我正在尝试怀孕的应用。我的应用程序工作正常，但有时我的应用程序获得java.lang.InstantiationException。
这是例外
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tupbebekailesi.medyasef.hamilelikrehberi/com.tupbebekailesi.medyasef.hamilelikrehberi.MotherActivity}: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.tupbebekailesi.medyasef.hamilelikrehberi.OpenActivity: make sure class name exists, is public, and has an empty constructor that is public
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2304)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
at android.app.ActivityThread.access$700(ActivityThread.java:165)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5450)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.tupbebekailesi.medyasef.hamilelikrehberi.OpenActivity: make sure class name exists, is public, and has an empty constructor that is public
at android.app.Fragment.instantiate(Fragment.java:600)
at android.app.FragmentState.instantiate(Fragment.java:97)
at android.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1767)
at android.app.Activity.onCreate(Activity.java:932)
at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:204)
at com.tupbebekailesi.medyasef.hamilelikrehberi.MotherActivity.onCreate(MotherActivity.java:92)
at android.app.Activity.performCreate(Activity.java:5369)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
... 11 more
Caused by: java.lang.InstantiationException: can't instantiate class com.tupbebekailesi.medyasef.hamilelikrehberi.OpenActivity; no empty constructor
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1130)
at android.app.Fragment.instantiate(Fragment.java:589)
我明白这段代码我的OpenActivity.java没有空构造函数。
这是打开的activity.java文件
public class OpenActivity extends Fragment implements View.OnClickListener {
private Button done,pregnant_button;
private Context mContext;
private Button numbered_date;
private EditText mom_name,pre_pregnant_weight;
public OpenActivity(Context mContext) {
this.mContext = mContext;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.open_calculator,container,false);
mom_name = (EditText) rootView.findViewById(R.id.mom_name);
pregnant_button = (Button) rootView.findViewById(R.id.pregnant_button);
pre_pregnant_weight = (EditText) rootView.findViewById(R.id.pre_pregnant_weight);
done = (Button) rootView.findViewById(R.id.done);
mom_name.setText(MotherActivity.preferences.getString(MotherActivity.USER_NS,""));
pregnant_button.setText(MotherActivity.preferences.getString(MotherActivity.USER_DUE_DATE,"-- / -- / --"));
pre_pregnant_weight.setText(MotherActivity.preferences.getString(MotherActivity.USER_PRE_WEIGHT,""));
pregnant_button.setOnClickListener(this);
done.setOnClickListener(this);
return rootView;
}
public void showDatePickerDialog() {
DialogFragment newFragment = new CalendarItem(pregnant_button);
newFragment.show(getFragmentManager(), "datePicker");
}
public boolean calculate_elapsed_time(long milisecondsdate) {
long gecen_zaman = System.currentTimeMillis() - milisecondsdate;
long toplamhamilelik = 280 * CalculateActivity.bir_gun;
if( milisecondsdate > System.currentTimeMillis() || gecen_zaman > toplamhamilelik) {
return true;
}
return false;
}
@Override
public void onClick(View v) {
String get_name_surname = mom_name.getText().toString();
String get_due_date = pregnant_button.getText().toString();
String get_pre_pregnant_weight = pre_pregnant_weight.getText().toString();
SharedPreferences.Editor editor = MotherActivity.preferences.edit();
if (v == pregnant_button) {
showDatePickerDialog();
}
else if( v == done ) {
long pregnant_date = MotherActivity.preferences.getLong(MotherActivity.USER_DUE_DATE_MS,0);
if(get_name_surname.equals("Adınız Soyadınız") || get_name_surname.equals("")) {
show_toast(R.string.empty_name_surname);
}
else if(get_due_date.equals("-- / -- / --")) {
show_toast(R.string.empty_due_date);
}
else if(calculate_elapsed_time(pregnant_date)){
show_toast(R.string.wrong_pregnant_date_calculate);
}
else if(get_pre_pregnant_weight.equals("")) {
show_toast(R.string.empty_pre_pregnant_warning);
}
else {
boolean get_due_date_state = MotherActivity.preferences.getBoolean(MotherActivity.DUE_DATE_ENTRY, false);
/*
Hesaplıyıcı sayfasında tamam butonuna basıldğında
hafta bitimine kalan gün değerini int olarak yolluyoruz.
Kullanıcı 6. gündeyse 1 değerini 7. gündeyse 0 değerini yolluyoruz.
Dinleyen dosya WeekAlarms.java
*/
Intent start_alarm = new Intent(MotherActivity.WEEK_ALARM_NAME);
getActivity().sendBroadcast(start_alarm);
int week_number = MotherActivity.week_number();
CRUD crud = new CRUD(mContext);
List<WeekToWeekWeights> wtw = new ArrayList<WeekToWeekWeights>();
/*
Uygulamaya ilk giriş olup olmadığını kontrol eder.
İlk giriş olup olmadığına göre
Kilo hesabı için kullanılan database şekli değişecektir.
*/
if(get_due_date_state){
int get_db_total_count = crud.db_total_count();
if(week_number > get_db_total_count) {
for (int i = get_db_total_count + 1; i <= week_number + 1 ; i++) {
wtw.add(new WeekToWeekWeights(i,"--",usualy_weight_val[i-1]));
}
crud.add_weight(wtw);
}
else if(week_number < get_db_total_count) {
crud.delete_weights(week_number+1);
crud.update_weight(String.valueOf(MotherActivity.preferences.getString(MotherActivity.USER_CURRENT_WEIGHT,"--")));
}
}
else {
for (int i = 1; i <= week_number + 1 ; i++) {
wtw.add(new WeekToWeekWeights(i,"--",usualy_weight_val[i-1]));
}
crud.add_weight(wtw);
}
editor.putString(MotherActivity.USER_NS,get_name_surname);
editor.putString(MotherActivity.USER_DUE_DATE,get_due_date);
editor.putString(MotherActivity.USER_PRE_WEIGHT,get_pre_pregnant_weight);
editor.putBoolean(MotherActivity.DUE_DATE_ENTRY,true);
editor.apply();
Intent go_entry_page = new Intent(mContext,MotherActivity.class);
go_entry_page.putExtra(MotherActivity.TARGET_RESPOND,"entry_page");
startActivity(go_entry_page);
}
}
}
public void show_toast(int value){
Toast.makeText(mContext,value,Toast.LENGTH_LONG).show();
}
}
抱歉英语不好。 请帮忙。谢谢
答案 0 :(得分：2)
嗯，你的答案就是问题......
来自stackStrace：
has an empty constructor that is public
所以你需要定义一个构造函数：
public OpenActivity() {
}
您可以使用getActivity()
如果您绝对想要私有Context（不建议使用...），请覆盖方法onAttach＆amp; onDetach：
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
mContext = activity;
}
@Override
public void onDetach() {
mContext = null;
super.onDetach();
}