Question

我是android的新手并实现了一个数据来自数据库的类，我使用了光标，但它给了我NumberformatException。

我的代码是：

package com.example.login;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
Button b,b1;
EditText e1,e2,e3;
SQLiteDatabase a;
database db;
Cursor r;
String s="";
String d="";
String w,t;
int q;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        b=(Button)findViewById(R.id.button1);
        e1=(EditText)findViewById(R.id.editText1);
        e2=(EditText)findViewById(R.id.editText2);
        e3=(EditText)findViewById(R.id.editText3);
        q=Integer.parseInt(e1.getText()+"");
        w=e2.getText()+"";
        t=e3.getText()+"";

        b1.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                a=db.getWritableDatabase();
                a.execSQL("insert into data values("+q+",'"+w+"','"+t+"');");
                db.close();
            }
        });
        b.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                a=db.getReadableDatabase();
                r=a.rawQuery("select name from data", null);
                System.out.println("========cursor======"+r.toString());
                if(r.getCount()>0){
                    r.moveToNext();
                    s+=r.getString(0);
                }
                s+=r.getString(0);
                db.close();
                /*a=db.getReadableDatabase();
                r=a.rawQuery("select pass from data", null);
                d+=r.getString(0);
                db.close();*/
                Toast.makeText(getBaseContext(), s, Toast.LENGTH_LONG).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}
class database extends SQLiteOpenHelper{

    public database(Context context) {
        super(context, "data", null, 2);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase arg0) {
        // TODO Auto-generated method stub
        arg0.execSQL("create table data(cd int,name string ,pass string);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub
        arg0.execSQL("drop table data;");
        onCreate(arg0);

    }

}

logcat的

07-28 17:06:47.988: E/AndroidRuntime(28379): Process: com.example.login, PID: 28379
07-28 17:06:47.988: E/AndroidRuntime(28379): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.login/com.example.login.MainActivity}: java.lang.NumberFormatException: Invalid int: ""
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2404)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread.access$900(ActivityThread.java:172)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.os.Handler.dispatchMessage(Handler.java:102)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.os.Looper.loop(Looper.java:146)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread.main(ActivityThread.java:5653)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at java.lang.reflect.Method.invokeNative(Native Method)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at java.lang.reflect.Method.invoke(Method.java:515)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at dalvik.system.NativeStart.main(Native Method)
07-28 17:06:47.988: E/AndroidRuntime(28379): Caused by: java.lang.NumberFormatException: Invalid int: ""
07-28 17:06:47.988: E/AndroidRuntime(28379):    at java.lang.Integer.invalidInt(Integer.java:137)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at java.lang.Integer.parseInt(Integer.java:358)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at java.lang.Integer.parseInt(Integer.java:331)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at com.example.login.MainActivity.onCreate(MainActivity.java:36)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.Activity.performCreate(Activity.java:5541)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
07-28 17:06:47.988: E/AndroidRuntime(28379):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2368)
07-28 17:06:47.988: E/AndroidRuntime(28379):    ... 11 more

Answer 1

错误应与此相关：

q=Integer.parseInt(e1.getText()+"");

我希望e1.getText()为空字符串。将其删除并使用数字初始化q。

Answer 2

你的例外是：

引起：java.lang.NumberFormatException：无效的int：＆＃34;＆＃34;

这意味着您必须确保要解析的值。 ""（无）不是数字。将文本设置为某个初始值，例如：e1.setText("42");以确保正确解析，或者如果String为null / empty则不解析。

请注意，onCreate不允许用户更改其数据。你基本上总是得到一个空值。

if(e1.getText()!=null && !e1.getText().isEmpty()){
   q=Integer.parseInt(e1.getText()+"");
} else {
   Log.v(YourTag,"no number to parse, setting -1 instead");
   q = -1;
}

Answer 3

e1.getText()返回空，因此Integer.parseInt(e1.getText()+"")尝试将空字符串解析为int。首先，您可以查看e1.getText().toString() is numeric.

private boolean checkStringIsNumeric(String string) {
    return string.matches("\\d+(?:\\.\\d+)?");
}

if (checkStringIsNumeric(e1.getText().toString()))
    q=Integer.parseInt(e1.getText().toString());

在android中获取数字格式异常

3 个答案: