NumberFormatException無效int「」

我想從EditText取得輸入值，我想將它保存到sqlite數據庫。我不知道如何使用logcat [也請解釋如何從LogCat中讀取錯誤]。NumberFormatException無效int「」

MainActivity.java：

package com.example.database; 

import android.support.v7.app.ActionBarActivity; 
import android.text.Editable; 
import android.app.Activity; 
import android.content.Context; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteDatabase.CursorFactory; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 


public class MainActivity extends Activity{ 

    EditText first,last,age,classc; 
    Button add,view; 

    String FirstName; 
    String LastName,Class; 
    Integer Age; 

    sqLit myDB; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     myDB = new sqLit(this); 
     Link(); 
     xmlToVar(); 
     add.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       Integer flag=myDB.insertValue(FirstName, LastName, Class, Age); 
       if (flag==1) 
       { 
        Context context=getApplicationContext(); 
        Toast toast = Toast.makeText(context, "Record Added" , Toast.LENGTH_LONG); 
        toast.show(); 
       } 
       else 
       { 
        Context context=getApplicationContext(); 
        Toast toast = Toast.makeText(context, "Error Occured" , Toast.LENGTH_LONG); 
        toast.show(); 
       } 
      } 
     }); 
    } 

    public void Link() 
    { 
     first=(EditText) findViewById(R.id.editFirst); 
     last=(EditText) findViewById(R.id.editLast); 
     classc=(EditText) findViewById(R.id.editClass); 
     age=(EditText) findViewById(R.id.editAge); 
     add=(Button) findViewById(R.id.Add); 
     view=(Button) findViewById(R.id.ViewAll); 
    } 

    public void xmlToVar() 
    { 
     FirstName = first.getText().toString(); 
     LastName = last.getText().toString(); 
     Class = classc.getText().toString(); 
     Age = Integer.parseInt(age.getText().toString()); 
    } 


}

sqLit.java：

package com.example.database; 

import org.w3c.dom.Text; 

import android.content.ContentValues; 
import android.content.Context; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
import android.database.sqlite.SQLiteDatabase.CursorFactory; 

public class sqLit extends SQLiteOpenHelper 
{ 

    public static final String DB_NAME="student12.db"; 
    public static final String TABLE_NAME="class1"; 

    public static final String COL_1="ROLL NO"; 
    public static final String COL_2="First Name"; 
    public static final String COL_3="Last Name"; 
    public static final String COL_4="Class"; 
    public static final String COL_5="Age"; 




    public sqLit(Context context) { 
     super(context, DB_NAME, null, 1); 
     // TODO Auto-generated constructor stub 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     // TODO Auto-generated method stub 
     db.execSQL("Create table " + TABLE_NAME + "(" + COL_1 + "INTEGER AUTOINCREMENT PRIMARY KEY," + COL_2 + "TEXT," + COL_3 + "TEXT," + COL_4 + "TEXT," + COL_5 + "INTEGER)"); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     // TODO Auto-generated method stub 
     db.execSQL("Drop Table If Exist" + TABLE_NAME); 
     onCreate(db); 
    } 

    public Integer insertValue(String FirstName, String LastName, String Class, Integer Age) 
    { 

     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentV = new ContentValues(); 
     contentV.put(COL_2, FirstName); 
     contentV.put(COL_3, LastName); 
     contentV.put(COL_4, Class); 
     contentV.put(COL_5, Age); 
     long isInserted = db.insert(TABLE_NAME, null, contentV); 
     if (isInserted == -1){ 
      return 0; 
     } 
     else 
     { 
      return 1; 
     } 
     } 




}

另外，請介紹一下如何使用logcat的，因爲我不知道如何讀它。

logcat的：

06-11 18:44:39.650: E/Trace(29536): error opening trace file: No such file or directory (2) 
06-11 18:44:39.660: D/AndroidRuntime(29536): Shutting down VM 
06-11 18:44:39.660: W/dalvikvm(29536): threadid=1: thread exiting with uncaught exception (group=0xb3f2b288) 
06-11 18:44:39.660: E/AndroidRuntime(29536): FATAL EXCEPTION: main 
06-11 18:44:39.660: E/AndroidRuntime(29536): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.database/com.example.database.MainActivity}: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread.access$600(ActivityThread.java:130) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.os.Looper.loop(Looper.java:137) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread.main(ActivityThread.java:4745) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at java.lang.reflect.Method.invokeNative(Native Method) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at java.lang.reflect.Method.invoke(Method.java:511) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at dalvik.system.NativeStart.main(Native Method) 
06-11 18:44:39.660: E/AndroidRuntime(29536): Caused by: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:44:39.660: E/AndroidRuntime(29536): at java.lang.Integer.invalidInt(Integer.java:138) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at java.lang.Integer.parseInt(Integer.java:359) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at java.lang.Integer.parseInt(Integer.java:332) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at com.example.database.MainActivity.xmlToVar(MainActivity.java:72) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at com.example.database.MainActivity.onCreate(MainActivity.java:34) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.Activity.performCreate(Activity.java:5008) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
06-11 18:44:39.660: E/AndroidRuntime(29536): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
06-11 18:44:39.660: E/AndroidRuntime(29536): ... 11 more 
06-11 18:46:03.652: D/dalvikvm(30256): Not late-enabling CheckJNI (already on) 
06-11 18:46:03.682: E/Trace(30256): error opening trace file: No such file or directory (2) 
06-11 18:46:03.712: D/AndroidRuntime(30256): Shutting down VM 
06-11 18:46:03.712: W/dalvikvm(30256): threadid=1: thread exiting with uncaught exception (group=0xb3f2b288) 
06-11 18:46:03.712: E/AndroidRuntime(30256): FATAL EXCEPTION: main 
06-11 18:46:03.712: E/AndroidRuntime(30256): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.database/com.example.database.MainActivity}: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread.access$600(ActivityThread.java:130) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.os.Looper.loop(Looper.java:137) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread.main(ActivityThread.java:4745) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at java.lang.reflect.Method.invokeNative(Native Method) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at java.lang.reflect.Method.invoke(Method.java:511) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at dalvik.system.NativeStart.main(Native Method) 
06-11 18:46:03.712: E/AndroidRuntime(30256): Caused by: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:46:03.712: E/AndroidRuntime(30256): at java.lang.Integer.invalidInt(Integer.java:138) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at java.lang.Integer.parseInt(Integer.java:359) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at java.lang.Integer.parseInt(Integer.java:332) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at com.example.database.MainActivity.xmlToVar(MainActivity.java:73) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at com.example.database.MainActivity.onCreate(MainActivity.java:35) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.Activity.performCreate(Activity.java:5008) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
06-11 18:46:03.712: E/AndroidRuntime(30256): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
06-11 18:46:03.712: E/AndroidRuntime(30256): ... 11 more 
06-11 18:53:33.378: E/Trace(2383): error opening trace file: No such file or directory (2) 
06-11 18:53:33.408: D/AndroidRuntime(2383): Shutting down VM 
06-11 18:53:33.408: W/dalvikvm(2383): threadid=1: thread exiting with uncaught exception (group=0xb3f2b288) 
06-11 18:53:33.408: E/AndroidRuntime(2383): FATAL EXCEPTION: main 
06-11 18:53:33.408: E/AndroidRuntime(2383): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.database/com.example.database.MainActivity}: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread.access$600(ActivityThread.java:130) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.os.Handler.dispatchMessage(Handler.java:99) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.os.Looper.loop(Looper.java:137) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread.main(ActivityThread.java:4745) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at java.lang.reflect.Method.invokeNative(Native Method) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at java.lang.reflect.Method.invoke(Method.java:511) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at dalvik.system.NativeStart.main(Native Method) 
06-11 18:53:33.408: E/AndroidRuntime(2383): Caused by: java.lang.NumberFormatException: Invalid int: "" 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at java.lang.Integer.invalidInt(Integer.java:138) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at java.lang.Integer.parseInt(Integer.java:359) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at java.lang.Integer.parseInt(Integer.java:332) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at com.example.database.MainActivity.xmlToVar(MainActivity.java:73) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at com.example.database.MainActivity.onCreate(MainActivity.java:35) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.Activity.performCreate(Activity.java:5008) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
06-11 18:53:33.408: E/AndroidRuntime(2383):  ... 11 more

來源

2015-06-11 Akshay

發表您的logcat＆也許有人可以幫助解釋發生了什麼:) – Galax

「致命」下的每件事物都是堆棧跟蹤。這是發生崩潰時執行的方法堆棧。「原因」部分（可能有幾個，通常看最後一個）是錯誤的根源。這是你應該看的一個。 '在com.example.database.MainActivity.xmlToVar（MainActivity.java:72）'是第一行提到你的代碼。這就是你的代碼導致異常的地方。（即文件和行號）。 '引發：java.lang.NumberFormatException：無效int：「」'是實際的異常。它告訴你出了什麼問題。你試圖把''「'分析爲int。 – njzk2

您從logcat發佈的信息稱爲堆棧跟蹤。有關如何閱讀它的信息，請參閱http://stackoverflow.com/questions/3988788/what-is-a-stack-trace-and-how-can-i-use-it-to-debug-my-application-錯誤。在Android中，您經常需要掃描從Android API傳遞的類和方法的引用，直到找到您自己創建的類的首次提及。 –

Caused by: java.lang.NumberFormatException: Invalid int: ""

（後FATAL EXCEPTION:）告訴我們你試圖解析int，但你正在試圖解析值是一個空String。

這條線（引用類第一）告訴我們這行是

at com.example.database.MainActivity.xmlToVar(MainActivity.java:72)

這種情況正在發生，因爲你是在onCreate()稱這是EditText之前已經輸入的數值。

從上面的線，我們可以看到，在MainActivity發生錯誤的方法xmlToVar在行72應該是

Age = Integer.parseInt(age.getText().toString());

爲了解決這個問題，你應該調用該方法在onClick或某些事件監聽器。你也應該圍繞它在try/catch或使用其他驗證檢查。

你應該閱讀有關詳細信息，下面的問題進行解答：

What is a stack trace, and how can I use it to debug my application errors?

Unfortunately MyApp has stopped. How can I solve this?

java.lang.NumberFormatException: Invalid int: "" in android

基本上，閱讀它給然後你看第一行中的錯誤其中提到你的班級。有時你需要更深入地閱讀，但通常情況下，基本的錯誤是足夠的。

也請解釋如何使用LogCat，因爲我是3天的Android程序員。我從未使用Eclipse。

請注意，stacktrace不是Eclipse甚至Java/Android特定的。你可以得到某種崩潰日誌中這樣的其他語言/的IDE /控制檯

來源

2015-06-11 13:48:24 codeMagic

嘿兄弟謝謝你的幫助..但你可以請告訴我你是如何發現問題？ – Akshay

我答案的第一部分解釋了我是如何找到它的。閱讀以「引起來的」開頭的錯誤，然後查找引用您的課程的行。它甚至會給你線路號碼。這裏是72行的MainActivity。在用戶有機會輸入任何內容之前，我看到你正在調用該行。 – codeMagic

我可以嘗試更好地解釋它，但我不確定哪一部分沒有意義。另外，閱讀上述鏈接應該會幫助你更好地理解。 – codeMagic

的問題是在這裏：

Age = Integer.parseInt(age.getText().toString());

age.getText().toString()等於""並導致NumberFormatException

來源

2015-06-11 13:49:04 isma3l

根本問題是'Integer.parseInt（「」）'拋出'NumberFormatException'因爲它認爲''「'是一個無效的'整數'（甚至不是零）。容易犯的錯誤我們都做過^^ – shkschneider

NumberFormatException無效int「」

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