Android Switch不断切换回以前的状态

Question

我在我的一个片段上进行了这个切换，从黑暗主题切换到光明主题。唯一的问题是，当我在打开开关的情况下离开片段时，当我回到片段时，开关是关闭的，而不是像我离开时那样打开

这是图片。

当我继续碎片：碎片关闭

当我拨动开关时：碎片开关打开

然后我离开片段，然后回到片段：片段在上时关闭

她是我的代码：

设置碎片.java：

package com.barzalou.lpapineau.test.ui.settings;
import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatDelegate;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProviders;
import com.barzalou.lpapineau.test.R;
import com.barzalou.lpapineau.test.ui.CheckedChangeCallback;
import java.util.Objects;
public class SettingsFragment extends Fragment {
private SettingsViewModel settingsViewModel;
private CheckedChangeCallback callback = null;
public void onAttach(final Activity activity) {
super.onAttach(activity);
if (activity instanceof CheckedChangeCallback) {
this.callback = (CheckedChangeCallback) activity;
}
}
public void onDetach() {
super.onDetach();
callback = null;
}
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup     container, Bundle savedInstanceState) {
settingsViewModel = ViewModelProviders.of(this).get(SettingsViewModel.class);
View root = inflater.inflate(R.layout.fragment_settings, container, false);
final TextView textView = root.findViewById(R.id.text_settings);
settingsViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
textView.setText(s);
}
});
return root;
}
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
final Switch DarkMode = (Switch) getView().findViewById(R.id.DarkModeSwitch);
final boolean DarkModeVal = DarkMode.isChecked();
Log.d("Dark Mode Checked Value", String.valueOf(DarkModeVal));
DarkMode.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
callback.onCheckedChange(isChecked);
}
});
}
}

设置ViewModel.java：

package com.barzalou.lpapineau.test.ui.settings;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
public class SettingsViewModel extends ViewModel {
private MutableLiveData<String> mText;
public SettingsViewModel() {
mText = new MutableLiveData<>();
mText.setValue("Settings");
}
public LiveData<String> getText() {
return mText;
}
}

CheckedChangeCallback.java：

package com.barzalou.lpapineau.test.ui;
public interface CheckedChangeCallback {
void onCheckedChange(boolean isChecked);
}

MainActivity.java:

package com.barzalou.lpapineau.test;
import android.content.Intent;
import android.content.SharedPreferences;
import android.media.audiofx.Equalizer;
import android.os.Bundle;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.view.Menu;
import android.widget.CompoundButton;
import android.widget.Switch;
import com.barzalou.lpapineau.test.ui.CheckedChangeCallback;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import com.google.android.material.navigation.NavigationView;
import androidx.appcompat.app.AppCompatDelegate;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
public class MainActivity extends AppCompatActivity implements CheckedChangeCallback {
private AppBarConfiguration mAppBarConfiguration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = findViewById(R.id.drawer_layout);
NavigationView navigationView = findViewById(R.id.nav_view);
// Passing each menu ID as a set of Ids because each
// menu should be considered as top level destinations.
mAppBarConfiguration = new AppBarConfiguration.Builder(
R.id.nav_home, R.id.nav_gallery, R.id.nav_slideshow)
.setDrawerLayout(drawer)
.build();
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
NavigationUI.setupWithNavController(navigationView, navController);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onSupportNavigateUp() {
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
return NavigationUI.navigateUp(navController, mAppBarConfiguration)
|| super.onSupportNavigateUp();
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == R.id.action_exit) {
finish();
System.exit(0);
}
return false;
}
public void onCheckedChange(boolean isChecked) {
Switch DarkMode = findViewById(R.id.DarkModeSwitch);
if (isChecked) {
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
Log.d("Dark Mode Switch State", "On");
DarkMode.setChecked(true);
}
else {
AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
Log.d("Dark Mode Switch State", "Off");
DarkMode.setChecked(false);
}
}
}

fragment_settings.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:id="@+id/relativeLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="#fff"
android:padding="10dp"
tools:context=".ui.home.HomeFragment">
<!-- Title -->
<TextView
android:id="@+id/text_settings"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:shadowColor="#bfbfbf"
android:shadowDx="5"
android:shadowDy="5"
android:shadowRadius="0.01"
android:text="@string/this_is_home"
android:textAlignment="center"
android:textColor="#000"
android:textSize="34sp" />
<!-- ...... -->
<!-- Card_View Settings -->
<androidx.cardview.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view_outer"
android:layout_width="match_parent"
android:layout_height="90dp"
android:layout_gravity="center"
android:translationY="60dp"
android:layout_marginLeft="3dp"
android:layout_marginStart="3dp"
android:layout_marginTop="3dp"
card_view:cardBackgroundColor="#d3d3d3"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="0dp" />
<androidx.cardview.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view_inner"
android:layout_width="match_parent"
android:layout_height="90dp"
android:layout_gravity="center"
android:translationY="60dp"
android:layout_marginRight="3dp"
android:layout_marginEnd="3dp"
card_view:cardBackgroundColor="#f5f5f5"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="3dp" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="10dp"
android:elevation="4dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:text="@string/Settings"
android:textSize="22sp"/>
<Switch
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:id="@+id/DarkModeSwitch"
android:text="@string/dark_mode"/>
</LinearLayout>
</androidx.cardview.widget.CardView>
<!-- .................. -->
<!-- Card_View 2 -->
<androidx.cardview.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view_1"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_gravity="center"
android:translationY="170dp"
android:layout_marginRight="3dp"
android:layout_marginEnd="3dp"
card_view:cardBackgroundColor="#f5f5f5"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="3dp" />
<androidx.cardview.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="@+id/card_view_2"
android:layout_width="match_parent"
android:layout_height="200dp"
android:layout_gravity="center"
android:translationY="170dp"
android:layout_marginLeft="3dp"
android:layout_marginStart="3dp"
android:layout_marginTop="3dp"
card_view:cardBackgroundColor="#d3d3d3"
card_view:cardCornerRadius="4dp"
card_view:cardElevation="0dp" >
</androidx.cardview.widget.CardView>
<!-- ........... -->
</RelativeLayout>

如何解决这个问题？我希望它在黑暗主题打开时保持翻转。

谢谢！

Answer 1

因为重新创建了片段，所以切换结果丢失。因此，您应该保存切换结果。例如，SharedPreference。