android 计算器

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
    <LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <TextView
    android:id="@+id/tvResult"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:height="50dp"
    android:text=""
        android:hint="结果"
    />
    </LinearLayout>
<LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <Button
    android:id="@+id/btnBackspace"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="150dp"
    android:layout_marginLeft="10dp"
    android:text="退格"/>
    <Button
    android:id="@+id/btnCE"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="150dp"
    android:text="清除"/>
    </LinearLayout>
<LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <Button
    android:id="@+id/btn7"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="10dp"
    android:width="75dp"
    android:text="7"/>
    <Button
    android:id="@+id/btn8"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="8"/>
    <Button
    android:id="@+id/btn9"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="9"/>
    <Button
    android:id="@+id/btnDiv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="/"/>
    </LinearLayout>
<LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <Button
    android:id="@+id/btn4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="10dp"
    android:width="75dp"
    android:text="4"/>
    <Button
    android:id="@+id/btn5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="5"/>
    <Button
    android:id="@+id/btn6"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="6"/>
    <Button
    android:id="@+id/btnMul"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="*"/>
    </LinearLayout>
<LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <Button
    android:id="@+id/btn1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="10dp"
    android:width="75dp"
    android:text="1"/>
    <Button
    android:id="@+id/btn2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="2"/>
    <Button
    android:id="@+id/btn3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="3"/>
    <Button
    android:id="@+id/btnAdd"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="+"/>
    </LinearLayout>
<LinearLayout android:layout_width="fill_parent"
    android:layout_height="wrap_content">
    <Button
    android:id="@+id/btn0"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="10dp"
    android:width="75dp"
    android:text="0"/>
    <Button
    android:id="@+id/btnC"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="C"/>
    <Button
    android:id="@+id/btnEqu"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="="/>
    <Button
    android:id="@+id/btnSub"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:width="75dp"
    android:text="-"/>
    </LinearLayout>
    </LinearLayout>

package com.example.yanlei.yl2;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View.OnClickListener;

public class MainActivity extends AppCompatActivity implements OnClickListener  {

    //声明一些控件
    Button btn0 = null;
    Button btn1 = null;
    Button btn2 = null;
    Button btn3 = null;
    Button btn4 = null;
    Button btn5 = null;
    Button btn6 = null;
    Button btn7 = null;
    Button btn8 = null;
    Button btn9 = null;
    Button btnBackspace = null;
    Button btnCE = null;
    Button btnC = null;
    Button btnAdd = null;
    Button btnSub = null;
    Button btnMul = null;
    Button btnDiv = null;
    Button btnEqu = null;
    TextView tvResult = null;
    //声明两个参数。接收tvResult前后的值
    double num1 = 0, num2 = 0;
    double Result = 0;//计算结果
    int op = 0;//判断操作数，
    boolean isClickEqu = false;//判断是否按了“=”按钮

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


        //从布局文件中获取控件，
        btn0 = (Button) findViewById(R.id.btn0);
        btn1 = (Button) findViewById(R.id.btn1);
        btn2 = (Button) findViewById(R.id.btn2);
        btn3 = (Button) findViewById(R.id.btn3);
        btn4 = (Button) findViewById(R.id.btn4);
        btn5 = (Button) findViewById(R.id.btn5);
        btn6 = (Button) findViewById(R.id.btn6);
        btn7 = (Button) findViewById(R.id.btn7);
        btn8 = (Button) findViewById(R.id.btn8);
        btn9 = (Button) findViewById(R.id.btn9);
        btnBackspace = (Button) findViewById(R.id.btnBackspace);
        btnCE = (Button) findViewById(R.id.btnCE);
        btnC = (Button) findViewById(R.id.btnC);
        btnEqu = (Button) findViewById(R.id.btnEqu);
        btnAdd = (Button) findViewById(R.id.btnAdd);
        btnSub = (Button) findViewById(R.id.btnSub);
        btnMul = (Button) findViewById(R.id.btnMul);
        btnDiv = (Button) findViewById(R.id.btnDiv);
        tvResult = (TextView) findViewById(R.id.tvResult);

        //添加监听
        btnBackspace.setOnClickListener(this);
        btnCE.setOnClickListener(MainActivity.this);

        btn0.setOnClickListener(MainActivity.this);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
        btn3.setOnClickListener(this);
        btn4.setOnClickListener(this);
        btn5.setOnClickListener(this);
        btn6.setOnClickListener(this);
        btn7.setOnClickListener(this);
        btn8.setOnClickListener(this);
        btn9.setOnClickListener(this);


        btnAdd.setOnClickListener(this);
        btnSub.setOnClickListener(this);
        btnMul.setOnClickListener(this);
        btnDiv.setOnClickListener(this);
        btnEqu.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            //btnBackspace和CE--------------------
            case R.id.btnBackspace:
                String myStr = tvResult.getText().toString();
                try {
                    tvResult.setText(myStr.substring(0, myStr.length() - 1));
                } catch (Exception e) {
                    tvResult.setText("");
                }

                break;
            case R.id.btnCE:
                tvResult.setText(null);
                break;

            //btn0--9---------------------------
            case R.id.btn0:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString = tvResult.getText().toString();
                myString += "0";
                tvResult.setText(myString);
                break;
            case R.id.btn1:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString1 = tvResult.getText().toString();
                myString1 += "1";
                tvResult.setText(myString1);
                break;
            case R.id.btn2:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString2 = tvResult.getText().toString();
                myString2 += "2";
                tvResult.setText(myString2);
                break;
            case R.id.btn3:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString3 = tvResult.getText().toString();
                myString3 += "3";
                tvResult.setText(myString3);
                break;
            case R.id.btn4:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString4 = tvResult.getText().toString();
                myString4 += "4";
                tvResult.setText(myString4);
                break;
            case R.id.btn5:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString5 = tvResult.getText().toString();
                myString5 += "5";
                tvResult.setText(myString5);
                break;
            case R.id.btn6:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString6 = tvResult.getText().toString();
                myString6 += "6";
                tvResult.setText(myString6);
                break;
            case R.id.btn7:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString7 = tvResult.getText().toString();
                myString7 += "7";
                tvResult.setText(myString7);
                break;
            case R.id.btn8:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString8 = tvResult.getText().toString();
                myString8 += "8";
                tvResult.setText(myString8);
                break;
            case R.id.btn9:
                if (isClickEqu) {
                    tvResult.setText(null);
                    isClickEqu = false;
                }
                String myString9 = tvResult.getText().toString();
                myString9 += "9";
                tvResult.setText(myString9);
                break;

            //btn+-*/=--------------------------------
            case R.id.btnAdd:
                String myStringAdd = tvResult.getText().toString();
                if (myStringAdd.equals(null)) {
                    return;
                }
                num1 = Double.valueOf(myStringAdd);
                tvResult.setText(null);
                op = 1;
                isClickEqu = false;
                break;

            case R.id.btnSub:
                String myStringSub = tvResult.getText().toString();
                if (myStringSub.equals(null)) {
                    return;
                }
                num1 = Double.valueOf(myStringSub);
                tvResult.setText(null);
                op = 2;
                isClickEqu = false;
                break;
            case R.id.btnMul:
                String myStringMul = tvResult.getText().toString();
                if (myStringMul.equals(null)) {
                    return;
                }
                num1 = Double.valueOf(myStringMul);
                tvResult.setText(null);
                op = 3;
                isClickEqu = false;
                break;
            case R.id.btnDiv:
                String myStringDiv = tvResult.getText().toString();
                if (myStringDiv.equals(null)) {
                    return;
                }
                num1 = Double.valueOf(myStringDiv);
                tvResult.setText(null);
                op = 4;
                isClickEqu = false;
                break;
            case R.id.btnEqu:
                String myStringEqu = tvResult.getText().toString();
                if (myStringEqu.equals(null)) {
                    return;
                }
                num2 = Double.valueOf(myStringEqu);
                tvResult.setText(null);
                switch (op) {
                    case 0:
                        Result = num2;
                        break;
                    case 1:
                        Result = num1 + num2;
                        break;
                    case 2:
                        Result = num1 - num2;
                        break;
                    case 3:
                        Result = num1 * num2;
                        break;
                    case 4:
                        Result = num1 / num2;
                        break;
                    default:
                        Result = 0;
                        break;
                }
                tvResult.setText(String.valueOf(Result));
                isClickEqu = true;
                break;

            default:
                break;
        }
    }
}