Android和内存泄漏

Question

我担心从泄漏金丝雀回来的信息。它显示了在UI上声明的所有变量，如片段中的材料按钮、材料卡片视图、文本视图、图像视图等，都导致了内存泄漏。我不知道为什么会这样。

private Window mWindow;
private Toolbar mToolbar;
private FloatingActionButton btnBack, btnNext;
private Button btnStart;
private TextView tvSetUpNotifications, tvTitle, tvDescription;
private ImageView ivToolbar;
private CardView cvNotification;
private Bundle args = new Bundle();
private NavController mNavController;
private View view;

@Override
public void onAttach(@NonNull Context context) {
    super.onAttach(context);
    ((BaseApplication) getActivity().getApplication()).getAppComponent().inject(this);
}

public WorkoutCheckInIntro() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.fragment_workout_checkin_intro, container, false);

    // configure the Window variable to enable the colour to be set
    mWindow = getActivity().getWindow();
    mWindow.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
    mWindow.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
    mWindow.setStatusBarColor(ContextCompat.getColor(getActivity(), R.color.calm));
    
    return view;
}

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    // Instantiate the Navigation Controller.
    mNavController = Navigation.findNavController(view);

    // Configure the bottom navbar
    BottomNavigationView navBar = getActivity().findViewById(R.id.bottom_navigation);
    navBar.setVisibility(View.VISIBLE);

    // Method calls
    assignVariables();
    setOnClickListeners();
}

/**
 * Method which assigns variables to elements in the XML file.
 */
private void assignVariables() {

    // Initialising variables from the xml file.
    btnStart = view.findViewById(R.id.checkInDailyButtonStart);
    tvSetUpNotifications = view.findViewById(R.id.setUpNotificationsTextView);
    cvNotification = view.findViewById(R.id.notification_cardView2);

    // Configure the top toolbar
    mToolbar = view.findViewById(R.id.toolbar_check_in_intro);
    btnBack = mToolbar.findViewById(R.id.toolbar_back_button);
    btnNext = mToolbar.findViewById(R.id.toolbar_next_button);
    btnNext.hide();
    tvTitle = mToolbar.findViewById(R.id.toolbar_workout_title);
    tvTitle.setVisibility(View.VISIBLE);
    tvTitle.setTextColor(ContextCompat.getColor(getActivity(), R.color.white));
    tvTitle.setText(getString(R.string.check_in));
    tvDescription = mToolbar.findViewById(R.id.toolbar_workout_description);
    tvDescription.setVisibility(View.GONE);
    tvDescription.setTextColor(ContextCompat.getColor(getContext(), R.color.white));
    ivToolbar = mToolbar.findViewById(R.id.toolbar_workout_background);
    ivToolbar.setVisibility(View.VISIBLE);
    ivToolbar.setImageResource(R.drawable.check_in_intro);
}

/**
 * Method which sets onClickListeners to buttons
 */
private void setOnClickListeners() {
    btnStart.setOnClickListener(this);
    btnBack.setOnClickListener(this);
    tvSetUpNotifications.setOnClickListener(this);
    cvNotification.setOnClickListener(this);
}

@Override
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.toolbar_back_button:
            if (mNavController.getCurrentDestination().getId() == R.id.workoutCheckInIntro) {
                mNavController.navigate(R.id.action_workoutCheckInIntro_to_workoutFragment);
            }
            break;
        case R.id.checkInDailyButtonStart:
            // Boolean used in the WorkoutCheckInDailyMood.Class so when the user clicks
            // the back button it will return them to this activity.
            args.putBoolean(WORKOUT_CHECKIN_DAILY_MOOD, true);
            if (mNavController.getCurrentDestination().getId() == R.id.workoutCheckInIntro) {
                mNavController.navigate(R.id.action_workoutCheckInIntro_to_workoutMood, args);
            }
            break;
        case R.id.notification_cardView2:
            // Boolean used in the NotificationsSetUp.Class so when the user clicks
            // the back button it will return them to this activity.
            args.putBoolean(RETURN_TO_CHECKIN_WORKOUT, true);
            if (mNavController.getCurrentDestination().getId() == R.id.workoutCheckInIntro) {
                mNavController.navigate(R.id.action_workoutCheckInIntro_to_notificationsSetUp, args);
            }
            break;
    }
}

@Override
public void onDestroyView() {
    super.onDestroyView();
    mToolbar = null;
    view = null;
    btnBack = null;
    btnNext = null;
    tvDescription = null;
    tvTitle = null;
    ivToolbar = null;
    btnStart = null;
    cvNotification = null;
    tvSetUpNotifications = null;
}
}


<?xml version="1.0" encoding="utf-8"?>
<androidx.core.widget.NestedScrollView  xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:fillViewport="true"
tools:context=".ui.workouts.checkin.WorkoutCheckInIntro">

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent">

    <include
        android:id="@+id/toolbar_check_in_intro"
        layout="@layout/toolbar_workout"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="20dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="20dp"
        android:text="Workout Length"
        android:textSize="@dimen/text_size_heading_16sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar_check_in_intro" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="20dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="20dp"
        android:text="3 MIN - 5 MIN"
        android:textSize="@dimen/text_size_timer"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="20dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="20dp"
        android:lineSpacingExtra="5sp"
        android:text="We recommend to do this workout daily to develop a habit to check in with yourself each day. This is helpful as many of us are so busy that we become disconnected from our own thoughts and emotions."
        android:textSize="@dimen/text_size_normal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <com.google.android.material.button.MaterialButton
        android:id="@+id/checkInDailyButtonStart"
        style="@style/btnStyleRed"
        android:layout_width="0dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="8dp"
        android:text="Start"
        app:icon="@drawable/ic_dumb_bell_white_16dp"
        app:iconGravity="textStart"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/notification_cardView2"
        app:layout_constraintVertical_bias="1.0"
        />


    <com.google.android.material.card.MaterialCardView
        android:id="@+id/notification_cardView2"
        android:layout_width="0dp"
        android:layout_height="200dp"
        android:layout_marginStart="32dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="32dp"
        android:clickable="true"
        app:cardCornerRadius="10dp"
        app:cardElevation="10dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView3">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:id="@+id/setUpNotificationsTextView"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginStart="32dp"
                android:layout_marginTop="8dp"
                android:layout_marginEnd="32dp"
                android:gravity="center"
                android:text="Set up daily notifications to remind you to check-in"
                android:textColor="@color/colorPrimary"
                android:textSize="@dimen/text_size_normal"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <ImageView
                android:id="@+id/appCompatImageView"
                android:layout_width="0dp"
                android:layout_height="0dp"
                android:layout_marginStart="16dp"
                android:layout_marginTop="8dp"
                android:layout_marginEnd="16dp"
                android:layout_marginBottom="16dp"
                android:adjustViewBounds="true"
                app:srcCompat="@drawable/brain_insight"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/setUpNotificationsTextView" />
        </androidx.constraintlayout.widget.ConstraintLayout>
    </com.google.android.material.card.MaterialCardView>

</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.core.widget.NestedScrollView>



───
│ GC Root: System class
│
├─ android.provider.FontsContract class
│    Leaking: NO (BaseApplication↓ is not leaking and a class is never leaking)
│    ↓ static FontsContract.sContext
├─ com.example.BaseApplication instance
│    Leaking: NO (WorkoutFragment↓ is not leaking and Application is a singleton)
│    ↓ BaseApplication.appComponent
├─ com.example.di.DaggerAppComponent instance
│    Leaking: NO (WorkoutFragment↓ is not leaking)
│    ↓ DaggerAppComponent.provideWorkoutAdapterProvider
├─ dagger.internal.DoubleCheck instance
│    Leaking: NO (WorkoutFragment↓ is not leaking)
│    ↓ DoubleCheck.instance
├─ com.example.adapters.RvAdapterWorkout instance
│    Leaking: NO (WorkoutFragment↓ is not leaking)
│    ↓ RvAdapterWorkout.mOnWorkoutListener
├─ com.example.ui.workouts.WorkoutFragment instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking and Fragment#mFragmentManager is not null)
│    ↓ WorkoutFragment.mFragmentManager
├─ androidx.fragment.app.FragmentManagerImpl instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ FragmentManagerImpl.mFragmentStore
├─ androidx.fragment.app.FragmentStore instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ FragmentStore.mActive
├─ java.util.HashMap instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ HashMap.table
├─ java.util.HashMap$Node[] array
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ HashMap$Node[].[3]
├─ java.util.HashMap$Node instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ HashMap$Node.value
├─ androidx.fragment.app.FragmentStateManager instance
│    Leaking: NO (WorkoutCheckInIntro↓ is not leaking)
│    ↓ FragmentStateManager.mFragment
├─ com.example.ui.workouts.checkin.WorkoutCheckInIntro instance
│    Leaking: NO (Fragment#mFragmentManager is not null)
│    ↓ WorkoutCheckInIntro.view
│                          ~~~~
╰→ androidx.core.widget.NestedScrollView instance
​     Leaking: YES (ObjectWatcher was watching this because com.example.ui.workouts.checkin.WorkoutCheckInIntro received Fragment#onDestroyView() callback (references to its views should be cleared to prevent leaks))
​     key = 53dc4388-0db6-402a-9ee3-2db6617c98f5
​     watchDurationMillis = 192734
​     retainedDurationMillis = 187732
​     mContext instance of com.example.ui.main.MainActivity with mDestroyed = false
​     View#mParent is null
​     View#mAttachInfo is null (view detached)
​     View.mWindowAttachCount = 1

METADATA

Build.VERSION.SDK_INT: 30
Build.MANUFACTURER: Google
LeakCanary version: 2.4
App process name: com.
Analysis duration: 22667 ms




23 Leaks
┬───
│ GC Root: System class
│
├─ android.provider.FontsContract class
│    Leaking: NO (BaseApplication↓ is not leaking and a class is never leaking)
│    ↓ static FontsContract.sContext
├─ com.example.BaseApplication instance
│    Leaking: NO (Application is a singleton)
│    ↓ BaseApplication.appComponent
│                      ~~~~~~~~~~~~
├─ com.example.di.DaggerAppComponent instance
│    Leaking: UNKNOWN
│    ↓ DaggerAppComponent.viewModelUsersProvider
│                         ~~~~~~~~~~~~~~~~~~~~~~
├─ dagger.internal.DoubleCheck instance
│    Leaking: UNKNOWN
│    ↓ DoubleCheck.instance
│                  ~~~~~~~~
╰→ com.example.persistence.viewmodel.ViewModelUsers instance
​     Leaking: YES (ObjectWatcher was watching this because com.example.persistence.viewmodel.ViewModelUsers received ViewModel#onCleared() callback)
​     key = 45b732d9-f6e0-4852-9b3c-8397c587f29f
​     watchDurationMillis = 223094
​     retainedDurationMillis = 218094

METADATA

Build.VERSION.SDK_INT: 30
Build.MANUFACTURER: Google
LeakCanary version: 2.4
App process name: com.
Analysis duration: 22667 ms

Answer 1

有一种比编写所有这些样板代码首先获取所有视图引用，然后将它们设置为null更方便的方法

它被称为视图绑定。您还可以使用数据绑定，它允许您更容易地与视图的数据交互。

然而，它指出：

与FindViewByID不同，视图绑定（以及数据绑定）确保空安全和类型安全。

在科特林，你还有一个选择。您可以使用Kotlin扩展（只是gradle文件中的另一个依赖项），并且可以直接通过视图的ID名称访问视图，而不需要findviewbyid。此方法与视图/数据绑定方法进行了比较。我想再次指出，视图/数据绑定可以在Java和Kotlin中使用。这就是android试图使您的开发努力最小化的方式。尤其是在许多片段之间移动时（并且避免/减少所有片段中的锅炉板代码）！