java – Android First App教程问题

我一直试图让它工作,甚至完全按照教程的说法复制和粘贴代码,但它似乎不起作用.我知道问题出在MainActivity或DisplayMessageActivity中,但我看不出有什么问题.我还将DisplayMessageActivity与MainActivity放在同一个文件夹中.

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

我已经习惯了一段时间,并且无法弄清楚我做错了什么.任何帮助深表感谢.

是)我有的,

AndroidManifest.xml中

~snip~


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);
    }
}

主要活动

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);
    }

}

UPDATE
Juned和Peter是对的.它不能立即工作的唯一原因是因为我弄乱了其他东西.多谢你们！


最佳答案
昨天我遇到了同样的问题(：
您需要在DisplayMessageActivity中添加导入

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

此外,您需要添加到依赖项部分中的build.gradle文件：

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

关于支持库您可以红色here.

java – Android First App教程问题

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