This question already has answers here:
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo
(40个答案)
5年前关闭。
启动应用程序时出现此错误,我该如何解决?
12112-12112 / com.javacodegeeks.androidqrcodeexample E / AndroidRuntime:
致命异常:主要
java.lang.RuntimeException:无法实例化活动ComponentInfo {com.javacodegeeks.androidqrcodeexample / com.javacodegeeks.androidqrcodeexample.Login}:
java.lang.NullPointerException
这是我的.xml文件:
这是我的活动:
内
(40个答案)
5年前关闭。
启动应用程序时出现此错误,我该如何解决?
12112-12112 / com.javacodegeeks.androidqrcodeexample E / AndroidRuntime:
致命异常:主要
java.lang.RuntimeException:无法实例化活动ComponentInfo {com.javacodegeeks.androidqrcodeexample / com.javacodegeeks.androidqrcodeexample.Login}:
java.lang.NullPointerException
这是我的.xml文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.javacodegeeks.androidqrcodeexample"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name="com.javacodegeeks.androidqrcodeexample.AndroidBarcodeQrExample"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.javacodegeeks.androidqrcodeexample.Login"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是我的活动:
package com.javacodegeeks.androidqrcodeexample;
/**
* Created by Andre on 14/06/15.
*/
import android.app.Activity;
import android.app.AlertDialog;
import android.content.ActivityNotFoundException;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class Login extends Activity {
EditText username = (EditText)findViewById(R.id.editText);
EditText password = (EditText)findViewById(R.id.editText2);
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
}
public void login(View view) {
if (username.getText().toString().equals("admin") && password.getText().toString().equals("admin")) {
Toast toast = Toast.makeText(this, "CORRECT PW", Toast.LENGTH_LONG);
toast.show();
//correcct password
Intent i = new Intent(getApplicationContext(), AndroidBarcodeQrExample.class);
i.putExtra("Disco", username.getText().toString());
startActivity(i);
} else {
Toast toast = Toast.makeText(this, "UNCORRECT PW", Toast.LENGTH_LONG);
toast.show();
//wrong password
}
}
}
最佳答案
移动线:
EditText username = (EditText)findViewById(R.id.editText);
EditText password = (EditText)findViewById(R.id.editText2);
内
onCreate
EditText username;
EditText password;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
username = (EditText)findViewById(R.id.editText);
password = (EditText)findViewById(R.id.editText2);
}
07-27 16:07