How to handle an Android (java) string array?
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I'm trying to use the Qt Android interface, #include <QAndroidJniObject>
I've got the basic calls working. For instance I can create a java string with
@QAndroidJniObject mixedCaseString = QAndroidJniObject::fromString("wHiCHcaSe");@
and I can manipulate it, for instance
@QAndroidJniObject lowercaseString = casedString.callObjectMethod("toLowerCase", "()Ljava/lang/String;");@
I can confirm these are both working by converting to QStrings with mixedCaseString.toString() and lowercaseString.toString().I can apparently split the first string using "H" as a separator, with
@ QAndroidJniObject splitter = QAndroidJniObject::fromString("H");
QAndroidJniObject mixedcaseStringSplit= mixedCaseString.callObjectMethod("split", "(Ljava/lang/String;)[Ljava/lang/String;",splitter.object<jstring>());@The array of strings in mixedcaseStringSplit appears to be valid, and mixedcaseStringSplit.toString() returns the value (reasonable in the context, not NULL)
@"[Ljava/lang/String;@b2e3d926"@But here I get stuck. How can I manipulate the elements in that array?
Even attempts just to extract the size of the array seems to fail, e.g.
@QAndroidJniObject mixedcaseStringSplitN = mixedcaseStringSplit.callObjectMethod("size", "()I");@
returns NULL (more precisely, mixedcaseStringSplitN.isValid() is false)
and
@jint mixedcaseStringSplitNf = mixedcaseStringSplit.getField<jint>("length");@
returns 0. From that string, the size of the split array should be 3 (["w","iC","caSe"]).Does anyone have a better idea on java (Android) string array handling?
I'm using Qt 5.2.1 from Digia's online package.
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Hmm, scrambling my java and C++. Java arrays have no size() method, so mixedcaseStringSplit.callObjectMethod("size", "()I") ought not to work.
But the length of a java array is given by the length property, so mixedcaseStringSplit.getField<jint>("length") ought to work. In Qt we access java properties with getField, right?
And once we do understand how to access java_array.length, how do we extract the elements? Java has no java_array.at( i ) function, only java_array[i]. Certainly, callObjectMethod("[]",...) does not work.
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Seems that Qt just can't do it, not directly. Have to go the long round instead, using "JNI":http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/jniTOC.html explicitly (via the "JNI array operations":http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/functions.html#array_operations).
With
@#include <QAndroidJniEnvironment>
QAndroidJniEnvironment jniEnv;@then
@int splitArrayLength = jniEnv->GetArrayLength(mixedcaseStringSplit.object<jarray>());@
gives the length of the array and
@ QAndroidJniObject arrayElement = jniEnv->GetObjectArrayElement(mixedcaseStringSplit.object<jobjectArray>(), i );@
gives a specific element in the array.