java - Android项目编译不成功(谷歌教程)

Question

我正在尝试学习 Android 编程。我找不到它无法编译的原因。

Ant 错误:

-compile:
[javac] Compiling 4 source files to C:\Documents and Settings\Jet\Desktop\My
FirstApp\bin\classes
    [javac] C:\Documents and Settings\Jet\Desktop\MyFirstApp\src\com\example\myf
irstapp\DisplayMessageActivity.java:40: error: cannot find symbol
    [javac]         if (id == R.id.action_settings)
    [javac]                       ^
    [javac]   symbol:   variable action_settings
    [javac]   location: class id
    [javac] C:\Documents and Settings\Jet\Desktop\MyFirstApp\src\com\example\myf
irstapp\DisplayMessageActivity.java:59: error: cannot find symbol
    [javac]               View rootView = inflater.inflate(R.layout.fragment_dis
play_message,
    [javac]                                                        ^
    [javac]   symbol:   variable fragment_display_message
    [javac]   location: class layout
    [javac] 2 errors

BUILD FAILED

以下是我的项目的文件。

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
<EditText android:id="@+id/edit_message"
    android:layout_height="wrap_content"
    android:hint="@string/edit_message"
    android:layout_weight="1"
    android:layout_width="0dp"
    />
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_send"
    android:onClick="sendMessage" />
</LinearLayout>

字符串.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">My First App</string>
    <string name="edit_message">Enter a message</string>
    <string name="button_send">Send</string>
    <string name="action_settings">Settings</string>
    <string name="title_activity_main">MainActivity</string>
    <string name="title_activity_display_message">My Message</string>
</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.example.myfirstapp"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:label="@string/app_name" android:icon="@drawable/ic_launcher">
        <activity android:name="MainActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.myfirstapp.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.example.myfirstapp.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.myfirstapp.MainActivity" />
        </activity>
    </application>
</manifest>

MainActivity.java

package com.example.myfirstapp;

import android.app.Activity;
import android.os.Bundle;
import android.content.Intent;
import android.support.v7.app.*;
import android.view.*;
import android.app.Fragment;
import android.widget.*;
import com.example.myfirstapp.R;

public class MainActivity extends ActionBarActivity
{
    /** Called when the activity is first created. */
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    /** Called when the user clicks the Send button */
    public void sendMessage(View view)
    {
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }
}

DisplayMessageActivity.java

package com.example.myfirstapp;

import android.app.Activity;
import android.os.Bundle;
import android.content.Intent;
import android.support.v7.app.*;
import android.view.*;
import android.app.Fragment;
import android.widget.*;
import com.example.myfirstapp.R;

public class DisplayMessageActivity extends ActionBarActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings)
        {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment
    {

        public PlaceholderFragment() { }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                  Bundle savedInstanceState)
        {
              View rootView = inflater.inflate(R.layout.fragment_display_message,
                      container, false);
              return rootView;
        }
    }
}

Answer 1

看起来文件 menu/main.xml 或其调用方式丢失。将定义菜单项settings 的位置。创建一个新项目，您将在 res/menu 文件夹中看到该文件。