Chrome on Android: adds jni_generator.

base/android/jni_generator/SampleForTests.java

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.example.jni_generator;
+
+// This class serves as a reference test for the bindings generator, and as example documentation
+// for how to use the jni generator.
+// The C++ counter-part is sample_for_tests.cc.
+// jni_generator.gyp has a jni_generator_tests target that will:
+//   * Generate a header file for the JNI bindings based on this file.
+//   * Compile sample_for_tests.cc using the generated header file.
+//   * link a native executable to prove the generated header + cc file are self-contained.
+// All comments are informational only, and are ignored by the jni generator.
+class SampleForTests {
+  // Classes can store their C++ pointer counter part as an int that is normally initialized by
+  // calling out a nativeInit() function.
+  int nativePtr;
+
+  // You can define methods and attributes on the java class just like any other.
+  // Methods without the @CalledByNative annotation won't be exposed to JNI.
+  public SampleForTests() {
+  }
+
+  public void startExample() {
+      // Calls native code and holds a pointer to the C++ class.
+      nativePtr = nativeInit("myParam");
+  }
+
+  public void doStuff() {
+      // This will call CPPClass::Method() using nativePtr as a pointer to the object. This must be
+      // done to:
+      // * avoid leaks.
+      // * using finalizers are not allowed to destroy the cpp class.
+      nativeMethod(nativePtr);
+  }
+
+  public void finishExample() {
+      // We're done, so let's destroy nativePtr object.
+      nativeDestroy(nativePtr);
+  }
+
+  // -----------------------------------------------------------------------------------------------
+  // The following methods demonstrate exporting Java methods for invocation from C++ code.
+  // Java functions are mapping into C global functions by prefixing the method name with
+  // "Java_<Class>_"
+  // This is triggered by the @CalledByNative annotation; the methods may be named as you wish.
+
+  // Exported to C++ as:
+  //   Java_Example_javaMethod(JNIEnv* env, jobject obj, jint foo, jint bar)
+  // Typically the C++ code would have obtained the jobject via the Init() call described above.
+  @CalledByNative
+  public int javaMethod(int foo,
+                        int bar) {
+      return 0;
+  }
+
+  // Exported to C++ as Java_Example_staticJavaMethod(JNIEnv* env)
+  // Note no jobject argument, as it is static.
+  @CalledByNative
+  public static boolean staticJavaMethod() {
+      return true;
+  }
+
+  // No prefix, so this method is package private. It will still be exported.
+  @CalledByNative
+  void packagePrivateJavaMethod() {}
+
+  // Note the "Unchecked" suffix. By default, @CalledByNative will always generate bindings that
+  // call CheckException(). With "@CalledByNativeUnchecked", the client C++ code is responsible to
+  // call ClearException() and act as appropriate.
+  // See more details at the "@CalledByNativeUnchecked" annotation.
+  @CalledByNativeUnchecked
+  void methodThatThrowsException() throws Exception {}
+
+  //------------------------------------------------------------------------------------------------
+  // Java fields which are accessed from C++ code must be annotated with @AccessedByNative to
+  // prevent them being eliminated when unreferenced code is stripped.
+  @AccessedByNative
+  private int javaField;
+
+  //------------------------------------------------------------------------------------------------
+  // The following methods demonstrate declaring methods to call into C++ from Java.
+  // The generator detects the "native" and "static" keywords, the type and name of the first
+  // parameter, and the "native" prefix to the function name to determine the C++ function
+  // signatures. Besides these constraints the methods can be freely named.
+
+  // This declares a C++ function which the application code must implement:
+  //   static jint Init(JNIEnv* env, jobject obj);
+  // The jobject parameter refers back to this java side object instance.
+  // The implementation must return the pointer to the C++ object cast to jint.
+  // The caller of this method should store it, and supply it as a the nativeCPPClass param to
+  // subsequent native method calls (see the methods below that take an "int native..." as first
+  // param).
+  private native int nativeInit();
+
+  // This defines a function binding to the associated C++ class member function. The name is
+  // derived from |nativeDestroy| and |nativeCPPClass| to arrive at CPPClass::Destroy() (i.e. native
+  // prefixes stripped).
+  // The |nativeCPPClass| is automatically cast to type CPPClass* in order to obtain the object on
+  // which to invoke the member function.
+  private native void nativeDestroy(int nativeCPPClass);
+
+  // This declares a C++ function which the application code must implement:
+  //   static jdouble GetDoubleFunction(JNIEnv* env, jobject obj);
+  // The jobject parameter refers back to this java side object instance.
+  private native double nativeGetDoubleFunction();
+
+  // Similar to nativeGetDoubleFunction(), but here the C++ side will receive a jclass rather than
+  // jobject param, as the function is declared static.
+  private static native float nativeGetFloatFunction();
+
+  // This function takes a non-POD datatype. We have a list mapping them to their full classpath in
+  // jni_generator.py JavaParamToJni. If you require a new datatype, make sure you add to that
+  // function.
+  private native void nativeSetNonPODDatatype(Rect rect);
+
+  // This declares a C++ function which the application code must implement:
+  //   static ScopedJavaLocalRef<jobject> GetNonPODDatatype(JNIEnv* env, jobject obj);
+  // The jobject parameter refers back to this java side object instance.
+  // Note that it returns a ScopedJavaLocalRef<jobject> so that you don' have to worry about
+  // deleting the JNI local reference.  This is similar with Strings and arrays.
+  private native Object nativeGetNonPODDatatype();
+
+  // Similar to nativeDestroy above, this will cast nativeCPPClass into pointer of CPPClass type and
+  // call its Method member function.
+  private native int nativeMethod(int nativeCPPClass);
+
+  // Similar to nativeMethod above, but here the C++ fully qualified class name is taken from the
+  // comment rather than parameter name, which can thus be chosen freely.
+  private native double nativeMethodOtherP0(int nativeCPPClass /* cpp_namespace::CPPClass */);
+
+  // An inner class has some special attributes for annotation.
+  class InnerClass {
+    @CalledByNative("InnerClass")
+    public float JavaInnerMethod() {
+    }
+
+    @CalledByNative("InnerClass")
+    public static void javaInnerFunction() {
+    }
+
+    @NativeCall("InnerClass")
+    private static native int nativeInnerFunction();
+
+    @NativeCall("InnerClass")
+    private static native String nativeInnerMethod(int nativeCPPClass);
+
+  }
+}