base/android/jni_android.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_ANDROID_JNI_ANDROID_H_
   6 #define BASE_ANDROID_JNI_ANDROID_H_
   7
   8 #include <jni.h>
   9 #include <sys/types.h>
  10
  11 #include <string>
  12
  13 #include "base/android/scoped_java_ref.h"
  14 #include "base/atomicops.h"
  15 #include "base/base_export.h"
  16 #include "base/compiler_specific.h"
  17
  18 namespace base {
  19 namespace android {
  20
  21 // Used to mark symbols to be exported in a shared library's symbol table.
  22 #define JNI_EXPORT __attribute__ ((visibility("default")))
  23
  24 // Contains the registration method information for initializing JNI bindings.
  25 struct RegistrationMethod {
  26   const char* name;
  27   bool (*func)(JNIEnv* env);
  28 };
  29
  30 // Attaches the current thread to the VM (if necessary) and return the JNIEnv*.
  31 BASE_EXPORT JNIEnv* AttachCurrentThread();
  32
  33 // Same to AttachCurrentThread except that thread name will be set to
  34 // |thread_name| if it is the first call. Otherwise, thread_name won't be
  35 // changed. AttachCurrentThread() doesn't regard underlying platform thread
  36 // name, but just resets it to "Thread-???". This function should be called
  37 // right after new thread is created if it is important to keep thread name.
  38 BASE_EXPORT JNIEnv* AttachCurrentThreadWithName(const std::string& thread_name);
  39
  40 // Detaches the current thread from VM if it is attached.
  41 BASE_EXPORT void DetachFromVM();
  42
  43 // Initializes the global JVM. It is not necessarily called before
  44 // InitApplicationContext().
  45 BASE_EXPORT void InitVM(JavaVM* vm);
  46
  47 // Returns true if the global JVM has been initialized.
  48 BASE_EXPORT bool IsVMInitialized();
  49
  50 // Initializes the global application context object. The |context| can be any
  51 // valid reference to the application context. Internally holds a global ref to
  52 // the context. InitVM and InitApplicationContext maybe called in either order.
  53 BASE_EXPORT void InitApplicationContext(JNIEnv* env,
  54                                         const JavaRef<jobject>& context);
  55
  56 // Initializes the global ClassLoader used by the GetClass and LazyGetClass
  57 // methods. This is needed because JNI will use the base ClassLoader when there
  58 // is no Java code on the stack. The base ClassLoader doesn't know about any of
  59 // the application classes and will fail to lookup anything other than system
  60 // classes.
  61 BASE_EXPORT void InitReplacementClassLoader(
  62     JNIEnv* env,
  63     const JavaRef<jobject>& class_loader);
  64
  65 // Gets a global ref to the application context set with
  66 // InitApplicationContext(). Ownership is retained by the function - the caller
  67 // must NOT release it.
  68 const BASE_EXPORT jobject GetApplicationContext();
  69
  70 // Finds the class named |class_name| and returns it.
  71 // Use this method instead of invoking directly the JNI FindClass method (to
  72 // prevent leaking local references).
  73 // This method triggers a fatal assertion if the class could not be found.
  74 // Use HasClass if you need to check whether the class exists.
  75 BASE_EXPORT ScopedJavaLocalRef<jclass> GetClass(JNIEnv* env,
  76                                                 const char* class_name);
  77
  78 // The method will initialize |atomic_class_id| to contain a global ref to the
  79 // class. And will return that ref on subsequent calls.  It's the caller's
  80 // responsibility to release the ref when it is no longer needed.
  81 // The caller is responsible to zero-initialize |atomic_method_id|.
  82 // It's fine to simultaneously call this on multiple threads referencing the
  83 // same |atomic_method_id|.
  84 BASE_EXPORT jclass LazyGetClass(
  85     JNIEnv* env,
  86     const char* class_name,
  87     base::subtle::AtomicWord* atomic_class_id);
  88
  89 // This class is a wrapper for JNIEnv Get(Static)MethodID.
  90 class BASE_EXPORT MethodID {
  91  public:
  92   enum Type {
  93     TYPE_STATIC,
  94     TYPE_INSTANCE,
  95   };
  96
  97   // Returns the method ID for the method with the specified name and signature.
  98   // This method triggers a fatal assertion if the method could not be found.
  99   template<Type type>
 100   static jmethodID Get(JNIEnv* env,
 101                        jclass clazz,
 102                        const char* method_name,
 103                        const char* jni_signature);
 104
 105   // The caller is responsible to zero-initialize |atomic_method_id|.
 106   // It's fine to simultaneously call this on multiple threads referencing the
 107   // same |atomic_method_id|.
 108   template<Type type>
 109   static jmethodID LazyGet(JNIEnv* env,
 110                            jclass clazz,
 111                            const char* method_name,
 112                            const char* jni_signature,
 113                            base::subtle::AtomicWord* atomic_method_id);
 114 };
 115
 116 // Returns true if an exception is pending in the provided JNIEnv*.
 117 BASE_EXPORT bool HasException(JNIEnv* env);
 118
 119 // If an exception is pending in the provided JNIEnv*, this function clears it
 120 // and returns true.
 121 BASE_EXPORT bool ClearException(JNIEnv* env);
 122
 123 // This function will call CHECK() macro if there's any pending exception.
 124 BASE_EXPORT void CheckException(JNIEnv* env);
 125
 126 }  // namespace android
 127 }  // namespace base
 128
 129 #endif  // BASE_ANDROID_JNI_ANDROID_H_