"Fix" for InputMethodManager leaking the last focused view: https://code.google.com/p/android/issues/detail?id=171190

IMMLeaks.java

import android.app.Activity;
import android.app.Application;
import android.content.Context;
import android.content.ContextWrapper;
import android.os.Bundle;
import android.os.Looper;
import android.os.MessageQueue;
import android.util.Log;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.inputmethod.InputMethodManager;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import static android.content.Context.INPUT_METHOD_SERVICE;
import static android.os.Build.VERSION.SDK_INT;
import static android.os.Build.VERSION_CODES.KITKAT;

public class IMMLeaks {

  static class ReferenceCleaner
      implements MessageQueue.IdleHandler, View.OnAttachStateChangeListener,
      ViewTreeObserver.OnGlobalFocusChangeListener {

    private final InputMethodManager inputMethodManager;
    private final Field mHField;
    private final Field mServedViewField;
    private final Method finishInputLockedMethod;

    ReferenceCleaner(InputMethodManager inputMethodManager, Field mHField, Field mServedViewField,
        Method finishInputLockedMethod) {
      this.inputMethodManager = inputMethodManager;
      this.mHField = mHField;
      this.mServedViewField = mServedViewField;
      this.finishInputLockedMethod = finishInputLockedMethod;
    }

    @Override public void onGlobalFocusChanged(View oldFocus, View newFocus) {
      if (newFocus == null) {
        return;
      }
      if (oldFocus != null) {
        oldFocus.removeOnAttachStateChangeListener(this);
      }
      Looper.myQueue().removeIdleHandler(this);
      newFocus.addOnAttachStateChangeListener(this);
    }

    @Override public void onViewAttachedToWindow(View v) {
    }

    @Override public void onViewDetachedFromWindow(View v) {
      v.removeOnAttachStateChangeListener(this);
      Looper.myQueue().removeIdleHandler(this);
      Looper.myQueue().addIdleHandler(this);
    }

    @Override public boolean queueIdle() {
      clearInputMethodManagerLeak();
      return false;
    }

    private void clearInputMethodManagerLeak() {
      try {
        Object lock = mHField.get(inputMethodManager);
        // This is highly dependent on the InputMethodManager implementation.
        synchronized (lock) {
          View servedView = (View) mServedViewField.get(inputMethodManager);
          if (servedView != null) {

            boolean servedViewAttached = servedView.getWindowVisibility() != View.GONE;

            if (servedViewAttached) {
              // The view held by the IMM was replaced without a global focus change. Let's make
              // sure we get notified when that view detaches.

              // Avoid double registration.
              servedView.removeOnAttachStateChangeListener(this);
              servedView.addOnAttachStateChangeListener(this);
            } else {
              // servedView is not attached. InputMethodManager is being stupid!
              Activity activity = extractActivity(servedView.getContext());
              if (activity == null || activity.getWindow() == null) {
                // Unlikely case. Let's finish the input anyways.
                finishInputLockedMethod.invoke(inputMethodManager);
              } else {
                View decorView = activity.getWindow().peekDecorView();
                boolean windowAttached = decorView.getWindowVisibility() != View.GONE;
                if (!windowAttached) {
                  finishInputLockedMethod.invoke(inputMethodManager);
                } else {
                  decorView.requestFocusFromTouch();
                }
              }
            }
          }
        }
      } catch (IllegalAccessException | InvocationTargetException unexpected) {
        Log.e("IMMLeaks", "Unexpected reflection exception", unexpected);
      }
    }

    private Activity extractActivity(Context context) {
      while (true) {
        if (context instanceof Application) {
          return null;
        } else if (context instanceof Activity) {
          return (Activity) context;
        } else if (context instanceof ContextWrapper) {
          Context baseContext = ((ContextWrapper) context).getBaseContext();
          // Prevent Stack Overflow.
          if (baseContext == context) {
            return null;
          }
          context = baseContext;
        } else {
          return null;
        }
      }
    }
  }

  /**
   * Fix for https://code.google.com/p/android/issues/detail?id=171190 .
   *
   * When a view that has focus gets detached, we wait for the main thread to be idle and then
   * check if the InputMethodManager is leaking a view. If yes, we tell it that the decor view got
   * focus, which is what happens if you press home and come back from recent apps. This replaces
   * the reference to the detached view with a reference to the decor view.
   *
   * Should be called from {@link Activity#onCreate(android.os.Bundle)} )}.
   */
  public static void fixFocusedViewLeak(Application application) {

    // Don't know about other versions yet.
    if (SDK_INT < KITKAT || SDK_INT > 22) {
      return;
    }

    final InputMethodManager inputMethodManager =
        (InputMethodManager) application.getSystemService(INPUT_METHOD_SERVICE);

    final Field mServedViewField;
    final Field mHField;
    final Method finishInputLockedMethod;
    final Method focusInMethod;
    try {
      mServedViewField = InputMethodManager.class.getDeclaredField("mServedView");
      mServedViewField.setAccessible(true);
      mHField = InputMethodManager.class.getDeclaredField("mServedView");
      mHField.setAccessible(true);
      finishInputLockedMethod = InputMethodManager.class.getDeclaredMethod("finishInputLocked");
      finishInputLockedMethod.setAccessible(true);
      focusInMethod = InputMethodManager.class.getDeclaredMethod("focusIn", View.class);
      focusInMethod.setAccessible(true);
    } catch (NoSuchMethodException | NoSuchFieldException unexpected) {
      Log.e("IMMLeaks", "Unexpected reflection exception", unexpected);
      return;
    }

    application.registerActivityLifecycleCallbacks(new LifecycleCallbacksAdapter() {
      @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        ReferenceCleaner cleaner =
            new ReferenceCleaner(inputMethodManager, mHField, mServedViewField,
                finishInputLockedMethod);
        View rootView = activity.getWindow().getDecorView().getRootView();
        ViewTreeObserver viewTreeObserver = rootView.getViewTreeObserver();
        viewTreeObserver.addOnGlobalFocusChangeListener(cleaner);
      }
    });
  }
}

LifecycleCallbacksAdapter.java

import android.app.Activity;
import android.app.Application;
import android.os.Bundle;

/** Helper to avoid implementing all lifecycle callback methods. */
public class LifecycleCallbacksAdapter implements Application.ActivityLifecycleCallbacks {
  @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) {

  }

  @Override public void onActivityStarted(Activity activity) {

  }

  @Override public void onActivityResumed(Activity activity) {

  }

  @Override public void onActivityPaused(Activity activity) {

  }

  @Override public void onActivityStopped(Activity activity) {

  }

  @Override public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

  }

  @Override public void onActivityDestroyed(Activity activity) {

  }
}

thank you @TreyCai

Thanks a lot for this fix!

Can I kindly ask you to replace

132 * Should be called from {@link Activity#onCreate(android.os.Bundle)} )}.

with

132 * Should be called from {@link Application#onCreate(android.os.Bundle)} )}.

in the source code?

Also, I tried to reproduce on different Android version (using Genymotion emulators):

4.3 (18) : could reproduce. Your code fixed the leak.

4.4.4 (19) : could reproduce. Your code fixed the leak.

5.0 (21) : could reproduce, your code created an exception with a null 'lock' object here:

Object lock = mHField.get(inputMethodManager);
// This is highly dependent on the InputMethodManager implementation.
synchronized (lock) {

Debugger showed that InputMethodManager.isActive() returns false and all fields of InputMethodManager are null, so lock being 'null' seems normal in this case.

03-09 08:08:33.137 9267-9267/com.elementique.calendar A/MessageQueue: IdleHandler threw exception
java.lang.NullPointerException: Null reference used for synchronization (monitor-enter)
at <my_app_packagename>.fix.IMMLeaks$ReferenceCleaner.clearInputMethodManagerLeak(IMMLeaks.java:77)
at <my_app_packagename>.fix.IMMLeaks$ReferenceCleaner.queueIdle(IMMLeaks.java:69)
at android.os.MessageQueue.next(MessageQueue.java:211)
at android.os.Looper.loop(Looper.java:122)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

So I added

if(lock != null) {

and no more exception

I am a bit puzzled, as reproducing the leak is not easy (I have to try many time the same 'scenario) and it's even less easy to reproduce the exception about null lock object.

But I think my simple experiments could be of some interest for you, so I am adding the outcome here.

Thanks a lot for this fix anyway :-)

it don't work,HUAWEI(Honor 6A) on Android 7.0
I use it in Application onCreate() Method

@pyricau To use this fix i just need to call IMMLeaks.fixFocusedViewLeak(this); from my custom Application.onCreate() ?

line 151 should be mHField = InputMethodManager.class.getDeclaredField("mH"); instead of mServedView

I've been experiencing following crash:

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState

Solution is to make parameter savedInstanceState nullable in onActivityCreated() callback.

In line 149 and 151 the same field (mServedView) is referenced. Is that on purpose?

This fix will be automatically running in LeakCanary 2.6 !

Here's the port: square/leakcanary#2001
Here's an update based on the feedback here (thanks everybody!) : square/leakcanary#2006

Here's how I fix:

Use onActivityStarted(Activity) instead of onActivityCreated(Activity, Bundle)

The most common reason why "requestFeature() must be called before adding content" thrown is because we call setContentView(int) before requestWindowFeature(int) . In fact, there're many ways to cause that exception, i.e. getWindow().getDecorView().

In PhoneWindow.getDecorView(), you can see that if mDecor == null, call installDecor().
In installDecor(), if mContentParent is null, then generateLayout(mDecor).
So, if now you call requestWindowFeature(), which means mContentParent is NOT null, then throws AndroidRuntimeException.

The method name in Application.ActivityLifecycleCallbacks is onActivityCreated. How does it know when the activity is being created? There is one line code in Activity.onCreate(Bundle):

getApplication().dispatchActivityCreated(this, savedInstanceState);

Now, everything is clear.

1. Your target activity calls super.onCreate()
2. Leads to call ActivityLifecycleCallbacks.onActivityCreated(Activity, Bundle)
3. Leads to call getDecorView()
4. Leads to the mContentParent is being generated
5. Your target activity calls requestWindowFeature(int) (even before setContentView(int))
6. AndroidRuntimeException thrown

We can call requestWindowFeature() before super.onCreate() to prevent this exception happens, but there're some activities in third-party libraries that we can't control, so I decide to use onActivityStarted instead.

Hope this helpful.

thanks,it's helpful