Android for loop不像java一樣工作

Question

這是我的Android Java代碼。我不明白爲什麼它不像Java代碼那樣工作。它是素數的例子。假設我們想要找到1到5之間的素數。所以我期待結果2,3,5。但我只有結果5。在我的Java代碼中，我得到了正確的結果。我的意思是2,3,5。請幫我弄清楚這個問題。

@Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_prime); 
     Button btn = (Button)this.findViewById(R.id.click_btn); 
     btn.setOnClickListener(new Button.OnClickListener(){ 
      @Override 
      public void onClick(View v) { 
       TextView resp = (TextView) findViewById(R.id.response); 
       // Get number from EditText 
       EditText startnumber = (EditText) findViewById(R.id.first_number); 
       EditText endnumber = (EditText) findViewById(R.id.second_number); 

       // get the Strings from the EditTexts 
       String number1 = startnumber.getText().toString(); 
       String number2 = endnumber.getText().toString(); 

       // Convert Strings to int 
       int x1number = Integer.parseInt(number1); 
       int x2number = Integer.parseInt(number2); 

       String str = "List of prime numbers between " + x1number + " and " + x1number + ": "; 
       //resp.setText(str); 
       for(int i = x1number; i <= x2number; i++){ 
        if(isPrime(i)){ 
         resp.setText(str + String.valueOf(i)); 
        } 
       } 

      } 
     }); 
    } 
    public static boolean isPrime(int n){ 
     if(n <= 1) { 
      return false; 
     } 
     for(int i = 2; i <= n/2; i++) { 
      if (n % i == 0) { 
       return false; 
      } 
     } 
     return true; 
    } 

這是我的Java代碼。

/* 
* To change this license header, choose License Headers in Project Properties. 
* To change this template file, choose Tools | Templates 
* and open the template in the editor. 
*/ 
package primenumberstwo; 
import java.util.Scanner; 

/** 
* 
* @author vubon 
*/ 
public class PrimeNumberstwo { 

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String[] args) { 
     // TODO code application logic here 
     Scanner s = new Scanner(System.in); 
     System.out.println("Enter your first number: "); 
     int start = s.nextInt(); 
     System.out.println("Enter your second number: "); 
     int end = s.nextInt(); 
     System.out.println("List of prime numbers bettween " + start + " and " + end); 
     for(int i = start; i <= end; i++){ 
      if(isPrime(i)){ 
       System.out.println(String.valueOf(i)); 

      } 
     } 
    } 

    public static boolean isPrime(int n){ 
     if(n <= 1) { 
      return false; 
     } 
     for(int i = 2; i <= n/2; i++) { 
      if (n % i == 0) { 
       return false; 
      } 
     } 
     return true; 
    } 
} 

Answer 1

問題是不是在Android的SDK。你的邏輯錯了。

  String str = "List of prime numbers between " + x1number + " and " + x1number + ": "; 
      //resp.setText(str); 
      for(int i = x1number; i <= x2number; i++){ 
       if(isPrime(i)){ 
        resp.setText(str += String.valueOf(i));//see change here 
       } 
      } 

Answer 2

嘗試用：

str = str + String.valueOf(i); 
resp.setText(str); 

Answer 3

要覆蓋TextView resp在每次迭代的內容就是爲什麼你看到的只是文件最後一個。

嘗試這樣：

String str = "List of prime numbers between " + x1number + " and " + x1number + ": "; 
    String result = ""; 
    for(int i = x1number; i <= x2number; i++){ 
     if(isPrime(i)){ 
      result = result + " " + i; 
     } 
    } 
    if(!("".equalsIgnoreCase(result.trim()))){ 
     resp.setText(str + result); 
    } 

Answer 4

你發現所有的素數，但與去年循環迭代最後一個重寫。

嘗試一下;

String str = "List of prime numbers between " + x1number + " and " + x1number + ": "; 
    resp.setText(str); 
    for(int i = x1number; i <= x2number; i++){ 
     if(isPrime(i)){ 
      resp.setText(resp.getText() + String.valueOf(i)); 
     } 
    }