初学者Android为什么要使用"id"是“未知成员"与R.id? [英] Beginner Android why is "id" is "Unknown member" with R.id?

问题描述

我确信这是一件非常简单的事情，因为这是我的第一个带有代码的android应用程序(我做的hello world示例只是将值赋给XML字符串).我的问题是，当尝试在变量中获取按钮的引用时，是否未定义R.id中的id?

I'm sure this is something dead simple as it's my first android app with code (the hello world example I did was just assigning a value to a string in XML). My problem is when trying to get the reference for my button in my variable then the id as in R.id is not defined?

在下面的代码中的注释中显示了编译器错误:

The compiler error is in a comment in the code below where it occurs:

package com.geeksonhugs.simplecalc;

import android.app.*;
import android.os.*;
import android.view.*;
import android.widget.*;

public class MainActivity extends Activity
{
    private Button AddButton;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        AddButton = (Button)findViewById(R.id.btnAdd);
//"Unknown member 'id' of 'com.geeksonhugs.simplecalc.R'"

        //AddButton.setOnClickListener(this);

    }   

}

XML布局文件:

<?xml version='1.0' encoding='utf-8' ?>
<LinearLayout 
        xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/LayoutRoot" 
    android:layout_height="match_parent" 
    android:layout_width="match_parent" 
    android:orientation="vertical">

<TextView 
    android:id="@+id/txtFirstNum" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="@string/strFirstNum" />

<EditText 
    android:id="@+id/edtFirstNum" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="" />

<TextView 
    android:id="@+id/txtSecondNum" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="@string/strSecondNum" />

<EditText 
    android:id="@+id/edtSecondNum" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="" />

<Button 
    android:id="@+id/btnAdd" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="@string/strAdd" 
    android:gravity="center" />

<TextView 
    android:id="@+id/txtResult" 
    android:layout_height="wrap_content" 
    android:layout_width="match_parent" 
    android:text="" />

</LinearLayout>

推荐答案

R 类是在构建项目时由Android构建工具为您生成的代码.这意味着有四种可能性:

The R class is code-generated for you by the Android build tools when you build your project. This means there are four possibilities:

1. 您还没有尝试构建项目，在这种情况下，请尝试一下.

1. You have not tried building the project yet, in which case, try that.

Eclipse出于某种原因认为不需要构建项目-尝试从Eclipse菜单中选择项目">清理"(当然，仅在使用Eclipse时才相关).

Eclipse doesn't think it needs to build the project for some reason -- try Project > Clean from the Eclipse menu (only relevant if you are using Eclipse, of course).

清单或您的资源之一中存在某些错误，阻止了 R 的构建.为此，应该有Eclipse错误指示器.

There is some bug in your manifest or one of your resources that is preventing R from being built. There should be Eclipse error indicators for this.

您的布局中没有 android:id 属性，因此没有 R.id .

You do not have an android:id attribute in your layout, and therefore there is no R.id available.

这篇关于初学者Android为什么要使用"id"是“未知成员"与R.id?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！