我已经在网上搜索并继续尝试了 5 个小时，但我找不到解决问题的方法。我想在方向改变后保持我的微调器的状态。
我有 2 个动态创建的微调器。他们通过 http 请求获取项目，第一个微调器通过 setOnItemSelectedListener() 方法更改第二个中的项目。我将字符串读入全局列表。
public class Global {
public static String userName;
public static String userType;
public static String serverIp;
public static int spinnerLeaguePos=0;
public static int spinnerMatchPos=0;
public static List<String> leagues;
public static List<String> matches;
}
我的第一个问题是阻止活动重新启动。
android:configChanges="orientation|keyboardHidden"
我在清单文件中进行了此更改，以自己处理方向更改并避免重新启动活动。
我找到了一种在互联网上处理方向变化的方法，但它对我不起作用。更改方向时出现空指针异常。
07-05 12:41:08.119: E/AndroidRuntime(26388): FATAL EXCEPTION: main
07-05 12:41:08.119: E/AndroidRuntime(26388): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.MatchSelectionActivity}: java.lang.NullPointerException
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3351)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.access$700(ActivityThread.java:123)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1151)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.os.Handler.dispatchMessage(Handler.java:99)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.os.Looper.loop(Looper.java:137)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.main(ActivityThread.java:4424)
07-05 12:41:08.119: E/AndroidRuntime(26388): at java.lang.reflect.Method.invokeNative(Native Method)
07-05 12:41:08.119: E/AndroidRuntime(26388): at java.lang.reflect.Method.invoke(Method.java:511)
07-05 12:41:08.119: E/AndroidRuntime(26388): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-05 12:41:08.119: E/AndroidRuntime(26388): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-05 12:41:08.119: E/AndroidRuntime(26388): at dalvik.system.NativeStart.main(Native Method)
07-05 12:41:08.119: E/AndroidRuntime(26388): Caused by: java.lang.NullPointerException
07-05 12:41:08.119: E/AndroidRuntime(26388): at com.example.MatchSelectionActivity.setLeagues(MatchSelectionActivity.java:90)
07-05 12:41:08.119: E/AndroidRuntime(26388): at com.example.MatchSelectionActivity.onCreate(MatchSelectionActivity.java:47)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.Activity.performCreate(Activity.java:4465)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
07-05 12:41:08.119: E/AndroidRuntime(26388): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
07-05 12:41:08.119: E/AndroidRuntime(26388): ... 12 more
这是我到目前为止所做的。我什至不确定我正在尝试这样做。因此，将不胜感激任何更合适的方法。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
spinnerLeague = (Spinner) findViewById(R.id.spinner_league);
spinnerMatch = (Spinner) findViewById(R.id.spinner_match);
if (savedInstanceState != null) {
setLeagues();
setMatches();
spinnerLeague.setSelection(Global.spinnerLeaguePos);
spinnerMatch.setSelection(Global.spinnerMatchPos);
}
else{
Global.leagues = new ArrayList<String>();
Global.matches = new ArrayList<String>();
Global.leagues.add(getString(R.string.league_select));
Global.matches.add(getString(R.string.match_select));
GetLeagues task = new GetLeagues();
String requestString = "http://" + Global.serverIp + ":8080/server/GetCurrentLeagues";
task.execute(new String[] { requestString });
}
setContentView(R.layout.match_selection_layout);
}
public class GetLeagues extends AsyncTask<String, Void, String[]> {
@Override
protected String[] doInBackground(String... urls) {
//this part works properly, and reads the leagues into Global.leagues List
}
@Override
protected void onPostExecute(String[] result) {
setLeagues();
}
}
public class GetMatches extends AsyncTask<String, Void, String[]> {
@Override
protected String[] doInBackground(String... urls) {
//this part works properly, and reads the matches into Global.matches List
}
@Override
protected void onPostExecute(String[] result) {
setMatches();
}
}
public void setLeagues() {
spinnerLeague = (Spinner) findViewById(R.id.spinner_league);
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, Global.leagues);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerLeague.setAdapter(dataAdapter);
spinnerLeague.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
spinnerLeague = (Spinner) findViewById(R.id.spinner_league);
if(position!=0){
spinnerMatch.setEnabled(true);
Global.spinnerLeaguePos=position;
GetMatches task = new GetMatches();
String requestString = "http://" + Global.serverIp +":8080/server/GetCurrentMatches/"+Global.spinnerLeaguePos;
task.execute(new String[] { requestString });
}
else{
setMatches();
spinnerMatch.setEnabled(false);
Global.spinnerLeaguePos=position;
}
}
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}
public void setMatches() {
spinnerMatch = (Spinner) findViewById(R.id.spinner_match);
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, Global.matches);
dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerMatch.setAdapter(dataAdapter);
spinnerMatch.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
Global.spinnerMatchPos=position;
}
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}