base/message_loop/message_pump_android.cc

   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 #include "base/message_loop/message_pump_android.h"
   6
   7 #include <jni.h>
   8
   9 #include "base/android/jni_android.h"
  10 #include "base/android/scoped_java_ref.h"
  11 #include "base/lazy_instance.h"
  12 #include "base/logging.h"
  13 #include "base/run_loop.h"
  14 #include "base/time/time.h"
  15 #include "jni/SystemMessageHandler_jni.h"
  16
  17 using base::android::ScopedJavaLocalRef;
  18
  19 // ----------------------------------------------------------------------------
  20 // Native JNI methods called by Java.
  21 // ----------------------------------------------------------------------------
  22 // This method can not move to anonymous namespace as it has been declared as
  23 // 'static' in system_message_handler_jni.h.
  24 static void DoRunLoopOnce(JNIEnv* env, jobject obj, jlong native_delegate,
  25     jlong delayed_scheduled_time_ticks) {
  26   base::MessagePump::Delegate* delegate =
  27       reinterpret_cast<base::MessagePump::Delegate*>(native_delegate);
  28   DCHECK(delegate);
  29   // This is based on MessagePumpForUI::DoRunLoop() from desktop.
  30   // Note however that our system queue is handled in the java side.
  31   // In desktop we inspect and process a single system message and then
  32   // we call DoWork() / DoDelayedWork().
  33   // On Android, the java message queue may contain messages for other handlers
  34   // that will be processed before calling here again.
  35   bool did_work = delegate->DoWork();
  36
  37   // In the java side, |SystemMessageHandler| keeps a single "delayed" message.
  38   // It's an expensive operation to |removeMessage| there, so this is optimized
  39   // to avoid those calls.
  40   //
  41   // At this stage, |next_delayed_work_time| can be:
  42   // 1) The same as previously scheduled: nothing to be done, move along. This
  43   // is the typical case, since this method is called for every single message.
  44   //
  45   // 2) Not previously scheduled: just post a new message in java.
  46   //
  47   // 3) Shorter than previously scheduled: far less common. In this case,
  48   // |removeMessage| and post a new one.
  49   //
  50   // 4) Longer than previously scheduled (or null): nothing to be done, move
  51   // along.
  52   //
  53   // Side note: base::TimeTicks is a C++ representation and can't be
  54   // compared in java. When calling |scheduleDelayedWork|, pass the
  55   // |InternalValue()| to java and then back to C++ so the comparisons can be
  56   // done here.
  57   // This roundtrip allows comparing TimeTicks directly (cheap) and
  58   // avoid comparisons with TimeDelta / Now() (expensive).
  59   base::TimeTicks next_delayed_work_time;
  60   did_work |= delegate->DoDelayedWork(&next_delayed_work_time);
  61
  62   if (!next_delayed_work_time.is_null()) {
  63     // Schedule a new message if there's nothing already scheduled or there's a
  64     // shorter delay than previously scheduled (see (2) and (3) above).
  65     if (delayed_scheduled_time_ticks == 0 ||
  66         next_delayed_work_time < base::TimeTicks::FromInternalValue(
  67             delayed_scheduled_time_ticks)) {
  68       Java_SystemMessageHandler_scheduleDelayedWork(env, obj,
  69           next_delayed_work_time.ToInternalValue(),
  70           (next_delayed_work_time -
  71            base::TimeTicks::Now()).InMillisecondsRoundedUp());
  72     }
  73   }
  74
  75   // This is a major difference between android and other platforms: since we
  76   // can't inspect it and process just one single message, instead we'll yeld
  77   // the callstack.
  78   if (did_work)
  79     return;
  80
  81   delegate->DoIdleWork();
  82 }
  83
  84 namespace base {
  85
  86 MessagePumpForUI::MessagePumpForUI()
  87     : run_loop_(NULL) {
  88 }
  89
  90 MessagePumpForUI::~MessagePumpForUI() {
  91 }
  92
  93 void MessagePumpForUI::Run(Delegate* delegate) {
  94   NOTREACHED() << "UnitTests should rely on MessagePumpForUIStub in"
  95       " test_stub_android.h";
  96 }
  97
  98 void MessagePumpForUI::Start(Delegate* delegate) {
  99   run_loop_ = new RunLoop();
 100   // Since the RunLoop was just created above, BeforeRun should be guaranteed to
 101   // return true (it only returns false if the RunLoop has been Quit already).
 102   if (!run_loop_->BeforeRun())
 103     NOTREACHED();
 104
 105   DCHECK(system_message_handler_obj_.is_null());
 106
 107   JNIEnv* env = base::android::AttachCurrentThread();
 108   DCHECK(env);
 109
 110   system_message_handler_obj_.Reset(
 111       Java_SystemMessageHandler_create(
 112           env, reinterpret_cast<intptr_t>(delegate)));
 113 }
 114
 115 void MessagePumpForUI::Quit() {
 116   if (!system_message_handler_obj_.is_null()) {
 117     JNIEnv* env = base::android::AttachCurrentThread();
 118     DCHECK(env);
 119
 120     Java_SystemMessageHandler_removeAllPendingMessages(env,
 121         system_message_handler_obj_.obj());
 122     system_message_handler_obj_.Reset();
 123   }
 124
 125   if (run_loop_) {
 126     run_loop_->AfterRun();
 127     delete run_loop_;
 128     run_loop_ = NULL;
 129   }
 130 }
 131
 132 void MessagePumpForUI::ScheduleWork() {
 133   DCHECK(!system_message_handler_obj_.is_null());
 134
 135   JNIEnv* env = base::android::AttachCurrentThread();
 136   DCHECK(env);
 137
 138   Java_SystemMessageHandler_scheduleWork(env,
 139       system_message_handler_obj_.obj());
 140 }
 141
 142 void MessagePumpForUI::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {
 143   DCHECK(!system_message_handler_obj_.is_null());
 144
 145   JNIEnv* env = base::android::AttachCurrentThread();
 146   DCHECK(env);
 147
 148   jlong millis =
 149       (delayed_work_time - TimeTicks::Now()).InMillisecondsRoundedUp();
 150   // Note that we're truncating to milliseconds as required by the java side,
 151   // even though delayed_work_time is microseconds resolution.
 152   Java_SystemMessageHandler_scheduleDelayedWork(env,
 153       system_message_handler_obj_.obj(),
 154       delayed_work_time.ToInternalValue(), millis);
 155 }
 156
 157 // static
 158 bool MessagePumpForUI::RegisterBindings(JNIEnv* env) {
 159   return RegisterNativesImpl(env);
 160 }
 161
 162 }  // namespace base