Android乱弹onLowMemory()和onTrimMemory()

@Override public void onLowMemory() { super.onLowMemory(); mContext = getApplicationContext(); }

public void onLowMemory() { Object[] callbacks = collectComponentCallbacks(); if (callbacks != null) { for (int i=0; i<callbacks.length; i++) { ((ComponentCallbacks)callbacks[i]).onLowMemory(); } } }

/** * This is called when the overall system is running low on memory, and * actively running processes should trim their memory usage. While * the exact point at which this will be called is not defined, generally * it will happen when all background process have been killed. * That is, before reaching the point of killing processes hosting * service and foreground UI that we would like to avoid killing. * * <p>You should implement this method to release * any caches or other unnecessary resources you may be holding on to. * The system will perform a garbage collection for you after returning from this method. * <p>Preferably, you should implement {@link ComponentCallbacks2#onTrimMemory} from * {@link ComponentCallbacks2} to incrementally unload your resources based on various * levels of memory demands. That API is available for API level 14 and higher, so you should * only use this {@link #onLowMemory} method as a fallback for older versions, which can be * treated the same as {@link ComponentCallbacks2#onTrimMemory} with the {@link * ComponentCallbacks2#TRIM_MEMORY_COMPLETE} level.</p> */ void onLowMemory();

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); } } } }

/** * Level for {@link #onTrimMemory(int)}: the process is nearing the end * of the background LRU list, and if more memory isn't found soon it will * be killed. */ static final int TRIM_MEMORY_COMPLETE = 80; /** * Level for {@link #onTrimMemory(int)}: the process is around the middle * of the background LRU list; freeing memory can help the system keep * other processes running later in the list for better overall performance. */ static final int TRIM_MEMORY_MODERATE = 60; /** * Level for {@link #onTrimMemory(int)}: the process has gone on to the * LRU list. This is a good opportunity to clean up resources that can * efficiently and quickly be re-built if the user returns to the app. */ static final int TRIM_MEMORY_BACKGROUND = 40; /** * Level for {@link #onTrimMemory(int)}: the process had been showing * a user interface, and is no longer doing so. Large allocations with * the UI should be released at this point to allow memory to be better * managed. */ static final int TRIM_MEMORY_UI_HIDDEN = 20; /** * Level for {@link #onTrimMemory(int)}: the process is not an expendable * background process, but the device is running extremely low on memory * and is about to not be able to keep any background processes running. * Your running process should free up as many non-critical resources as it * can to allow that memory to be used elsewhere. The next thing that * will happen after this is {@link #onLowMemory()} called to report that * nothing at all can be kept in the background, a situation that can start * to notably impact the user. */ static final int TRIM_MEMORY_RUNNING_CRITICAL = 15; /** * Level for {@link #onTrimMemory(int)}: the process is not an expendable * background process, but the device is running low on memory. * Your running process should free up unneeded resources to allow that * memory to be used elsewhere. */ static final int TRIM_MEMORY_RUNNING_LOW = 10; /** * Level for {@link #onTrimMemory(int)}: the process is not an expendable * background process, but the device is running moderately low on memory. * Your running process may want to release some unneeded resources for * use elsewhere. */ static final int TRIM_MEMORY_RUNNING_MODERATE = 5; /** * Called when the operating system has determined that it is a good * time for a process to trim unneeded memory from its process. This will * happen for example when it goes in the background and there is not enough * memory to keep as many background processes running as desired. You * should never compare to exact values of the level, since new intermediate * values may be added -- you will typically want to compare if the value * is greater or equal to a level you are interested in. * * <p>To retrieve the processes current trim level at any point, you can * use {@link android.app.ActivityManager#getMyMemoryState * ActivityManager.getMyMemoryState(RunningAppProcessInfo)}. * * @param level The context of the trim, giving a hint of the amount of * trimming the application may like to perform. May be * {@link #TRIM_MEMORY_COMPLETE}, {@link #TRIM_MEMORY_MODERATE}, * {@link #TRIM_MEMORY_BACKGROUND}, {@link #TRIM_MEMORY_UI_HIDDEN}, * {@link #TRIM_MEMORY_RUNNING_CRITICAL}, {@link #TRIM_MEMORY_RUNNING_LOW}, * or {@link #TRIM_MEMORY_RUNNING_MODERATE}. */ void onTrimMemory(int level);