无法启动活动ComponentInfo：java.lang.NumberFormatException：对于输入字符串：“”

Question

I have a list of check boxes and if checked, they add the day of the week to an array list. I want to pass that arraylist to another class as seen in the sendTo()

here is my code from the Sel_Dates class:

 package com.example.joshpc.bluetoothattendee;

 import android.content.Intent;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.Button;
 import android.widget.CheckBox;

 import java.util.ArrayList;

public class Sel_Dates extends AppCompatActivity {
CheckBox mon;
CheckBox tues;
CheckBox wed;
CheckBox thur;
CheckBox fri;
Button selectBut;
ArrayList<String> days = new ArrayList<String>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sel_dates);

    mon = (CheckBox) findViewById(R.id.cbMon);
    tues = (CheckBox) findViewById(R.id.cbTues);
    wed = (CheckBox) findViewById(R.id.cbWed);
    thur = (CheckBox) findViewById(R.id.cbThurs);
    fri = (CheckBox) findViewById(R.id.cbFri);
    selectBut  = (Button) findViewById(R.id.bSelectDate);

    selectBut.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            getDates();
            sendTo();
        }
    });
}

private void getDates(){
    if(mon.isChecked())
        days.add("monday");
    if(tues.isChecked())
        days.add("tuesday");
    if(wed.isChecked())
        days.add("wednesday");
    if(thur.isChecked())
        days.add("thursday");
    if(fri.isChecked())
        days.add("friday");
}
private void sendTo(){
    Intent intent = new Intent(this, Create_Class.class);
    intent.putStringArrayListExtra("days", days);
    startActivity(intent);
}
}

and my debug output:

 FATAL EXCEPTION: main
              Process: com.example.joshpc.bluetoothattendee, PID: 2318
              java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.joshpc.bluetoothattendee/com.example.joshpc.bluetoothattendee.Create_Class}: java.lang.NumberFormatException: For input string: ""
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                  at android.app.ActivityThread.-wrap12(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
               Caused by: java.lang.NumberFormatException: For input string: ""
                  at java.lang.Integer.parseInt(Integer.java:533)
                  at java.lang.Integer.parseInt(Integer.java:556)
                  at com.example.joshpc.bluetoothattendee.Create_Class.onCreate(Create_Class.java:38)
                  at android.app.Activity.performCreate(Activity.java:6679)
                  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                  at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6119) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

Create_Class code:

 package com.example.joshpc.bluetoothattendee;

 import android.content.Intent;
 import android.provider.ContactsContract;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.Button;
 import android.widget.EditText;

 import com.google.firebase.auth.FirebaseAuth;
 import com.google.firebase.auth.FirebaseUser;
 import com.google.firebase.database.DatabaseReference;
 import com.google.firebase.database.FirebaseDatabase;

 import java.util.ArrayList;

 public class Create_Class extends AppCompatActivity {


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_create_class);

    final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    final DatabaseReference fbRef = FirebaseDatabase.getInstance().getReference();

    Button createBut = (Button) findViewById(R.id.bCreate);
    EditText etstartTime = (EditText) findViewById(R.id.etStartTime);
    EditText etclassID = (EditText) findViewById(R.id.etID);
    EditText etname = (EditText) findViewById(R.id.etClassName);

    final ArrayList<String> days = getIntent().getStringArrayListExtra("days");
    final String teacherID = user.getUid();
    final String name = etname.getText().toString();
    final String classID = etclassID.getText().toString();
    final int startTime = Integer.parseInt(etstartTime.getText().toString());

    createBut.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            ClassObj newClass = new ClassObj(name, classID, teacherID, startTime, days);
            fbRef.child(user.getUid()).setValue(newClass);
            sendTo(Main__Menu.class);
        }
    });

}

private void sendTo(Class s){
    Intent intent = new Intent(this, s);
    startActivity(intent);
}
}

edit: I think the problem is coming from these lines of code

 final int startTime = Integer.parseInt(etstartTime.getText().toString());

    createBut.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            ClassObj newClass = new ClassObj(name, classID, teacherID, startTime, days);
            fbRef.child(user.getUid()).setValue(newClass);
            sendTo(Main__Menu.class);
        }
    });

specifically where I parse startTime which is read in as a string in the format HH:MM. going to change this to a string value rather than an int and see what happens.

Answer 1

您不能将空字符串添加到数字数据中，如果为空则应为0。

Answer 2

You are getting number format exception because you are parsing "" blank string. Please check string should not be blank before parsing it.

Please make sure it should not be blank or null before parsing it. To avoid this exception please properly handle try catch block or make default value of string "0".

String str="0";
   try {
        int val=Integer.parseInt(str);
   }catch (NumberFormatException e){
       System.out.println("not a number"); 
   } 

Answer 3

代替intent.putStringArrayListExtra("days", days)尝试此intent.putExtra("days", days)