Android第一个应用程序字符串无法解析或不是字段错误 [英] Android first application String cannot be resolved or is not a field error

问题描述

我正在浏览此URL- http://developer.android .com/training/basics/firstapp/creating-project.html 并得到此错误EXTRA_MESSAGE无法解决或不是字段:

I was going through this URL -http://developer.android.com/training/basics/firstapp/creating-project.html and getting this error EXTRA_MESSAGE cannot be resolved or is not a field:

明尼苏达

<?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" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.myfirstapp.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

MainActivity.java

package com.example.myfirstapp;

import android.os.Bundle;
import android.view.View;
import android.app.Activity;
import android.view.Menu;
import android.content.Intent;
import android.widget.EditText;

public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";



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


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}


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

DisplayMessageActivity

package com.example.myfirstapp;

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

import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.app.NavUtils;
import android.annotation.TargetApi;
import android.os.Build;

public class DisplayMessageActivity extends Activity {


@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    Intent intent = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
    setContentView(R.layout.activity_display_message);
    // Create the text view
    TextView textView = new TextView(this);
    textView.setTextSize(40);
    textView.setText(message);

    // Show the Up button in the action bar.
    setupActionBar();

}

/**
 * Set up the {@link android.app.ActionBar}, if the API is available.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        getActionBar().setDisplayHomeAsUpEnabled(true);
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.display_message, menu);
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
     case android.R.id.home:
        // This ID represents the Home or Up button. In the case of this
        // activity, the Up button is shown. Use NavUtils to allow users
        // to navigate up one level in the application structure. For
        // more details, see the Navigation pattern on Android Design:
        //

        //
        NavUtils.navigateUpFromSameTask(this);
        return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

请指导.

推荐答案

将此内容包含在您的主要活动课程中

Include this in your main activity class

public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

感谢 https://www.androidpit.com/forum/632071/error-cannot-find-symbol-variable-extra-message-in-android-studio

这篇关于Android第一个应用程序字符串无法解析或不是字段错误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！