All Editexts be replace by same value after pop a Fragment

问题

I have a strange issue, I have 2 fragment, in first fragment, I have some custom EditText, and a button to replace this by second fragment (addToBackStack = true), then, in second fragment, I try to using popBackStack() to back to first fragment, the issue occur, all custom EditText have same value.

Below is all my code

FirstFragment

class FirstFragment : BaseFragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_first, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        btn_next.setOnClickListener {
            val transaction = requireActivity().supportFragmentManager!!.beginTransaction()
                .replace(R.id.contentFrame, SecondFragment(), "")
            commitTransaction(transaction, true, -1)
        }
    }
}

SecondFragment

class SecondFragment : BaseFragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_second, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        btn_back.setOnClickListener {
            requireActivity().supportFragmentManager.popBackStack()
        }
    }
}

fragment_first.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >
    <com.sogia.replacefragmentdemo.CustomView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />

    <com.sogia.replacefragmentdemo.CustomView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />
    <Button
        android:id="@+id/btn_next"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="next"
        />
</LinearLayout>

fragment_second.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <Button
        android:id="@+id/btn_back"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="back"
        />
</LinearLayout>

CustomView

class CustomView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : LinearLayout(context, attrs, defStyleAttr) {
    init {
        inflate(context, R.layout.layout_custom_view, this)
    }
}

layout_custom_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    >
    <EditText
        android:id="@+id/edt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="input something"
        />
</LinearLayout>

Any response would be appreciated.

回答1:

You're not adding to the back stack, you're replacing, try this to open the second fragment, this will keep the state of FirstFragment intact and in stack

btn_next.setOnClickListener {
            val transaction = requireActivity().supportFragmentManager!!.beginTransaction()
                .add(R.id.contentFrame, SecondFragment(), "")
            commitTransaction(transaction, true, -1)
        }

Also both of your EditTexts have the same ids android:id="@+id/edt" thus the synthesizer function which runs findViewById will point to the same object of EditText

回答2:

Finally I find out the root cause and the solution, Thanks @abhradeep ghosh, @Eselfar, @MadScientist and another one else who response this post.

Cause: view IDs should be unique! Otherwise your state will be overwritten by another view with the same ID. In my case I have 2 views with id @id/edt, so my states container holds only 1 instance of it - whichever came last during state store process.

Here is my solution, (from this post),

First, create new class for save sate of view

class SavedState(superState: Parcelable) : View.BaseSavedState(superState) {
    var childrenStates: SparseArray<Any>? = null

    override fun writeToParcel(out: Parcel, flags: Int) {
        super.writeToParcel(out, flags)
        childrenStates?.let {
            out.writeSparseArray(it)
        }
    }
}

And in my CustomView

@Suppress("UNCHECKED_CAST")
    public override fun onSaveInstanceState(): Parcelable? {
        val superState = super.onSaveInstanceState()
        val ss = SavedState(superState)
        ss.childrenStates = SparseArray()
        for (i in 0 until childCount) {
            getChildAt(i).saveHierarchyState(ss.childrenStates as SparseArray<Parcelable>)
        }
        return ss
    }

    @Suppress("UNCHECKED_CAST")
    public override fun onRestoreInstanceState(state: Parcelable) {
        val ss = state as SavedState
        super.onRestoreInstanceState(ss.superState)
        for (i in 0 until childCount) {
            getChildAt(i).restoreHierarchyState(ss.childrenStates as SparseArray<Parcelable>)
        }
    }

    override fun dispatchSaveInstanceState(container: SparseArray<Parcelable>) {
        dispatchFreezeSelfOnly(container)
    }

    override fun dispatchRestoreInstanceState(container: SparseArray<Parcelable>) {
        dispatchThawSelfOnly(container)
    }

回答3:

I would try adding a different ID to each of your custom views in the layout. Like :

com.sogia.replacefragmentdemo.CustomView
    android:id="@+id/custom1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
/>

com.sogia.replacefragmentdemo.CustomView
    android:id="@+id/custom2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />

回答4:

Having same id can be a problem as managing state could get messy. Check this one for an solution: Restore fragment with two views having the same id

来源：https://stackoverflow.com/questions/52268043/all-editexts-be-replace-by-same-value-after-pop-a-fragment