CustomView中的DialogFragment导致内存泄漏

Question

我有一个MainActivity，它的布局中有一个customView(DatePicker(。DatePicker customView有一个按钮和一个CustomDialogFragment。单击DatePicker上的按钮时，会显示CustomDialogFragment。应用程序运行良好，但泄漏Canary显示泄漏。这是代码(为了简洁起见，删除了一些代码(

主要活动.class

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
date_picker.calendarDialog = getCalendarDialog()
}
private fun getCalendarDialog(): CalendarDialog {
return CalendarDialog()
}
}

activity_main.xml

<androidx.constraintlayout.widget.ConstraintLayout>
<com.example.testproject.customViews.DatePicker
android:id="@+id/date_picker"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</com.example.testproject.customViews.DatePicker>
</androidx.constraintlayout.widget.ConstraintLayout>

DatePicker.class

class DatePicker : FrameLayout {
var calendarDialog: CalendarDialog? = null
init {
View.inflate(context, R.layout.date_picker, this)
open_calendar.setOnClickListener {
calendarDialog?.show((context as MainActivity).supportFragmentManager.beginTransaction(), "Calendar")
}
}
}

日历对话框.class

class CalendarDialog: DialogFragment() {
override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
val builder = AlertDialog.Builder(context!!)
builder.setView(view)
.setMessage("This is a dummy message")
.setPositiveButton("OK") { dialog, which -> }
.setNegativeButton("Cancel") { dialog, which -> }
return builder.create()
}
}

堆分析结果====================================1个应用程序泄漏

References underlined with "~~~" are likely causes.
Learn more at https://squ.re/leaks.
1437 bytes retained by leaking objects
Signature: 1eb8b5c7c3fd403a9a6851729c4044c8a6ce7cf6
┬───
│ GC Root: System class
│
├─ android.view.inputmethod.InputMethodManager class
│    Leaking: NO (InputMethodManager↓ is not leaking and a class is never leaking)
│    ↓ static InputMethodManager.sInstance
├─ android.view.inputmethod.InputMethodManager instance
│    Leaking: NO (DecorView↓ is not leaking and InputMethodManager is a singleton)
│    ↓ InputMethodManager.mNextServedView
├─ com.android.internal.policy.DecorView instance
│    Leaking: NO (LinearLayout↓ is not leaking and View attached)
│    mContext instance of com.android.internal.policy.DecorContext, wrapping activity com.example.testproject.MainActivity with mDestroyed = false
│    Parent android.view.ViewRootImpl not a android.view.View
│    View#mParent is set
│    View#mAttachInfo is not null (view attached)
│    View.mWindowAttachCount = 1
│    ↓ DecorView.mContentRoot
├─ android.widget.LinearLayout instance
│    Leaking: NO (MainActivity↓ is not leaking and View attached)
│    mContext instance of com.example.testproject.MainActivity with mDestroyed = false
│    View.parent com.android.internal.policy.DecorView attached as well
│    View#mParent is set
│    View#mAttachInfo is not null (view attached)
│    View.mWindowAttachCount = 1
│    ↓ LinearLayout.mContext
├─ com.example.testproject.MainActivity instance
│    Leaking: NO (DatePicker↓ is not leaking and Activity#mDestroyed is false)
│    ↓ MainActivity._$_findViewCache
├─ java.util.HashMap instance
│    Leaking: NO (DatePicker↓ is not leaking)
│    ↓ HashMap.table
├─ java.util.HashMap$Node[] array
│    Leaking: NO (DatePicker↓ is not leaking)
│    ↓ HashMap$Node[].[0]
├─ java.util.HashMap$Node instance
│    Leaking: NO (DatePicker↓ is not leaking)
│    ↓ HashMap$Node.value
├─ com.example.testproject.customViews.DatePicker instance
│    Leaking: NO (View attached)
│    mContext instance of com.example.testproject.MainActivity with mDestroyed = false
│    View.parent androidx.constraintlayout.widget.ConstraintLayout attached as well
│    View#mParent is set
│    View#mAttachInfo is not null (view attached)
│    View.mID = R.id.date_picker
│    View.mWindowAttachCount = 1
│    ↓ DatePicker.calendarDialog
│                 ~~~~~~~~~~~~~~
╰→ com.example.testproject.customViews.CalendarDialog instance
​     Leaking: YES (ObjectWatcher was watching this because com.example.testproject.customViews.CalendarDialog received Fragment#onDestroy() callback and Fragment#mFragmentManager is null)
​     key = e176896c-49c6-4b17-a21e-4a6ca7cde260
​     watchDurationMillis = 11213
​     retainedDurationMillis = 6208
​     key = f3a2f22a-c77f-4c8e-a281-d803d110acff
​     watchDurationMillis = 11214
====================================
0 LIBRARY LEAKS
Library Leaks are leaks coming from the Android Framework or Google libraries.
====================================
METADATA
Please include this in bug reports and Stack Overflow questions.
Build.VERSION.SDK_INT: 28
Build.MANUFACTURER: Google
LeakCanary version: 2.2
App process name: com.example.testproject
Analysis duration: 4191 ms
Heap dump file path: /data/user/0/com.example.testproject/files/leakcanary/2020-03-11_10-15-46_729.hprof
Heap dump timestamp: 1583936152876
====================================

到目前为止，这些都是我尝试过的，但没有成功。

1. 我已尝试在不同位置初始化CalendarDialog
2. 在CalendarDialog类中创建一个侦听器，并在取消对话框时使"CalendarDialog"实例为null。而且很少

Answer 1

您可以将CalendarDialog放在WeakReference中，这样就不必通过回调将其显式设置为null。垃圾收集器会自动清理它，这样就可以避免内存泄漏。

有关WeakReference的更多信息：https://developer.android.com/reference/java/lang/ref/WeakReference

Answer 2

当CalendarDialog片段被丢弃时，该片段将被垃圾收集。然而，在这里我们可以看到DatePicker布局保留了对它的引用，防止它被垃圾收集。DatePicker仍然是附加的，因此它仍然存在是有意义的，但当对话框被解除时，它应该将其DatePicker.calendarDialog字段设置为null。

Answer 3

将日历对话框作为实用程序函数

class CalendarDialog {
fun onCreateDialog(context: Context): Dialog {
val builder = AlertDialog.Builder(context)
builder
.setMessage("This is a dummy message")
.setPositiveButton("OK") { dialog, which -> }
.setNegativeButton("Cancel") { dialog, which -> }
return builder.create()
}
}

和

class DatePicker(context: Context, attr: AttributeSet) : FrameLayout(context, attr) {
var calendarDialog: CalendarDialog? = null
init {
View.inflate(context, R.layout.date_picker, this)
open_calendar.setOnClickListener {
calendarDialog?.onCreateDialog(context)?.show()
}
}
override fun onDetachedFromWindow() {
super.onDetachedFromWindow()
calendarDialog = null
open_calendar.setOnClickListener(null)
}
}

活动不知道对话框片段是否存在于您的案例中。

Answer 4

我以前也有过类似的经历。我所做的只是将supportFragmentManager改为childFragmentManager。所以我建议改变这个：

calendarDialog?.show((context as MainActivity).supportFragmentManager.beginTransaction(), "Calendar")

到此：

calendarDialog?.show((context as MainActivity).childFragmentManager.beginTransaction(), "Calendar")

此外，查找任何其他supportFragmentManager(如果有(。