jint x = QAndroidJniObject::callMethod<jint>("getSize");
QAndroidJniObject::callMethod<void>("touch");

// Java class
package org.qtproject.qt5;
class TestClass
{
   static String fromNumber(int x) { ... }
   static String[] stringArray(String s1, String s2) { ... }
}

// C++ code
QAndroidJniObject stringNumber = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
                                                                           "fromNumber"
                                                                           "(I)Ljava/lang/String;",
                                                                           10);

// C++ code
QAndroidJniObject string1 = QAndroidJniObject::fromString("String1");
QAndroidJniObject string2 = QAndroidJniObject::fromString("String2");
QAndroidJniObject stringArray = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
                                                                          "stringArray"
                                                                          "(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;"
                                                                           string1.object<jstring>(),
                                                                           string2.object<jstring>());

void functionException()
{
    QAndroidJniObject myString = QAndroidJniObject::fromString("Hello");
    jchar c = myString.callMethod<jchar>("charAt", "(I)C", 1000);
    QAndroidJniEnvironment env;
    if (env->ExceptionCheck()) {
        // Handle exception here.
        env->ExceptionClear();
    }
}

class FooJavaClass
{
    public static void foo(int x)
    {
        if (x < 100)
            callNativeOne(x);
        else
            callNativeTwo(x);
    }

private static native void callNativeOne(int x);
private static native void callNativeTwo(int x);

}

static void fromJavaOne(JNIEnv *env, jobject thiz, jint x)
{
    Q_UNUSED(env)
    Q_UNUSED(thiz)
    qDebug() << x << "< 100";
}

static void fromJavaTwo(JNIEnv *env, jobject thiz, jint x)
{
    Q_UNUSED(env)
    Q_UNUSED(thiz)
    qDebug() << x << ">= 100";
}

void registerNativeMethods() {
    JNINativeMethod methods[] {{"callNativeOne", "(I)V", reinterpret_cast<void *>(fromJavaOne)},
                               {"callNativeTwo", "(I)V", reinterpret_cast<void *>(fromJavaTwo)}};

    QAndroidJniObject javaClass("my/java/project/FooJavaClass");
    QAndroidJniEnvironment env;
    jclass objectClass = env->GetObjectClass(javaClass.object<jobject>());
    env->RegisterNatives(objectClass,
                         methods,
                         sizeof(methods) / sizeof(methods[0]));
    env->DeleteLocalRef(objectClass);
}

void foo()
{
    QAndroidJniObject::callStaticMethod<void>("my/java/project/FooJavaClass", "foo", "(I)V", 10);  // Output: 10 < 100
    QAndroidJniObject::callStaticMethod<void>("my/java/project/FooJavaClass", "foo", "(I)V", 100); // Output: 100 >= 100
}

Member Function Documentation

QAndroidJniObject::​QAndroidJniObject()

Constructs an invalid QAndroidJniObject.

See also isValid().

QAndroidJniObject::​QAndroidJniObject(const char * className)

Constructs a new QAndroidJniObject by calling the default constructor of className.

...
QAndroidJniObject myJavaString("java/lang/String");
...

QAndroidJniObject::​QAndroidJniObject(const char * className, const char * signature, ...)

Constructs a new QAndroidJniObject by calling the constructor of className with signature and arguments.

...
jstring myJStringArg = ...;
QAndroidJniObject myNewJavaString("java/lang/String", "(Ljava/lang/String;)V", myJStringArg);
...

QAndroidJniObject::​QAndroidJniObject(jclass clazz)

Constructs a new QAndroidJniObject by calling the default constructor of clazz.

Note: The QAndroidJniObject will create a new reference to the class clazz and releases it again when it is destroyed. References to the class created outside the QAndroidJniObject needs to be managed by the caller.

QAndroidJniObject::​QAndroidJniObject(jclass clazz, const char * signature, ...)

Constructs a new QAndroidJniObject from clazz by calling the constructor with signature and arguments.

jclass myClazz = ...;
QAndroidJniObject::QAndroidJniObject(myClazz, "(I)V", 3);

QAndroidJniObject::​QAndroidJniObject(jobject object)

Constructs a new QAndroidJniObject around the Java object object.

Note: The QAndroidJniObject will hold a reference to the Java object object and release it when destroyed. Any references to the Java object object outside QAndroidJniObject needs to be managed by the caller.

QAndroidJniObject::​~QAndroidJniObject()

Destroys the QAndroidJniObject and releases any references held by the QAndroidJniObject.

T QAndroidJniObject::​callMethod(const char * methodName) const

Calls the method methodName and returns the value.

QAndroidJniObject myJavaString = ...;
jint size = myJavaString.callMethod<jint>("length");

T QAndroidJniObject::​callMethod(const char * methodName, const char * signature, ...) const

Calls the method methodName with signature and returns the value.

QAndroidJniObject myJavaString = ...;
jint index = myJavaString.callMethod<jint>("indexOf", "(I)I", 0x0051);

QAndroidJniObject QAndroidJniObject::​callObjectMethod(const char * methodName) const

Calls the Java objects method methodName and returns a new QAndroidJniObject for the returned Java object.

...
QAndroidJniObject myJavaString1 = ...;
QAndroidJniObject myJavaString2 = myJavaString1.callObjectMethod<jstring>("toString");
...

QAndroidJniObject QAndroidJniObject::​callObjectMethod(const char * methodName, const char * signature, ...) const

Calls the Java object's method methodName with the signature signature and arguments

QAndroidJniObject myJavaString; ==> "Hello, Java"
QAndroidJniObject mySubstring = myJavaString.callObjectMethod("substring", "(II)Ljava/lang/String;" 7, 10);

[static] T QAndroidJniObject::​callStaticMethod(const char * className, const char * methodName)

Calls the static method methodName on class className and returns the value.

jint value = QAndroidJniObject::callStaticMethod<jint>("MyClass", "staticMethod");

[static] T QAndroidJniObject::​callStaticMethod(const char * className, const char * methodName, const char * signature, ...)

Calls the static method with methodName with signature on class className with optional arguments.

...
jint a = 2;
jint b = 4;
jint max = QAndroidJniObject::callStaticMethod<jint>("java/lang/Math", "max", "(II)I", a, b);
...

[static] T QAndroidJniObject::​callStaticMethod(jclass clazz, const char * methodName)

Calls the static method methodName on clazz and returns the value.

...
jclass javaMathClass = ...; // ("java/lang/Math")
jdouble randNr = QAndroidJniObject::callStaticMethod<jdouble>(javaMathClass, "random");
...

[static] T QAndroidJniObject::​callStaticMethod(jclass clazz, const char * methodName, const char * signature, ...)

Calls the static method methodName with signature on clazz and returns the value.

...
jclass javaMathClass = ...; // ("java/lang/Math")
jint a = 2;
jint b = 4;
jint max = QAndroidJniObject::callStaticMethod<jint>(javaMathClass, "max", "(II)I", a, b);
...

[static] QAndroidJniObject QAndroidJniObject::​callStaticObjectMethod(const char * className, const char * methodName)

Calls the static method with methodName on the class className.

QAndroidJniObject string = QAndroidJniObject::callStaticObjectMethod<jstring>("CustomClass", "getClassName");

[static] QAndroidJniObject QAndroidJniObject::​callStaticObjectMethod(const char * className, const char * methodName, const char * signature, ...)

Calls the static method with methodName and signature on the class className.

QAndroidJniObject thread = QAndroidJniObject::callStaticObjectMethod("java/lang/Thread", "currentThread", "()Ljava/lang/Thread;");
QAndroidJniObject string = QAndroidJniObject::callStaticObjectMethod("java/lang/String", "valueOf", "(I)Ljava/lang/String;", 10);

[static] QAndroidJniObject QAndroidJniObject::​callStaticObjectMethod(jclass clazz, const char * methodName)

Calls the static method with methodName on clazz.

[static] QAndroidJniObject QAndroidJniObject::​callStaticObjectMethod(jclass clazz, const char * methodName, const char * signature, ...)

Calls the static method with methodName and signature on class clazz.

[static] QAndroidJniObject QAndroidJniObject::​fromString(const QString & string)

Creates a Java string from the QString string and returns a QAndroidJniObject holding that string.

...
QString myQString = "QString";
QAndroidJniObject myJavaString = QAndroidJniObject::fromString(myQString);
...

See also toString().

T QAndroidJniObject::​getField(const char * fieldName) const

Retrieves the value of the field fieldName.

QAndroidJniObject volumeControl = ...;
jint fieldValue = volumeControl.getField<jint>("MAX_VOLUME");

QAndroidJniObject QAndroidJniObject::​getObjectField(const char * fieldName) const

Retrieves the object of field fieldName.

QAndroidJniObject field = jniObject.getObjectField<jstring>("FIELD_NAME");

QAndroidJniObject QAndroidJniObject::​getObjectField(const char * fieldName, const char * signature) const

Retrieves the object from the field with signature and fieldName.

Note: Since Qt 5.3 this function can be used without a template type.

QAndroidJniObject field = jniObject.getObjectField("FIELD_NAME", "Ljava/lang/String;");

[static] T QAndroidJniObject::​getStaticField(const char * className, const char * fieldName)

Retrieves the value from the static field fieldName on the class className.

[static] T QAndroidJniObject::​getStaticField(jclass clazz, const char * fieldName)

Retrieves the value from the static field fieldName on clazz.

[static] QAndroidJniObject QAndroidJniObject::​getStaticObjectField(const char * className, const char * fieldName)

Retrieves the object from the field fieldName on the class className.

QAndroidJniObject jobj = QAndroidJniObject::getStaticObjectField<jstring>("class/with/Fields", "FIELD_NAME");

[static] QAndroidJniObject QAndroidJniObject::​getStaticObjectField(const char * className, const char * fieldName, const char * signature)

Retrieves the object from the field with signature and fieldName on class className.

Note: Since Qt 5.3 this function can be used without a template type.

QAndroidJniObject jobj = QAndroidJniObject::getStaticObjectField("class/with/Fields", "FIELD_NAME", "Ljava/lang/String;");

[static] QAndroidJniObject QAndroidJniObject::​getStaticObjectField(jclass clazz, const char * fieldName)

Retrieves the object from the field fieldName on clazz.

QAndroidJniObject jobj = QAndroidJniObject::getStaticObjectField<jstring>(clazz, "FIELD_NAME");

[static] QAndroidJniObject QAndroidJniObject::​getStaticObjectField(jclass clazz, const char * fieldName, const char * signature)

Retrieves the object from the field with signature and fieldName on clazz.

Note: Since Qt 5.3 this function can be used without a template type.

QAndroidJniObject jobj = QAndroidJniObject::getStaticObjectField(clazz, "FIELD_NAME", "Ljava/lang/String;");

[static] bool QAndroidJniObject::​isClassAvailable(const char * className)

Returns true if the Java class className is available.

...
if (QAndroidJniObject::isClassAvailable("java/lang/String")) {
   ...
}
...

bool QAndroidJniObject::​isValid() const

Returns true if this instance holds a valid Java object.

...
QAndroidJniObject qjniObject;                        ==> isValid() == false
QAndroidJniObject qjniObject(0)                      ==> isValid() == false
QAndroidJniObject qjniObject("could/not/find/Class") ==> isValid() == false
...

T QAndroidJniObject::​object() const

Returns the object held by the QAndroidJniObject as type T.

QAndroidJniObject string = QAndroidJniObject::fromString("Hello, JNI");
jstring jstring = string.object<jstring>();

Note: The returned object is still owned by the QAndroidJniObject. If you want to keep the object valid you should create a new QAndroidJniObject or make a new global reference to the object and free it yourself.

void functionScope()
{
    QString helloString("Hello");
    jstring myJString = 0;
    {
        QAndroidJniObject string = QAndroidJniObject::fromString(helloString);
        myJString = string.object<jstring>();
    }

   // Ops! myJString is no longer valid.
}

Note: Since Qt 5.3 this function can be used without a template type, if the returned type is a jobject.

jobject object = jniObject.object();

void QAndroidJniObject::​setField(const char * fieldName, T value)

Sets the value of fieldName to value.

...
QAndroidJniObject obj;
obj.setField<jint>("AN_INT_FIELD", 10);
jstring myString = ...
obj.setField<jstring>("A_STRING_FIELD", myString);
...

void QAndroidJniObject::​setField(const char * fieldName, const char * signature, T value)

Sets the value of fieldName with signature to value.

QAndroidJniObject stringArray = ...;
QAndroidJniObject obj = ...;
obj.setField<jobjectArray>("KEY_VALUES", "([Ljava/lang/String;)V", stringArray.object<jobjectArray>())

[static] void QAndroidJniObject::​setStaticField(const char * className, const char * fieldName, const char * signature, T value)

Sets the static field with fieldName and signature to value on class className.

[static] void QAndroidJniObject::​setStaticField(const char * className, const char * fieldName, T value)

Sets the value of the static field fieldName in class className to value.

[static] void QAndroidJniObject::​setStaticField(jclass clazz, const char * fieldName, const char * signature, T value)

Sets the static field with fieldName and signature to value on class clazz.

[static] void QAndroidJniObject::​setStaticField(jclass clazz, const char * fieldName, T value)

Sets the static field fieldName of the class clazz to value.

QString QAndroidJniObject::​toString() const

Returns a QString with a string representation of the java object. Calling this function on a Java String object is a convenient way of getting the actual string data.

QAndroidJniObject string = ...; //  "Hello Java"
QString qstring = string.toString(); // "Hello Java"

See also fromString().

QAndroidJniObject & QAndroidJniObject::​operator=(T object)

Replace the current object with object. The old Java object will be released.