Question

我正在使用片段和 viewpager 制作一个应用程序，它将用户数据发送到主要活动。数据将从多个片段收集并在提交按钮（包含在主活动中）被按下到活动时发送。示例截图：

Text

我不确定如何获取片段编辑文本数据。我尝试使用 R.findViewById 在提交按钮的 onClick 侦听器中获取它，但似乎我错过了一个重要步骤。我尝试查看视频/教程，但我只能找到在片段中按下按钮时获取数据的适用视频/教程，或者反向操作的视频/教程（片段从活动中获取数据）。

这是我的代码： formActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.PagerAdapter;
import androidx.viewpager.widget.ViewPager;

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.google.android.material.tabs.TabLayout;


public class FormActivity extends AppCompatActivity {

    private static final String TAG = "PROCESS";
    TabLayout tabLayout;
    ViewPager viewPager;

    //or set to 0 and change it dynamically in the onPageSelected method
    private int numFrags = 2;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_formactivity);
        viewPager = findViewById(R.id.viewPager);
        tabLayout = findViewById(R.id.tabLayout);
        getTabs();

        //Add onPageChangeListener to get the position of the current tab and change the button text based on the position
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int position) {
                Button back = findViewById(R.id.backButton);
                Button next = findViewById(R.id.nextButton);
                Button mainReturn = findViewById(R.id.mainReturn);
                Button submit = findViewById(R.id.submitButton);
                PagerAdapter adapter = viewPager.getAdapter();
                //numFrags = viewPager.getAdapter().getCoBunt() -1; - dynamically get new frags

                if (position == 0) {
                    back.setVisibility(View.GONE);
                    next.setVisibility(View.VISIBLE);
                    mainReturn.setVisibility(View.VISIBLE);

                }
                else if (adapter != null && position == numFrags) {
                    back.setVisibility(View.VISIBLE);
                    next.setVisibility(View.GONE);
                    submit.setVisibility(View.VISIBLE);

                    }
                else {
                    back.setVisibility(View.VISIBLE);
                    next.setVisibility(View.VISIBLE);
                    mainReturn.setVisibility(View.GONE);
                    submit.setVisibility(View.GONE);
                }
            }
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            }
            @Override
            public void onPageScrollStateChanged(int state) {
            }
        });
    }

    //Add fragments to viewPager using the object ViewPagerAdapter
    public void getTabs(){
       final ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());

        new Handler().post(new Runnable() {
            @Override
            public void run() {
                viewPagerAdapter.addFragment(oneFragment.getInstance(),null); // this line can cause crashes
                viewPagerAdapter.addFragment(twoFragment.getInstance(),null); // this line can cause crashes
                viewPagerAdapter.addFragment(threeFragment.getInstance(),null); // this line can cause crashes

                viewPager.setAdapter(viewPagerAdapter);
                tabLayout.setupWithViewPager(viewPager);
            }
        });
    }

    //METHODS FOR THE BUTTON LISTENERS
    public void goBack(View view) {
        viewPager.setCurrentItem(viewPager.getCurrentItem()-1);

    }
    public void goNext(View view) {
        viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
    }

    public void submitFormEntries(View view) {
        Log.d(TAG, "returnToMainMenu: ");
    }

    public void returnToMainMenu(View view) {
        Log.d(TAG, "returnToMainMenu: ");
    }
}

ViewPagerAdapter.java

import java.util.ArrayList;
import java.util.List;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentStatePagerAdapter;

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

    private List<Fragment> fragmentList = new ArrayList<>(); // this line can cause crashes
    private List<String> stringList = new ArrayList<>();


    public ViewPagerAdapter(@NonNull FragmentManager fm) {
        super(fm);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        return fragmentList.get(position);
    }

    @Override
    public int getCount() {
        return fragmentList.size();
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        return stringList.get(position);
    }

    public void addFragment(Fragment fragment, String title){
        fragmentList.add(fragment); // this line can cause crashes
        stringList.add(title);
    }

}

oneFragment.java

import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class oneFragment extends Fragment {

    public static oneFragment getInstance(){
        oneFragment oneFragment = new oneFragment();
        return oneFragment;
    }

    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
    }


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.page_one, container,false);

        return view;
    }
}

activity_formactivity.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    tools:context=".FormActivity">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true">

        <Button
            android:id="@+id/backButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/back"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:onClick="goBack"
            android:visibility="gone"/>

        <Button
            android:id="@+id/mainReturn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/mainReturn"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:onClick="returnToMainMenu"
            android:visibility="visible"/>

        <Button
            android:id="@+id/nextButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/next"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:onClick="goNext"/>

        <Button
            android:id="@+id/submitButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/submit"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:onClick="submitFormEntries"
            android:visibility="gone"/>

        <com.google.android.material.tabs.TabLayout
            android:id="@+id/tabLayout"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:tabBackground="@drawable/tab_selector"
            app:tabIndicatorHeight="0dp" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</RelativeLayout>

page_one.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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">

    <TextView
        android:id="@+id/titleOne"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="@string/title_one"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="32sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/questionOne"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:text="@string/questionOne"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="18sp"
        app:layout_constraintBottom_toTopOf="@+id/descriptionOne"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <TextView
        android:id="@+id/descriptionOne"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:text="@string/descriptionOne"
        android:textSize="18sp"
        app:layout_constraintBottom_toTopOf="@+id/answerOne"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <EditText
        android:id="@+id/answerOne"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="@string/answerHintOne"
        android:inputType="textMultiLine"
        android:maxLines="4"
        android:minLines="4"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

我很新，所以任何替代建议以及答案也将不胜感激。

Answer 1

您可以使用 SharedPreferences 来存储数据并在需要时检索数据。示例：

在首选项中设置值：

SharedPreferences.Editor editor = getSharedPreferences(MY_PREFS_NAME, MODE_PRIVATE).edit();
 editor.putString("key", "your answer");
 editor.apply();

从偏好中检索数据：

SharedPreferences prefs = getSharedPreferences(MY_PREFS_NAME, MODE_PRIVATE); 
String answer= prefs.getString("key", "");

Answer 2

如何使用与 ViewModel 相关联的 FormActivity 并将编辑文本值保存在那里 https://developer.android.com/topic/libraries/architecture/viewmodel?gclid=Cj0KCQiA3NX_BRDQARIsALA3fIJFaBMomx-KDhghEHZghVGwGaafvDwMpGzFxQFGm3M3_e0lv9Bzt1UaAoq7EALw_wcB&gclsrc=aw.ds

class FormViewModel : ViewModel() {
   val answers: Map<String, String> = mutableMapOf()
}

来自片段

editText.addTextChangedListener(object : TextWatcher {
      override fun afterTextChanged(s: Editable?) {
         val viewmodel = ViewModelProviders.of(requireActivity()).get(FormViewModel::class.java) 
         viewModel.answer["SOME_KEY_HERE"] = s.toString()
      }
      
    
      override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
      }
    
      override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
      }
    })

从活动中你可以访问这样的价值

ViewModelProvider.of(this).get(FormViewModel::class.java).answer

抱歉，我是用 kotlin 写的，但你应该能够理解这个想法

Answer 3

实现常规 FragmentPagerAdapter 的正确方法是：

public class ViewPagerAdapter extends FragmentPagerAdapter {
    public ViewPagerAdapter(FragmentManager fragmentManager) {
        super(fragmentManager);
    }

    @Override
    public Fragment getItem(int position) {
        if(position == 0) return new RulesFragment();
        if(position == 1) return new TreeFragment();
        if(position == 2) return new PredictionFragment();

        throw new IllegalStateException("Unexpected position " + position);
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        if(position == 0) return "TREE RULES";
        if(position == 1) return "REGRESSION TREE";
        if(position == 2) return "PREDICTION";
      
        throw new IllegalStateException("Unexpected position " + position);
    }
}

要获取对 ViewPager 创建的 Fragment 的引用，请使用以下 findFragmentByTag 方案：

Fragment fragment = supportFragmentManager.findFragmentByTag("android:switcher:" + viewPager.getId() + ":" + fragmentPosition)

在多个片段之间进行通信的正确方法是使用范围限定为共享范围（在本例中，可能是活动）的 ViewModel。

为此，请参阅https://developer.android.com/codelabs/kotlin-android-training-view-model#0

Answer 4

使用捆绑包。举个例子：

Fragment fragment = new Fragment();
Bundle bundle = new Bundle();
bundle.putInt(key, value);
fragment.setArguments(bundle);

Bundle 有很多数据类型的 put 方法。看到这个

然后在您的 Fragment 中，使用以下命令检索数据（例如在 onCreate() 方法中）：

Bundle bundle = this.getArguments();
if (bundle != null) {
        int myInt = bundle.getInt(key, defaultValue);
}

在 bundle.setArguments 中设置第一个片段的值和第二个片段的 onCreate() 使用 bundle.getInt() 获取值在第二个片段中放置与 bundle.setArguemnts 相同的第一个片段和第二个片段的值，因此在第三个片段中您将获得第一个和第二个片段的值。

片段 1：

 Bundle bundle = new Bundle();
        bundle.putString("FRAGEMNT1", "VALUE FRAGEMENT 1");
        fragment.setArguments(bundle);

在片段 2 的 onCrete()

Bundle bundle = this.getArguments();
if (bundle != null) {
    String frag1Value = bundle.getString("FRAGEMNT1");
}

现在将两个值都放在片段 2 中

Bundle bundle = new Bundle();
        bundle.putString("FRAGEMNT1", "VALUE FRAGEMENT 1");
        bundle.putString("FRAGEMNT2, "VALUE FRAGEMENT 2);
        fragment.setArguments(bundle);

在片段 3 onCrete()

Bundle bundle = this.getArguments();
if (bundle != null) {
    String frag1Value = bundle.getString("FRAGEMNT1");
     String frag2Value = bundle.getString("FRAGEMNT2");
}

现在将两个值都放在片段 3 中

Bundle bundle = new Bundle();
        bundle.putString("FRAGEMNT1", "VALUE FRAGEMENT 1");
        bundle.putString("FRAGEMNT2, "VALUE FRAGEMENT 2);
        bundle.putString("FRAGEMNT3, "VALUE FRAGEMENT 3");
        fragment.setArguments(bundle);

现在在 Activit 的 onCrete

Bundle bundle = this.getArguments();
if (bundle != null) {
    String frag1Value=bundle.getString("FRAGEMNT1");
    String frag2Value=bundle.getString("FRAGEMNT2");
    String frag3Value=bundle.getString("FRAGEMNT3");
}

如何在片段中没有按钮的情况下将片段编辑文本数据发送到活动

4 个答案: