MainParkActivity

Question

我试图在我的主要活动中显示一个RecyclerView的片段。我没有收到任何错误，但是该片段仍然为空，并且找不到该问题的解决方案。我只是有一个包含recyclerview的片段，我在HomeFragment.java中配置了recyclerview，然后在MainParkActivity中，我有一个FrameLayout，它被HomeFragment取代了。

MainParkActivity

package com.example.ipark;

import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;;

public class MainParkActivity extends AppCompatActivity {

    private static final String TAG = "MainParkActivity";

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        Fragment homeFragment = new HomeFragment();
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("iParc");

        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, homeFragment).commit();
    }
}

HomeFragment

package com.example.ipark;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import java.util.ArrayList;

public class HomeFragment extends Fragment {

    private static final String TAG = "HomeFragment";

    private ArrayList<String> mNames = new ArrayList<>();
    private ArrayList<String> mImageUrls = new ArrayList<>();

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        return rootView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        RecyclerView recyclerView = view.findViewById(R.id.recycler_view);

        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

        giveInformation();

        RecyclerViewAdapter adapter = new RecyclerViewAdapter(getContext(), mNames, mImageUrls);
        recyclerView.setAdapter(adapter);

    }

    private void giveInformation() {
        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("BMW");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Audi");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Hyundai");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Mercedes");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("BMW");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Audi");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Hyundai");

        mImageUrls.add("https://loremflickr.com/300/300/bmw");
        mNames.add("Mercedes");
    }
}

RecyclerViewAdapter

package com.example.ipark;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;

import java.util.ArrayList;

import de.hdodenhof.circleimageview.CircleImageView;

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

    private static final String TAG = "RecyclerViewAdapter";

    private ArrayList<String> mImageNames;
    private ArrayList<String> mImages;
    private Context mContext;

    public RecyclerViewAdapter(Context mContext, ArrayList<String> mImageNames, ArrayList<String> mImages) {
        this.mImageNames = mImageNames;
        this.mImages = mImages;
        this.mContext = mContext;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_listitem, parent, false);
        ViewHolder holder;
        holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, final int position) {
        Log.d(TAG, "onBindViewHolder: called.");

        Glide.with(mContext)
                .asBitmap()
                .load(mImages.get(position))
                .into(holder.image);

        holder.imageName.setText(mImageNames.get(position));

        holder.parentLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d(TAG, "onClick: clicked on: " + mImageNames.get(position));

                Toast.makeText(mContext, mImageNames.get(position), Toast.LENGTH_SHORT).show();
            }
        });
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {

        CircleImageView image;
        TextView imageName;
        RelativeLayout parentLayout;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            image = itemView.findViewById(R.id.image);
            imageName = itemView.findViewById(R.id.image_name);
            parentLayout = itemView.findViewById(R.id.parent_layout);
        }
    }
}

}

activity_main的XML

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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"
    tools:context=".MainParkActivity"
    android:clipToPadding="false">

    <include
        android:id="@+id/toolbar"
        layout="@layout/toolbar" />

    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar">

    </FrameLayout>


</android.support.constraint.ConstraintLayout>

fragment_home的XML

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toTopOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


</android.support.constraint.ConstraintLayout>

Answer 1

在您的 fragment_home.xml 中，您的Recyclerview具有layout_height和layout_width 0dp 。将其更改为match_parent。您代码中的所有其他内容都是正确的。我已经对此发表了评论，但是我目前没有评论特权！如果发现有帮助，请接受！

Answer 2

在activity_main布局中，您有app:layout_constraintBottom_toTopOf="parent"

应为app:layout_constraintBottom_toBottomOf="parent"

您的布局当前显示在您片段的屏幕上方。

Answer 3

使用

adapter.notifyDataSetChanged();

为RecycleView设置适配器后。

持有RecyclerView的片段未在MainActivity中显示

MainParkActivity

HomeFragment

RecyclerViewAdapter

activity_main的XML

fragment_home的XML

3 个答案: