Trigger GC and drop compiled code on low memory

Reviewed By: astreet

Differential Revision: D2658693

fb-gh-sync-id: 8cba49b67ac45a2dbf8b4c9c404d6fb9c97693f6

ReactAndroid/src/main/java/com/facebook/react/MemoryPressureRouter.java

@@ -0,0 +1,93 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react;
+
+import javax.annotation.Nullable;
+
+import android.annotation.TargetApi;
+import android.app.Activity;
+import android.content.ComponentCallbacks2;
+import android.content.Context;
+import android.content.res.Configuration;
+import android.os.Build;
+
+import com.facebook.react.bridge.CatalystInstance;
+import com.facebook.react.bridge.MemoryPressure;
+import com.facebook.react.bridge.ReactContext;
+
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_BACKGROUND;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_MODERATE;
+import static android.content.ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL;
+
+/**
+ * Translates and routes memory pressure events to the current catalyst instance.
+ */
+public class MemoryPressureRouter {
+  // Trigger this by sending an intent to your activity with adb shell:
+  // am start -a "com.facebook.catalyst.ACTION_TRIM_MEMORY" --activity-single-top -n <activity>
+  private static final String ACTION_TRIM_MEMORY ="com.facebook.catalyst.ACTION_TRIM_MEMORY";
+
+  private @Nullable CatalystInstance mCatalystInstance;
+  private final ComponentCallbacks2 mCallbacks = new ComponentCallbacks2() {
+    @Override
+    public void onTrimMemory(int level) {
+      trimMemory(level);
+    }
+
+    @Override
+    public void onConfigurationChanged(Configuration newConfig) {
+    }
+
+    @Override
+    public void onLowMemory() {
+    }
+  };
+
+  @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
+  public static boolean handleDebugIntent(Activity activity, String action) {
+    switch (action) {
+      case ACTION_TRIM_MEMORY:
+        simulateTrimMemory(activity, TRIM_MEMORY_MODERATE);
+        break;
+      default:
+        return false;
+    }
+
+    return true;
+  }
+
+  MemoryPressureRouter(Context context) {
+    context.getApplicationContext().registerComponentCallbacks(mCallbacks);
+  }
+
+  public void onNewReactContextCreated(ReactContext reactContext) {
+    mCatalystInstance = reactContext.getCatalystInstance();
+  }
+
+  public void onReactInstanceDestroyed() {
+    mCatalystInstance = null;
+  }
+
+  public void destroy(Context context) {
+    context.getApplicationContext().unregisterComponentCallbacks(mCallbacks);
+  }
+
+  private void trimMemory(int level) {
+    if (level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
+      dispatchMemoryPressure(MemoryPressure.CRITICAL);
+    } else if (level >= TRIM_MEMORY_BACKGROUND || level == TRIM_MEMORY_RUNNING_CRITICAL) {
+      dispatchMemoryPressure(MemoryPressure.MODERATE);
+    }
+  }
+
+  private void dispatchMemoryPressure(MemoryPressure level) {
+    if (mCatalystInstance != null) {
+      mCatalystInstance.handleMemoryPressure(level);
+    }
+  }
+
+  private static void simulateTrimMemory(Activity activity, int level) {
+    activity.getApplication().onTrimMemory(level);
+    activity.onTrimMemory(level);
+  }
+}