Android-如何停止碎片自动恢复其状态？

Question

我创建了一个全新的项目来展示我的问题。基本上，我的片段有两个RadioButton。在使用CreateView时，我总是使用RadioButtonFirst.SetChecked（true）；。但是，如果我检查RadioButtonSecond，然后通过按后退按钮向外导航，下次打开它时，它会自动检查RadioButtonSecond。那种行为打破了我的逻辑。

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private WeirdFragment weirdFragment;
    private FragmentManager fragmentManager;
    private FragmentTransaction fragmentTransaction;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        weirdFragment = new WeirdFragment();
        fragmentManager = getSupportFragmentManager();
    }
    public void openFragment(View v){
        fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.container, weirdFragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }
}

weirdfragment.java

public class WeirdFragment extends Fragment {
    private RadioButton radioButtonFirst;
    private RadioButton radioButtonSecond;
    private Button buttonReturn;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_weird, container, false);
        radioButtonFirst = view.findViewById(R.id.radio_button_first);
        radioButtonSecond = view.findViewById(R.id.radio_button_second);
        buttonReturn = view.findViewById(R.id.button_return);

        radioButtonFirst.setChecked(true);

        // I decide to set a listener right here, to see what happened to my radio button. So this listener will be removed in my real project.
        radioButtonSecond.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                Log.v("weird", "i got here");
            }
        });
        buttonReturn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getFragmentManager().beginTransaction().remove(WeirdFragment.this).commit();
            }
        });
        return view;
    }
}

<Button
    android:id="@+id/button_open"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="openFragment"
    android:text="Open"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<FrameLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintTop_toBottomOf="@id/button_open" />

<RadioGroup
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintTop_toTopOf="parent">

    <RadioButton
        android:id="@+id/radio_button_first"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:checked="true"
        android:text="First" />

    <RadioButton
        android:id="@+id/radio_button_second"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Second" />
</RadioGroup>

<Button
    android:id="@+id/button_return"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Return"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent" />

onCheckedChanged:31, WeirdFragment$1 (com.peanut.myweirdradiobutton)
setChecked:154, CompoundButton (android.widget)
toggle:113, CompoundButton (android.widget)
toggle:78, RadioButton (android.widget)
performClick:118, CompoundButton (android.widget)
run:19866, View$PerformClick (android.view)
handleCallback:739, Handler (android.os)
dispatchMessage:95, Handler (android.os)
loop:135, Looper (android.os)
main:5254, ActivityThread (android.app)
invoke:-1, Method (java.lang.reflect)
invoke:372, Method (java.lang.reflect)
run:903, ZygoteInit$MethodAndArgsCaller (com.android.internal.os)
main:698, ZygoteInit (com.android.internal.os)

onCheckedChanged:31, WeirdFragment$1 (com.peanut.myweirdradiobutton)
setChecked:154, CompoundButton (android.widget)
onRestoreInstanceState:522, CompoundButton (android.widget)
dispatchRestoreInstanceState:13740, View (android.view)
dispatchRestoreInstanceState:2893, ViewGroup (android.view)
dispatchRestoreInstanceState:2893, ViewGroup (android.view)
restoreHierarchyState:13718, View (android.view)
restoreViewState:494, Fragment (android.support.v4.app)
moveToState:1486, FragmentManagerImpl (android.support.v4.app)
moveFragmentToExpectedState:1784, FragmentManagerImpl (android.support.v4.app)
moveToState:1852, FragmentManagerImpl (android.support.v4.app)
executeOps:802, BackStackRecord (android.support.v4.app)
executeOps:2625, FragmentManagerImpl (android.support.v4.app)
executeOpsTogether:2411, FragmentManagerImpl (android.support.v4.app)
removeRedundantOperationsAndExecute:2366, FragmentManagerImpl (android.support.v4.app)
execPendingActions:2273, FragmentManagerImpl (android.support.v4.app)
run:733, FragmentManagerImpl$1 (android.support.v4.app)
handleCallback:739, Handler (android.os)
dispatchMessage:95, Handler (android.os)
loop:135, Looper (android.os)
main:5254, ActivityThread (android.app)
invoke:-1, Method (java.lang.reflect)
invoke:372, Method (java.lang.reflect)
run:903, ZygoteInit$MethodAndArgsCaller (com.android.internal.os)
main:698, ZygoteInit (com.android.internal.os)

因此，我可以看到它是onRestoreInstanceState检查我的RadioButtonSecond。但我不知道如何预防。我正在考虑的事情：

1. 在OnViewStateRestored中执行我的逻辑。但这是一个相当不干净的解决方案。
2. 重新创建我的片段，每次我需要打开它。但是我在创建新片段时的初始化阶段代价很高，我不应该这样做。

在我真正的项目中，这个片段就像我的应用程序中的一个设置，它有一个取消和一个确定按钮。因此，我希望片段在每次打开时都处于默认状态，因为我认为，例如，用户可能会配置很多东西，但然后按取消，那么看到所有视图都处于默认状态是合理的，而不是配置的状态（也许这种想法导致了我的问题，这是一个好的用户体验吗？）

那么，如何防止我的片段在未经我允许的情况下恢复其状态呢？

Answer 1

如果我理解正确的话，您希望在用户离开片段之前重置RadioButton的状态，以便为稍后重新输入片段做准备。

由于您希望在用户每次离开片段后重新输入片段时检查第一个radioButton，但（我想）不是在用户刚刚离开应用程序半小时，然后返回到他们停止的地方继续时，您应该使用savedInstanceState包确保radioButton具有正确的状态，这取决于具体情况：

让我们引入一个字段私有布尔isFirstButtonChecked=true；。

保持OnCheckedChangeListener以跟踪RadioButton的选中状态，使用

isFirstButtonChecked = radioButtonFirst.isChecked();

除此之外，在OnClickListener中将Boolean设置为true

buttonReturn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            isFirstButtonChecked = true;
            getFragmentManager().beginTransaction().remove(WeirdFragment.this).commit();
        }
});

     @Override
public void onSaveInstanceState(@NonNull Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBoolean("FIRST_RB_STATE", isFirstButtonChecked);
}

@Override
public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
    super.onViewStateRestored(savedInstanceState);
    isFirstButtonChecked = savedInstanceState == null 
            ? true 
            : savedInstanceState.getBoolean("FIRST_RB_STATE");
    radioButtonFirst.setChecked(isFirstButtonChecked);
}