QAndroidJniObject Class

  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.

See also fromLocalRef().

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::fromLocalRef(jobject localRef)

Creates a QAndroidJniObject from the local JNI reference localRef. This function takes ownership of localRef and frees it before returning.

Note: Only call this function with a local JNI reference. For example, most raw JNI calls, through the JNI environment, returns local references to a java object.

  jobject localRef = env->GetObjectArrayElement(array, index);
  QAndroidJniObject element = QAndroidJniObject::fromLocalRef(localRef);

This function was introduced in Qt 5.7.

[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.