在片段列表视图中更改文本颜色，菜单项单击上的适配器

Question

祝大家美好的一天，在此应用程序中，需要在菜单项单击时更改文本颜色。文本视图在自定义行布局中，由适配器和适配器设置在两个片段选项卡中膨胀。在菜单项上，单击需要更改列表视图整个列表视图的文本颜色。在正常应用程序上，它工作正常，但在片段上，如果有人可以提供帮助，它会在空对象引用上给出错误"Adaptor.setTextColor(int("。谢谢 问题是适配器未在主活动中初始化，而是在片段中初始化。所以在每个片段中都需要像这样思考

public void setColor(int color) 
adapter.setTextColor(color); 
adapter.notifyDataSetChanged(); }

它的主要活动选项菜单

Fragment fragment=new Fragment(); 
fragment.setColor(Color.BLACK); –

主要活动.java

private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
NewsAdaptor adaptor;
protected void onCreate ( Bundle savedInstanceState ) {
super.onCreate(savedInstanceState);
Context mContext = getApplicationContext();
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.setOffscreenPageLimit(10);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
}

@Override
public boolean onCreateOptionsMenu ( Menu menu ) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@SuppressLint("ResourceType")
@Override
public boolean onOptionsItemSelected ( MenuItem item ) {
int id = item.getItemId();
if (id == R.id.chagecolor) {
Fragment fragment=new Fragment(); 
fragment.setColor(Color.BLACK); –
}
return super.onOptionsItemSelected(item);
}

新闻阿帕特.java

public class NewsAdaptor extends BaseAdapter {
TextView tvtitle;
private int color;
Context context;
public NewsAdaptor ( Context context, ArrayList <NewsItem> newsList ) {
this.context = context;
this.newsList = newsList;
this.color = Color.RED;
}
ArrayList<NewsItem> newsList;
@Override
public int getCount () {
return newsList.size();
}
@Override
public Object getItem ( int position ) {
return newsList.get(position);
}
@Override
public long getItemId ( int position ) {
return 0;
}
@Override
public View getView ( int position, View convertView, ViewGroup parent ) {
if (convertView == null){
convertView=View.inflate(context, R.layout.newsitemlist_layout,null);
}
NewsItem currentNews = newsList.get(position);
tvtitle = (TextView) convertView.findViewById(R.id.textView1id);
tvtitle.setText(currentNews.getTitle());
tvtitle.setTextColor(color);
return convertView;
}
public void setTextColor(int color) {
this.color = color;
}

}

现在它在实现适配器的片段中

贸易.java

public class TRADE extends Fragment {

public TRADE () {
// Required empty public constructor
}
ArrayList<NewsItem> newsItemsList;
ListView ali;
NewsAdaptor adapter;
@Override
public View onCreateView ( LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState ) {
View view= inflater.inflate(R.layout.fragment_trade, container, false);
newsItemsList = new ArrayList<>();
ali = (ListView)view. findViewById(R.id.listtrade);
RequestQueue requestQueue = Volley.newRequestQueue(getContext());
StringRequest stringRequest = new StringRequest("https://urdu.geo.tv/rss/1/3", new Response.Listener <String>() {
@Override
public void onResponse ( String response ) {
Document document = Jsoup.parse(response);
Elements itemElements = document.getElementsByTag("item");
for (int i = 0; i < itemElements.size(); i++) {
Element item = itemElements.get(i);
String title = rem(item.child(0).text());
NewsItem news = new NewsItem();
news.title = title;
newsItemsList.add(news);
}
adapter = new NewsAdaptor(getContext(), newsItemsList);
ali.setAdapter(adapter);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse ( VolleyError error ) {

}
});
requestQueue.add(stringRequest);
public void setColor(int color) 
adapter.setTextColor(color); 
adapter.notifyDataSetChanged(); }

体育

.java

public class TRADE extends Fragment {

public SPORT() {
// Required empty public constructor
}
ArrayList<NewsItem> newsItemsList;
ListView ali;
NewsAdaptor adapter;
@Override
public View onCreateView ( LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState ) {
View view= inflater.inflate(R.layout.fragment_trade, container, false);
newsItemsList = new ArrayList<>();
ali = (ListView)view. findViewById(R.id.listtrade);
RequestQueue requestQueue = Volley.newRequestQueue(getContext());
StringRequest stringRequest = new StringRequest("https://urdu.geo.tv/rss/1/3", new Response.Listener <String>() {
@Override
public void onResponse ( String response ) {
Document document = Jsoup.parse(response);
Elements itemElements = document.getElementsByTag("item");
for (int i = 0; i < itemElements.size(); i++) {
Element item = itemElements.get(i);
String title = rem(item.child(0).text());
NewsItem news = new NewsItem();
news.title = title;
newsItemsList.add(news);
}
adapter = new NewsAdaptor(getContext(), newsItemsList);
ali.setAdapter(adapter);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse ( VolleyError error ) {

}
});
requestQueue.add(stringRequest);
public void setColor(int color) 
adapter.setTextColor(color); 
adapter.notifyDataSetChanged(); }

newsitemlist_layout.xml

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/textView1id"
android:layout_width="237dp"
android:layout_height="83dp"
android:layout_alignEnd="@+id/pubDateid"
android:layout_alignParentTop="true"
android:layout_alignRight="@+id/pubDateid"
android:ellipsize="end"
android:gravity="right"
android:text="News TITLE"
android:textSize="18sp"
android:textStyle="bold" />
</RelativeLayout>

Answer 1

我想你不是在对适配器说你做了改变。

public void setTextColor(int color) {
this.color = color;
notifyDataSetChanged()
}

希望对您有所帮助。

Answer 2

In MainActivity：

@SuppressLint("ResourceType")
@Override
public boolean onOptionsItemSelected ( MenuItem item ) {
int id = item.getItemId();
if (id == R.id.chagecolor) {
adaptor.setTextColor(Color.GREEN);
adaptor.notifyDataSetChanged();
}
return super.onOptionsItemSelected(item);
}

调用adaptor.setTextColor(Color.GREEN);时，adaptor字段null，因为您从未设置过它。在主活动中的某个地方，您必须执行adaptor=...