学步园

step 1:定义一个监听接口

public static interface OnLowMemoryListener {
        void onLowMemoryReceived();
    }

step 2:android application文件中添加如下代码

//初始化

private ArrayList<WeakReference<OnLowMemoryListener>> mLowMemoryListeners;

public MyApp() {
        mLowMemoryListeners = new ArrayList<WeakReference<OnLowMemoryListener>>();
    }

//注册监听

public void registerOnLowMemoryListener(OnLowMemoryListener listener) {
        if (listener != null) {
            mLowMemoryListeners
                    .add(new WeakReference<MyApp.OnLowMemoryListener>(listener));
        }
    }
//移除监听
    public void unregisterOnLowMemoryListener(OnLowMemoryListener listener) {
        if (listener != null) {
            int i = 0;
            while (i < mLowMemoryListeners.size()) {
                final OnLowMemoryListener l = mLowMemoryListeners.get(i).get();
                if (l == null || l == listener) {
                    mLowMemoryListeners.remove(i);
                } else {
                    i++;
                }
            }
        }
    }

//内存空间过低的时候，被系统调用

@Override
    public void onLowMemory() {
        super.onLowMemory();
        int i = 0;
        while (i < mLowMemoryListeners.size()) {
            final OnLowMemoryListener l = mLowMemoryListeners.get(i).get();
            if (l == null) {
                mLowMemoryListeners.remove(i);
            } else {
                l.onLowMemoryReceived();
                i++;
            }
        }
    }

step 3：那些浪费内存的地方，比如图片缓存，可以实现并注册这个监听