android-数据在viewPage中丢失

要须心地收汗马，孔孟行世目杲杲。这篇文章主要讲述android-数据在viewPage中丢失相关的知识，希望能为你提供帮助。
在我的应用中，我使用“查看”页面进行了注册。当我滑动下一个或上一个数据时，还是在那里，但是当我在最后一页（第三页）中时，下一个按钮变为完成按钮，当我按完成并尝试读取值时，所有内容都为空。
我读到一种解决方案是添加-

viewPager = (ViewPager) findViewById(R.id.view_pager); viewPager.setOffscreenPageLimit(3);所以我做到了，但没有解决问题。我也读过那些用片段做的人，而不是-

getactivity().getSupportFragmentmanager()已用-

getChildFragmentManager()这为他们解决了问题，但我没有使用片段。

我的java代码：（我删除了不相关的代码以使其更短）。

package com.technion.cue.BusinessFeatures; import android.app.TimePickerDialog; import android.content.Context; import android.content.Intent; import android.graphics.Color; import java.text.SimpleDateFormat; import android.net.Uri; import android.os.Build; import android.os.Bundle; import androidx.annotation.NonNull; import androidx.viewpager.widget.PagerAdapter; import androidx.viewpager.widget.ViewPager; import androidx.appcompat.app.AppCompatActivity; import android.text.html; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.view.WindowManager; import android.widget.ArrayAdapter; import android.widget.AutoCompleteTextView; import android.widget.Button; import android.widget.EditText; import android.widget.LinearLayout; import android.widget.TextView; import android.widget.Toast; import java.util.Calendar; import java.text.ParseException; import com.google.android.gms.tasks.OnFailureListener; import com.google.android.gms.tasks.OnSuccessListener; import com.google.android.material.textfield.TextInputEditText; import com.google.firebase.auth.AuthResult; import com.google.firebase.auth.FirebaseAuth; import com.google.firebase.auth.FirebaseUser; import com.google.firebase.firestore.FirebaseFirestore; import com.technion.cue.R; import com.technion.cue.SignInActivity; import com.technion.cue.annotations.ModuleAuthor; import com.technion.cue.data_classes.Business; import androidx.appcompat.widget.AppCompatEditText; import java.util.Date; import java.util.HashMap; import java.util.Map; import static com.technion.cue.FirebaseCollections.BUSINESSES_COLLECTION; @ModuleAuthor("Topaz") public class BusinessSignUp2 extends AppCompatActivity {private ViewPager viewPager; private MyViewPagerAdapter myViewPagerAdapter; private LinearLayout dotsLayout; private TextView[] dots; private int[] layouts; private Button btnPrev, btnNext; private PrefManager prefManager; private static final int GET_LOGO = 0; FirebaseAuth mAuth; FirebaseFirestore db; Uri logoData; Map< String, String> open_hours = new HashMap< > (); String lastUsedKey; View bo_signup1; View bo_signup2; View bo_signup3; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.layout_bo_sign_up_activity); final LayoutInflater factory = getLayoutInflater(); bo_signup1 = factory.inflate(R.layout.activity_bo_sign_up, null); bo_signup2 = factory.inflate(R.layout.activity_bo_sign_up2, null); bo_signup3 = factory.inflate(R.layout.activity_bo_sign_up3, null); mAuth = FirebaseAuth.getInstance(); db = FirebaseFirestore.getInstance(); viewPager = (ViewPager) findViewById(R.id.view_pager); viewPager.setOffscreenPageLimit(3); dotsLayout = (LinearLayout) findViewById(R.id.layoutDots); btnPrev = (Button) findViewById(R.id.btn_prev); btnNext = (Button) findViewById(R.id.btn_next); layouts = new int[]{ R.layout.activity_bo_sign_up, R.layout.activity_bo_sign_up2, R.layout.activity_bo_sign_up3}; // adding bottom dots addBottomDots(0); // making notification bar transparent changeStatusBarColor(); myViewPagerAdapter = new MyViewPagerAdapter(); viewPager.setAdapter(myViewPagerAdapter); viewPager.addOnPageChangeListener(viewPagerPageChangeListener); btnPrev.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //check if first page int current = getItem(-1); if (current > = 0) { viewPager.setCurrentItem(current); } else { //Todo: what else? } } }); btnNext.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // checking for last page int current = getItem(+1); if (current < layouts.length) { // move to next screen viewPager.setCurrentItem(current); } else { //last page - done was clicked Toast.makeText(BusinessSignUp2.this, "done was clicked", Toast.LENGTH_LONG).show(); TextInputEditText email = bo_signup1.findViewById(R.id.businessEmailEditText); TextInputEditText password = (bo_signup1.findViewById(R.id.businessPasswordEditText)); TextInputEditText boFullName = (bo_signup1.findViewById(R.id.businessFullNameEditText)); TextInputEditText businessName = (bo_signup2.findViewById(R.id.businessNameEditText)); TextInputEditText businessDescription = (bo_signup2.findViewById(R.id.businessDescriptionEditText)); TextInputEditText phone = (bo_signup2.findViewById(R.id.businessPhoneEditText)); TextInputEditText state = (bo_signup3.findViewById(R.id.businessStateEditText)); TextInputEditText city = (bo_signup3.findViewById(R.id.businessCityEditText)); TextInputEditText address = (bo_signup3.findViewById(R.id.businessAddressEditText)); TextView openHours = (bo_signup3.findViewById(R.id.openingHoursEditText)); TextView closeHours = bo_signup3.findViewById(R.id.closingHoursEditText); boolean res = check_if_input_valid(); if (res) { mAuth.createUserWithEmailAndPassword(email.getText().toString(), password.getText().toString()).addOnSuccessListener(new OnSuccessListener< AuthResult> () { @Override public void onSuccess(AuthResult authResult) { FirebaseUser user = mAuth.getCurrentUser(); Business business = new Business(businessName.getText().toString(), boFullName.getText().toString(), phone.getText().toString(), businessDescription.getText().toString()); db.collection(BUSINESSES_COLLECTION) .document(user.getUid()) .set(business); finish(); } }).addOnFailureListener(new OnFailureListener() { @Override public void onFailure(@NonNull Exception e) { // If sign in fails, display a message to the user. Toast.makeText(BusinessSignUp2.this, "failed", Toast.LENGTH_LONG).show(); } }); } else{ Toast.makeText(BusinessSignUp2.this, "Please check the fields!", Toast.LENGTH_LONG).show(); } } }}); }private void addBottomDots(int currentPage) { dots = new TextView[layouts.length]; int[] colorsActive = getResources().getIntArray(R.array.array_dot_active); int[] colorsInactive = getResources().getIntArray(R.array.array_dot_inactive); dotsLayout.removeAllViews(); for (int i = 0; i < dots.length; i++) { dots[i] = new TextView(this); dots[i].setText(Html.fromHtml("& #8226; ")); dots[i].setTextSize(35); dots[i].setTextColor(colorsInactive[currentPage]); dotsLayout.addView(dots[i]); }if (dots.length > 0) dots[currentPage].setTextColor(colorsActive[currentPage]); }private int getItem(int i) { return viewPager.getCurrentItem() + i; }//viewpager change listener ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {@Override public void onPageSelected(int position) { addBottomDots(position); if (position == layouts.length - 1) { // last page btnNext.setText(getString(R.string.done)); btnPrev.setText(getString(R.string.previous)); } else if (position == 0){ // first page. don't need the prev button btnNext.setText(getString(R.string.next)); }else { // still pages are left btnNext.setText(getString(R.string.next)); btnPrev.setText(getString(R.string.previous)); } }@Override public void onPageScrolled(int arg0, float arg1, int arg2) {}@Override public void onPageScrollStateChanged(int arg0) {} }; /** * View pager adapter */ public class MyViewPagerAdapter extends PagerAdapter { private LayoutInflater layoutInflater; public MyViewPagerAdapter() { }@Override public Object instantiateItem(ViewGroup container, int position) { layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); View view = layoutInflater.inflate(layouts[position], container, false); container.addView(view); return view; }@Override public int getCount() { return layouts.length; }@Override public boolean isViewFromObject(View view, Object obj) { return view == obj; }@Override public void destroyItem(ViewGroup container, int position, Object object) { View view = (View) object; container.removeView(view); } } }layout_bo_sign_up_activity.xml为：

< ?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:layout_width="match_parent" android:layout_height="match_parent" tools:showIn="@layout/layout_bo_sign_up_activity"> < androidx.viewpager.widget.ViewPager android:id="@+id/view_pager" android:layout_width="match_parent" android:layout_height="match_parent" /> < LinearLayout android:id="@+id/layoutDots" android:layout_width="match_parent" android:layout_height="@dimen/dots_height" android:layout_alignParentBottom="true" android:layout_marginBottom="@dimen/dots_margin_bottom" android:gravity="center" android:orientation="horizontal"> < /LinearLayout> < View android:layout_width="match_parent" android:layout_height="1dp" android:alpha=".5" android:layout_above="@id/layoutDots" android:background="@android:color/white" /> < Button android:id="@+id/btn_next" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentRight="true" android:background="@null" android:text="@string/next" android:textColor="@android:color/white" /> < Button android:id="@+id/btn_prev" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentLeft="true" android:background="@null" android:text="@string/previous" android:textColor="@android:color/white" /> < /RelativeLayout>例如，activity_bo_sign_up.xml是：

< ?xml version="1.0" encoding="utf-8"?> < LinearLayout 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:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".BusinessFeatures.BusinessSignUp2" android:id="@+id/business_sign_up1"> < TextView android:id="@+id/bo_join_community" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:text="@string/bo_sign_up_text" android:textColor="@color/colorPrimaryDark" android:textAppearance="@style/TextAppearance.AppCompat.Display1" /> < com.google.android.material.textfield.TextInputLayout android:id="@+id/b_email_address" style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox" android:layout_width="360dp" android:layout_height="wrap_content" android:layout_marginLeft="24dp" android:layout_marginRight="24dp" android:layout_marginStart="24dp" android:layout_marginTop="24dp" android:hint="@string/email_hint" android:textSize="14sp" app:counterEnabled="true" app:counterMaxLength="30"> < com.google.android.material.textfield.TextInputEditText android:id="@+id/businessEmailEditText" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="textEmailAddress"/> < /com.google.android.material.textfield.TextInputLayout> < com.google.android.material.textfield.TextInputLayout android:id="@+id/b_password" style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox" android:layout_width="360dp" android:layout_height="wrap_content" android:layout_marginLeft="24dp" android:layout_marginRight="24dp" android:layout_marginStart="24dp" android:layout_marginTop="24dp" android:hint="@string/password_hint" android:textSize="14sp" app:counterEnabled="true" app:counterMaxLength="30"> < com.google.android.material.textfield.TextInputEditText android:id="@+id/businessPasswordEditText" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="textPassword"/> < /com.google.android.material.textfield.TextInputLayout> < com.google.android.material.textfield.TextInputLayout android:id="@+id/b_full_name" style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox" android:layout_width="360dp" android:layout_height="wrap_content" android:layout_marginLeft="24dp" android:layout_marginRight="24dp" android:layout_marginStart="24dp" android:layout_marginTop="24dp" android:hint="@string/full_name_hint" android:textSize="14sp" app:counterEnabled="true" app:counterMaxLength="30"> < com.google.android.material.textfield.TextInputEditText android:id="@+id/businessFullNameEditText" android:layout_width="match_parent" android:layout_height="wrap_content" android:inputType="textPersonName"/> < /com.google.android.material.textfield.TextInputLayout> < /LinearLayout>

在我的应用中，我使用“查看”页面进行了注册。当我滑动下一个或上一个数据时，但当我在最后一页（第三页）中时，下一个按钮变为完成按钮，当我按完成并尝试...
答案【android-数据在viewPage中丢失】[尝试以共同的偏好来存储价值。返回该页面时，然后使用共享的首选项值填充edittext。