java.lang.InstantiationException：java.lang.Class <com.wavedevelopers.eventsplanning.BookingForm>没有零参数的构造函数

Question

我想使用timepicker和datepicker做一个表单，但坚持这个错误。我只是一个初学者，所以请简单点。 我创建了2个内部类DateDialogs和TimeDialogs。

这是java类。

package com.wavedevelopers.eventsplanning; 
 

 
import android.app.DatePickerDialog; 
 
import android.app.Dialog; 
 
import android.app.TimePickerDialog; 
 
import android.content.Context; 
 
import android.os.Bundle; 
 
import android.support.design.widget.FloatingActionButton; 
 
import android.support.design.widget.Snackbar; 
 
import android.support.v4.app.DialogFragment; 
 
import android.support.v4.app.FragmentActivity; 
 
import android.support.v7.app.AppCompatActivity; 
 
import android.support.v7.widget.Toolbar; 
 
import android.text.format.DateFormat; 
 
import android.view.View; 
 
import android.widget.Button; 
 
import android.widget.DatePicker; 
 
import android.widget.EditText; 
 
import android.widget.TimePicker; 
 
import android.widget.Toast; 
 

 
import java.util.Calendar; 
 

 
public class BookingForm extends AppCompatActivity implements DatePickerDialog.OnDateSetListener,TimePickerDialog.OnTimeSetListener { 
 

 
    BackgroundWorker backgroundWorker; 
 

 
    Context ctx; 
 

 
    public BookingForm(Context ctx) { 
 
     this.ctx = ctx; 
 
    } 
 

 
    @Override 
 
    protected void onCreate(Bundle savedInstanceState) { 
 
     super.onCreate(savedInstanceState); 
 
     setContentView(R.layout.activity_booking_form); 
 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
 
     setSupportActionBar(toolbar); 
 

 
     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
 
     fab.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View view) { 
 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
 
         .setAction("Action", null).show(); 
 
      } 
 
     }); 
 

 

 

 
     Button doneButton = (Button) findViewById(R.id.doneButton); 
 
     Button datePickerButton = (Button) findViewById(R.id.datePickerButton); 
 
     Button timePickerButton = (Button) findViewById(R.id.timePickerButton); 
 

 
     final EditText name = (EditText) findViewById(R.id.userNameEditText); 
 
     final EditText cnic = (EditText) findViewById(R.id.userCNICEditText); 
 
     final EditText phone = (EditText) findViewById(R.id.userPhoneEditText); 
 

 
     doneButton.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View view) { 
 
         backgroundWorker = new BackgroundWorker(ctx); 
 
         backgroundWorker.doInBackground(name.getText().toString(),cnic.getText().toString(),phone.getText().toString()); 
 
         backgroundWorker.execute(); 
 
      } 
 
     }); 
 

 
     datePickerButton.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View view) { 
 
       DateDialogs pickerDialogs = new DateDialogs(); 
 
       pickerDialogs.show(getSupportFragmentManager(),"date_picker"); 
 
      } 
 
     }); 
 

 
     timePickerButton.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View view) { 
 
       TimeDialogs timeDialogs = new TimeDialogs(); 
 
       timeDialogs.show(getSupportFragmentManager(),"time_picker"); 
 
      } 
 
     }); 
 

 

 

 
    } 
 

 
    @Override 
 
    public void onDateSet(DatePicker datePicker, int year, int monthOfYear, int dayOfMonth) { 
 
     Toast.makeText(this,"Selected Date: " + monthOfYear + "/" + dayOfMonth + "/" + year,Toast.LENGTH_LONG).show(); 
 
    } 
 

 
    @Override 
 
    public void onTimeSet(TimePicker timePicker, int hourOfDay, int minute) { 
 
     Toast.makeText(this,"Selected Time: " + hourOfDay + " : " + minute ,Toast.LENGTH_LONG).show(); 
 
    } 
 

 
    public static class DateDialogs extends DialogFragment { 
 

 
     @Override 
 
     public Dialog onCreateDialog(Bundle savedInstanceState) { 
 

 
      BookingForm bookingForm = new BookingForm(getActivity()); 
 
      Calendar calendar = Calendar.getInstance(); 
 
      int year = calendar.get(Calendar.YEAR); 
 
      int month = calendar.get(Calendar.MONTH); 
 
      int day = calendar.get(Calendar.DAY_OF_MONTH); 
 

 

 
      DatePickerDialog datePickerDialog; 
 
      datePickerDialog = new DatePickerDialog(getActivity(), bookingForm,year,month,day); 
 

 
      return datePickerDialog; 
 
     } 
 
    } 
 

 
    public static class TimeDialogs extends DialogFragment { 
 

 
     @Override 
 
     public Dialog onCreateDialog(Bundle savedInstanceState) { 
 

 
      BookingForm bookingForm = new BookingForm(getActivity()); 
 
      Calendar calendar = Calendar.getInstance(); 
 
      int hour = calendar.get(Calendar.HOUR_OF_DAY); 
 
      int min = calendar.get(Calendar.MINUTE); 
 

 

 
      TimePickerDialog timePickerDialog; 
 
      timePickerDialog = new TimePickerDialog(getActivity(),bookingForm,hour,min, DateFormat.is24HourFormat(getActivity())); 
 

 
      return timePickerDialog; 
 
     } 
 
    } 
 

 

 

 

 

 
}

这是错误日志。

10-04 19:28:28.278 32605-32605/com.wavedevelopers.eventsplanning E/AndroidRuntime: FATAL EXCEPTION: main 
 
                        Process: com.wavedevelopers.eventsplanning, PID: 32605 
 
                        java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.wavedevelopers.eventsplanning/com.wavedevelopers.eventsplanning.BookingForm}: java.lang.InstantiationException: java.lang.Class<com.wavedevelopers.eventsplanning.BookingForm> has no zero argument constructor 
 
                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2337) 
 
                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2490) 
 
                         at android.app.ActivityThread.-wrap11(ActivityThread.java) 
 
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354) 
 
                         at android.os.Handler.dispatchMessage(Handler.java:102) 
 
                         at android.os.Looper.loop(Looper.java:148) 
 
                         at android.app.ActivityThread.main(ActivityThread.java:5443) 
 
                         at java.lang.reflect.Method.invoke(Native Method) 
 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728) 
 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 
 
                        Caused by: java.lang.InstantiationException: java.lang.Class<com.wavedevelopers.eventsplanning.BookingForm> has no zero argument constructor 
 
                         at java.lang.Class.newInstance(Native Method) 
 
                         at android.app.Instrumentation.newActivity(Instrumentation.java:1090) 
 
                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327) 
 
                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2490)  
 
                         at android.app.ActivityThread.-wrap11(ActivityThread.java)  
 
                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354)  
 
                         at android.os.Handler.dispatchMessage(Handler.java:102)  
 
                         at android.os.Looper.loop(Looper.java:148)  
 
                         at android.app.ActivityThread.main(ActivityThread.java:5443)  
 
                         at java.lang.reflect.Method.invoke(Native Method)  
 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)  
 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)  
 
10-04 19:28:30.855 32605-32605/com.wavedevelopers.eventsplanning I/Process: Sending signal. PID: 32605 SIG: 9

Answer 1

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.wavedevelopers.eventsplanning/com.wavedevelopers.eventsplanning.BookingForm}: java.lang.InstantiationException: java.lang.Class<com.wavedevelopers.eventsplanning.BookingForm> has no zero argument constructor 

这行告诉我，该计划希望你让你的类BookingForm它没有参数的构造函数。

您可能要添加类似：

// Constructor with no arguments. 
public BookingForm() { 
    this.ctx = null; 
}