android学习-11 oom产生的原因及解决方案(handler的内存泄漏问题）

oom：https://www.jianshu.com/p/b0451684b4d5
静态变量生命周期：https://blog.csdn.net/ctcwri/article/details/8858414
单例模式的内存泄漏问题：https://blog.csdn.net/qq_39830579/article/details/100516883

Handler的内存泄漏问题：

在java中非静态内部类和匿名内部类都会隐式持有当前类的外部引用，由于Handler是非静态内部类所以其持有当前Activity的隐式引用，如果Handler没有被释放，其所持有的外部引用也就是Activity也不可能被释放，当一个对象一句不需要再使用了，本来该被回收时，而有另外一个正在使用的对象持有它的引用从而导致它不能被回收，这导致本该被回收的对象不能被回收而停留在堆内存中，这就产生了内存泄漏

解决方案：

用弱引用持有当前activity

public class SampleActivity extends Activity {

    /**
     * Instances of static inner classes do not hold an implicit
     * reference to their outer class.
     */
    private static class MyHandler extends Handler {
        private final WeakReference<SampleActivity> mActivity;

        public MyHandler(SampleActivity activity) {
            mActivity = new WeakReference<SampleActivity>(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            SampleActivity activity = mActivity.get();
            if (activity != null) {
                // ...
            }
        }
    }

    private final MyHandler mHandler = new MyHandler(this);

    /**
     * Instances of anonymous classes do not hold an implicit
     * reference to their outer class when they are "static".
     */
    private static final Runnable sRunnable = new Runnable() {
        @Override
        public void run() { /* ... */ }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Post a message and delay its execution for 10 minutes.
        mHandler.postDelayed(sRunnable, 1000 * 60 * 10);
    
        // Go back to the previous Activity.
        finish();
    }
}