instance, jobject bitmap){
jobject myHashMap= ...
/* every thing is working good here */
return myHashMap;
}
If I change the signature of testBitmapJNI to return void, it no longer crashes. I believe the signature in mapping table is not correct. It will be great if someone can suggest the correct signature to use in the table or another approach to fix / implement the same.
android jni asked Nov 20 '18 at 10:50
user1155172user1155172
284
I need to return a HashMap from Android native implementation. On Running the app I am getting following crash:
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Below are implementation details.
Method signature on Java side:
private native HashMap<String, Double> testBitmapJNI(Bitmap bitmap);
in C++ code:
static const JNINativeMethod g_NativeMethods = {
....
{"testBitmapJNI", "(Landroid/graphics/Bitmap;)Ljava/util/HashMap;",
(void*)testBitmapJNI},
....
};
jobject testBitmapJNI(JNIEnv* env, jobject instance, jobject bitmap){
jobject myHashMap= ...
/* every thing is working good here */
return myHashMap;
}
If I change the signature of testBitmapJNI to return void, it no longer crashes. I believe the signature in mapping table is not correct. It will be great if someone can suggest the correct signature to use in the table or another approach to fix / implement the same.
android jni android jni asked Nov 20 '18 at 10:50
user1155172user1155172
284
asked Nov 20 '18 at 10:50
user1155172user1155172
284
asked Nov 20 '18 at 10:50
user1155172user1155172
284
asked Nov 20 '18 at 10:50
user1155172user1155172
284
asked Nov 20 '18 at 10:50
user1155172user1155172
284
284
1
jobject myHashMap= ...and/* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.
– Andrew Henle
Nov 20 '18 at 10:53
How do you create the myHashMap object? Is it really aHashMap<String, Double>?
– Alex Cohn
Nov 20 '18 at 12:06
One problem could be that you don't create (boxing)Doublevalue. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.
– Alex Cohn
Nov 20 '18 at 12:13
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16
add a comment |
1
jobject myHashMap= ...and/* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.
– Andrew Henle
Nov 20 '18 at 10:53
How do you create the myHashMap object? Is it really aHashMap<String, Double>?
– Alex Cohn
Nov 20 '18 at 12:06
One problem could be that you don't create (boxing)Doublevalue. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.
– Alex Cohn
Nov 20 '18 at 12:13
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16
1
1
jobject myHashMap= ... and /* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.– Andrew Henle
Nov 20 '18 at 10:53
jobject myHashMap= ... and /* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.– Andrew Henle
Nov 20 '18 at 10:53
How do you create the myHashMap object? Is it really a
HashMap<String, Double>?– Alex Cohn
Nov 20 '18 at 12:06
How do you create the myHashMap object? Is it really a
HashMap<String, Double>?– Alex Cohn
Nov 20 '18 at 12:06
One problem could be that you don't create (boxing)
Double value. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.– Alex Cohn
Nov 20 '18 at 12:13
One problem could be that you don't create (boxing)
Double value. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.– Alex Cohn
Nov 20 '18 at 12:13
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16
add a comment |
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1
jobject myHashMap= ...and/* every thing is working good here */?!?! How do you know it's "working good"? You don't know why it's not working else you wouldn't be asking the question. Post all the code.– Andrew Henle
Nov 20 '18 at 10:53
How do you create the myHashMap object? Is it really a
HashMap<String, Double>?– Alex Cohn
Nov 20 '18 at 12:06
One problem could be that you don't create (boxing)
Doublevalue. See e.g. stackoverflow.com/questions/18501229/…. In stackoverflow.com/questions/38591185/… there is a mini-example of returning a Map from C++ to Java.– Alex Cohn
Nov 20 '18 at 12:13
I've done a lot of JNI work, and there is ample opportunity for things to go wrong. One thing to note: convert all of your java objects (both key and value) that are going to go into the hashmap, into global references, and delete the original local references. This will solve two potential problems: (1) running out of local references (2) storing local references persistently. And post all of your code.
– Wheezil
Nov 26 '18 at 15:16