I am learning Android so I want to keep things simple.
I have to add two numbers and display the result in a single editbox. To add with the second number you have store the first number in a variable. Then later add using this variable with the second number in the edit text.
If you look at the xml and Java Code below you will have a better idea. Thanks in advance.
<?xml version="1.0" encoding="utf-8" ?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent">
<RelativeLayout android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/relativeLayout1" android:layout_gravity="bottom">
<Button android:text="1" android:padding="20px" android:layout_marginTop="38dp" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/button1" android:layout_alignParentLeft="true"></Button>
<Button android:text="2" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignTop="@+id/button1" android:id="@+id/button2" android:layout_toRightOf="@+id/button1"></Button>
<Button android:text="3" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignTop="@+id/button2" android:id="@+id/button3" android:layout_toRightOf="@+id/button2"></Button>
<Button android:text="4" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignTop="@+id/button3" android:id="@+id/button4" android:layout_toRightOf="@+id/button3"></Button>
<Button android:text="5" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/button5" android:layout_below="@+id/button1" android:layout_alignParentLeft="true"></Button>
<Button android:text="6" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignTop="@+id/button5" android:layout_alignLeft="@+id/button2" android:id="@+id/button6"></Button>
<Button android:text="7" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignTop="@+id/button6" android:layout_alignLeft="@+id/button3" android:id="@+id/button7"></Button>
<Button android:text="8" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignLeft="@+id/button4" android:id="@+id/button8" android:layout_below="@+id/button4"></Button>
<Button android:text="=" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignLeft="@+id/button11" android:id="@+id/button15" android:layout_below="@+id/button12"></Button>
<Button android:text="clear" android:layout_alignRight="@+id/button8" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_alignBottom="@+id/button15" android:layout_alignLeft="@+id/button12" android:id="@+id/button16" android:layout_below="@+id/button12"></Button>
<Button android:text="-" android:layout_alignRight="@+id/button8" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/button12" android:layout_below="@+id/button8"></Button>
<Button android:text="+" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_above="@+id/button15" android:layout_toLeftOf="@+id/button16" android:id="@+id/button11"></Button>
<Button android:text="/" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_toLeftOf="@+id/button7" android:layout_alignTop="@+id/button15" android:id="@+id/button14"></Button>
<Button android:text="0" android:layout_alignRight="@+id/button14" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_above="@+id/button14" android:id="@+id/button0"></Button>
<Button android:text="*" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_toLeftOf="@+id/button10" android:layout_alignTop="@+id/button14" android:id="@+id/button13"></Button>
<Button android:text="9" android:padding="20px" android:layout_height="wrap_content" android:layout_width="wrap_content" android:layout_above="@+id/button13" android:id="@+id/button9" android:layout_alignParentLeft="true"></Button>
<EditText android:id="@+id/editText1" android:layout_height="wrap_content" android:layout_width="fill_parent" android:layout_below="@+id/button14"></EditText>
</RelativeLayout>
</LinearLayout>
Java code
package calci.tor;
import android.R.integer;
import android.R.string;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class CalculatorActivity extends Activity {
/** Called when the activity is first created. */
public EditText display;
TextView edt;
Integer c;
String a="",b;
//int d=0;
Button b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
edt=(EditText)findViewById(R.id.editText1);
b1=(Button)findViewById(R.id.button1);
b2=(Button)findViewById(R.id.button2);
b3=(Button)findViewById(R.id.button3);
b4=(Button)findViewById(R.id.button4);
b5=(Button)findViewById(R.id.button5);
b6=(Button)findViewById(R.id.button6);
b7=(Button)findViewById(R.id.button7);
b8=(Button)findViewById(R.id.button8);
b9=(Button)findViewById(R.id.button9);
b10=(Button)findViewById(R.id.button0);
b11=(Button)findViewById(R.id.button11);
b12=(Button)findViewById(R.id.button12);
b13=(Button)findViewById(R.id.button13);
b14=(Button)findViewById(R.id.button14);
b15=(Button)findViewById(R.id.button15);
b16=(Button)findViewById(R.id.button16);
b1.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "1");
}
});
b2.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "2");
}
});
b3.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
edt.setText(a+ "3");
}
});
b4.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
edt.setText(a+ "4");
}
});
b5.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
edt.setText(a+ "5");
}
});
b6.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "6");
}
});
b7.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
edt.setText(a+ "7");
}
});
b8.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "8");
}
});
b9.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "9");
}
});
b10.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
edt.setText(a+ "0");
}
});
b11.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
String aa;
aa=a; //To Store the first number displayed in edit text to aa
edt.setText("+");
edt.setText("");
//d=1;
c=Integer.parseInt(aa)+Integer.parseInt(a);
}
});
b12.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
edt.setText("-");
}
});
b13.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
edt.setText("*");
}
});
b14.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
edt.setText("/");
}
});
b15.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
//int c=Integer.parseInt(a)+Integer.parseInt(b);
//edt.setText(c);
display.setText(c);
}
});
b16.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
edt.setText("");
}
});
}
}
If your calculator has no ( / ) and you don't allow entering negative numbers then a simple algorithm to calculate a constant input of numbers and operations could work like this:
You have one variable which represents the result (that you probably want to display each step in the EditText) and one to buffer unfinished results
if the operation is * or /:
apply it to the buffer
if the operation is + or -:
add buffer to result, overwrite buffer with new input
2 * 4 + 3 + 5 * 2 * 3 - 1 + 2
initially final result = 0, buffer = 1
2-> result = 0, buffer = 2 (careful here, I interpreted the initial step as*2)* 4-> result = 0, buffer = (2*4) = 8+ 3-> result = (0+8) = 8, buffer = 3+ 5-> result = (8+3) = 11, buffer = 5* 2-> result = 11, buffer = (5*2) = 10* 3-> result = 11, buffer = (10*3) = 30- 1-> result = (11+30) = 41, buffer = -1+ 2-> result = (41-1) = 40, buffer = 2
-> finally (e.g. when pressing =) add both together: Answer = 42
//Below having correct programming .
//I did some changes in your code.This code was working nicely try this.
//`import android.os.Bundle;
import android.R.integer;
import android.R.string;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
public EditText display;
TextView edt;
Integer c,d,r,b;
String a="0",aa;
Button b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edt=(EditText)findViewById(R.id.editText1);
b1=(Button)findViewById(R.id.button1);
b2=(Button)findViewById(R.id.button2);
b3=(Button)findViewById(R.id.button3);
b4=(Button)findViewById(R.id.button4);
b5=(Button)findViewById(R.id.button5);
b6=(Button)findViewById(R.id.button6);
b7=(Button)findViewById(R.id.button7);
b8=(Button)findViewById(R.id.button8);
b9=(Button)findViewById(R.id.button9);
b10=(Button)findViewById(R.id.button0);
b11=(Button)findViewById(R.id.button11);
b12=(Button)findViewById(R.id.button12);
b13=(Button)findViewById(R.id.button13);
b14=(Button)findViewById(R.id.button14);
b15=(Button)findViewById(R.id.button15);
b16=(Button)findViewById(R.id.button16);
b1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"1";
edt.setText(a);
}
});
b2.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"2";
edt.setText(a);
}
});
b3.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
a=a+"3";
edt.setText(a);
}
});
b4.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
a=a+"4";
edt.setText(a);
}
});
b5.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
a=a+"5";
edt.setText(a);
}
});
b6.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"6";
edt.setText(a);
}
});
b7.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
a=edt.getText().toString();
a=a+"7";
edt.setText(a);
}
});
b8.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"8";
edt.setText(a);
}
});
b9.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"9";
edt.setText(a);
}
});
b10.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
a=edt.getText().toString();
a=a+"0";
edt.setText(a);
}
});
b11.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
aa=a;
b=1;
a="";
edt.setText("+");
edt.setText("");
}
});
b12.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
aa=a;
b=2;
a="";
edt.setText("-");
edt.setText("");
}
});
b13.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
aa=a;
b=3;
a="";
edt.setText("*");
edt.setText("");
}
});
b14.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
aa=a;
b=4;
a="";
edt.setText("/");
edt.setText("");
}
});
b15.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
if(b==1){
c=Integer.parseInt(aa);
d=Integer.parseInt(a);
r=c+d;
}
else
if(b==4){
c=Integer.parseInt(aa);
d=Integer.parseInt(a);
r=c/d;
}else
if(b==2){
c=Integer.parseInt(aa);
d=Integer.parseInt(a);
r=c-d;
}
else
if(b==3){
c=Integer.parseInt(aa);
d=Integer.parseInt(a);
r=c*d;
}
Toast.makeText(MainActivity.this, "Result is::"+r, 10000).show();
c=0;
b=0;
d=0;
a="";
aa="";
edt.setText("");
}
});
b16.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
// TODO Auto-generated method stub
edt.setText("");
}
});
}`
BVR
Your above code was almost correct but small logic was missed in that programming . After clicking button it will store string values into "a" its ok . After that we click on operator symbol "a" will store into "aa" variable.
example:
a="4";
aa=a;//aa="4"
//After you do like this below way .
c=Integer.parseInt(aa)+Integer.parseInt(a);
//In the above line c (storing integer values) = 4+4;
//a having "4" and aa="4".
来源：https://stackoverflow.com/questions/10280263/how-do-a-simple-calculator-in-android-how-to-do-it-using-buttons-and-single-edi