使用 Retrofit 從服務器獲取多個視圖項來創建 RecyclerView

Question

設想：

我正在嘗試創建一個 RecyclerView，它將在一個列表中顯示幾種不同類型的項目（食物、書籍、食譜）。 當用戶在搜索欄中輸入一些關鍵字時，數據將在改造的幫助下從服務器獲取。 所以，我有一個帶有搜索欄的活動，另一個在回收站視圖中顯示數據。

到目前為止所做的工作： 1. 在搜索的回收器視圖的幫助下從服務器獲取數據。 2. 將數據（以可序列化的）形式從搜索活動發送到顯示活動。 3. 創建一個帶有多個視圖適配器的回收器視圖（借助下面列出的一些教程）。

鏈接：

1. 示例 1

2. 示例 2

部分相關項目：

1. 一些示例項目

理解

到目前為止我所理解的是，為了在回收器視圖中顯示多種類型的項目，我們需要為每個對象創建一個抽象視圖持有者和單獨的視圖持有者。 它們還必須具有相應的布局，並且它們的布局會動態膨脹到回收器視圖持有者中。

問題：

1. 嘗試將適配器設置為我的回收站視圖適配器會出錯。
2. 我面臨的問題是我似乎無法將從服務器收到的數據與相應的視圖持有者綁定。

代碼：

我將省略我正在獲取數據的活動，因為它正在工作。

SearhResultActivity （此活動從 SearchActivity 接收數據，並應該顯示帶有數據的回收站視圖）

package com.example.naisse.Activity;

import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v7.widget.RecyclerView;
import android.widget.FrameLayout;
import com.example.naisse.AdapterAndClass.ResultAdaptar;
import com.example.naisse.AdapterAndClass.SearchRecyclerAdapter;
import com.example.naisse.Api.Model.Search.Article;
import com.example.naisse.Api.Model.Search.Food;
import com.example.naisse.Api.Model.Search.Hadith;
import com.example.naisse.Api.Model.Search.Manuscript;
import com.example.naisse.Api.Model.Search.Quran;
import com.example.naisse.Fragment.SearchTabFragment;
import com.example.naisse.R;
import java.util.ArrayList;
import java.util.List;
import butterknife.BindView;

public class SearchResultActivity extends HomeActivity {

private static final String TAG = "SearchResultActivity";

@BindView(R.id.search_result_recycler)
RecyclerView recyclerView;

private SearchRecyclerAdapter searchRecyclerAdapter;

private List<String> dataList;

protected FrameLayout frames;
private FragmentManager mFragmentManager;
private ResultAdaptar resultAdaptar;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_search_result);

    frames = findViewById(R.id.search_bar_holder);
    mFragmentManager = (this).getSupportFragmentManager();
    mFragmentManager.beginTransaction().add(R.id.search_bar_holder, new SearchTabFragment()).commit();


    Food foodData = new Food();
    ArrayList<Book> getBookArray = new ArrayList<>();
    ArrayList<Recipe> getRecipe = new ArrayList<>();

    foodData = (Food) getIntent().getSerializableExtra("foodDetails");
    getBookArray = (ArrayList<Book>) getIntent().getSerializableExtra("bookList");
    getRecipe = (ArrayList<Recipe>) getIntent().getSerializableExtra("recipeList");

    /*There is something wrong here, it says "Attempt to invoke virtual method on a null object reference" for searchRecyclerAdapter*/
    searchRecyclerAdapter = new SearchRecyclerAdapter(this);
    recyclerView.setAdapter(searchRecyclerAdapter);

}

}

SearchRecyclerAdapter （這個適配器持有聲明和將所有viewHolder連接到抽象viewHolder並連接到回收器視圖的代碼）

package com.example.naisse.AdapterAndClass;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.example.naisse.Api.Model.Search.Food;
import com.example.naisse.Api.Model.Search.Quran;
import com.example.naisse.R;
import java.util.ArrayList;
import java.util.List;
import butterknife.BindView;
import butterknife.ButterKnife;

public class SearchRecyclerAdapter extends RecyclerView.Adapter<SearchRecyclerAdapter.AbstractViewHolder>{

private static final String TAG = "SearchRecyclerAdapter";

public static final int TYPE_FOOD = 0;
public static final int TYPE_BOOK = 1;


private Context context;
private List<Object> data;

/*I belive im missing something here*/
public SearchRecyclerAdapter(Context context){
    this.context = context;
}

public void add(List searchData){
    if(data == null){
        data = new ArrayList<>();
    }
    data.clear();
    data.addAll(searchData);
    notifyDataSetChanged();
}


@Override
public AbstractViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {

    switch (i){
        case TYPE_FOOD:{
            /*search_result_fragment is the xml layout for food adapter*/
            View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.search_result_fragment, viewGroup, false);
            return new FoodViewAdapter(view);
        }
        case TYPE_BOOK:{
            /*search_result_fragment is the xml layout for book adapter*/
            View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.viewholder_book, viewGroup, false);
            return new BooksViewAdapter(view);
        }

        default:
            throw new IllegalArgumentException("Invalid view type");

    }

}

@Override
public void onBindViewHolder(AbstractViewHolder abstractViewHolder, int i) {
    Object object = data.get(i);
    abstractViewHolder.bind(object);
}

@Override
public int getItemViewType(int i){
    Object object = data.get(i);

    if (object instanceof Food){
        return TYPE_FOOD;
    }else if (object instanceof Book){
        return TYPE_BOOK;
    }

    throw new IllegalArgumentException("Invalid position");
}

@Override
public int getItemCount() {
    return data == null ? 0 : data.size();
}

public abstract class AbstractViewHolder<T> extends RecyclerView.ViewHolder{

    public AbstractViewHolder(@NonNull View itemView) {
        super(itemView);

        ButterKnife.bind(this, itemView);
    }

    public abstract void bind(T type);
}


public class FoodViewAdapter extends AbstractViewHolder<Food> {
    @BindView(R.id.result_food_title)
    TextView foodTitle;
    @BindView(R.id.result_food_content)
    TextView content;

    private FoodViewAdapter(View itemView){
        super(itemView);
    }

    @Override
    public void bind(Food type) {
        foodTitle.setText("Food");
        content.setText("title");
    }

}

public class BooksViewAdapter extends AbstractViewHolder<Book> {
    @BindView(R.id.result_book_title)
    TextView bookTitle;
    @BindView(R.id.result_book_content)
    TextView content;

    private BooksViewAdapter(View itemView){
        super(itemView);
    }

    @Override
    public void bind(Book type) {
        bookTitle.setText("title");
        content.setText("Text");
    }

}

}

題：

如何設置適配器以及如何將數據綁定到相應的視圖？

PS 如果您想查看其他類或 XML 布局，請告訴我。

邏輯貓

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.naisse, PID: 12570
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.naisse/com.example.naisse.Activity.SearchResultActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference
    at com.example.naisse.Activity.SearchResultActivity.onCreate(SearchResultActivity.java:67)
    at android.app.Activity.performCreate(Activity.java:7136)
    at android.app.Activity.performCreate(Activity.java:7127)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6669) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 

Answer 1

您使用黃油刀而忘記在活動中添加綁定視圖

只需添加這一行

ButterKnife.bind(this);

到 SearchResultActivity 的onCreate()

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_search_result);
    ButterKnife.bind(this);
    //other codes
}

第二部分

對於第二部分，您需要將數據添加到您的recycelerView （適配器）

為此，我們更改了您在適配器中的添加功能。 使用此代碼而不是您的

public void add(ArrayList newData){
    if(data == null){
        data = new ArrayList<>();
    }
    data.addAll(searchData);
    notifyDataSetChanged();
}

現在在SearchResultActivity嘗試像這樣將您的數據發送到適配器

searchRecyclerAdapter = new SearchRecyclerAdapter(this);
recyclerView.setAdapter(searchRecyclerAdapter);
searchRecyclerAdapter.add(foodData);
searchRecyclerAdapter.add(getBookArray);
searchRecyclerAdapter.add(getRecipe);