我使用主/详细模式制作Android应用程序。所以我有
这一切都很完美，但是当我更改屏幕方向时，它会再次调用AsyncTask并重新加载所有数据。
以下是我处理所有逻辑的 ListActivity 类的代码：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
getActionBar().setTitle("Dnevni horoskop");
if(findViewById(R.id.details_container) != null){
//Tablet
mTwoPane = true;
//Fragment stuff
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
DetailsFragment df = new DetailsFragment();
ft.add(R.id.details_container, df);
ft.commit();
}
pb = (ProgressBar) findViewById(R.id.pb_list);
tvNoConnection = (TextView) findViewById(R.id.tv_no_internet);
ivNoConnection = (ImageView) findViewById(R.id.iv_no_connection);
list = (GridView) findViewById(R.id.gv_list);
if(mTwoPane == true){
list.setNumColumns(1);
//list.setPadding(16,16,16,16);
}
adapter = new CustomListAdapter();
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position,
long arg3) {
pos = position;
if(mTwoPane == false){
Bundle bundle = new Bundle();
bundle.putSerializable("zodiac", zodiacFeed);
Intent i = new Intent(getApplicationContext(), DetailsActivity.class);
i.putExtra("position", position);
i.putExtras(bundle);
startActivity(i);
overridePendingTransition(R.anim.right_in, R.anim.right_out);
}
else if(mTwoPane == true){
DetailsFragment fragment = (DetailsFragment) getSupportFragmentManager().findFragmentById(R.id.details_container);
fragment.setHoroscopeText(zodiacFeed.getItem(position).getText());
fragment.setLargeImage(zodiacFeed.getItem(position).getLargeImage());
fragment.setSign("Dnevni horoskop - "+zodiacFeed.getItem(position).getName());
fragment.setSignDuration(zodiacFeed.getItem(position).getDuration());
// inflate menu from xml
/*if(menu != null){
MenuItem item = menu.findItem(R.id.share);
Toast.makeText(getApplicationContext(), item.getTitle().toString(), Toast.LENGTH_SHORT).show();
}*/
}
}
});
if(!Utils.isConnected(getApplicationContext())){
pb.setVisibility(View.GONE);
tvNoConnection.setVisibility(View.VISIBLE);
ivNoConnection.setVisibility(View.VISIBLE);
}
//Calling AsyncTask to load data
Log.d("TAG", "loading");
HoroscopeAsyncTask task = new HoroscopeAsyncTask(pb);
task.execute();
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
// TODO Auto-generated method stub
super.onConfigurationChanged(newConfig);
}
class CustomListAdapter extends BaseAdapter {
private LayoutInflater layoutInflater;
public CustomListAdapter() {
layoutInflater = (LayoutInflater) getBaseContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
// TODO Auto-generated method stub
// Set the total list item count
return names.length;
}
public Object getItem(int arg0) {
// TODO Auto-generated method stub
return null;
}
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return 0;
}
public View getView(int position, View convertView, ViewGroup parent) {
// Inflate the item layout and set the views
View listItem = convertView;
int pos = position;
zodiacItem = zodiacList.get(pos);
if (listItem == null && mTwoPane == false) {
listItem = layoutInflater.inflate(R.layout.list_item, null);
}
else if(mTwoPane == true){
listItem = layoutInflater.inflate(R.layout.tablet_list_item, null);
}
// Initialize the views in the layout
ImageView iv = (ImageView) listItem.findViewById(R.id.iv_horoscope);
iv.setScaleType(ScaleType.CENTER_CROP);
TextView tvName = (TextView) listItem.findViewById(R.id.tv_zodiac_name);
TextView tvDuration = (TextView) listItem.findViewById(R.id.tv_duration);
iv.setImageResource(zodiacItem.getImage());
tvName.setText(zodiacItem.getName());
tvDuration.setText(zodiacItem.getDuration());
Animation animation = AnimationUtils.loadAnimation(getBaseContext(), R.anim.push_up);
listItem.startAnimation(animation);
animation = null;
return listItem;
}
}
private void getHoroscope() {
String urlString = "http://balkanandroid.com/download/horoskop/examples/dnevnihoroskop.php";
try {
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(urlString);
HttpResponse response = client.execute(post);
resEntity = response.getEntity();
response_str = EntityUtils.toString(resEntity);
if (resEntity != null) {
Log.i("RESPONSE", response_str);
runOnUiThread(new Runnable() {
public void run() {
try {
Log.d("TAG", "Response from server : n "
+ response_str);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
} catch (Exception ex) {
Log.e("TAG", "error: " + ex.getMessage(), ex);
}
}
private class HoroscopeAsyncTask extends AsyncTask<String, Void, Void> {
public HoroscopeAsyncTask(ProgressBar pb1){
pb = pb1;
}
@Override
protected void onPreExecute() {
pb.setVisibility(View.VISIBLE);
super.onPreExecute();
}
@Override
protected Void doInBackground(String... params) {
getHoroscope();
try {
Log.d("TAG", "test u try");
JSONObject jsonObject = new JSONObject(response_str);
JSONArray jsonArray = jsonObject.getJSONArray("horoscope");
for(int i=0;i<jsonArray.length();i++){
Log.d("TAG", "test u for");
JSONObject horoscopeObj = jsonArray.getJSONObject(i);
String horoscopeSign = horoscopeObj.getString("name_sign");
String horoscopeText = horoscopeObj.getString("txt_hrs");
zodiacItem = new ZodiacItem(horoscopeSign, horoscopeText, duration[i], images[i], largeImages[i]);
zodiacList.add(zodiacItem);
zodiacFeed.addItem(zodiacItem);
//Treba u POJO klasu ubaciti sve.
Log.d("TAG", "ZNAK: "+zodiacItem.getName()+" HOROSKOP: "+zodiacItem.getText());
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e("TAG", "error: " + e.getMessage(), e);
}
return null;
}
@Override
protected void onPostExecute(Void result) {
pb.setVisibility(View.GONE);
list.setAdapter(adapter);
adapter.notifyDataSetChanged();
super.onPostExecute(result);
}
}
以下是 ListFragment 类的代码：
public class ListFragment extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
// Retain this fragment across configuration changes.
setRetainInstance(true);
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
View view = inflater.inflate(R.layout.fragment_list, container, false);
return view;
}
}
答案 0 :(得分：0)
我认为部分问题可能是方向改变再次调用onCreate。
See this question，然后检查第二个答案。
只需将configChanges添加到android清单就不会解决问题，但是如果你覆盖onConfigurationChanged，你可以设置一个SharedPreferences值，你说＆＃34; AsynTaskStarted = true＆＃34;或类似的东西，所以当方向改变时，你可以检查这个标志，如果不存在则启动AsyncTask，如果它已经在运行，则跳过它。
This other question，由链接的第一个问题的第一个答案引用，似乎有更多信息。
答案 1 :(得分：0)
当方向更改时，您可以使用以下内容保留任务：
@Override
public HoroscopeAsyncTask onRetainCustomNonConfigurationInstance() {
return task;
}
然后在你的onCreate（）中你可以这样做：
task = (HoroscopeAsyncTask)this.getLastCustomNonConfigurationInstance();
if(task != null) {
//pass the new progressbar reference to the asynctask
//implement a method in the asynctask that returns the task result
//e.g. result = task.getResult();
// if the result is not null, it means the task finished its work while orientation
// changed, if the result is null, onPostExecute will take care of that.
//if(result != null) { //set the result in the listview }
} else {
HoroscopeAsyncTask task = new HoroscopeAsyncTask(pb);
task.execute();
}
如果没有（应用程序启动）执行新的asynctask，如果有一个（方向更改）使用现有的运行asynctask，则代码试图获取保留的tak。
答案 2 :(得分：-1)
在清单m8 android:configChanges="orientation|keyboardHidden"