从 RecyclerView 使用 Firebase 数据打开一个新 Activity

Question

我正在创建一个 TripAdvisor 克隆应用程序，该应用程序从 Firebase 数据库中获取数据并显示其中的数据。我想向 RecyclerView 添加一个侦听器，该侦听器打开一个名为 locationInDetailActivity 的新 Activity，它显示有关所选元素的信息。以下是 MainActivity 和 RecyclerView 适配器的代码。

MainActivity.java

package com.example.progettocv19ingsw;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

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

import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {

    private Button to_advanced_filters;
    private RecyclerView recyclerView;
    private LinearLayoutManager linearLayoutManager;
    private DatabaseReference reference;
    private RecyclerViewAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        to_advanced_filters = (Button) findViewById(R.id.advancedFilters);
        recyclerView = findViewById(R.id.locationRecyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        to_advanced_filters.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openAdvancedFilterActivity();
            }
        });

        reference = FirebaseDatabase.getInstance().getReference();
        FirebaseRecyclerOptions<locationClass> options = new FirebaseRecyclerOptions.Builder<locationClass>().setQuery(FirebaseDatabase.getInstance().getReference().child("locations"), locationClass.class).build();
        adapter = new RecyclerViewAdapter(options);
        recyclerView.setAdapter(adapter);
    }
    public void openAdvancedFilterActivity(){
        Intent open = new Intent(this, AdvancedFilters.class);
        startActivity(open);
    }

    @Override
    protected void onStart() {
        super.onStart();
        adapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        adapter.stopListening();
    }
}

RecyclerViewAdapter.java

package com.example.progettocv19ingsw;

import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.bumptech.glide.Glide;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;

public class RecyclerViewAdapter extends FirebaseRecyclerAdapter<locationClass, RecyclerViewAdapter.myViewHolder> {

    private static final String TAG = "RecyclerView";

    public RecyclerViewAdapter(@NonNull FirebaseRecyclerOptions options) {
        super(options);
    }

    @Override
    protected void onBindViewHolder(@NonNull myViewHolder viewHolder, int i, @NonNull locationClass location) {
        viewHolder.locationName.setText(location.getLocationName());
        viewHolder.locationType.setText(location.getLocationType());
        Glide.with(viewHolder.locationImage.getContext()).load(location.getLocationPic()).into(viewHolder.locationImage);
        viewHolder.reviewNumber.setText(String.valueOf(location.getReviewNumber()));
        viewHolder.averageRatingBar.setRating(location.getAverageRating());
        viewHolder.averageRatingBar.setStepSize(location.getAverageRating());
    }

    @Override
    public int getItemCount() {
        return super.getItemCount();
    }

    @NonNull
    @Override
    public myViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.location_recyclerrow, parent, false);
        return new myViewHolder(v);
    }

    class myViewHolder  extends RecyclerView.ViewHolder {

        ImageView locationImage;
        TextView locationName;
        TextView locationType;
        RatingBar averageRatingBar;
        TextView reviewNumber;
        Context context;

        public myViewHolder(@NonNull View itemView) {
            super(itemView);
            locationImage = (ImageView) itemView.findViewById(R.id.locationPicture);
            locationName = (TextView) itemView.findViewById(R.id.locationName);
            locationType = (TextView) itemView.findViewById(R.id.locationType);
            reviewNumber = (TextView) itemView.findViewById(R.id.reviewNumber);
            averageRatingBar = (RatingBar) itemView.findViewById(R.id.averageRating);
        }
    }
}

locationInDetailActivity.java

package com.example.progettocv19ingsw;

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

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

public class locationInDetailActivity extends AppCompatActivity {
    private static final String TAG = "locationDetailActivity";

    private Button toReviews;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.location_data);
        Log.d(TAG, "onCreate: Started");
        toReviews.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                openReviewActivity();
            }
        });
    }

    private void openReviewActivity() {
        Intent intent = new Intent(this, reviewActivity.class);
    }
}

我尝试添加一个 OnClick 侦听器，但它给我“无法解析方法”或 NullPointerException() 错误。我该怎么办？

Answer 1

Colin Degen 是对的，但你可以做一些更通用的事情。

为点击事件创建一个接口：

public interface IClickListener {
    void onItemClick(int position, View view);
    void onItemLongClick(int position, View view);
}

创建一个满足您需求的回收器视图适配器：

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {

private IClickListener clickListener;
private List<String> models;

public class ViewHolder extends RecyclerView.ViewHolder implements View.OnLongClickListener, View.OnClickListener {

    public TextView textView;

    public ViewHolder(View itemView) {
        super(itemView);

        textView = itemView.findViewById(R.id.textView);

        itemView.setOnClickListener(this);
        itemView.setOnLongClickListener(this);
    }


    @Override
    public void onClick(View view) {
        clickListener.onItemClick(getAdapterPosition(), view);
    }

    @Override
    public boolean onLongClick(View view) {
        clickListener.onItemLongClick(getAdapterPosition(), view);
        return false;
    }
}


public RecyclerViewAdapter(List<String> models) {
    this.models = models;
}


public void setOnItemClickListener(IClickListener clickListener) {
    this.clickListener = clickListener;
}


@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    Context context = parent.getContext();
    LayoutInflater inflater = LayoutInflater.from(context);

    View view = inflater.inflate(R.layout.list_item, parent, false);

    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    final String model = models.get(position);

    TextView textView = holder.textView;
    textView.setText(model);
}

@Override
public int getItemCount() {
    return models.size();
}}

然后，当您想使用回收站视图时，您可以执行以下操作：

ArrayList<String> dataSource = new ArrayList<String>()
// Add some data to the dataSource

RecyclerViewAdapter adapter = new RecyclerViewAdapter(dataSource);
adapter.setOnItemClickListener(new IClickListener() {
        @Override
        public void onItemClick(int position, View view) {
            String model = dataSource.get(position);
            // Do stuff with your model like passing data to the next activity
        }

});

Answer 2

您必须为 RecyclerView 中的每个元素定义一个 OnClickListener。

    private final OnClickListener mOnClickListener = new MyOnClickListener(){
        @Override
        public void onClick(final View view) {
           int itemPosition = mRecyclerView.getChildLayoutPosition(view);
           YourItem item = mList.get(itemPosition);
           //Do stuff and start your activity
        }
    }

    @NonNull
    @Override
    public myViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.location_recyclerrow, parent, false);
        view.setOnClickListener(mOnClickListener);
        return new myViewHolder(v);
    }

然后将 RecyclerView 实例传递给适配器的构造函数

    private RecyclerView mRecyclerView;

    public RecyclerViewAdapter(@NonNull FirebaseRecyclerOptions options, RecyclerView rV) {
        super(options);
        mRecyclerView = rV;
    }