android简易计算器

activity_main.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.demo07.MainActivity"
android:background="#000000"
android:orientation="vertical"
>

<EditText
android:layout_width="fill_parent"
android:layout_height="60dip"
android:id="@+id/et_input"
android:background="@drawable/white_bg"
android:editable="false"
android:gravity="right|bottom"
/>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:orientation="horizontal"
android:gravity="center_horizontal"
>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="C"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_clear"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="DEL"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_del"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="/"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_divide"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="*"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_multiply"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:orientation="horizontal"
android:gravity="center_horizontal"
>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="7"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_7"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="8"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_8"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="9"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_9"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="-"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_minus"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:orientation="horizontal"
android:gravity="center_horizontal"
>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="4"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_4"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="5"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_5"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="6"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_6"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="+"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_plus"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
</LinearLayout>

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_marginTop="10dp"
android:gravity="center_horizontal"
>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="1"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_1 "
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="2"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_2"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="3"
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_3"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>

</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_marginTop="10dp"
>
<Button
android:layout_width="130dp"
android:layout_height="55dp"
android:text="0"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_0 "
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
<Button
android:layout_width="60dp"
android:layout_height="55dp"
android:text="."
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_point"
android:background="@drawable/white_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
</LinearLayout>
</LinearLayout>
<Button
android:layout_width="60dp"
android:layout_height="120dp"
android:text="="
android:layout_marginLeft="10dp"
android:textSize="20sp"
android:gravity="right|bottom"
android:id="@+id/btn_equal"
android:background="@drawable/orange_selector"
android:paddingRight="10dp"
android:paddingBottom="10dp"
/>
</LinearLayout>

</LinearLayout>

MainActivity.java:

package com.example.demo07;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends ActionBarActivity implements OnClickListener{

Button btn_0;
Button btn_1;
Button btn_2;
Button btn_3;
Button btn_4;
Button btn_5;
Button btn_6;
Button btn_7;
Button btn_8;
Button btn_9;
Button btn_point;
Button btn_clear;
Button btn_del;
Button btn_plus;
Button btn_minus;
Button btn_multiply;
Button btn_divide;
Button btn_equal;

EditText et_input;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_0=(Button) findViewById(R.id.btn_0);
btn_1=(Button) findViewById(R.id.btn_1);
btn_2=(Button) findViewById(R.id.btn_2);
btn_3=(Button) findViewById(R.id.btn_3);
btn_4=(Button) findViewById(R.id.btn_4);
btn_5=(Button) findViewById(R.id.btn_5);
btn_6=(Button) findViewById(R.id.btn_6);
btn_7=(Button) findViewById(R.id.btn_7);
btn_8=(Button) findViewById(R.id.btn_8);
btn_9=(Button) findViewById(R.id.btn_9);
btn_point=(Button) findViewById(R.id.btn_point);
btn_clear=(Button) findViewById(R.id.btn_clear);
btn_del=(Button) findViewById(R.id.btn_del);
btn_plus=(Button) findViewById(R.id.btn_plus);
btn_minus=(Button) findViewById(R.id.btn_minus);
btn_multiply=(Button) findViewById(R.id.btn_multiply);
btn_divide=(Button) findViewById(R.id.btn_divide);
btn_equal=(Button) findViewById(R.id.btn_equal);
//以上是实例化按钮
et_input=(EditText) findViewById(R.id.et_input);

btn_0.setOnClickListener(this);
btn_1.setOnClickListener(this);
btn_2.setOnClickListener(this);
btn_3.setOnClickListener(this);
btn_4.setOnClickListener(this);
btn_5.setOnClickListener(this);
btn_6.setOnClickListener(this);
btn_7.setOnClickListener(this);
btn_8.setOnClickListener(this);
btn_9.setOnClickListener(this);
btn_point.setOnClickListener(this);
btn_clear.setOnClickListener(this);
btn_del.setOnClickListener(this);
btn_plus.setOnClickListener(this);
btn_minus.setOnClickListener(this);
btn_multiply.setOnClickListener(this);
btn_divide.setOnClickListener(this);
btn_equal.setOnClickListener(this);
}

@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);
}

@Override
public void onClick(View v) {
String str=et_input.getText().toString();
switch(v.getId()){
case R.id.btn_0:
case R.id.btn_1:
case R.id.btn_2:
case R.id.btn_3:
case R.id.btn_4:
case R.id.btn_5:
case R.id.btn_6:
case R.id.btn_7:
case R.id.btn_8:
case R.id.btn_9:
case R.id.btn_point:
et_input.setText(str+((Button)v).getText());
break;
case R.id.btn_clear:
et_input.setText("");
break;
case R.id.btn_del:
if(str!=null&&!str.equals("")){
et_input.setText(str.substring(0,str.length()-1));
}
break;
case R.id.btn_plus:
case R.id.btn_minus:
case R.id.btn_multiply:
case R.id.btn_divide:
et_input.setText(str+" "+((Button)v).getText()+" ");
break;
case R.id.btn_equal:
getResult();
break;
}
}
private void getResult(){
String exp=et_input.getText().toString();
if(exp==null||exp.equals("")){
return;
}
if(!exp.contains(" ")){
return;
}
double result = 0;
String s1=exp.substring(0,exp.indexOf(" "));//运算符前面的字符
String op=exp.substring(exp.indexOf(" ")+1,exp.indexOf(" ")+2);//运算符
String s2=exp.substring(exp.indexOf(" ")+3);//运算符后面的字符
if(!s1.equals("")&&!s2.equals("")){
double d1=Double.parseDouble(s1);
double d2=Double.parseDouble(s2);
if(op.equals("+")){
result=d1+d2;
}else if(op.equals("-")){
result=d1-d2;
}else if(op.equals("*")){
result=d1*d2;
}else if(op.equals("/")){
if(d2==0){
result=0;
}else{
result=d1/d2;
}
}
if(!s1.contains(".")&&!s2.contains(".")){
int r=(int)result;
et_input.setText(r+"");
}else{
et_input.setText(result+"");
}
}else if(!s1.equals("")&&s2.equals("")){
et_input.setText(exp);
}else if(s1.equals("")&&!s2.equals("")){
double d2=Double.parseDouble(s2);
if(op.equals("+")){
result=0+d2;
}else if(op.equals("-")){
result=0-d2;
}else if(op.equals("*")){
result=0;
}else if(op.equals("/")){
result=0;
}
if(!s2.contains(".")){
int r=(int)result;
et_input.setText(r+"");
}else{
et_input.setText(result+"");
}
}else{
et_input.setText("");
}
}
}