尝试制作斐波那契 Android 应用程序

Question

我是一名新手 android 应用程序开发人员，我想通过制作一个应用程序来挑战自己，该应用程序接受用户输入、转换为整数并输入斐波那契公式。结果应显示所有斐波那契数，将公式循环用户给定的次数。

到目前为止，我认为我已将问题隔离到 ContentViewer，但再次感谢任何帮助。顺便说一句，如果有帮助，我正在使用 Eclipse Juno

MainActivity.java

package com.example.myfirstapp;

//importing the API for this app
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;


public class MainActivity extends Activity {
//I based this on the first app I learnt (as I haven't done much app development so far)
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

//this method creates a default layout when a "new app" is started
@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;
}

@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);
}

//This method sends the information of the user input to a second activity screen,
//through the use of intents
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
    // Do something in response to button
    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);
}
}

输入进入名为 DisplayMessageActivity.java 的第二个活动屏幕

package com.example.myfirstapp;

//import all the relevant API for this app
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.TextView;

//main class extending Activity superclass
public class DisplayMessageActivity extends Activity {

//This main method is where the fibonacci formula is worked out the result is shown
//For some reason, the ContentViewer is not working for me.
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display_message);
    Intent intent = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

    int messages = Integer.parseInt(message);
    int[] fib = new int[messages  + 1];
    fib[0] = 1;
    fib[1] = 1;

    for (int i=2; i <= messages; i++)
       {
        fib[i] = fib[i-1] + fib[i-2];
       }

    // Create the text view
    TextView textView = new TextView(this);
    textView.setTextSize(60);
    StringBuilder builder = new StringBuilder();
    for (int j : fib)
    {
        builder.append(j);
    }
    String text = builder.toString();
    textView.setText(text);
    }


    // 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);
}
}

我得到的错误信息是

DisplayMessageActivity.java
activity_display_message cannot be resolved or is not a field (Line 18)
Return type for this method is missing (Line 46)
Syntax error on token "textView", VariableDeclaratorId expected after this token (Line 46)
textView cannot be resolved to a type (Line 46)

希望这是足够的信息。有趣的是，我按照 developer.android.com 教程制作了第一个应用，并进行了一些调整以使其符合斐波那契。

非常感谢。

编辑：感谢您的快速回复。我检查并没有activity_display_message.xml，所以我只是创建了它并从activity_main.xml 中复制了所有内容。我还将 textviewer 移动到 onCreate 方法内部。现在我正在整理一切，谢谢你让我从另一个不眠之夜中解脱出来。

Answer 1

您显然没有创建 activity_display_message（或者另一个不太可能的可能性是您指的是不在 layouts 文件夹中的文件）。您正在将视图设置为不存在的文件。同样从代码中，我可以看到您将 setContentView() 放在某个随机位置。它应该在方法的主体内（在您的情况下最好在 onCreate() 内）。

Answer 2

setContentView(textView); 在方法之外，我的意思是它是一个全局的，确保它在 onCreate 方法中