安卓端的简单计算器

1.通过xml来设置按钮样式（创建xml时选择shape）

1）solid设置背景颜色2）<corners android:radius="5dip"/>设置圆角边框3）<gradient        android:startColor="@color/colorWhite"     android:endColor="@color/colorAccent"        />设置渐变色

1.通过xml来设置按钮颜色变化（创建xml时选择sselector）

1）<item android:drawable="@drawable/tu" android:state_pressed="true"/>按下时的颜色2）<item android:drawable="@drawable/or"/>默认状态下（即为按下时的按钮颜色）

在xml里设置计算器上的按钮（这里就不在写了）
在主类中编写代码

package mooc.java.jisuanqi;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.view.Window;import android.widget.Button;import android.widget.EditText;public class MainActivity extends AppCompatActivity implements OnClickListener{    private Button btn_0;    private Button btn_1;    private Button btn_2;    private Button btn_3;    private Button btn_4;    private Button btn_5;    private Button btn_6;    private Button btn_7;    private Button btn_8;    private Button btn_9;    private Button btn_jia;    private Button btn_jian;    private Button btn_cheng;    private Button btn_chu;    private Button btn_clear;    private Button btn_del;    private Button btn_equal;    private Button btn_point;    private EditText et;    boolean needclear;//清空表示    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_main);        init();        click();    }    protected void click() {        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_equal.setOnClickListener(this);        btn_jia.setOnClickListener(this);        btn_jian.setOnClickListener(this);        btn_cheng.setOnClickListener(this);        btn_chu.setOnClickListener(this);        btn_point.setOnClickListener(this);        btn_clear.setOnClickListener(this);        btn_del.setOnClickListener(this);    }    protected void init() {        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_jia = (Button) findViewById(R.id.btn_sub);        btn_jian = (Button) findViewById(R.id.btn_jian);        btn_cheng = (Button) findViewById(R.id.btn_cheng);        btn_chu = (Button) findViewById(R.id.btn_chu);        btn_equal = (Button) findViewById(R.id.btn_deng);        btn_clear = (Button) findViewById(R.id.btn_clear);        btn_point = (Button) findViewById(R.id.btn_dian);        btn_del = (Button) findViewById(R.id.btn_del);        et = (EditText) findViewById(R.id.et);    }    @Override    public void onClick(View v) {       String str = et.getText().toString();//得到界面上输入的值，并转成字符串        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_dian:                if (needclear) {                    needclear=false;                    str="";                    et.setText("");                }                et.setText(str+((Button)v).getText());                break;            case R.id.btn_sub:            case R.id.btn_jian:            case R.id.btn_cheng:            case R.id.btn_chu:                if (needclear) {                    needclear=false;                }                et.setText(str+" "+((Button)v).getText()+" ");                break;            case R.id.btn_deng:                getResult();                break;            case R.id.btn_clear:                needclear=false;                str="";                et.setText("");                break;            case R.id.btn_del:                if (needclear) {                    needclear=false;                    str="";                    et.setText("");                }else if(str!=null&&!str.equals("")) {                    et.setText(str.substring(0,str.length()-1));                }                break;            default:                break;        }    }    //获取运算结果    private void getResult() {        String exp = et.getText().toString();        if(exp==null||exp.equals("")) {            return;        }        if(!exp.contains(" ")) {            return;        }        if(needclear) {            needclear=false;            return;        }        needclear=true;        double r=0;        int space = exp.indexOf(" ");//用于搜索空格的位置        String s1 = exp.substring(0, space);//用于保存第一个运算数        String op = exp.substring(space + 1, space + 2);//用于保存运算符        String s2 = exp.substring(space + 3);//s2用于保存第二个运算数        Log.i("exp",exp);        Log.i("space",space+"");        Log.i("s1",s1);        Log.i("op",op);        Log.i("s2",s2);        if(!s1.equals("")&&!s2.equals("")) {            double arg1 = Double.parseDouble(s1);//把运算数由字符串型转换为double型            double arg2 = Double.parseDouble(s2);            if(op.equals("＋")) {                r=arg1+arg2;            }else if(op.equals("－")) {                r=arg1-arg2;            }else if(op.equals("×")) {                r=arg1*arg2;            }else if(op.equals("÷")) {                if (arg2 == 0) {                    r = 0;                } else {                    r = arg1 / arg2;                }            }if(!s1.contains(".")&&!s2.contains(".")&&!op.equals("÷")) {//两个数都是整数                int result = (int)r;                et.setText(result+"");            }else{                et.setText(r+"");            }        } else if(!s1.equals("")&&s2.equals("")) {            et.setText(exp);        }else if(s1.equals("")&&!s2.equals("")) {            exp="0 "+exp;            space = exp.indexOf(" ");//用于搜索空格的位置            s1 = exp.substring(0, space);//用于保存第一个运算数            op = exp.substring(space + 1, space + 2);//用于保存运算符            s2 = exp.substring(space + 3);//s2用于保存第二个运算数            Log.i("tag",exp);            Log.i("tag",space+"");            Log.i("tag",s1);            Log.i("tag",op);            Log.i("tag",s2);            double arg2 = Double.parseDouble(s2);            if(op.equals("＋")) {                r=0+arg2;            }else if(op.equals("－")) {                r=0-arg2;            }else if(op.equals("×")) {                r=0;            }else if(op.equals("÷")) {               r=0;            }if(!s2.contains(".")) {//两个数都是整数                int result = (int)r;                et.setText(result+"");            }else{                et.setText(r+"");                Log.i("tag",r+"");            }        }else{            et.setText("");        }    }}