Android首次应用教程问题 [英] Android First App Tutorial Issue

问题描述

我一直在试图得到这个工作，甚至抄袭，准确地粘贴code作为教程说，但它似乎并没有工作。我知道这个问题是MainActivity或DisplayMessageActivity，但我看不出有什么不对。我也有相​​同的文件夹MainActivity的DisplayMessageActivity。

I've been trying to get this to work, even copying and pasting the code exactly as the tutorial says it, but it doesn't seem to work. I know the issue is in MainActivity or DisplayMessageActivity, but I can't see what's wrong. I also have the DisplayMessageActivity in the same folder as MainActivity.

我收到以下错误。

DisplayMessageActivity
Gradle: error: cannot find symbol class SuppressLint
Gradle: error: package R does not exist
Gradle: error: cannot find symbol variable NavUtils

MainActivity
Gradle: error: cannot find symbol class DisplayMessageActivity

我一直在摆弄这个一段时间，并不能找出我做错了。任何帮助深表AP preciated。

I have been fiddling with this for awhile, and cannot figure out what I am doing wrong. Any help is much appreciated.

我有什么，

AndroidManifest.xml中

AndroidManifest.xml

~snip~
        <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>
~snip~

DisplayMessageActivity

DisplayMessageActivity

import android.app.Activity;
import android.os.Build;
import android.os.Bundle;
import android.view.MenuItem;



public class DisplayMessageActivity extends Activity {

    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);

        // Make sure we're running on Honeycomb or higher to use ActionBar APIs
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // Show the Up button in the action bar.
            getActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                NavUtils.navigateUpFromSameTask(this);
                return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

MainActivity

MainActivity

package com.example.myfirstapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
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);
    }

}

更新

Juned和彼得是正确的。它不工作的时候了，唯一原因是因为我搞砸了别的东西了。谢谢你们！

Juned and Peter were correct. The only reason it wasn't working right away was because I had messed something else up. Thanks guys!

推荐答案

我有同样的问题昨天（：
您需要在 DisplayMessageActivity

I had the same problem yesterday (: You need to add to your imports in DisplayMessageActivity

import android.annotation.SuppressLint;
import android.support.v4.app.NavUtils;

此外，您还需要添加到您的的build.gradle 文件中的依赖部分：

compile 'com.android.support:support-v4:18.0.+'

关于支持库可以红这里。

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