final void handleLowMemory() {
    ArrayList<ComponentCallbacks2> callbacks;

    synchronized (mPackages) {
        callbacks = collectComponentCallbacksLocked(true, null);
    }

    final int N = callbacks.size();
    for (int i=0; i<N; i++) {
        callbacks.get(i).onLowMemory();
    }

    // Ask SQLite to free up as much memory as it can, mostly from its page caches.
    if (Process.myUid() != Process.SYSTEM_UID) {
        int sqliteReleased = SQLiteDatabase.releaseMemory();
        EventLog.writeEvent(SQLITE_MEM_RELEASED_EVENT_LOG_TAG, sqliteReleased);
    }

    // Ask graphics to free up as much as possible (font/image caches)
    Canvas.freeCaches();

    // Ask text layout engine to free also as much as possible
    Canvas.freeTextLayoutCaches();

    BinderInternal.forceGc("mem");
}
 

final void handleTrimMemory(int level) {
    if (DEBUG_MEMORY_TRIM) Slog.v(TAG, "Trimming memory to level: " + level);

    final WindowManagerImpl windowManager = WindowManagerImpl.getDefault();
    windowManager.startTrimMemory(level);

    ArrayList<ComponentCallbacks2> callbacks;
    synchronized (mPackages) {
        callbacks = collectComponentCallbacksLocked(true, null);
    }

    final int N = callbacks.size();
    for (int i = 0; i < N; i++) {
        callbacks.get(i).onTrimMemory(level);
    }

    windowManager.endTrimMemory();        
}
 

final void handleLowMemory() {
    ArrayList<ComponentCallbacks2> callbacks;

    synchronized (mPackages) {
        callbacks = collectComponentCallbacksLocked(true, null);
    }

    final int N = callbacks.size();
    for (int i=0; i<N; i++) {
        callbacks.get(i).onLowMemory();
    }

    // Ask SQLite to free up as much memory as it can, mostly from its page caches.
    if (Process.myUid() != Process.SYSTEM_UID) {
        int sqliteReleased = SQLiteDatabase.releaseMemory();
        EventLog.writeEvent(SQLITE_MEM_RELEASED_EVENT_LOG_TAG, sqliteReleased);
    }

    // Ask graphics to free up as much as possible (font/image caches)
    Canvas.freeCaches();

    BinderInternal.forceGc("mem");
}
 

public void trimMemory(int level) {
    if (ThreadedRenderer.isAvailable()) {
        if (shouldDestroyEglContext(level)) {
            // Destroy all hardware surfaces and resources associated to
            // known windows
            synchronized (mLock) {
                for (int i = mRoots.size() - 1; i >= 0; --i) {
                    mRoots.get(i).destroyHardwareResources();
                }
            }
            // Force a full memory flush
            level = ComponentCallbacks2.TRIM_MEMORY_COMPLETE;
        }

        ThreadedRenderer.trimMemory(level);

        if (ThreadedRenderer.sTrimForeground) {
            doTrimForeground();
        }
    }
}
 

private void doTrimForeground() {
    boolean hasVisibleWindows = false;
    synchronized (mLock) {
        for (int i = mRoots.size() - 1; i >= 0; --i) {
            final ViewRootImpl root = mRoots.get(i);
            if (root.mView != null && root.getHostVisibility() == View.VISIBLE
                    && root.mAttachInfo.mThreadedRenderer != null) {
                hasVisibleWindows = true;
            } else {
                root.destroyHardwareResources();
            }
        }
    }
    if (!hasVisibleWindows) {
        ThreadedRenderer.trimMemory(
                ComponentCallbacks2.TRIM_MEMORY_COMPLETE);
    }
}
 

@Override
public void onTrimMemory(int i) {
    ActivityManager am = (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
    List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
    Log.d("topActivity", "CURRENT Activity ::"
            + taskInfo.get(0).topActivity.getClassName());

    if (taskInfo != null && taskInfo.size() > 0) {
        ComponentName componentInfo = taskInfo.get(0).topActivity;
        packageName = componentInfo.getPackageName();
    }
    if (!packageName.equals(getPackageName()) && i == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
        // We're in the Background
        wentToBg = true;
        Log.d(TAG, "wentToBg: " + wentToBg);
    }
}
 

@Test
public void testBackgroundStateChangeCallbacks() {
  FirebaseApp firebaseApp = FirebaseApp.initializeApp(targetContext, OPTIONS, "myApp");
  firebaseApp.setAutomaticResourceManagementEnabled(true);
  final AtomicBoolean backgroundState = new AtomicBoolean();
  final AtomicInteger callbackCount = new AtomicInteger();
  firebaseApp.addBackgroundStateChangeListener(
      background -> {
        backgroundState.set(background);
        callbackCount.incrementAndGet();
      });
  assertThat(callbackCount.get()).isEqualTo(0);

  // App moves to the background.
  backgroundDetector.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);
  assertThat(callbackCount.get()).isEqualTo(1);
  assertThat(backgroundState.get()).isTrue();

  // App moves to the foreground.
  backgroundDetector.onActivityResumed(null);
  assertThat(callbackCount.get()).isEqualTo(2);
  assertThat(backgroundState.get()).isFalse();
}
 

@Test
public void testRemovedBackgroundStateChangeCallbacksDontFire() {
  FirebaseApp firebaseApp = FirebaseApp.initializeApp(targetContext, OPTIONS, "myApp");
  final AtomicInteger callbackCount = new AtomicInteger();
  FirebaseApp.BackgroundStateChangeListener listener =
      background -> callbackCount.incrementAndGet();
  firebaseApp.addBackgroundStateChangeListener(listener);
  firebaseApp.removeBackgroundStateChangeListener(listener);

  // App moves to the background.
  backgroundDetector.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);

  // App moves to the foreground.
  backgroundDetector.onActivityResumed(null);

  assertThat(callbackCount.get()).isEqualTo(0);
}
 

@Override
public void onTrimMemory(int level) {

    // Determine which lifecycle or system event was raised.
    switch (level) {

        case ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN:
        case ComponentCallbacks2.TRIM_MEMORY_BACKGROUND:
        case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
        case ComponentCallbacks2.TRIM_MEMORY_COMPLETE:
            // Curently ignore these levels. They are handled somewhere else.
            break;
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE:
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW:
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL:
            // It looks like these come in all at the same time so just always suspend inactive Sessions.
            Log.d(LOGTAG, "Memory pressure, suspending inactive sessions.");
            SessionStore.get().suspendAllInactiveSessions();
            break;
        default:
            Log.e(LOGTAG, "onTrimMemory unknown level: " + level);
            break;
    }
}
 

/**
 * Used by applications to simulate a memory pressure signal. By throwing certain intent
 * actions.
 */
public static boolean handleDebugIntent(Activity activity, String action) {
    if (ACTION_LOW_MEMORY.equals(action)) {
        simulateLowMemoryPressureSignal(activity);
    } else if (ACTION_TRIM_MEMORY.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_COMPLETE);
    } else if (ACTION_TRIM_MEMORY_RUNNING_CRITICAL.equals(action)) {
        simulateTrimMemoryPressureSignal(activity,
                ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL);
    } else if (ACTION_TRIM_MEMORY_MODERATE.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_MODERATE);
    } else {
        return false;
    }

    return true;
}
 

@Override
public void onTrimMemory(int level) {
    ImageLoader imageLoader = SubsonicActivity.getStaticImageLoader(this);
    if (imageLoader != null) {
        Log.i(TAG, "Memory Trim Level: " + level);
        if (level < ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
            if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL) {
                imageLoader.onLowMemory(0.75f);
            } else if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW) {
                imageLoader.onLowMemory(0.50f);
            } else if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE) {
                imageLoader.onLowMemory(0.25f);
            }
        } else if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE) {
            imageLoader.onLowMemory(0.25f);
        }
    }
}
 

@Override
public void onTrimMemory(int level) {
    switch(level) {
        // Trims memory when it reaches a moderate level and the session is inactive
        case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE:
            if(session.isActive()) break;

            // Trims memory when it reaches a critical level
        case ComponentCallbacks2.TRIM_MEMORY_COMPLETE:
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL:

            Log.w(TAG, "Control resources are being removed due to system's low memory (Level: " + level + ")");
            destroy();
            break;
    }
}
 

@CalledByNative
private static void registerSystemCallback() {
    ContextUtils.getApplicationContext().registerComponentCallbacks(
            new ComponentCallbacks2() {
                @Override
                public void onTrimMemory(int level) {
                    maybeNotifyMemoryPresure(level);
                }

                @Override
                public void onLowMemory() {
                    nativeOnMemoryPressure(MemoryPressureLevel.CRITICAL);
                }

                @Override
                public void onConfigurationChanged(Configuration configuration) {
                }
            });
}
 

/**
 * Used by applications to simulate a memory pressure signal. By throwing certain intent
 * actions.
 */
public static boolean handleDebugIntent(Activity activity, String action) {
    if (ACTION_LOW_MEMORY.equals(action)) {
        simulateLowMemoryPressureSignal(activity);
    } else if (ACTION_TRIM_MEMORY.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_COMPLETE);
    } else if (ACTION_TRIM_MEMORY_RUNNING_CRITICAL.equals(action)) {
        simulateTrimMemoryPressureSignal(activity,
                ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL);
    } else if (ACTION_TRIM_MEMORY_MODERATE.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_MODERATE);
    } else {
        return false;
    }

    return true;
}
 

/**
 * Register ComponentCallbacks2 to receive memory pressure signals.
 *
 */
@CalledByNative
private static void registerComponentCallbacks() {
    sCallbacks = new ComponentCallbacks2() {
            @Override
            public void onTrimMemory(int level) {
                if (level != ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
                    nativeOnTrimMemory(level);
                }
            }
            @Override
            public void onLowMemory() {
                // Don't support old onLowMemory().
            }
            @Override
            public void onConfigurationChanged(Configuration config) {
            }
        };
    ContextUtils.getApplicationContext().registerComponentCallbacks(sCallbacks);
}
 

@Override
public void onTrimMemory(int level) {
	ImageLoader imageLoader = SubsonicActivity.getStaticImageLoader(this);
	if(imageLoader != null && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
		Log.i(TAG, "Memory Trim Level: " + level);
		if (level < ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
			if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL) {
				imageLoader.onLowMemory(0.75f);
			} else if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW) {
				imageLoader.onLowMemory(0.50f);
			} else if(level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE) {
				imageLoader.onLowMemory(0.25f);
			}
		} else if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE) {
			imageLoader.onLowMemory(0.25f);
		} else if(level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
			imageLoader.onLowMemory(0.75f);
		}
	}
}
 

/**
 * @inheritDoc
 */
@Override
public void trimMemory(int level) {

    if(level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
        emptyCache(); //dump the cache
    }
    else if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE){
        trimCache(0.5f); // trim to half the max size
    }
    else if (level >= ComponentCallbacks2.TRIM_MEMORY_BACKGROUND){
        trimCache(0.7f); // trim to one seventh max size
    }
    else if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL){
        trimCache(0.2f); // trim to one fifth max size
    }
}
 

/**
 * 获取修剪级别的名称
 */
@NonNull
public static String getTrimLevelName(int level) {
    switch (level) {
        case ComponentCallbacks2.TRIM_MEMORY_COMPLETE:
            return "COMPLETE";
        case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
            return "MODERATE";
        case ComponentCallbacks2.TRIM_MEMORY_BACKGROUND:
            return "BACKGROUND";
        case ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN:
            return "UI_HIDDEN";
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL:
            return "RUNNING_CRITICAL";
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW:
            return "RUNNING_LOW";
        case ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE:
            return "RUNNING_MODERATE";
        default:
            return "UNKNOWN";
    }
}
 

@CalledByNative
private static void registerSystemCallback(Context context) {
    context.registerComponentCallbacks(
        new ComponentCallbacks2() {
              @Override
              public void onTrimMemory(int level) {
                  maybeNotifyMemoryPresure(level);
              }

              @Override
              public void onLowMemory() {
                  nativeOnMemoryPressure(MemoryPressureLevelList.MEMORY_PRESSURE_CRITICAL);
              }

              @Override
              public void onConfigurationChanged(Configuration configuration) {
              }
        });
}
 

/**
 * Used by applications to simulate a memory pressure signal. By throwing certain intent
 * actions.
 */
public static boolean handleDebugIntent(Activity activity, String action) {
    if (ACTION_LOW_MEMORY.equals(action)) {
        simulateLowMemoryPressureSignal(activity);
    } else if (ACTION_TRIM_MEMORY.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_COMPLETE);
    } else if (ACTION_TRIM_MEMORY_RUNNING_CRITICAL.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_MODERATE);
    } else if (ACTION_TRIM_MEMORY_MODERATE.equals(action)) {
        simulateTrimMemoryPressureSignal(activity,
                ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL);
    } else {
        return false;
    }

    return true;
}
 

@CalledByNative
private static void registerSystemCallback(Context context) {
    context.registerComponentCallbacks(
        new ComponentCallbacks2() {
              @Override
              public void onTrimMemory(int level) {
                  maybeNotifyMemoryPresure(level);
              }

              @Override
              public void onLowMemory() {
                  nativeOnMemoryPressure(MemoryPressureLevelList.MEMORY_PRESSURE_CRITICAL);
              }

              @Override
              public void onConfigurationChanged(Configuration configuration) {
              }
        });
}
 

/**
 * Used by applications to simulate a memory pressure signal. By throwing certain intent
 * actions.
 */
public static boolean handleDebugIntent(Activity activity, String action) {
    if (ACTION_LOW_MEMORY.equals(action)) {
        simulateLowMemoryPressureSignal(activity);
    } else if (ACTION_TRIM_MEMORY.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_COMPLETE);
    } else if (ACTION_TRIM_MEMORY_RUNNING_CRITICAL.equals(action)) {
        simulateTrimMemoryPressureSignal(activity, ComponentCallbacks2.TRIM_MEMORY_MODERATE);
    } else if (ACTION_TRIM_MEMORY_MODERATE.equals(action)) {
        simulateTrimMemoryPressureSignal(activity,
                ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL);
    } else {
        return false;
    }

    return true;
}
 

final void handleTrimMemory(int level) {
    WindowManagerImpl.getDefault().trimMemory(level);
    ArrayList<ComponentCallbacks2> callbacks;

    synchronized (mPackages) {
        callbacks = collectComponentCallbacksLocked(true, null);
    }

    final int N = callbacks.size();
    for (int i=0; i<N; i++) {
        callbacks.get(i).onTrimMemory(level);
    }
}
 

public static boolean shouldDestroyEglContext(int trimLevel) {
    // On low-end gfx devices we trim when memory is moderate;
    // on high-end devices we do this when low.
    if (trimLevel >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
        return true;
    }
    if (trimLevel >= ComponentCallbacks2.TRIM_MEMORY_MODERATE
            && !ActivityManager.isHighEndGfx()) {
        return true;
    }
    return false;
}
 

@CallSuper
public void onTrimMemory(int level) {
    Object[] callbacks = collectComponentCallbacks();
    if (callbacks != null) {
        for (int i=0; i<callbacks.length; i++) {
            Object c = callbacks[i];
            if (c instanceof ComponentCallbacks2) {
                ((ComponentCallbacks2)c).onTrimMemory(level);
            }
        }
    }
}
 

@Override
public void onTrimMemory(int level) {
    super.onTrimMemory(level);
    //当应用所有UI隐藏时应该释放UI上所有占用的资源
    if(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN == level)
        GlideApp.get(this).clearMemory();
    //根据level级别来清除一些图片缓存
    GlideApp.get(this).onTrimMemory(level);
}
 

@Override
public void onTrimMemory(int level) {
    super.onTrimMemory(level);

    if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW) {
        clearMemoryCache();
    }
}
 

@Test
public void testBackgroundStateChangeCallbacksDontFire_AutomaticResourceManagementTurnedOff() {
  FirebaseApp firebaseApp = FirebaseApp.initializeApp(targetContext, OPTIONS, "myApp");
  firebaseApp.setAutomaticResourceManagementEnabled(true);
  final AtomicInteger callbackCount = new AtomicInteger();
  final AtomicBoolean backgroundState = new AtomicBoolean();
  FirebaseApp.BackgroundStateChangeListener listener =
      background -> {
        backgroundState.set(background);
        callbackCount.incrementAndGet();
      };
  firebaseApp.addBackgroundStateChangeListener(listener);

  // App moves to the background.
  backgroundDetector.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);

  assertThat(callbackCount.get()).isEqualTo(1);

  // Turning off automatic resource management fires foreground event, if the current state
  // is background.
  assertThat(backgroundDetector.isInBackground()).isTrue();
  firebaseApp.setAutomaticResourceManagementEnabled(false);
  assertThat(callbackCount.get()).isEqualTo(2);
  assertThat(backgroundState.get()).isFalse();

  // No more callbacks.
  backgroundDetector.onActivityResumed(null);
  backgroundDetector.onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN);
  assertThat(callbackCount.get()).isEqualTo(2);
}
 

@Override
public void onTrimMemory(int level) {
    super.onTrimMemory(level);
    //当应用所有UI隐藏时应该释放UI上所有占用的资源
    if(ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN == level)
        GlideApp.get(this).clearMemory();
    //根据level级别来清除一些图片缓存
    GlideApp.get(this).onTrimMemory(level);
}
 

@Override
public void onTrimMemory(int level) {
    Log.w(TAG, "------------onTrimMemory level = " + level + " ----------------");
    try {
        if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE) { // 60：后台，内存紧张
            clearMemoryCaches();
        } else if (level == ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL) {//15:前台，内存紧张
            clearMemoryCaches();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}