Android:无法启动活动
虽然我使用了AsyncTask创建了一个新线程,用于从服务器调用数据,但当我转到此活动时,应用程序仍然会崩溃。我无法指定错误的原因。有什么帮助吗Android:无法启动活动,android,eclipse,android-asynctask,Android,Eclipse,Android Asynctask,虽然我使用了AsyncTask创建了一个新线程,用于从服务器调用数据,但当我转到此活动时,应用程序仍然会崩溃。我无法指定错误的原因。有什么帮助吗 public class CustomizedListView extends Activity { static final String URL = "http://www.Vatrina-eg.com/men_tops.xml"; static final String KEY_SONG = "song"; // parent node stat
public class CustomizedListView extends Activity {
static final String URL = "http://www.Vatrina-eg.com/men_tops.xml";
static final String KEY_SONG = "song"; // parent node
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_THUMB_URL = "thumb_url";
ListView list;
LazyAdapter adapter;
private class DownloadFilesTask extends AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
protected ArrayList<HashMap<String, String>> doInBackground(String... strings) {
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
// adding HashList to ArrayList
songsList.add(map);
// Getting adapter by passing xml data ArrayList
adapter=new LazyAdapter(CustomizedListView.this, songsList);
list.setAdapter(adapter);
}
return songsList;
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainlistview);
list=(ListView)findViewById(R.id.list_listview);
new DownloadFilesTask().execute(URL);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
}
当您尝试在
onCreate()
中访问列表时,列表很可能仍然为空。请将onCreate更改为:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainlistview);
list = (ListView)findViewById(R.id.list_listview);
new DownloadFilesTask().execute(URL);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
@覆盖
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.mainlistview);
list=(ListView)findViewById(R.id.list\u ListView);
新建下载文件任务().execute(URL);
list.setOnItemClickListener(新的OnItemClickListener(){
@凌驾
public void onItemClick(AdapterView父级、视图、,
内部位置,长id){
}
});
}
您从未初始化列表
。我初始化了它,但没有更改<代码>列表视图列表=(列表视图)findViewById(R.id.list\u列表视图)代码>将其更改为list=(ListView)findViewById(R.id.list\u ListView)代码>。在前面添加列表视图
,使其成为局部变量。完成。那么,如何初始化列表?请参见下面的答案。删除您添加的初始化,因为它不在正确的方法中。完成。但仍然崩溃<代码>09-12 22:04:26.263:E/AndroidRuntime(17627):致命异常:AsyncTask#1 09-12 22:04:26.263:E/AndroidRuntime(17627):进程:com.vatrina.eg,PID:17627 09-12 22:04:26.263:E/AndroidRuntime(17627):java.lang.RuntimeException:执行doInBackground()09-12 22:04:26.263:E/AndroidRuntime(17627)时出错:在android.os.AsyncTask$3.done(AsyncTask.java:300)09-12 22:04:26.263:E/AndroidRuntime(17627):在java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
日志中还有其他内容吗?用新的logcat错误编辑您的问题。重要部分在您粘贴到此处的部分之后。此外,您还应该移动将列表适配器分配给onPostExecute方法的命令。它应该只执行一次,而不是循环的每次迭代。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainlistview);
list = (ListView)findViewById(R.id.list_listview);
new DownloadFilesTask().execute(URL);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}