前言
上篇文章中我講述了如何實現Tabs 頻道頁面切換，接下來我們進一步實現 Tab Channel 中的新聞卡片列表渲染。
項目倉庫
簡易今日頭條 - Github
Display
具體實現
由於一種的渲染方法比較簡單，通常設計者是卡在顯示多種類型的 RecyclerView Item，在多種卡片 item 的設計這裡我只需要設計一種 DataModel ，然後在 DataModel 中添加 type 成員變量判斷是哪種類型的卡片。
以下我舉出實現的 Example，簡化的部份 Code，這裡的 Code 去掉： HTTP 請求的渲染、Pull To ReFresh、Load More。後面會再一一舉例。
layout/fragment_news_channel.xml
在需要渲染列表的地方加上 RecyclerView 組件。
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<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.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/fragment_news_channel"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".ui.page.newsChannel.NewsChannelFragment">
<LinearLayout
android:id="@+id/linearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:ignore="MissingClass,MissingConstraints">
<TextView
android:id="@+id/text_view_section_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view_card_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginBottom="5dp"
android:nestedScrollingEnabled="true"
android:scrollbars="vertical" />
</LinearLayout>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
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layout/no_image_card_item.xml、layout/one_image_card_item.xml、three_images_card_item.xml
這是我們需要渲染的三種新聞卡片，我這裡就舉出第一種卡片 no_image_card_item，其他的可以自己去設計，不多贅述一一放出來。
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<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView 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="wrap_content"
android:layout_margin="5dp"
app:cardCornerRadius="10dp"
app:cardElevation="2dp">
<TextView
android:id="@+id/text_view_source_url"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
android:layout_marginRight="16dp"
android:layout_marginBottom="8dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/image_view_card_avatar"
android:layout_width="25dp"
android:layout_height="25dp"
android:layout_marginEnd="10dp"
tools:ignore="MissingConstraints"
tools:srcCompat="@drawable/avatar_1"
android:contentDescription="@string/avatar" />
<TextView
android:id="@+id/text_view_card_title"
style="@style/TextAppearance.MaterialComponents.Headline6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/title_goes_here"
app:layout_constraintBottom_toTopOf="@+id/avatar"
app:layout_constraintStart_toEndOf="@+id/avatar"
app:layout_constraintTop_toBottomOf="@+id/avatar"
tools:ignore="MissingConstraints" />
</LinearLayout>
<TextView
android:id="@+id/text_view_card_subtitle"
style="@style/TextAppearance.MaterialComponents.Caption"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="@string/subtitle_goes_here"
app:layout_constraintStart_toStartOf="@+id/card_title"
app:layout_constraintTop_toBottomOf="@+id/card_title" />
<TextView
android:id="@+id/text_view_card_bottom_text"
style="@style/TextAppearance.MaterialComponents.Overline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="@string/comment"
app:layout_constraintStart_toStartOf="@+id/card_subtitle"
app:layout_constraintTop_toBottomOf="@+id/card_subtitle" />
</LinearLayout>
</androidx.cardview.widget.CardView>
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ui/card/newsCardList/NewsCardItemDataModel.java
我在 ui/card/newsCardList/ 創建了兩個文件：NewsCardItemDataModel.java、NewsCardAdapter.java，分別代表卡片的數據模型和 RecyclerView 適配器。
我這裡寫了三種構造類方法對應三種不同類型的卡片所需數據，並使用 mItemType 判斷卡片類型。
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package com.example.toutiao.ui.card.newsCardList;
import java.util.ArrayList;
import java.util.Locale;
/**
* CardItemDataModel class: the card item data model in New Channel Fragment
*/
public class NewsCardItemDataModel {
public static final int NO_IMAGE_TYPE = 0;
public static final int ONE_IMAGE_TYPE = 1;
public static final int THREE_IMAGE_TYPE = 2;
private int mItemType; // cart type
private String mId; //id
private String mAvatar; // avatar
private ArrayList<String> mThreeImageDrawable; // three image
private String mImageDrawable; // one image
private String mTitle; // title
private String mSubTitle; // subtitle
private String mBottomText; // bottom text
private String mDetailUrl; // detail text to jump
// no image style constructor
public NewsCardItemDataModel(int itemType,
String id,
String newsTitle,
String newsAbstract,
int newsCommentsCount,
String newsSource,
String newsMediaAvatarUrl,
String newsSourceUrl
) {
mItemType = itemType;
mId = id;
mAvatar = newsMediaAvatarUrl;
mTitle = String.format(Locale.CHINESE, "%s", newsTitle);
mSubTitle = String.format(Locale.CHINESE, "%s", newsAbstract);
mBottomText = String.format(Locale.CHINESE, "%s %d 评论", newsSource, newsCommentsCount);
mDetailUrl = newsSourceUrl;
}
// one image style constructor
public NewsCardItemDataModel(int itemType,
String id,
String newsTitle,
String newsAbstract,
int newsCommentsCount,
String newsSource,
String newsMediaAvatarUrl,
String newsSourceUrl,
String imageDrawable
) {
mItemType = itemType;
mId = id;
mAvatar = newsMediaAvatarUrl;
mTitle = String.format(Locale.CHINESE, "%s", newsTitle);
mSubTitle = String.format(Locale.CHINESE, "%s", newsAbstract);
mBottomText = String.format(Locale.CHINESE, "%s %d 评论", newsSource, newsCommentsCount);
mDetailUrl = newsSourceUrl;
// one
mImageDrawable = imageDrawable;
}
// three image style constructor
public NewsCardItemDataModel(int itemType,
String id,
String newsTitle,
String newsAbstract,
int newsCommentsCount,
String newsSource,
String newsMediaAvatarUrl,
String newsSourceUrl,
ArrayList<String> threeImageDrawable
) {
mItemType = itemType;
mId = id;
mAvatar = newsMediaAvatarUrl;
mTitle = String.format(Locale.CHINESE, "%s", newsTitle);
mSubTitle = String.format(Locale.CHINESE, "%s", newsAbstract);
mBottomText = String.format(Locale.CHINESE, "%s %d 评论", newsSource, newsCommentsCount);
mDetailUrl = newsSourceUrl;
// three
mThreeImageDrawable = threeImageDrawable;
}
public int getItemType() {
return mItemType;
}
public void setItemType(int itemType) {
mItemType = itemType;
}
public String getId() {
return mId;
}
public void setId(String id) {
mId = id;
}
public String getAvatar() {
return mAvatar;
}
public void setAvatar(String avatar) {
mAvatar = avatar;
}
public String getBottomText() {
return mBottomText;
}
public void setBottomText(String bottomText) {
mBottomText = bottomText;
}
public String getTitle() {
return mTitle;
}
public void setTitle(String title) {
mTitle = title;
}
public String getSubTitle() {
return mSubTitle;
}
public void setSubTitle(String subTitle) {
mSubTitle = subTitle;
}
public ArrayList<String> getThreeImageDrawable() {
return mThreeImageDrawable;
}
public void setThreeImageDrawable(ArrayList<String> threeImageDrawable) {
mThreeImageDrawable = threeImageDrawable;
}
public String getImageDrawable() {
return mImageDrawable;
}
public void setImageDrawable(String imageDrawable) {
mImageDrawable = imageDrawable;
}
public String getDetailUrl() {
return mDetailUrl;
}
public void setDetailUrl(String detailUrl) {
mDetailUrl = detailUrl;
}
}
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ui/card/newsCardList/NewsCardAdapter.java
這是渲染卡片的 RecyclerView 適配器類，三種卡片類型就會有三種 ViewHolder 子類。
onCreateViewHolder 綁定 UI 文件，onBindViewHolder 綁定數據。
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package com.example.toutiao.ui.card.newsCardList;
// ...
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.toutiao.R;
import com.example.toutiao.activity.NewsDetailActivity;
import com.squareup.picasso.Picasso;
import org.jetbrains.annotations.NotNull;
import java.util.ArrayList;
import java.util.List;
/**
* A card adapter to help perform to control card item's render in news channel fragment
*/
public class NewsCardAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private final List<NewsCardItemDataModel> mDataModelList;
private final Context mContext;
public NewsCardAdapter(List<NewsCardItemDataModel> modelList, Context context) {
mDataModelList = modelList;
mContext = context;
}
@Override
public int getItemViewType(final int position) {
switch (mDataModelList.get(position).getItemType()) {
case NewsCardItemDataModel.NO_IMAGE_TYPE:
return NewsCardItemDataModel.NO_IMAGE_TYPE;
case NewsCardItemDataModel.ONE_IMAGE_TYPE:
return NewsCardItemDataModel.ONE_IMAGE_TYPE;
case NewsCardItemDataModel.THREE_IMAGE_TYPE:
return NewsCardItemDataModel.THREE_IMAGE_TYPE;
default:
return -1;
}
}
/**
* load more news and add to mDataModelList
*
* @param modelList
*/
public void setDataModelList(List<NewsCardItemDataModel> modelList) {
mDataModelList.addAll(modelList);
}
@Override
public int getItemCount() {
return mDataModelList.size();
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view;
switch (viewType) {
case NewsCardItemDataModel.NO_IMAGE_TYPE:
view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.no_image_card_item, parent, false);
return new NoImageCardViewHolder(view);
case NewsCardItemDataModel.ONE_IMAGE_TYPE:
view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.one_image_card_item, parent, false);
return new OneImageCardViewHolder(view);
case NewsCardItemDataModel.THREE_IMAGE_TYPE:
view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.three_images_card_item, parent, false);
return new ThreeImageCardViewHolder(view);
default:
return null;
}
}
@Override
public void onBindViewHolder(@NotNull final RecyclerView.ViewHolder holder, final int position) {
NewsCardItemDataModel object = mDataModelList.get(position);
if (object != null) {
switch (object.getItemType()) {
case NewsCardItemDataModel.NO_IMAGE_TYPE:
NoImageCardViewHolder holder1 = (NoImageCardViewHolder) holder;
holder1.bindData(object, mContext);
break;
case NewsCardItemDataModel.ONE_IMAGE_TYPE:
OneImageCardViewHolder holder2 = (OneImageCardViewHolder) holder;
holder2.bindData(object, mContext);
break;
case NewsCardItemDataModel.THREE_IMAGE_TYPE:
ThreeImageCardViewHolder holder3 = (ThreeImageCardViewHolder) holder;
holder3.bindData(object, mContext);
break;
default:
break;
}
}
}
// No image style card view holder
class NoImageCardViewHolder extends RecyclerView.ViewHolder {
private final ImageView mAvatarView;
private final TextView mTitleTextView;
private final TextView mSubTitleTextView;
private final TextView mBottomTextView;
private final TextView mSourceUrlTextView;
public NoImageCardViewHolder(@NonNull View itemView) {
super(itemView);
mAvatarView = itemView.findViewById(R.id.image_view_card_avatar);
mTitleTextView = itemView.findViewById(R.id.text_view_card_title);
mSubTitleTextView = itemView.findViewById(R.id.text_view_card_subtitle);
mBottomTextView = itemView.findViewById(R.id.text_view_card_bottom_text);
mSourceUrlTextView = itemView.findViewById(R.id.text_view_source_url);
}
public void bindData(NewsCardItemDataModel dataModel, Context context) {
Picasso.get().load(dataModel.getAvatar()).into(mAvatarView);
// deal with title's length and subtitle's length
String title = dataModel.getTitle();
if (title.length() > 15) {
title = title.substring(0, 16);
title += "...";
}
mTitleTextView.setText(title);
String subTitle = dataModel.getSubTitle();
if (subTitle.length() > 70) {
subTitle = subTitle.substring(0, 69);
subTitle += "...";
}
mSubTitleTextView.setText(subTitle);
mBottomTextView.setText(dataModel.getBottomText());
mSourceUrlTextView.setText(dataModel.getDetailUrl());
}
}
// One image style card view holder
class OneImageCardViewHolder extends RecyclerView.ViewHolder {
private final ImageView mAvatarView;
private final TextView mTitleTextView;
private final TextView mSubTitleTextView;
private final TextView mBottomTextView;
private final TextView mSourceUrlTextView;
private final ImageView mCardImageView;
public OneImageCardViewHolder(@NonNull View itemView) {
super(itemView);
mAvatarView = itemView.findViewById(R.id.image_view_card_avatar);
mTitleTextView = itemView.findViewById(R.id.text_view_card_title);
mSubTitleTextView = itemView.findViewById(R.id.text_view_card_subtitle);
mBottomTextView = itemView.findViewById(R.id.text_view_card_bottom_text);
mSourceUrlTextView = itemView.findViewById(R.id.text_view_source_url);
mCardImageView = itemView.findViewById(R.id.image_view_card_image);
}
public void bindData(NewsCardItemDataModel dataModel, Context context) {
Picasso.get().load(dataModel.getAvatar()).into(mAvatarView);
Picasso.get().load(dataModel.getImageDrawable()).into(mCardImageView);
String title = dataModel.getTitle();
// deal with title's length and subtitle's length
if (title.length() > 15) {
title = title.substring(0, 14);
title += "...";
}
mTitleTextView.setText(title);
String subTitle = dataModel.getSubTitle();
if (subTitle.length() > 70) {
subTitle = subTitle.substring(0, 69);
subTitle += "...";
}
mSubTitleTextView.setText(subTitle);
mBottomTextView.setText(dataModel.getBottomText());
mSourceUrlTextView.setText(dataModel.getDetailUrl());
}
}
// Three image style card view holder
class ThreeImageCardViewHolder extends RecyclerView.ViewHolder {
private final ImageView mAvatarView;
private final TextView mTitleTextView;
private final TextView mSubTitleTextView;
private final TextView mBottomTextView;
private final TextView mSourceUrlTextView;
private final ImageView mCardImageView1;
private final ImageView mCardImageView2;
private final ImageView mCardImageView3;
public ThreeImageCardViewHolder(@NonNull View itemView) {
super(itemView);
mAvatarView = itemView.findViewById(R.id.image_view_card_avatar);
mTitleTextView = itemView.findViewById(R.id.text_view_card_title);
mSubTitleTextView = itemView.findViewById(R.id.text_view_card_subtitle);
mBottomTextView = itemView.findViewById(R.id.text_view_card_bottom_text);
mSourceUrlTextView = itemView.findViewById(R.id.text_view_source_url);
mCardImageView1 = itemView.findViewById(R.id.image_view_image_1);
mCardImageView2 = itemView.findViewById(R.id.image_view_image_2);
mCardImageView3 = itemView.findViewById(R.id.image_view_image_3);
}
public void bindData(NewsCardItemDataModel dataModel, Context context) {
Picasso.get().load(dataModel.getAvatar()).into(mAvatarView);
ArrayList<String> images = dataModel.getThreeImageDrawable();
Picasso.get().load(images.get(0)).into(mCardImageView1);
Picasso.get().load(images.get(1)).into(mCardImageView2);
Picasso.get().load(images.get(2)).into(mCardImageView3);
// deal with title's length and subtitle's length
String title = dataModel.getTitle();
if (title.length() > 15) {
title = title.substring(0, 16);
title += "...";
}
mTitleTextView.setText(title);
String subTitle = dataModel.getSubTitle();
if (subTitle.length() > 70) {
subTitle = subTitle.substring(0, 69);
subTitle += "...";
}
mSubTitleTextView.setText(subTitle);
mBottomTextView.setText(dataModel.getBottomText());
mSourceUrlTextView.setText(dataModel.getDetailUrl());
}
}
}
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ui/page/newsChannel/newsChannelFragment.java
在需要渲染的 Fragment，添加渲染 Code。
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package com.example.toutiao.ui.page.newsChannel;
// ...
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.example.toutiao.R;
import com.example.toutiao.ui.card.newsCardList.NewsCardAdapter;
import com.example.toutiao.ui.card.newsCardList.NewsCardItemDataModel;
/**
* A simple {@link Fragment} subclass.
* Use the {@link NewsChannelFragment#newInstance} factory method to
* create an instance of this fragment.
*/
public class NewsChannelFragment extends Fragment {
private String mCategory;
private int mIndex;
private RecyclerView mCardListRecyclerView;
private NewsCardAdapter mCardListAdapter;
private RecyclerView.LayoutManager mCardListLayoutManager;
private final List<NewsCardItemDataModel> mCardDataModelList = new ArrayList<>();
public NewsChannelFragment() {
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*/
public static NewsChannelFragment newInstance(String category, int index) {
NewsChannelFragment fragment = new NewsChannelFragment();
Bundle bundle = new Bundle();
bundle.putString("category", category);
bundle.putInt("index", index);
fragment.setArguments(bundle);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// ...
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_news_channel, container, false);
// ...
for (int i = 0; i < 10; i++) {
int type = i % 3;
String newsId = i;
String newsTitle = "你好";
String newsAbstract = "我是卡片";
int newsCommentsCount = 100;
String newsSource = "https://example.com/e.png";
String newsMediaAvatarUrl = "https://example.com/e.png";
String newsSourceUrl = "www.google.com";
if (type == NO_IMAGE_TYPE) {
mCardDataModelList.add(new NewsCardItemDataModel(
NO_IMAGE_TYPE,
newsId,
newsTitle,
newsAbstract,
newsCommentsCount,
newsSource,
newsMediaAvatarUrl,
newsSourceUrl
));
} else if (type == ONE_IMAGE_TYPE) {
String middleImage = "https://example.com/e.png";
mCardDataModelList.add(new NewsCardItemDataModel(
ONE_IMAGE_TYPE,
newsId,
newsTitle,
newsAbstract,
newsCommentsCount,
newsSource,
newsMediaAvatarUrl,
newsSourceUrl,
middleImage
));
} else if (type == THREE_IMAGE_TYPE) {
ArrayList<String> newsThreeImage = new ArrayList()<>;
newsThreeImage.add("https://example.com/e.png");
newsThreeImage.add("https://example.com/e.png");
newsThreeImage.add("https://example.com/e.png");
mCardDataModelList.add(new NewsCardItemDataModel(
THREE_IMAGE_TYPE,
newsId,
newsTitle,
newsAbstract,
newsCommentsCount,
newsSource,
newsMediaAvatarUrl,
newsSourceUrl,
newsThreeImage
));
}
}
// cardList
mCardListRecyclerView = view.findViewById(R.id.recycler_view_card_list);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
mCardListRecyclerView.setHasFixedSize(true);
// use a linear layout manager
mCardListLayoutManager = new LinearLayoutManager(getContext());
mCardListRecyclerView.setLayoutManager(mCardListLayoutManager);
// specify an adapter and pass in our data model list
mCardListAdapter = new NewsCardAdapter(mCardDataModelList, getContext());
mCardListRecyclerView.setAdapter(mCardListAdapter);
return view;
}
}
|
Reference
Rem Blog