前言：开始学习安卓，费了好大劲，才完成今天的作业。
计算器的界面：
在UI那块采用的是网格布局，代码如下：
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent"
android:rowCount="6"
android:columnCount="4"> 设置计算器网格为 6行 4列
<TextView
android:id="@+id/textview1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_columnSpan="4"
android:layout_marginLeft="4px"
android:gravity="left"
android:text="0"
android:textSize="50dip"
/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_columnSpan="4"
android:text="清除"
android:textSize="26sp"
android:id="@+id/btn_clear"
android:layout_weight="1"
android:background="#ffffff"/>
<Button android:text="1" android:textSize="26sp"
android:id="@+id/btn_1"
android:layout_weight="1"
android:background="#FFFFCC"/>
<Button android:text="2" android:textSize="26sp"
android:id="@+id/btn_2"
android:layout_weight="1"
android:background="#FFFFCC"/>
<Button android:text="3" android:textSize="26sp" android:id="@+id/btn_3"
android:layout_weight="1"
android:background="#FFFFCC"
/>
<Button android:text="+" android:textSize="26sp"
android:id="@+id/btn_plus"
android:layout_weight="1"
android:background="#ffffff"/>
<Button android:text="4" android:textSize="26sp"
android:id="@+id/btn_4"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="5" android:textSize="26sp"
android:id="@+id/btn_5"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="6" android:textSize="26sp"
android:id="@+id/btn_6"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="-" android:textSize="26sp"
android:id="@+id/btn_minus"
android:layout_weight="1"
android:background="#ffffff"/>
<Button android:text="7" android:textSize="26sp"
android:id="@+id/btn_7"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="8" android:textSize="26sp"
android:id="@+id/btn_8"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="9" android:textSize="26sp"
android:id="@+id/btn_9"
android:layout_weight="1"
android:background="#ffffcc"/>
<Button android:text="*" android:textSize="26sp"
android:id="@+id/btn_multiply"
android:layout_weight="1"
android:background="#ffffff"/>
<Button android:text="." android:textSize="26sp"
android:id="@+id/btn_point"
android:layout_weight="1"
android:background="#FFFFFF"/>
<Button android:text="0" android:textSize="26sp"
android:id="@+id/btn_0"
android:background="#FFFFCC"
android:layout_weight="1"/>
<Button android:text="=" android:textSize="26sp"
android:id="@+id/btn_equal"
android:background="#99CCFF"
android:layout_weight="1"/>
<Button android:text="/" android:textSize="26sp"
android:id="@+id/btn_divide"
android:layout_weight="1"
android:background="#ffffff" />
</GridLayout>逻辑代码
1.在主体部分
思路：就是 按照按钮点击事件的套路，每当点击按钮时，就会执行onClick()的方法，我们在这个方法里加入个switch循环，每个case：是按钮的id,我们申请个private StringBuilder的字符串。每按一个按钮，只要满足要求，不是错误的输入，就调用append()方法。
下面是主体代码
package com.example.myapplication;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Button;
import java.util.Arrays;
public class MainActivity extends AppCompatActivity implements View.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; //小数点
Button btn_clear; //清除
Button btn_del; //删除
Button btn_plus;
Button btn_minus;
Button btn_multiply;
Button btn_divide;
Button btn_equal;
Button btn_left;
Button btn_right;
private TextView et_input;
private StringBuilder pending = new StringBuilder();
private void initView() {
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_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);
et_input=findViewById(R.id.textview1);
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_plus.setOnClickListener(this);
btn_equal.setOnClickListener(this);
btn_minus.setOnClickListener(this);
btn_multiply.setOnClickListener(this);
btn_divide.setOnClickListener(this);
btn_clear.setOnClickListener(this);
btn_divide.setOnClickListener(this);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
public void onClick(View v) {
int last = 0;
if(pending.length()!=0)
{
last = pending.codePointAt(pending.length()-1);
}
switch (v.getId()) {
case R.id.btn_0:
pending = pending.append("0");
et_input.setText(pending);
break;
case R.id.btn_1:
pending = pending.append("1");
et_input.setText(pending);
break;
case R.id.btn_2:
pending = pending.append("2");
et_input.setText(pending);
break;
case R.id.btn_3:
pending = pending.append("3");
et_input.setText(pending);
break;
case R.id.btn_4:
pending = pending.append("4");
et_input.setText(pending);
break;
case R.id.btn_5:
pending = pending.append("5");
et_input.setText(pending.toString());
break;
case R.id.btn_6:
pending = pending.append("6");
et_input.setText(pending);
break;
case R.id.btn_7:
pending = pending.append("7");
et_input.setText(pending);
break;
case R.id.btn_8:
pending = pending.append("8");
et_input.setText(pending);
break;
case R.id.btn_9:
pending = pending.append("9");
et_input.setText(pending);
break;
case R.id.btn_plus:
//if (last >= '0' && last <= '9' ) {
pending = pending.append("+");
// }
et_input.setText(pending);
break;
case R.id.btn_minus:
//if (last >= '0' && last <= '9') {
pending = pending.append("-");
// }
et_input.setText(pending);
break;
case R.id.btn_multiply:
// if (last >= '0' && last <= '9' ) {
pending = pending.append("*");
// }
et_input.setText(pending);
break;
case R.id.btn_divide:
// if (last >= '0' && last <= '9' ) {
pending = pending.append("/");
// }
et_input.setText(pending);
break;
case R.id.btn_point:
if (judje1()) {
pending = pending.append(".");
et_input.setText(pending);
}
break;
case R.id.btn_clear: //清空
pending = pending.delete(0, pending.length());
et_input.setText(pending);
break;
case R.id.btn_equal: // =等于
if ((pending.length() > 1)) {
InfixInToDuffix inf = new InfixInToDuffix();
String jieguo;
try {
String a = inf.toSuffix(pending);
jieguo = inf.dealEquation(a);
} catch (Exception ex) {
jieguo = "出错";
}
et_input.setText(pending + "=" + jieguo);
pending = pending.delete(0, pending.length());
if (Character.isDigit(jieguo.charAt(0))) {
pending = pending.append(jieguo);
}
}
break;
default:
break;
}
}
private boolean judje1() {
String a = "+-*/.";
int[] b = new int[a.length()];
int max;
for (int i = 0; i < a.length(); i++) {
String c = "" + a.charAt(i);
b[i] = pending.lastIndexOf(c);
}
Arrays.sort(b);
if (b[a.length() - 1] == -1) {
max = 0;
} else {
max = b[a.length() - 1];
}
if (pending.indexOf(".", max) == -1) {
return true;
} else {
return false;
}
}
private int judje2(){
int a=0,b=0;
for(int i = 0 ; i < pending.length() ;i++){
if(pending.charAt(i)=='(' ) {
a++;
}
if(pending.charAt(i)==')' ) {
b++;
}
}
if(a == b)
return 0;
if(a > b)
return 1;
return 2;
}
}
自己很菜，有很大的进步空间。