java - MyFirstApp 教程 Android Studio 2.3 Build Errors re EXTRA_MESSAGE 和 textview

Question

MyFirstApp 教程 Android Studio 在应用程序内接收消息时出现问题。

构建错误如下:

Error:(17, 60) error: cannot find symbol variable EXTRA_MESSAGE
Error:(20, 57) error: cannot find symbol variable textView

我的消息接收器代码如下所示:

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display_message);

    // Get the Intent that started this activity and extract the 
       string
    Intent intent = getIntent();
    String message = 
      intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

    // Capture the layout's TextView and set the string as its text
    TextView textView = (TextView) findViewById(R.id.textView);
    textView.setText(message);
}

注意:EXTRA_MESSAGE 和 textview 为红色。

发送代码如下所示:

    public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    /** Called when the user taps the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, 
             DisplayMessageActivity.class);
    EditText editText = (EditText) findViewById(R.id.editText);
    String message = editText.getText().toString();
    intent.putExtra(EXTRA_MESSAGE, message);
    startActivity(intent);
    }
}

注意:在我上面的代码中的这一行:

public void sendMessage(View view) 

第一个“View”有一条浅水平线穿过它，我收到一条错误消息，例如 sendMessage(View view) is depreciated。

我认为问题可能与

public void sendMessage(View view) 

及其折旧代码消息...(？)

出现问题的教程的链接:

https://developer.android.com/training/basics/firstapp/starting-activity.html

Answer 1

检查您的 MainActivity.java 文件中的这一行，您的代码中是否缺少。

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