从其他类访问变量时获取NullPointerException。
下面是我在活动中的RSS提要解析器工作得很好，但是当我尝试在另一个类中访问RemoteView（主屏幕小组件）的相同参数时，该参数返回空指针异常，这显然意味着值为null。任何想法我如何使用相同的代码片段并从那里选择价值。在代码中我提到了行“PICK VALUE（从哪个参数值中选择）”和PUT VALUE（放在哪里）以便更好地理解。
我的目标是在“populateListItem（）”方法中的ListProvider类中使用TwitterAdapter，其中我写了“PUT VALUE”。在那里我想访问这个值“imageAndTexts1.get（position）.getTitle（）;”来自TwitterAdapter类。我怎么能这样做？
如果我在方法populateListItem（）中尝试这样，我将得到以下异常：
private void populateListItem() {
//for (int i = 0; i < 10; i++) {
ListItem listItem = new ListItem();
TwitterAdapter abc = new TwitterAdapter(null, imageAndTexts1); //TRIED TO ACCESS VALUE
String a = abc.passtitletowidget; // TRIED TO ACCESS VALUE
listItem.heading = a;
listItem.content = "This is the content of the app widget listview.Nice content though";
listItemList.add(listItem);
//}
}
例外细节：
02-28 13:42:22.271: E/AndroidRuntime(26600): FATAL EXCEPTION: main
02-28 13:42:22.271: E/AndroidRuntime(26600): java.lang.RuntimeException: Unable to bind to service com.wordpress.laaptu.WidgetService@42a2f118 with Intent { dat=intent: cmp=com.itcuties.multicategoryrssreader/com.wordpress.laaptu.WidgetService (has extras) }: java.lang.NullPointerException
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.app.ActivityThread.handleBindService(ActivityThread.java:2739)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.app.ActivityThread.access$1800(ActivityThread.java:168)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.os.Handler.dispatchMessage(Handler.java:99)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.os.Looper.loop(Looper.java:137)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.app.ActivityThread.main(ActivityThread.java:5493)
02-28 13:42:22.271: E/AndroidRuntime(26600): at java.lang.reflect.Method.invokeNative(Native Method)
02-28 13:42:22.271: E/AndroidRuntime(26600): at java.lang.reflect.Method.invoke(Method.java:525)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
02-28 13:42:22.271: E/AndroidRuntime(26600): at dalvik.system.NativeStart.main(Native Method)
02-28 13:42:22.271: E/AndroidRuntime(26600): Caused by: java.lang.NullPointerException
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.widget.ArrayAdapter.init(ArrayAdapter.java:310)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.rssfeed.adapter.TwitterAdapter.<init>(TwitterAdapter.java:47)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.wordpress.laaptu.ListProvider.populateListItem(ListProvider.java:42)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.wordpress.laaptu.ListProvider.<init>(ListProvider.java:34)
02-28 13:42:22.271: E/AndroidRuntime(26600): at com.wordpress.laaptu.WidgetService.onGetViewFactory(WidgetService.java:19)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.widget.RemoteViewsService.onBind(RemoteViewsService.java:241)
02-28 13:42:22.271: E/AndroidRuntime(26600): at android.app.ActivityThread.handleBindService(ActivityThread.java:2726)
** PACKAGE ONE
TwitterAdapter.java
public class TwitterAdapter extends ArrayAdapter<RssFeedStructure> {
List<RssFeedStructure> imageAndTexts1 = null;
Context context;
public static String passtitletowidget;
public TwitterAdapter(Activity activity,List<RssFeedStructure> imageAndTexts) {
super(activity, 0, imageAndTexts);
imageAndTexts1 = imageAndTexts;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
context = getContext();
Activity activity = (Activity) getContext();
LayoutInflater inflater = activity.getLayoutInflater();
View rowView = inflater.inflate(R.layout.twitteradapter, null);
TextView textView = (TextView) rowView.findViewById(R.id.feed_text);
TextView timeFeedText = (TextView) rowView.findViewById(R.id.feed_updatetime);
ImageView imageView = (ImageView) rowView.findViewById(R.id.feed_image);
try {
passtitletowidget = imageAndTexts1.get(position).getTitle(); //PICK VALUE
Log.d("rssfeed", "imageAndTexts1.get(position).getImgLink() :: " + imageAndTexts1.get(position).getImgLink() + " :: " + imageAndTexts1.get(position).getTitle());
//Underline HashTags -- To identify Mentioned user name; use this "@([A-Za-z0-9_-]+)"
SpannableString hashtagintitle = new SpannableString(imageAndTexts1.get(position).getTitle());
Matcher matcher = Pattern.compile("#([A-Za-z0-9_-]+)").matcher(hashtagintitle);
while (matcher.find())
{
hashtagintitle.setSpan(new ForegroundColorSpan(Color.BLUE), matcher.start(), matcher.end(), 0);
}
textView.setText(hashtagintitle);
timeFeedText.setText(imageAndTexts1.get(position).getPubDate());
//Underline Date
/*SpannableString content = new SpannableString(imageAndTexts1.get(position).getPubDate());
content.setSpan(new UnderlineSpan(), 0, 13, 0);
timeFeedText.setText(content);*/
if (imageAndTexts1.get(position).getImgLink() != null) {
URL feedImage = new URL(imageAndTexts1.get(position)
.getImgLink().toString());
if (!feedImage.toString().equalsIgnoreCase("null")) {
HttpURLConnection conn = (HttpURLConnection) feedImage
.openConnection();
InputStream is = conn.getInputStream();
Bitmap img = BitmapFactory.decodeStream(is);
imageView.setImageBitmap(img);
} else {
imageView.setBackgroundResource(R.drawable.rss_tab_tweets);
}
}
//Share Button
Button Button1= (Button) rowView.findViewById(R.id.sharebutton);
Button1.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
//Share Data
String shareBody = imageAndTexts1.get(position).getDescription();
Intent sharingIntent = new Intent(android.content.Intent.ACTION_SEND);
sharingIntent.setType("text/plain");
sharingIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, "Subject Here");
sharingIntent.putExtra(android.content.Intent.EXTRA_TEXT, shareBody);
context.startActivity(Intent.createChooser(sharingIntent, shareBody));
//Share Data ends
}
});
//Share Button ends
//OpenWith Button
Button Button2= (Button) rowView.findViewById(R.id.openwith);
Button2.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v)
{
//OpenWith Data
Intent i = new Intent(Intent.ACTION_VIEW);
// We have to set data for our new Intent
i.setData(Uri.parse(imageAndTexts1.get(position).getLink()));
// And start activity with our Intent
context.startActivity(i);
//OpenWith Data ends
}
});
//OpenWith Button ends
} catch (MalformedURLException e) {
} catch (IOException e) {
}
return rowView;
}
}
TwitterFeeds.java
public class TwitterFeeds extends Activity {
/** Called when the activity is first created. */
ListView _rssFeedListView;
List<JSONObject> jobs;
List<RssFeedStructure> rssStr;
private TwitterAdapter _adapter;
TextView textview;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listview);
_rssFeedListView = (ListView) findViewById(R.id.rssfeed_listview);
textview = (TextView) findViewById(R.id.loading);
RssFeedTask rssTask = new RssFeedTask();
rssTask.execute();
}
public class RssFeedTask extends AsyncTask<String, Void, String> {
// private String Content;
private ProgressDialog Dialog;
String response = "";
@Override
public void onPreExecute() {
}
@Override
public String doInBackground(String... urls) {
try {
String feed = "https://script.google.com/macros/s/AKfycbyRHtGY0TW5WRifXwMMRDQdtseKXxrYUbTcUlx1QxvUz-aap7Q/exec?action=timeline&q=SriSri";
XmlHandler rh = new XmlHandler();
rssStr = rh.getLatestArticles(feed);
} catch (Exception e) {
}
return response;
}
@Override
public void onPostExecute(String result) {
if (rssStr != null) {
_adapter = new TwitterAdapter(TwitterFeeds.this, rssStr);
_rssFeedListView.setAdapter(_adapter);
textview.setVisibility(View.INVISIBLE);
_rssFeedListView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//Toast.makeText(getBaseContext(), "TwitterFeeds", Toast.LENGTH_LONG).show();
// TODO Auto-generated method stub
}
});
}
}
}
}
RssFeedStructure.java
public class RssFeedStructure {
// private long articleId;
// private long feedId;
private String title;
private String description;
private String imgLink;
private String pubDate;
private String link;
private String published;
private String content;
private URL url;
private String encodedContent;
/*
* public long getArticleId() { return articleId; }
*
* public void setArticleId(long articleId) { this.articleId = articleId; }
*
* public long getFeedId() { return feedId; }
*
*
* public void setFeedId(long feedId) { this.feedId = feedId; }
*/
public String getTitle() {
return title;
}
public void setTitle(String title) {
String noHTMLStringtitle = title.replaceAll("\\<.*?>", "");
String replaceampersandtitle = noHTMLStringtitle.replace("&", "&");
String yesHTMLStringtitle = Html.fromHtml(replaceampersandtitle)
.toString();
this.title = yesHTMLStringtitle;
}
public URL getUrl() {
return url;
}
public void setUrl(URL url) {
this.url = url;
}
public void setDescription(String description) {
String noHTMLStringDes = description.replaceAll("\\<.*?>", "");
String replaceampersand = noHTMLStringDes.replace("&", "&");
String yesHTMLStringDes = Html.fromHtml(replaceampersand).toString();
this.description = yesHTMLStringDes;
// Link to understand unicode characters -
// http://bohemianalps.com/tools/characters/?faveAlph=frac14,frac12,frac34,copy,reg,trade,laquo,raquo&faveNum=171,187,40,41,8216,8217,8220,8221,169,174,64,8482,x2122,8211,8212,225,233,241
}
public String getDescription() {
return description;
}
public void setPubDate(String pubDate) {
this.pubDate = pubDate;
}
public String getPubDate() {
return pubDate;
}
public void setEncodedContent(String encodedContent) {
// this.encodedContent = encodedContent;
// String noHTMLString = encodedContent.replaceAll("\\<.*?>","");
// String replaceampersand = noHTMLString.replace("&", "&");
// String yesHTMLString= Html.fromHtml(replaceampersand).toString();
// this.encodedContent = yesHTMLString;
// Link to understand unicode characters -
// http://bohemianalps.com/tools/characters/?faveAlph=frac14,frac12,frac34,copy,reg,trade,laquo,raquo&faveNum=171,187,40,41,8216,8217,8220,8221,169,174,64,8482,x2122,8211,8212,225,233,241
/*if (encodedContent.contains("<img ")){
String img = encodedContent.substring(encodedContent.indexOf("<img "));
String cleanUp = img.substring(0, img.indexOf(">")+1);
img = img.substring(img.indexOf("src=") + 5);
int indexOf = img.indexOf("'");
if (indexOf==-1){
indexOf = img.indexOf("\"");
}
img = img.substring(0, indexOf);
this.encodedContent = this.encodedContent.replace(cleanUp, "");
}*/
String removeimages = encodedContent.replaceAll("<img.+?>", "");
this.encodedContent = removeimages;
}
public String getEncodedContent() {
return encodedContent;
}
public void setImgLink(String imgLink) {
this.imgLink = imgLink;
}
public String getImgLink() {
return imgLink;
}
public void setLink(String link) {
this.link = link;
}
public String getLink() {
return link;
}
public void setContent(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public void setPublished(String published) {
this.published = published;
}
public String getPublished() {
return published;
}
}
** PACKAGE TWO
ListProvider.java
public class ListProvider implements RemoteViewsFactory {
private ArrayList<ListItem> listItemList = new ArrayList<ListItem>();
private Context context = null;
private int appWidgetId;
static String passtitletowidget;
List<RssFeedStructure> imageAndTexts1 = null;
public ListProvider(Context context, Intent intent) {
this.context = context;
appWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID,
AppWidgetManager.INVALID_APPWIDGET_ID);
populateListItem();
}
private void populateListItem() {
//for (int i = 0; i < 10; i++) {
ListItem listItem = new ListItem();
listItem.heading = "passtitletowidget"; //PUT VALUE
listItem.content = "This is the content of the app widget listview.Nice content though";
listItemList.add(listItem);
//}
}
@Override
public int getCount() {
return listItemList.size();
}
@Override
public long getItemId(int position) {
return position;
}
/*
*Similar to getView of Adapter where instead of View
*we return RemoteViews
*
*/
@Override
public RemoteViews getViewAt(int position) {
final RemoteViews remoteView = new RemoteViews(
context.getPackageName(), R.layout.list_row);
ListItem listItem = listItemList.get(position);
remoteView.setTextViewText(R.id.heading, listItem.heading);
remoteView.setTextViewText(R.id.content, listItem.content);
return remoteView;
}
@Override
public RemoteViews getLoadingView() {
return null;
}
@Override
public int getViewTypeCount() {
return 1;
}
@Override
public boolean hasStableIds() {
return true;
}
@Override
public void onCreate() {
}
@Override
public void onDataSetChanged() {
}
@Override
public void onDestroy() {
}
}
ListItem.java
public class ListItem {
public String heading, content;
}
WidgetProvider.java
public class WidgetProvider extends AppWidgetProvider {
/*
* this method is called every 30 mins as specified on widgetinfo.xml
* this method is also called on every phone reboot
*/
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager,
int[] appWidgetIds) {
final int N = appWidgetIds.length;
/*int[] appWidgetIds holds ids of multiple instance of your widget
* meaning you are placing more than one widgets on your homescreen*/
for (int i = 0; i < N; ++i) {
RemoteViews remoteViews = updateWidgetListView(context,
appWidgetIds[i]);
appWidgetManager.updateAppWidget(appWidgetIds[i], remoteViews);
}
super.onUpdate(context, appWidgetManager, appWidgetIds);
}
private RemoteViews updateWidgetListView(Context context, int appWidgetId) {
//which layout to show on widget
RemoteViews remoteViews = new RemoteViews(context.getPackageName(),
R.layout.widget_layout);
//RemoteViews Service needed to provide adapter for ListView
Intent svcIntent = new Intent(context, WidgetService.class);
//passing app widget id to that RemoteViews Service
svcIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
//setting a unique Uri to the intent
//don't know its purpose to me right now
svcIntent.setData(Uri.parse(svcIntent.toUri(Intent.URI_INTENT_SCHEME)));
//setting adapter to listview of the widget
remoteViews.setRemoteAdapter(appWidgetId, R.id.listViewWidget,svcIntent);
//setting an empty view in case of no data
remoteViews.setEmptyView(R.id.listViewWidget, R.id.empty_view);
return remoteViews;
}
}
WidgetService.java
public class WidgetService extends RemoteViewsService {
/*
* So pretty simple just defining the Adapter of the listview
* here Adapter is ListProvider
* */
@Override
public RemoteViewsFactory onGetViewFactory(Intent intent) {
int appWidgetId = intent.getIntExtra(
AppWidgetManager.EXTRA_APPWIDGET_ID,
AppWidgetManager.INVALID_APPWIDGET_ID);
return (new ListProvider(this.getApplicationContext(), intent));
}
}
答案 0 :(得分：0)
您需要在ListProvider文件中安装TwitterAdapter实例。在初始化ListProvider时，您可以将TwitterAdapter实例作为参数发送到ListProvider构造函数。
可能你必须在主要活动中初始化TwitterAdapter＆amp; ListProvider。