android學習-11 oom產生的原因及解決方案(handler的內存泄漏問題）

oom：https://www.jianshu.com/p/b0451684b4d5
靜態變量生命週期：https://blog.csdn.net/ctcwri/article/details/8858414
單例模式的內存泄漏問題：https://blog.csdn.net/qq_39830579/article/details/100516883

Handler的內存泄漏問題：

在java中非靜態內部類和匿名內部類都會隱式持有當前類的外部引用，由於Handler是非靜態內部類所以其持有當前Activity的隱式引用，如果Handler沒有被釋放，其所持有的外部引用也就是Activity也不可能被釋放，當一個對象一句不需要再使用了，本來該被回收時，而有另外一個正在使用的對象持有它的引用從而導致它不能被回收，這導致本該被回收的對象不能被回收而停留在堆內存中，這就產生了內存泄漏

解決方案：

用弱引用持有當前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();
    }
}