我创建了一个全新的项目来展示我的问题。基本上,我的Fragment里有两个RadioButton
。在onCreateView方法中,我总是使用radioButtonFirst.setChecked(true);
。但如果我勾选了radioButtonSecond
,然后通过按下返回按钮导航出去,再次打开它时,它会自动勾选radioButtonSecond
。这种行为破坏了我的逻辑。
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;
}
}
activity_main.xml
<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" />
fragment_weird.xml
<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" />
我在日志语句处设置了一个断点。当用户触发该断点时,堆栈跟踪将如下所示:
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)
但是当这个断点从无处被触发时,堆栈跟踪看起来像这样:
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)
所以我发现是onRestoreInstanceState检查了我的radioButtonSecond。但我不知道如何阻止它。我正在考虑以下几种方法:
- 在onViewStateRestored中执行我的逻辑。但这不是一个很好的解决方案。
- 每次需要打开它时重新创建我的fragment。但是,创建新fragment时我的初始化阶段比较耗时,所以不能这样做。
那么,如何防止我的fragment在没有我的允许下恢复它的状态呢?