Question

Basically I’m trying to replace “?” by pressing any keypad button. For example, if the question shows as “0+1=?”, I want “1” to replace the question mark.

My code for Java is:

package org.example.question;

import java.util.Random;



import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class QuestionActivity extends Activity implements View.OnClickListener {
    /** Called when the activity is first created. */

    //variable for different questions
    int fnum0, snum0,fnum1, snum1,fnum2, snum2,fnum3, snum3,
    fnum4, snum4,fnum5, snum5,fnum6, snum6,fnum7, snum7,
    fnum8, snum8,fnum9, snum9, answer;


    //variable and type declaration for buttons and text
Button keyOne;
Button keyTwo;
Button keyThree;
Button keyFour;
Button keyFive;
Button keySix;
Button keySeven;
Button keyEight;
Button keyNine;
Button keyDel;
Button keyZero;
Button keyHash;
Button keySubtract;
TextView display;
TextView display1;
TextView answer0;
int question=0;
boolean q;




    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);  

        //display text on screen

        display1 = (TextView)findViewById(R.id.Guess);
        display = (TextView)findViewById(R.id.Title);
        answer0 = (TextView)findViewById(R.id.Answer);

        ///Code for correct and incorrect

        //assigning names to each keypad
        keyOne= (Button) findViewById(R.id.keypad_1);
        keyTwo= (Button) findViewById(R.id.keypad_2);
        keyThree= (Button) findViewById(R.id.keypad_3);
        keyFour= (Button) findViewById(R.id.keypad_4);
        keyFive = (Button) findViewById(R.id.keypad_5);
        keySix= (Button) findViewById(R.id.keypad_6);
        keySeven = (Button) findViewById(R.id.keypad_7);
        keyEight = (Button) findViewById(R.id.keypad_8);
        keyNine = (Button) findViewById(R.id.keypad_9);
        keyZero = (Button) findViewById(R.id.keypad_0);
        keySubtract = (Button) findViewById(R.id.keypad_subtract);
        keyHash = (Button) findViewById(R.id.keypad_hash);
        keyDel = (Button) findViewById(R.id.delete);

        //setting button to produce an event when each button is pressed
        keyOne.setOnClickListener(this);     keyTwo.setOnClickListener(this);     keyThree.setOnClickListener(this); 
        keyFour.setOnClickListener(this);    keyFive.setOnClickListener(this);     keySix.setOnClickListener(this);     
        keySeven.setOnClickListener(this);    keyEight.setOnClickListener(this);  keyNine.setOnClickListener(this);    
        keySubtract.setOnClickListener(this);   keyHash.setOnClickListener(this);  keyDel.setOnClickListener(this);

}

    public void onClick(View arg0) {

        switch(arg0.getId()){   
        case R.id.keypad_hash:

            //Generates random numbers
            fnum0 = (int) ((double) ((Math.random() * 10))); 
            snum0 = (int) ((double) ((Math.random() * 10))); 
            String str = ""; 

            //genrates random number between 0 to 9
            int operation = (int) ((double) ((Math.random() * 10)));
            Log.d("debug", "operation value: " + operation);


            if(operation == 0)  
               str = fnum0+  "+"  +  snum0+  "="+ "??"; 

            else if(operation == 1) 
               str = fnum0 +  "-"  +  snum0+  "="+ "??"; 
            else if(operation == 2)  
               str = fnum0 +  "*"  +  snum0+  "="+ "??" ; 
            else  
               str = fnum0 +  "/"  +  snum0+  "="+ "??"; 
            display.setText(str); 
            break;

        case R.id.keypad_1:
            if(q="?" )
            {
                display.setText("1");
            }
            else
            {
                return;
            }

            break;

        case R.id.keypad_2:
            display.setText("2");
            break;

        case R.id.keypad_3:
            display.setText("3");
            break;

        case R.id.keypad_4:
            display.setText("4");
            break;

        case R.id.keypad_5:
            display.setText("5");
            break;

        case R.id.keypad_6:
            display.setText("6");
            break;

        case R.id.keypad_7:
            display.setText("7");
            break;

        case R.id.keypad_8:
            display.setText("8");
            break;

        case R.id.keypad_9:
            display.setText("9");
            break;

        case R.id.delete:
            display.setText("");
            break;

        case R.id.keypad_0:
            display.setText("0");
            break;

        case R.id.keypad_subtract:
            display.setText("-");
            break;   
        }   
     }
    public void requestFocus() {
        // TODO Auto-generated method stub

    }
}

However at the moment its displaying the question “0+1=” but when I press one it removes the question and display “1” on its own on the screen.

UPDATE for ERROR

case R.id.keypad_1:

public void onClick(View arg0) {
            String str=null;
        switch(arg0.getId()){   
        case R.id.keypad_hash:

            //Generates random numbers
            fnum0 = (int) ((double) ((Math.random() * 10))); 
            snum0 = (int) ((double) ((Math.random() * 10))); 


            //genrates random number between 0 to 9
            int operation = (int) ((double) ((Math.random() * 10)));
            Log.d("debug", "operation value: " + operation);


            if(operation == 0)  
               str = fnum0+  "+"  +  snum0+  "="+ "??"; 

            else if(operation == 1) 
               str = fnum0 +  "-"  +  snum0+  "="+ "??"; 
            else if(operation == 2)  
               str = fnum0 +  "*"  +  snum0+  "="+ "??" ; 
            else  
               str = fnum0 +  "/"  +  snum0+  "="+ "??"; 
            display.setText(str); 
            break;

        case R.id.keypad_1:
            if(str.equals("??"))
            {
                String str1 = display.getText().toString(); 
                display.setText(str1.replace("??", "1")); 
            }
            else
            {
                return;
            }

            break;

The application is crashing now…..

Answer 1

Instead of

display.setText("1");

write

display.setText(str.replace("??", "1"));

The replace method indicates that replace the “??” text on the str String with the “1” text, so searches the “??” text and replace it by the “1” text on this String.

To compare Strings should use equals method, for example instead of str==?, write:

str.equals("?");

Replace the code of the keypad_1 case for this one (deleting the if):

case R.id.keypad_1:
      String str1 = display.getText().toString(); 
      display.setText(str1.replace("??", "1")); 
break;

Hope it helps.