LeakCanary 的几个 bug

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神器 LeakCanary 并不是完美的，它仍然有一些问题待完善。

检测不到内存泄漏的 bug

1163

问题描述：

使用 LeakCanary version: 1.6.2 / master cefc33d 检查如下代码中的内存泄漏。

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public class MainActivity extends Activity {

  static class Lol {
    static Object foo;
  }

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

    Lol.foo = this;

  }
}

检查结果：

  • On API 26, no leak is detected
  • On API 21, the leak is detected

问题原因：

Snapshot.getGCRoots() only returns the GC Roots from the first heap. In both API 21 and API 26, we had 4 heaps, however on API 21 only the first heap has GC Roots, while on API 26 the first 3 heaps had GC Roots. The missing gc roots lived in subsequent heaps.

最新版本的 LeakCanary 中已修复这个问题。

Fragment View 内存泄漏问题

1061

问题描述：

如下代码中，如果没有在 onDestroyView 中及时清理 leakingView，就会产生内存泄漏问题。

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public class ViewLeakingFragment extends Fragment {

  public static void addToBackstack(final TestActivity activity) {
    InstrumentationRegistry.getInstrumentation().runOnMainSync(new Runnable() {
      @Override public void run() {
        activity.getSupportFragmentManager()
            .beginTransaction()
            .addToBackStack(null)
            .replace(R.id.fragments, new ViewLeakingFragment())
            .commit();
      }
    });
  }

  private View leakingView;

  @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,
      Bundle savedInstanceState) {
    return new View(container.getContext());
  }

  @Override
  public void onViewCreated(View view, Bundle savedInstanceState) {
    // Leak: this fragment will stay in memory after being replaced, leakingView should be cleared
    // onDestroyView()
    leakingView = view;
  }
}

Fragment view 内存泄漏容易发生的两个时机：

  • replace + addToBackStack fragment transaction is executed.
  • This also occurs when you use detach regardless of the backstack.

最新 LeakCanary 中已增加对 fragment 以及 fragment view 内存泄漏的检查。