Android 學習之《第一行程式碼》第二版 筆記(十)探究碎片(二)
阿新 • • 發佈:2018-11-10
一個簡易版的新聞應用
同時相容手機和平板的應用程式
一、佈局
news_content_frag.xml額我的程式碼裡面是news_content_fragment.xml,圖片打錯了
二、程式碼編寫
1. 實體類(News.java)
//新聞實體類
public class News {
private String title; //新聞標題
private String content; //新聞內容
//成員變數的get和set函式
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
2. 新聞內容佈局(news_content_fragment.xml)
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="@+id/visibility_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:visibility="invisible">
<TextView
android:id="@+id/news_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:padding="10dp"
android:textSize="20sp"/>
<!--新聞標題-->
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#000"/>
<!--水平黑色直線-->
<TextView
android:id="@+id/news_content"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:padding="15dp"
android:textSize="18sp"/>
<!--新聞內容-->
</LinearLayout>
<View
android:layout_width="1dp"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:background="#000"/>
<!--豎直黑色直線-->
</RelativeLayout>
3. 新聞內容碎片(NewsContentFragment.java)
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class NewsContentFragment extends Fragment {
private View view;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.news_content_fragment,container,false);
return view;
}
//重新整理新聞
public void refresh(String newsTitle,String newsContent){
View visibilityLayout = view.findViewById(R.id.visibility_layout);//新聞碎片所在佈局控制元件
visibilityLayout.setVisibility(View.VISIBLE);//預設不顯示該佈局
//當點選新聞標題重新整理該佈局時,設定其可見屬性使其顯示
TextView newsTitleText = (TextView) view.findViewById(R.id.news_title);//獲取新聞標題控制元件
TextView newsContentText = (TextView) view.findViewById(R.id.news_content);//獲取新聞內容控制元件
newsTitleText.setText(newsTitle);//重新整理新聞的標題
newsContentText.setText(newsContent);//重新整理新聞的內容
}
}
4. 手機上的新聞內容,需要新建一個活動,點選標題進入該活動,並在此活動的佈局顯示內容。(NewsContentActivity.java)
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
public class NewsContentActivity extends AppCompatActivity {
public static void actionStart(Context context,String newsTitle,String newsContent){
Intent intent = new Intent(context,NewsContentActivity.class);
intent.putExtra("news_title",newsTitle);
intent.putExtra("news_content",newsContent);
context.startActivity(intent);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.news_content);
String newsTitle = getIntent().getStringExtra("news_title");//獲取傳入的新聞標題
String newsContent = getIntent().getStringExtra("news_content");//獲取傳入的新聞內容
//活動中使用碎片方法
NewsContentFragment newsContentFragment = (NewsContentFragment)
getSupportFragmentManager().findFragmentById(R.id.news_content_fragment);
newsContentFragment.refresh(newsTitle,newsContent);//重新整理NewsContentFragment介面
}
}
5. 手機上的新聞內容佈局,引入先前的新聞內容碎片,發揮程式碼複用性(news_content.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.thinkpad.fragmentbestpractice.NewsContentActivity">
<fragment
android:id="@+id/news_content_fragment"
android:name="com.example.thinkpad.fragmentbestpractice.NewsContentFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<!--充分發揮程式碼的複用性,直接在佈局中引入NewsContentFragment-->
</LinearLayout>
6. 新聞列表的碎片佈局(news_title_fragment.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/news_title_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
7. 新聞列表的子項佈局(news_item.xml)
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/news_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:singleLine="true"
android:ellipsize="end"
android:textSize="18sp"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:paddingTop="15dp"
android:paddingBottom="15dp">
<!--RecyclerView的子項佈局-->
<!--singleLine的true表示這個TextView只能單行顯示-->
<!--ellipsize的end表示當文字內容超出控制元件寬度時,文字的縮略方式為在尾部進行縮略-->
</TextView>
8. 新聞列表的碎片(NewsTitleFragment.java)
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class NewsTitleFragment extends Fragment {
private boolean isTwoPane;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.news_title_fragment, container, false);
RecyclerView newsTitleRecyclerView = (RecyclerView) view.findViewById(R.id.news_title_recycler_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
newsTitleRecyclerView.setLayoutManager(layoutManager);
NewsAdapter adapter = new NewsAdapter(getNews());
newsTitleRecyclerView.setAdapter(adapter);
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (getActivity().findViewById(R.id.news_content_layout) != null) {
isTwoPane = true; //可以找到news_content_layout 佈局時,為雙頁模式
} else {
isTwoPane = false; //找不到news_content_layout 佈局時,為單頁模式
}
}
private List<News> getNews() {
List<News> newsList = new ArrayList<>();
for (int i = 1; i <= 50; i++) {
News news = new News();
news.setTitle("This is news title " + i);
news.setContent(getRandomLengthContent("This is news content " + i + ". "));
newsList.add(news);
}
return newsList;
}
private String getRandomLengthContent(String content) {
Random random = new Random();
int length = random.nextInt(20) + 1;
StringBuilder builder = new StringBuilder();
for (int i = 0; i < length; i++) {
builder.append(content);
}
return builder.toString();
}
//內部類NewsAdapter作為RecyclerView介面卡
class NewsAdapter extends RecyclerView.Adapter<NewsAdapter.ViewHolder> {
private List<News> mNewsList;
class ViewHolder extends RecyclerView.ViewHolder {
TextView newsTitleText;
public ViewHolder(View view) {
super(view);
newsTitleText = (TextView) view.findViewById(R.id.news_title);
}
}
public NewsAdapter(List<News> newsList) {
mNewsList = newsList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item, parent, false);
final ViewHolder holder = new ViewHolder(view);
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
News news = mNewsList.get(holder.getAdapterPosition());
if (isTwoPane) {
//若為雙頁模式,則重新整理NewsContentFragment中的內容
NewsContentFragment newsContentFragment = (NewsContentFragment)
getFragmentManager().findFragmentById(R.id.news_content_fragment);
newsContentFragment.refresh(news.getTitle(), news.getContent());
} else {
//若為單頁模式,則直接啟動NewsContentActivity
NewsContentActivity.actionStart(getActivity(), news.getTitle(), news.getContent());
}
}
});
return holder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
News news = mNewsList.get(position);
holder.newsTitleText.setText(news.getTitle());
}
@Override
public int getItemCount() {
return mNewsList.size();
}
}
}
9. 主活動佈局–手機(layout/activity_main.xml)
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/news_title_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:id="@+id/news_title_fragment"
android:name="com.example.thinkpad.fragmentbestpractice.NewsTitleFragment"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
10. 主活動佈局–平板(layout-sw600dp/activity_main.xml)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.thinkpad.fragmentbestpractice.MainActivity">
<fragment
android:id="@+id/news_title_fragment"
android:name="com.example.thinkpad.fragmentbestpractice.NewsTitleFragment"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight=