首先在activity_main.xml加入一个EditText
通过xml的方式来沈成一个图像
在drawable中新建一个white_bg.xml文件，同时选择一个shape标签
corners设置圆角
<corners android:radius="5dp"/>
gradient设置颜色渐变
<gradient android:startColor="#FFFFFF" android:endColor="#00FFFF" />
stroke设置边框的宽度和颜色
<stroke android:color="#FFFFFF" android:width="1dp" />
将white_bg.xml部署到activity_main.xml的EditText的android:background属性中
android:background="@drawable/white_bg"
但是我们现在要做的计算器的EditText有特定的要求，所以注释掉white_bg.xml里面的gradient和stroke属性，添加solid属性。
<solid android:color="#FFFFFF"/>
需要对当前这个activity更改一下背景颜色为黑色并且没有标题栏，所以需要修改一下AndroidManifest.xml中activity的android:theme。
android:theme="@android:style/Theme.Black.NoTitleBar"
这里遇到了一个问题，就是在AndroidManifest.xml中修改了activity的android:theme属性后调试的时候程序出现闪退的情况，原来是因为我的MainActivity类继承自ActionBarActivity，将MainActivity类改为继承自FragmentActivity类即可解决这个问题。
但是EditText中的内容是不可以编辑的，并且文字需要显示在右下方，所以需要设置EditText的editable和gravity属性
android:editable="false"
android:gravity="right|bottom"
然后就是繁琐的进行Button的布局的管理，因为这里用的是LinearLayout，所以要特别注意layout_weight的使用
android:layout_weight的真实含义是:一旦View设置了该属性(假设有效的情况下)，那么该 View的宽度等于原有宽度(android:layout_width)加上剩余空间的占比！
Google官方推荐，当使用weight属性时，将width设为0dip即可，效果跟设成wrap_content是一样的。这样weight就可以理解为占比了。
修改按钮样式
修改按钮默认颜色白色，点击后颜色红色。
修改“=”键默认颜色绿色，点击后颜色蓝色。
在drawable/目录下新建集中不同颜色对应的xml文件（并在创建时选择shape）
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" > <corners android:radius="5dp"/> <solid android:color="#FFFFFF"/> </shape>
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" > <corners android:radius="5dp"/> <solid android:color="#FFFF00"/> </shape>
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" > <corners android:radius="5dp"/> <solid android:color="#00FF00"/> </shape>
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" > <corners android:radius="5dp"/> <solid android:color="#0000FF"/> </shape>
在drawable/目录下再创建两个样式xml文件（并在创建时选择selector），一个样式要求在没有按下时显示白色，按下时显示绿色。
<item android:drawable="@drawable/white_bg" android:state_pressed="false" />
<item android:drawable="@drawable/green_bg" android:state_pressed="true" />
另一个样式要求在没有按下时显示黄色，按下时显示蓝色。
<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android" > <item android:drawable="@drawable/white_bg" android:state_pressed="false" /> <item android:drawable="@drawable/green_bg" android:state_pressed="true" /> </selector>
<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android" > <item android:drawable="@drawable/yellow_bg" android:state_pressed="false" /> <item android:drawable="@drawable/blue_bg" android:state_pressed="true" /> </selector>
最后给每一个button添加“android:background="@drawable/white_selector"”实现样式的转换。
因为文字太靠边了，需设置一下内边距：android:paddingRight和android:padding:bottom。
实例化对象
button_0 = (Button) findViewById(R.id.btn_0); button_1 = (Button) findViewById(R.id.btn_1); button_2 = (Button) findViewById(R.id.btn_2); button_3 = (Button) findViewById(R.id.btn_3); button_4 = (Button) findViewById(R.id.btn_4); button_5 = (Button) findViewById(R.id.btn_5); button_6 = (Button) findViewById(R.id.btn_6); button_7 = (Button) findViewById(R.id.btn_7); button_8 = (Button) findViewById(R.id.btn_8); button_9 = (Button) findViewById(R.id.btn_9); button_divide = (Button) findViewById(R.id.btn_divide); button_multiply = (Button) findViewById(R.id.btn_multiply); button_minus = (Button) findViewById(R.id.btn_minus); button_plus = (Button) findViewById(R.id.btn_plus); button_clear = (Button) findViewById(R.id.btn_clear); button_delete = (Button) findViewById(R.id.btn_delete); button_dot = (Button) findViewById(R.id.btn_dot); button_equals = (Button) findViewById(R.id.btn_equals);
然后就是业务逻辑的实现
@Override public void onClick(View view) { // TODO Auto-generated method stub String s = editText.getText().toString(); if (view == button_clear) { s = ""; } else if (view == button_delete) { s = s.length() == 0 ? s : s.substring(0, s.length()-1); } else if (view == button_equals) { int index = -1; for (String ss : new String[] { "x", "/", "+", "-" }) { int tmpIndex = s.indexOf(ss); if (tmpIndex != -1) { index = tmpIndex; break; } } if (index != -1) { String outputFormat = "%.2f"; try { double x = Double.parseDouble(s.substring(0, index)); double y = Double.parseDouble(s.substring(index+1)); switch (s.charAt(index)) { case 'x': s = String.format(outputFormat, x * y); break; case '/': s = String.format(outputFormat, x / y); break; case '+': s = String.format(outputFormat, x + y); break; case '-': s = String.format(outputFormat, x - y); break; default: break; } } catch (Exception e) { s = "我只会算两个数的运算，这题我不会"; } } } else { s += ((Button) view).getText() + ""; } editText.setText(s); }
package com.example.calculator; import android.os.Bundle; import android.support.v4.app.FragmentActivity; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; public class MainActivity extends FragmentActivity implements OnClickListener { private Button button_0; private Button button_1; private Button button_2; private Button button_3; private Button button_4; private Button button_5; private Button button_6; private Button button_7; private Button button_8; private Button button_9; private Button button_clear; private Button button_delete; private Button button_divide; private Button button_multiply; private Button button_minus; private Button button_plus; private Button button_dot; private Button button_equals; private EditText editText; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button_0 = (Button) findViewById(R.id.btn_0); button_1 = (Button) findViewById(R.id.btn_1); button_2 = (Button) findViewById(R.id.btn_2); button_3 = (Button) findViewById(R.id.btn_3); button_4 = (Button) findViewById(R.id.btn_4); button_5 = (Button) findViewById(R.id.btn_5); button_6 = (Button) findViewById(R.id.btn_6); button_7 = (Button) findViewById(R.id.btn_7); button_8 = (Button) findViewById(R.id.btn_8); button_9 = (Button) findViewById(R.id.btn_9); button_divide = (Button) findViewById(R.id.btn_divide); button_multiply = (Button) findViewById(R.id.btn_multiply); button_minus = (Button) findViewById(R.id.btn_minus); button_plus = (Button) findViewById(R.id.btn_plus); button_clear = (Button) findViewById(R.id.btn_clear); button_delete = (Button) findViewById(R.id.btn_delete); button_dot = (Button) findViewById(R.id.btn_dot); button_equals = (Button) findViewById(R.id.btn_equals); editText = (EditText) findViewById(R.id.editText1); button_0.setOnClickListener(this); button_1.setOnClickListener(this); button_2.setOnClickListener(this); button_3.setOnClickListener(this); button_4.setOnClickListener(this); button_5.setOnClickListener(this); button_6.setOnClickListener(this); button_7.setOnClickListener(this); button_8.setOnClickListener(this); button_9.setOnClickListener(this); button_divide.setOnClickListener(this); button_plus.setOnClickListener(this); button_minus.setOnClickListener(this); button_multiply.setOnClickListener(this); button_clear.setOnClickListener(this); button_delete.setOnClickListener(this); button_dot.setOnClickListener(this); button_equals.setOnClickListener(this); } @Override public void onClick(View view) { // TODO Auto-generated method stub String s = editText.getText().toString(); if (view == button_clear) { s = ""; } else if (view == button_delete) { s = s.length() == 0 ? s : s.substring(0, s.length()-1); } else if (view == button_equals) { int index = -1; for (String ss : new String[] { "x", "/", "+", "-" }) { int tmpIndex = s.indexOf(ss); if (tmpIndex != -1) { index = tmpIndex; break; } } if (index != -1) { String outputFormat = "%.2f"; try { double x = Double.parseDouble(s.substring(0, index)); double y = Double.parseDouble(s.substring(index+1)); switch (s.charAt(index)) { case 'x': s = String.format(outputFormat, x * y); break; case '/': s = String.format(outputFormat, x / y); break; case '+': s = String.format(outputFormat, x + y); break; case '-': s = String.format(outputFormat, x - y); break; default: break; } } catch (Exception e) { s = "我只会算两个数的运算，这题我不会"; } } } else { s += ((Button) view).getText() + ""; } editText.setText(s); } }
<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" android:orientation="vertical" > <EditText android:id="@+id/editText1" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" android:background="@drawable/white_bg" android:editable="false" android:gravity="right|bottom" android:textSize="40sp" android:layout_margin="10dp" > </EditText> <LinearLayout android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" android:orientation="horizontal" android:layout_gravity="center_horizontal" > <Button android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="CLS" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="DEL" android:textSize="20sp" android:gravity="right|bottom" android:id="@+id/btn_delete" android:background="@drawable/white_selector" android:paddingRight="10dp" android:paddingBottom="10dp" /> <Button android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="/" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="x" 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="0dp" android:layout_weight="1" android:orientation="horizontal" android:layout_gravity="center_horizontal" > <Button android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="1" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="8" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="9" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="-" 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="0dp" android:layout_weight="1" android:orientation="horizontal" android:layout_gravity="center_horizontal" > <Button android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="1" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="5" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="6" 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="match_parent" android:layout_height="match_parent" android:layout_weight="1" android:text="+" 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="0dp" android:layout_weight="2" android:layout_gravity="center_vertical" android:orientation="horizontal" > <LinearLayout android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="3" android:orientation="vertical" > <LinearLayout android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" android:layout_gravity="center_vertical" android:orientation="horizontal" > <Button android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="1" 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="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:text="2" 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="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:text="3" 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="fill_parent" android:layout_height="0dp" android:layout_weight="1" android:layout_gravity="center_vertical" android:orientation="horizontal" > <Button android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="2" 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="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:text="." android:textSize="20sp" android:gravity="right|bottom" android:id="@+id/btn_dot" android:background="@drawable/white_selector" android:paddingRight="10dp" android:paddingBottom="10dp" /> </LinearLayout> </LinearLayout> <Button android:layout_width="0dp" android:layout_height="fill_parent" android:layout_weight="1" android:text="=" android:textSize="20sp" android:gravity="right|bottom" android:id="@+id/btn_equals" android:background="@drawable/yellow_selector" android:paddingRight="10dp" android:paddingBottom="10dp" /> </LinearLayout> </LinearLayout>
项目代码：https://github.com/moonlightpoet/Calculator
apk下载：https://raw.githubusercontent.com/moonlightpoet/Calculator/master/bin/resources.ap_
效果：
