java - 如何在选项卡式 Activity 中实现连接到 firebase 数据库的 recyclerView？

Question

我想知道如何使用连接到 firebase 数据库以提取数据的回收器和 cardview 实现选项卡式 Activity (4 个 fragment )。

-我是否必须为每个 fragment 或相同的适配器创建一个适配器，但每个 fragment 都会过滤它需要的数据？

-我是否必须从主 Activity 调用 getInstance 并引用 Firebase 数据库？ 我是 recyclerView 的新手，请给我所有可能的详细信息。

-对于cardview，将创建一个名为“property”的对象，2个textview和1个imageview。这将如何融入整个代码，我指的是属性类及其实例。

-我可以将要在卡片 View 中使用的图像存储在 Firebase 存储上吗？如果是如何查询？

这是代码

package com.realty.drake.kunuk;

import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import android.support.v4.app.Fragment;

import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;

import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;


public class MainActivity extends AppCompatActivity {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        Log.d("debugg", "OnCreate started");
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);


        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));

        FloatingActionButton fab = (FloatingActionButton) 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();
            }
        });

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }


    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {


        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            Log.d("DEBUGG","getItem called" );
            //Returning the current tab
            switch (position) {
                case 0:
                    Tab1Buy tab1 = new Tab1Buy();
                    return tab1;
                case 1:
                    Tab2Rent tab2 = new Tab2Rent();
                    return  tab2;
                case 2:
                    Tab3Lot tab3 = new Tab3Lot();
                    return  tab3;
                case 3:
                    Tab4Saved tab4 = new Tab4Saved();
                    return tab4;
                default:
                    return  null;
            }



        }

        @Override
        public int getCount() {
            // Show 4 total pages.
            return 4;
        }

        @Override
        public CharSequence getPageTitle(int position){
            Log.d("Debugg", "getPageTitle: Executed");
            switch (position) {
                case 0:
                    return "BUY";
                case 1:
                    return "RENT";
                case 2:
                    return "LOT";
                case 3:
                    return "SAVED";
            }
            return null;
        }
    }
}

    package com.realty.drake.kunuk;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by drake on 4/11/18.
 */

public class Tab1Buy extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.tab1buy, container, false);

        return rootView;
    }
}

    package com.realty.drake.kunuk;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by drake on 4/11/18.
 */

public class Tab2Rent extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.tab2rent, container, false);

        return rootView;
    }
}


    <?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.realty.drake.kunuk.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/appbar_padding_top"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:layout_weight="1"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/AppTheme.PopupOverlay"
            app:title="@string/app_name">

        </android.support.v7.widget.Toolbar>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabMaxWidth="0dp"
            app:tabGravity="fill"
            app:tabMode="fixed">

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_1" />

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_2" />

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_3" />

        </android.support.design.widget.TabLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="@dimen/fab_margin"
        app:srcCompat="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

    <?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#dfdfdf"
    android:orientation="vertical">
<!-- TODO Add white icon -->
    <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:card_view="http://schemas.android.com/tools"
        android:id="@+id/property"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:cardUseCompatPadding="true"
        card_view:cardCornerRadius="4dp"
        card_view:cardElevation="4dp">

        <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="290dp"
            android:orientation="vertical">

            <ImageView
                android:id="@+id/post_image"
                android:contentDescription="@string/property"
                android:layout_width="0dp"
                android:layout_height="0dp"
                android:layout_marginBottom="71dp"
                android:scaleType="centerCrop"
                android:src="@drawable/house1"
                app:layout_constraintBottom_toTopOf="@+id/number_bedroom"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <TextView
                android:id="@+id/post_title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginBottom="8dp"
                android:layout_marginStart="5dp"
                android:layout_marginTop="8dp"
                android:text="55,000$"
                android:textColor="@color/colorPrimary"
                android:textSize="20sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.79" />

            <TextView
                android:id="@+id/post_desc"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginBottom="10dp"
                android:layout_marginStart="5dp"
                android:layout_marginTop="1dp"
                android:text="23,Rue Duvivier-hall, Les Cayes, "
                android:textColor="#737373"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/post_title"
                app:layout_constraintVertical_bias="0.0" />

            <ImageView
                android:id="@+id/bathroom"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginBottom="5dp"
                android:layout_marginStart="100dp"
                android:layout_marginTop="2dp"
                android:background="#ff9100"
                android:src="@drawable/bathtub"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.976" />

            <ImageView
                android:id="@+id/bedroom"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginBottom="5dp"
                android:layout_marginStart="25dp"
                android:layout_marginTop="2dp"
                android:background="#ff9100"
                android:src="@drawable/bedroom"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.976" />

            <TextView
                android:id="@+id/number_bathroom"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="8dp"
                android:text="2"
                android:textColor="#ff9100"
                android:textStyle="bold"
                app:layout_constraintBottom_toBottomOf="@+id/bathroom"
                app:layout_constraintEnd_toStartOf="@+id/bathroom" />

            <TextView
                android:id="@+id/number_bedroom"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="8dp"
                android:text="3"
                android:textColor="#ff9100"
                android:textStyle="bold"
                app:layout_constraintBottom_toBottomOf="@+id/bedroom"
                app:layout_constraintEnd_toStartOf="@+id/bedroom" />

            <TextView
                android:id="@+id/number_garage"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="8dp"
                android:text="1"
                android:textColor="#ff9100"
                android:textStyle="bold"
                app:layout_constraintBottom_toBottomOf="@+id/garage"
                app:layout_constraintEnd_toStartOf="@+id/garage" />

            <ImageView
                android:id="@+id/garage"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginBottom="5dp"
                android:layout_marginStart="175dp"
                android:layout_marginTop="2dp"
                android:background="#ff9100"
                android:src="@drawable/garage"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.976" />

        </android.support.constraint.ConstraintLayout>

    </android.support.v7.widget.CardView>

</LinearLayout>

    <?xml version="1.0" encoding="utf-8"?>
<!--TODO add recyclerView layout-->
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/rv_items">

    </android.support.v7.widget.RecyclerView>


</FrameLayout>

谢谢你的帮助

Answer 1

-我是否必须为每个 fragment 或相同的适配器创建一个适配器，但每个 fragment 都会过滤它需要的数据？ 答:我让每个 fragment 都有自己对 firebase 数据库的引用，每个 fragment 都查询一个子 fragment 。在 firebase 数据库中，查看图像，每个 Fragment 调用一个子项:Buy、Lot、Rent..

-我是否必须从主 Activity 调用 getInstance 并引用 Firebase 数据库？我是 recyclerView 的新手，请给我所有可能的详细信息。

A:我改为在每个 fragment 中调用 getIntance，

public class Tab1Buy extends Fragment {
private DatabaseReference propertyRef;
private RecyclerView mPropertyRecyclerView;
FirebaseRecyclerAdapter<Property, PropertyViewHolder> mPropertyAdapter;


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.property_tab, container, false);
    mPropertyRecyclerView = rootView.findViewById(R.id.property_recyclerView);
    return rootView;
}


//TODO Check internet and display error msg if internet down
@Override
public void onViewCreated(final View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    mPropertyRecyclerView.hasFixedSize();
    mPropertyRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    final ProgressBar progressBar = view.findViewById(R.id.progressBar);
    progressBar.setVisibility(View.VISIBLE);

    propertyRef = FirebaseDatabase.getInstance()
            .getReference()
            .child("Buy");
    propertyRef.keepSynced(true);

    // keyQuery - the Firebase location containing the list of keys to be found in dataRef
    //Query personQuery = propertyRef.orderByKey();


    FirebaseRecyclerOptions<Property> options =
            new FirebaseRecyclerOptions.Builder<Property>()
                    .setQuery(propertyRef, Property.class)
                    .build();

    mPropertyAdapter = new FirebaseRecyclerAdapter<Property, PropertyViewHolder>(options) {


        @Override
        // Bind the Property object to the ViewHolder PropertyHolder
        public void onBindViewHolder(@NonNull PropertyViewHolder holder,
                                     final int position, @NonNull final Property model) {
            holder.setPrice(model.getPrice());
            holder.setAddress(model.getAddress());
            holder.setNumberOfBed(model.getNumberOfBed());
            holder.setNumberOfBath(model.getNumberOfBath());
            holder.setNumberOfCar(model.getNumberOfCar());
            holder.setPropertyImage(model.getPropertyImage());

        //This Intent send Parcelable from Property to PropertyDetail
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().startActivity(new Intent(getActivity(), PropertyDetail.class)
                .putExtra("Property", model));

            }
        });


        }

        @Override
        public PropertyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            // Create a new instance of the ViewHolder, in this case we are using a custom
            // layout called R.layout.property_card for each item
            View view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.property_card, parent, false);
            return new PropertyViewHolder(view);

        }

        @Override
        public void onDataChanged() {
            // Called each time there is a new data snapshot. You may want to use this method
            // to hide a loading spinner or check for the "no documents" state and update your UI.
            // ...
            progressBar.setVisibility(View.GONE);
        }

        //TODO Implement onError
        @Override
        public void onError(@NonNull DatabaseError e) {
            // Called when there is an error getting data. You may want to update
            // your UI to display an error message to the user.
            // ...
            progressBar.setVisibility(View.GONE);
            Toast.makeText(getActivity(), "DatabaseError", Toast.LENGTH_SHORT).show();
        }

    };
    mPropertyRecyclerView.setAdapter(mPropertyAdapter);



}

@Override
public void onStart() {
    super.onStart();
    mPropertyAdapter.startListening();
}

@Override
public void onStop() {
    super.onStop();
    mPropertyAdapter.stopListening();
}


public class PropertyViewHolder extends RecyclerView.ViewHolder {
    View mView;

    public PropertyViewHolder(View itemView) {
        super(itemView);
        mView = itemView;
    }

    public void setPrice(int price) {
        String currencyPrice = NumberFormat //Format the price variable in currency form
                .getCurrencyInstance(Locale.US)
                .format(price);
        TextView Price = mView.findViewById(R.id.post_price);
        Price.setText(currencyPrice);
    }

    public void setAddress(String address){
        TextView Address = mView.findViewById(R.id.post_address);
        Address.setText(String.valueOf(address));
    }

    public void setNumberOfBed(int numberOfBed){
        TextView NumberOfBed = mView.findViewById(R.id.post_bedroom);
        NumberOfBed.setText(String.valueOf(numberOfBed));
    }

    public void setNumberOfBath(int numberOfBath){
        TextView NumberOfBath = mView.findViewById(R.id.post_bathroom);
        NumberOfBath.setText(String.valueOf(numberOfBath));
    }

    public  void  setNumberOfCar(int numberOfCar) {
        TextView NumberOfCar = mView.findViewById(R.id.post_garage);
        NumberOfCar.setText(String.valueOf(numberOfCar));
    }

    public void setPropertyImage(String propertyImage){
        ImageView imageView = mView.findViewById(R.id.post_propertyImage);

        //take one long string containing multiple url in and parse it
        String propertyImageArray[] = propertyImage.split(",");

        //Loading circle for placeholder, ColorAccent has been used
        CircularProgressDrawable progressDrawable =
                new CircularProgressDrawable(getContext());
        progressDrawable.setStrokeWidth(5f);
        progressDrawable.setCenterRadius(30f);
        progressDrawable.setColorSchemeColors(Color.argb(1,255,145,0));
        progressDrawable.start();

        // Download directly from StorageReference using Glide
        // (See MyAppGlideModule for Loader registration)
        GlideApp.with(getContext())
                .load(propertyImageArray[0])
                .placeholder(progressDrawable)
                .fitCenter()
                .into(imageView);
    }
}

}

-对于cardview，将创建一个名为“property”的对象，2个textview和1个imageview。这将如何融入整个代码，我指的是属性类及其实例。

A:创建一个新的 ViewHolder 实例，在这种情况下，我们为每个项目使用一个名为 R.layout.property_card 的自定义布局。看上面的代码，特别是那一行 public PropertyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

-我可以将要在卡片 View 中使用的图像存储在 Firebase 存储上吗？如果是如何查询？

A:是的，我将图像存储在 Firebase Storage 中，然后我使用它们生成的 url 传入 Glide 方法。看看上面的代码。

我只显示第一个 fragment ，因为它们看起来都很相似，除了 firebase 中的子引用不同。