android中的java.lang.nullpointerexception [英] java.lang.nullpointerexception in android

问题描述

嗨所有:)



当我尝试午餐登录活动时我有这个例外



01-12 21：04：28.994：E / AndroidRuntime（1442）：java.lang.RuntimeException：无法启动活动ComponentInfo {com.msagroup.sbhmg / com.msagroup.sbhmg.LogIn}：java.lang。 NullPointerException



这里是我的.XML文件：

hi all :)

I have this exception when I try to lunch log in activity in android

01-12 21:04:28.994: E/AndroidRuntime(1442): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.msagroup.sbhmg/com.msagroup.sbhmg.LogIn}: java.lang.NullPointerException

here is my .XML file:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent" >


    <EditText

        android:id="@+id/etmail"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_alignParentTop="true"

        android:layout_marginTop="41dp"

        android:inputType="textEmailAddress"

        android:text="@string/email" >

        <requestFocus />
    </EditText>


    <EditText

        android:id="@+id/etpassword"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_below="@+id/etmail"

        android:layout_marginTop="16dp"

        android:inputType="textPassword" 

        android:text="@string/password"/>


    <Button

        android:id="@+id/btnlogin"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_below="@+id/etpassword"

        android:layout_marginTop="16dp"

        android:text="@string/login" />


    <TextView

        android:id="@+id/tvcomment"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentLeft="true"

        android:layout_centerVertical="true"

        android:text="@string/empty" />

</RelativeLayout>

< br $>


和.Java文件：

and .Java file:

package com.msagroup.sbhmg;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class LogIn extends Activity {
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        
        Button _gotousermain = (Button) findViewById(R.id.btngotoenglishmain);
        EditText _etmail = (EditText) findViewById(R.id.etmail);
        EditText _etpassword = (EditText) findViewById(R.id.etmail);
        final String _email = _etmail.getText().toString();
        final String _pass = _etpassword.getText().toString();
        final TextView _tvcomm = (TextView) findViewById(R.id.tvcomment);
        
        _gotousermain.setOnClickListener(new OnClickListener() {
			
			public void onClick(View v) {
				if(_email == "[e-mail]" && _pass == "123")
				{
					startActivity(new Intent(LogIn.this, ArMain.class));
				}
				else
				{
					if(_email == "[e-mail]" && _pass == "123")
					{
						startActivity(new Intent(LogIn.this, ArMain.class));
					}
					else
					{
						_tvcomm.setText("Invalid Info. !");
					}
				}
			}
		});
	}
}

谢谢大家：）

thank you all :)

推荐答案

我发现了问题



这是一个愚蠢的问题：\



IDbtngotoenglishmain



at



Button _gotousermain =（Button ）findViewById（R.id.btngotoenglishmain）;



在xml文件中不存在



谢谢大家：）

I found the problem

it was a stupid one :\

the ID "btngotoenglishmain"

at

Button _gotousermain = (Button) findViewById(R.id.btngotoenglishmain);

is not exists at the xml file

thank you all :)

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