Question

我的应用程序在运行时崩溃了。我需要帮助。非常感谢你提前。

我对android studio有点新鲜，不知道我做错了什么。

错误：

09-14 02:55:11.013 4502-4502/com.example.adrian.loginregister E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.example.adrian.loginregister, PID: 4502
                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.adrian.loginregister/com.example.adrian.loginregister.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java)
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                    at android.os.Looper.loop(Looper.java:148)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                                 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                                    at com.example.adrian.loginregister.LoginActivity.onCreate(LoginActivity.java:23)
                                                                                    at android.app.Activity.performCreate(Activity.java:6237)
                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                                                    at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                    at android.os.Looper.loop(Looper.java:148) 
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

以下是LoginActivity.java

package com.example.adrian.loginregister;

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.EditText;
import android.widget.TextView;

public class LoginActivity extends AppCompatActivity {

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

        final EditText etUsername = (EditText) findViewById(R.id.etUsername);
        final EditText etPassword = (EditText) findViewById(R.id.etPassword);
        final Button bLogin = (Button) findViewById(R.id.bLogin);
        final TextView bRegister = (TextView) findViewById(R.id.bRegister);

        bRegister.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                Intent registerIntent = new Intent(LoginActivity.this, RegisterActivity.class);
                LoginActivity.this.startActivity(registerIntent);
            }
        });
    }
}

这是activty_login.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.adrian.loginregister.LoginActivity">

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/etUsername"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:hint="Username" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/etPassword"
        android:layout_below="@+id/etUsername"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignRight="@+id/etUsername"
        android:layout_alignEnd="@+id/etUsername"
        android:hint="Password" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Login"
        android:id="@+id/bLogin"
        android:layout_below="@+id/etPassword"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Register here"
        android:id="@+id/tvRegister"
        android:layout_below="@+id/bLogin"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

我一直想弄清楚几个小时。似乎无法让它发挥作用。每次我尝试运行它都会崩溃。

Answer 1

尝试改变

final TextView bRegister = (TextView) findViewById(R.id.bRegister);

行到

final TextView bRegister = (TextView) findViewById(R.id.tvRegister);

请将xml Register TextView文件Id tvRegister提交给Id。你在初始化中给出了错误的gulp.task('task-name',function(value){ var anotherValue = value; });。

Android Studio :: E / AndroidRuntime：致命异常：

1 个答案: