BaseAdapter 类不会在 Asynctask 中设置适配器 - Android
Posted
技术标签:
【中文标题】BaseAdapter 类不会在 Asynctask 中设置适配器 - Android【英文标题】：BaseAdapter class wont setAdapter inside Asynctask - Android 【发布时间】：2013-07-16 14:58:13 【问题描述】：我有收集用户名、cmets 和数字的异步任务。它将它们放入字符串中，然后假设调用 BaseAdapter 类，创建一个适配器，并将适配器设置为该类。但是我的代码不起作用，它使应用程序崩溃，这是我的代码
public class DashboardActivity extends ListActivity
String comments[];
String usernames[];
String numbers[];
ListView lstComments;
class CreateCommentLists extends BaseAdapter
Context ctx_invitation;
String[] listComments;
String[] listNumbers;
String[] listUsernames;
public CreateCommentLists(String[] comments, String[] usernames, String[] numbers)
super();
listComments = comments;
listNumbers = usernames;
listUsernames = numbers;
@Override
public int getCount()
if(null == listComments)
return 0;
// TODO Auto-generated method stub
return listComments.length;
@Override
public Object getItem(int position)
// TODO Auto-generated method stub
return listComments[position];
@Override
public long getItemId(int position)
// TODO Auto-generated method stub
return 0;
@Override
public View getView(int position, View convertView, ViewGroup parent)
// TODO Auto-generated method stub
View v = null;
try
String inflater = Context.LAYOUT_INFLATER_SERVICE;
LayoutInflater li = (LayoutInflater)ctx_invitation.getSystemService(inflater);
v = li.inflate(R.layout.list_item, null);
TextView commentView = (TextView)v.findViewById(R.id.listComment);
TextView NumbersView = (TextView)v.findViewById(R.id.listNumber);
TextView usernamesView = (TextView)v.findViewById(R.id.listPostedBy);
commentView.setText(listComments[position]);
NumbersView.setText(listNumbers[position]);
usernamesView.setText(listUsernames[position]);
catch(Exception e)
e.printStackTrace();
return v;
class loadComments extends AsyncTask<JSONObject, String, JSONObject>
@Override
protected void onPreExecute()
super.onPreExecute();
@Override
protected void onProgressUpdate(String... values)
super.onProgressUpdate(values);
protected JSONObject doInBackground(JSONObject... params)
JSONObject json2 = CollectComments.collectComments(usernameforcomments, offsetNumber);
return json2;
@Override
protected void onPostExecute(JSONObject json2)
try
if (json2.getString(KEY_SUCCESS) != null)
registerErrorMsg.setText("");
String res2 = json2.getString(KEY_SUCCESS);
if(Integer.parseInt(res2) == 1)
JSONArray commentArray = json2.getJSONArray(KEY_COMMENT);
String comments[] = new String[commentArray.length()];
for ( int i=0; i<commentArray.length(); i++ )
comments[i] = commentArray.getString(i);
JSONArray numbersArray = json2.getJSONArray(KEY_NUMBER);
String numbers[] = new String[numbersArray.length()];
for ( int i=0; i<numbersArray.length(); i++ )
numbers[i] = numbersArray.getString(i);
JSONArray usernameArray = json2.getJSONArray(KEY_USERNAME);
String usernames[] = new String[usernameArray.length()];
for ( int i=0; i<usernameArray.length(); i++ )
usernames[i] = usernameArray.getString(i);
CreateCommentLists mycmlist = new CreateCommentLists(comments, usernames, numbers);
lstComments = (ListView)findViewById(android.R.id.list);
lstComments.setAdapter(mycmlist);
//end if key is == 1
else
// Error in registration
registerErrorMsg.setText(json2.getString(KEY_ERROR_MSG));
//end else
//end if
//end try
catch (JSONException e)
e.printStackTrace();
//end catch
new loadComments().execute();
这是我的 logCat
07-17 17:07:13.436: E/AndroidRuntime(23880): FATAL EXCEPTION: main
07-17 17:07:13.436: E/AndroidRuntime(23880): java.lang.NullPointerException
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.measureScrapChild(ListView.java:1163)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.measureHeightOfChildren(ListView.java:1294)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.onMeasure(ListView.java:1155)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.RelativeLayout.measureChild(RelativeLayout.java:579)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:392)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1017)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:555)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.navdrawer.SimpleSideDrawer.onMeasure(SimpleSideDrawer.java:443)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2162)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1091)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2505)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.os.Handler.dispatchMessage(Handler.java:99)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.os.Looper.loop(Looper.java:154)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.app.ActivityThread.main(ActivityThread.java:4945)
07-17 17:07:13.436: E/AndroidRuntime(23880): at java.lang.reflect.Method.invokeNative(Native Method)
07-17 17:07:13.436: E/AndroidRuntime(23880): at java.lang.reflect.Method.invoke(Method.java:511)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-17 17:07:13.436: E/AndroidRuntime(23880): at dalvik.system.NativeStart.main(Native Method)
【问题讨论】：
请看我的回答。我添加了一些代码。 【参考方案1】：您是否检查过您从 getView() 方法返回的 View v 是否为空？捕获Exception 捕获所有异常。在我看来不是很有帮助。这里发生的事情是你还没有发起Context ctx_invitation。您应该在构造函数中执行此操作。现在，由于ctx_invitation 为空，它会导致NullPointerException 被catch 块捕获。并且View v 保持为空。
更改 CreateCommentLists 的构造函数：
public CreateCommentLists(String[] comments, String[] usernames, String[] numbers, DashboardActivity context)
super();
listComments = comments;
listNumbers = usernames;
listUsernames = numbers;
ctx_invitation = context;
同时更改以下内容：
CreateCommentLists mycmlist = new CreateCommentLists(comments, usernames, numbers, DashboardActivity.this);
【讨论】：
ctx_invitation 我也应该设置什么？因为当我尝试将它放在 CreateCommentLists mycmlist = new CreateCommentLists(cmets, usernames, numbers);声明它会导致错误【参考方案2】：我希望这可能会有所帮助，
onPostExecute 包含（在 AsyncTask 内）
ExampleAdapter sectionedAdapter = new EfficientAdapter(ClassInfoThread.this,getBaseContext()); listView.setAdapter(sectionedAdapter);
在你的适配器类中添加这个构造函数
public ExampleAdapter(ExampleThread exampleThread,Context context) mInflater = LayoutInflater.from(context);
祝你好运。
南达基肖 P
【讨论】：
【参考方案3】：现在 ctx_invitation 永远不会被赋值。您可能需要一个构造函数来为 ctx_invitation 赋值。
【讨论】：
【参考方案4】：四处搜索，查看this question 看起来您可能正在从适配器的 getView 方法返回一个空视图。尝试在 getView 方法中设置一些断点并找出返回空视图的位置。
另外，您将 ctx_invitation 的引用存储在 BaseAdapter 的什么位置。
在构造函数中你可能想把它传入
【讨论】：
以上是关于BaseAdapter 类不会在 Asynctask 中设置适配器 - Android的主要内容，如果未能解决你的问题，请参考以下文章
android -BaseAdapter 不会向 listView 添加新项目
为啥我的 BaseAdapter 类不增加 getView 中的位置？
如何在 Android 中获取 BaseAdapter 的上下文