layout文件：

  1 <?xml version="1.0" encoding="utf-8"?>
  2 <GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
  3     android:layout_width="match_parent"
  4     android:layout_height="match_parent"
  5     android:rowCount="6"
  6     android:columnCount="4"
  7     xmlns:tools="http://schemas.android.com/tools"
  8     tools:context="com.hanqi.testapp2.PractiseActivity5">
  9     <TextView
 10         android:layout_width="match_parent"
 11         android:layout_height="200dp"
 12         android:layout_columnSpan="4"
 13         android:gravity="bottom|right"
 14         android:id="@+id/tv_1"
 15         android:textSize="50sp"
 16         android:paddingRight="10dp"
 17         android:textColor="#0F0"/>
 18     <Button
 19         android:layout_width="0dp"
 20         android:layout_height="0dp"
 21         android:text="c"
 22         android:layout_columnWeight="1"
 23         android:layout_rowWeight="1"
 24         android:textSize="25sp"
 25         android:id="@+id/bt_c"/>
 26     <Button
 27         android:layout_width="0dp"
 28         android:layout_height="0dp"
 29         android:text="←"
 30         android:layout_columnWeight="1"
 31         android:layout_rowWeight="1"
 32         android:textSize="25sp"
 33         android:id="@+id/bt_tui"/>
 34     <Button
 35         android:layout_width="0dp"
 36         android:layout_height="0dp"
 37         android:text="÷"
 38         android:layout_columnWeight="1"
 39         android:layout_rowWeight="1"
 40         android:textSize="25sp"
 41         android:id="@+id/bt_chu"
 42         android:onClick="bt_chu_onClick"/>
 43     <Button
 44         android:layout_width="0dp"
 45         android:layout_height="0dp"
 46         android:text="×"
 47         android:layout_columnWeight="1"
 48         android:layout_rowWeight="1"
 49         android:textSize="25sp"
 50         android:id="@+id/bt_cheng"
 51         android:onClick="bt_cheng_onClick"/>
 52     <Button
 53         android:layout_width="0dp"
 54         android:layout_height="0dp"
 55         android:text="7"
 56         android:layout_columnWeight="1"
 57         android:layout_rowWeight="1"
 58         android:textSize="25sp"
 59         android:onClick="bt_onClick"
 60         android:id="@+id/bt7"/>
 61     <Button
 62         android:layout_width="0dp"
 63         android:layout_height="0dp"
 64         android:text="8"
 65         android:layout_columnWeight="1"
 66         android:layout_rowWeight="1"
 67         android:textSize="25sp"
 68         android:onClick="bt_onClick"
 69         android:id="@+id/bt8"/>
 70     <Button
 71         android:layout_width="0dp"
 72         android:layout_height="0dp"
 73         android:text="9"
 74         android:layout_columnWeight="1"
 75         android:layout_rowWeight="1"
 76         android:textSize="25sp"
 77         android:onClick="bt9_onClick"
 78         android:id="@+id/bt9"/>
 79     <Button
 80         android:layout_width="0dp"
 81         android:layout_height="0dp"
 82         android:text="－"
 83         android:layout_columnWeight="1"
 84         android:layout_rowWeight="1"
 85         android:textSize="25sp"
 86         android:id="@+id/bt_jian"
 87         android:onClick="bt_jian_onClick"/>
 88     <Button
 89         android:layout_width="0dp"
 90         android:layout_height="0dp"
 91         android:text="4"
 92         android:layout_columnWeight="1"
 93         android:layout_rowWeight="1"
 94         android:textSize="25sp"
 95         android:id="@+id/bt4"/>
 96     <Button
 97         android:layout_width="0dp"
 98         android:layout_height="0dp"
 99         android:text="5"
100         android:layout_columnWeight="1"
101         android:layout_rowWeight="1"
102         android:textSize="25sp"
103         android:id="@+id/bt5"/>
104     <Button
105         android:layout_width="0dp"
106         android:layout_height="0dp"
107         android:text="6"
108         android:layout_columnWeight="1"
109         android:layout_rowWeight="1"
110         android:textSize="25sp"
111         android:id="@+id/bt6"/>
112     <Button
113         android:layout_width="0dp"
114         android:layout_height="0dp"
115         android:text="＋"
116         android:layout_columnWeight="1"
117         android:layout_rowWeight="1"
118         android:textSize="25sp"
119         android:id="@+id/bt_jia"
120         android:onClick="bt_jia_onClick"/>
121     <Button
122         android:layout_width="0dp"
123         android:layout_height="0dp"
124         android:text="1"
125         android:layout_columnWeight="1"
126         android:layout_rowWeight="1"
127         android:textSize="25sp"
128         android:id="@+id/bt1"/>
129     <Button
130         android:layout_width="0dp"
131         android:layout_height="0dp"
132         android:text="2"
133         android:layout_columnWeight="1"
134         android:layout_rowWeight="1"
135         android:textSize="25sp"
136         android:id="@+id/bt2"/>
137     <Button
138         android:layout_width="0dp"
139         android:layout_height="0dp"
140         android:text="3"
141         android:layout_columnWeight="1"
142         android:layout_rowWeight="1"
143         android:textSize="25sp"
144         android:id="@+id/bt3"/>
145     <Button
146         android:layout_width="0dp"
147         android:layout_height="0dp"
148         android:text="="
149         android:layout_columnWeight="1"
150         android:layout_rowSpan="2"
151         android:layout_rowWeight="1"
152         android:textSize="25sp"
153         android:layout_gravity="fill"
154         android:id="@+id/bt_deng"/>
155     <Button
156         android:layout_width="0dp"
157         android:layout_height="0dp"
158         android:text="0"
159         android:layout_columnWeight="1"
160         android:layout_columnSpan="2"
161         android:layout_rowWeight="1"
162         android:textSize="25sp"
163         android:id="@+id/bt0"/>
164     <Button
165         android:layout_width="0dp"
166         android:layout_height="0dp"
167         android:text="."
168         android:layout_columnWeight="1"
169         android:layout_rowWeight="1"
170         android:textSize="25sp"
171         android:id="@+id/bt_dian"/>
172 </GridLayout>

java类：

  1 package com.hanqi.testapp2;
  2 
  3 import android.os.Bundle;
  4 import android.support.v7.app.AppCompatActivity;
  5 import android.view.View;
  6 import android.widget.Button;
  7 import android.widget.TextView;
  8 
  9 public class PractiseActivity5 extends AppCompatActivity {
 10 
 11     TextView tv_1;
 12     Button bt9;
 13     Button bt4;
 14     Button bt5;
 15     Button bt6;
 16     Button bt_jia;
 17     Button bt_jian;
 18     Button bt1;
 19     Button bt2;
 20     Button bt3;
 21     Button bt_cheng;
 22     Button bt0;
 23     Button bt_dian;
 24     Button bt_chu;
 25     Button bt_tui;
 26     Button bt7;
 27     Button bt8;
 28     Button bt_deng;
 29     Button bt_c;
 30 
 31     //s1存储数据
 32     double s1 = 0;
 33     //判断运算
 34     int s2 = 0;
 35     //承载连续运算数字
 36     double s3 = 0;
 37     //显示结果
 38     double s4;
 39     //运算完成后使用结果直接下次运算
 40     int s5=0;
 41     //确认小数点输入一次
 42     int s6=0;
 43 
 44     @Override
 45     protected void onCreate(Bundle savedInstanceState) {
 46         super.onCreate(savedInstanceState);
 47         setContentView(R.layout.activity_practise5);
 48         tv_1 = (TextView)findViewById(R.id.tv_1);
 49         bt0 = (Button)findViewById(R.id.bt0);
 50         bt1 = (Button)findViewById(R.id.bt1);
 51         bt2 = (Button)findViewById(R.id.bt2);
 52         bt3 = (Button)findViewById(R.id.bt3);
 53         bt4 = (Button)findViewById(R.id.bt4);
 54         bt5 = (Button)findViewById(R.id.bt5);
 55         bt6 = (Button)findViewById(R.id.bt6);
 56         bt7 = (Button)findViewById(R.id.bt7);
 57         bt8 = (Button)findViewById(R.id.bt8);
 58         bt9 = (Button)findViewById(R.id.bt9);
 59         bt_jia = (Button)findViewById(R.id.bt_jia);
 60         bt_jian = (Button)findViewById(R.id.bt_jian);
 61         bt_cheng = (Button)findViewById(R.id.bt_cheng);
 62         bt_dian = (Button)findViewById(R.id.bt_dian);
 63         bt_chu = (Button)findViewById(R.id.bt_chu);
 64         bt_tui = (Button)findViewById(R.id.bt_tui);
 65         bt_deng = (Button)findViewById(R.id.bt_deng);
 66         bt_c = (Button)findViewById(R.id.bt_c);
 67         bt_tui = (Button)findViewById(R.id.bt_tui);
 68 
 69         bt_onClick bt_l = new bt_onClick();
 70         bt_dian_onClick bt_dian1 = new bt_dian_onClick();
 71         bt_jia_onClick bt_jia1 = new bt_jia_onClick();
 72         bt_jian_onClick bt_jian1 = new bt_jian_onClick();
 73         bt_cheng_onClick bt_cheng1 = new bt_cheng_onClick();
 74         bt_chu_onClick bt_chu1 = new bt_chu_onClick();
 75         bt_deng_onClick bt_deng1 = new bt_deng_onClick();
 76         bt_c_onClick bt_c1 = new bt_c_onClick();
 77         bt_tui_onClick bt_tui1 = new bt_tui_onClick();
 78 
 79         bt0.setOnClickListener(bt_l);
 80         bt1.setOnClickListener(bt_l);
 81         bt2.setOnClickListener(bt_l);
 82         bt3.setOnClickListener(bt_l);
 83         bt4.setOnClickListener(bt_l);
 84         bt5.setOnClickListener(bt_l);
 85         bt6.setOnClickListener(bt_l);
 86         bt7.setOnClickListener(bt_l);
 87         bt8.setOnClickListener(bt_l);
 88         bt9.setOnClickListener(bt_l);
 89         bt_dian.setOnClickListener(bt_dian1);
 90         bt_jia.setOnClickListener(bt_jia1);
 91         bt_jian.setOnClickListener(bt_jian1);
 92         bt_chu.setOnClickListener(bt_chu1);
 93         bt_cheng.setOnClickListener(bt_cheng1);
 94         bt_deng.setOnClickListener(bt_deng1);
 95         bt_c.setOnClickListener(bt_c1);
 96         bt_tui.setOnClickListener(bt_tui1);
 97     }
 98     class bt_onClick implements View.OnClickListener
 99     {
100         @Override
101         public void onClick(View v) {
102             if (s5 == 1) {
103                 tv_1.setText(null);
104                 s1 = 0;
105                 s2 = 0;
106                 s3 = 0;
107                 s4 = 0;
108                 s5 = 0;
109             }
110             String str = tv_1.getText().toString();
111             //转成按钮
112             Button bt = (Button)v;
113             //取得按钮上的文字
114             String str2 = bt.getText().toString();
115             str += str2;
116             tv_1.setText(str);
117         }
118     }
119     class bt_dian_onClick implements View.OnClickListener {
120         public void onClick(View v) {
121             if(s5==1)
122             {
123                 tv_1.setText(null);
124                 s1=0;
125                 s2=0;
126                 s3=0;
127                 s4=0;
128                 s5=0;
129             }
130 
131             if(s6==1)
132             {
133                 return;
134             }
135             Button bt = (Button) v;
136             String str = tv_1.getText().toString();
137 
138             if(str.length()==0||str.equals("0.")){
139                 tv_1.setText("0.");
140                 return;
141             }
142 
143             String str2 = bt.getText().toString();
144             str += str2;
145             tv_1.setText(str);
146             s6=1;
147         }
148     }
149     class bt_jia_onClick implements View.OnClickListener
150     {
151         @Override
152         public void onClick(View v) {
153             s5 = 0;
154             String str=tv_1.getText().toString();
155             if (str.length()==0)
156             {
157                 return;
158             }
159             if (s1 == 0) {
160                 s1 = Double.parseDouble(str);
161 
162             } else {
163                 s3 = Double.parseDouble(str);
164                 if (s2 == 0)
165                 {
166                     s1 = s3;
167                 }
168                 if (s2 == 1)
169                 {
170                     s1 += s3;
171                 }
172                 if (s2 == 2)
173                 {
174                     s1 -= s3;
175                 }
176                 if (s2 == 3)
177                 {
178                     s1 *= s3;
179                 }
180                 if (s2==4&&s3!=0)
181                 {
182                     s1 /= s3;
183                 }
184                 if (s2==4&&s3==0)
185                 {
186                     s1=0;
187                     s2=0;
188                     s3=0;
189                     s4=0;
190                     s5=0;
191                 }
192             }
193             tv_1.setText(null);
194             s2 = 1;
195             s6=0;
196         }
197     }
198     class bt_jian_onClick implements View.OnClickListener
199     {
200         @Override
201         public void onClick(View v) {
202             s5 = 0;
203             String str=tv_1.getText().toString();
204             if (str.length()==0)
205             {
206                 return;
207             }
208             if (s1 == 0) {
209                 s1 = Double.parseDouble(str);
210 
211             } else {
212                 s3 = Double.parseDouble(str);
213                 if (s2 == 0)
214                 {
215                     s1 = s3;
216                 }
217                 if (s2 == 1)
218                 {
219                     s1 += s3;
220                 }
221                 if (s2 == 2)
222                 {
223                     s1 -= s3;
224                 }
225                 if (s2 == 3)
226                 {
227                     s1 *= s3;
228                 }
229                 if (s2==4&&s3!=0)
230                 {
231                     s1 /= s3;
232                 }
233                 if (s2==4&&s3==0)
234                 {
235                     s1=0;
236                     s2=0;
237                     s3=0;
238                     s4=0;
239                     s5=0;
240                 }
241             }
242             tv_1.setText(null);
243             s2 = 2;
244             s6=0;
245         }
246     }
247     class bt_cheng_onClick implements View.OnClickListener
248     {
249         @Override
250         public void onClick(View v) {
251             s5 = 0;
252             String str=tv_1.getText().toString();
253             if (str.length()==0)
254             {
255                 return;
256             }
257             if (s1 == 0) {
258                 s1 = Double.parseDouble(str);
259 
260             } else {
261                 s3 = Double.parseDouble(str);
262                 if (s2 == 0)
263                 {
264                     s1 = s3;
265                 }
266                 if (s2 == 1)
267                 {
268                     s1 += s3;
269                 }
270                 if (s2 == 2)
271                 {
272                     s1 -= s3;
273                 }
274                 if (s2 == 3)
275                 {
276                     s1 *= s3;
277                 }
278                 if (s2==4&&s3!=0)
279                 {
280                     s1 /= s3;
281                 }
282                 if (s2==4&&s3==0)
283                 {
284                     s1=0;
285                     s2=0;
286                     s3=0;
287                     s4=0;
288                     s5=0;
289                 }
290             }
291             tv_1.setText(null);
292             s2 = 3;
293             s6=0;
294         }
295     }
296     class bt_chu_onClick implements View.OnClickListener
297     {
298         @Override
299         public void onClick(View v) {
300             s5 = 0;
301             String str=tv_1.getText().toString();
302             if (str.length()==0)
303             {
304                 return;
305             }
306             if (s1 == 0) {
307                 s1 = Double.parseDouble(str);
308 
309             } else {
310                 s3 = Double.parseDouble(str);
311                 if (s2 == 0)
312                 {
313                     s1 = s3;
314                 }
315                 if (s2 == 1)
316                 {
317                     s1 += s3;
318                 }
319                 if (s2 == 2)
320                 {
321                     s1 -= s3;
322                 }
323                 if (s2 == 3)
324                 {
325                     s1 *= s3;
326                 }
327                 if (s2==4&&s3!=0)
328                 {
329                     s1 /= s3;
330                 }
331                 if (s2==4&&s3==0)
332                 {
333                     s1=0;
334                     s2=0;
335                     s3=0;
336                     s4=0;
337                     s5=0;
338                 }
339             }
340             tv_1.setText(null);
341             s2 = 4;
342             s6=0;
343         }
344     }
345     class bt_deng_onClick implements View.OnClickListener {
346         public void onClick(View v) {
347             String str = tv_1.getText().toString();
348             if(str.length()==0)
349             {
350                 return;
351             }
352             s3 = Double.parseDouble(str);
353             if(s3==0&&s2==4)
354             {
355                 return;
356             }
357             if(s2==0)
358             {
359                 s4=s3;
360             }
361             if(s2==1)
362             {
363                 s4=s1+s3;
364             }
365             if(s2==2)
366             {
367                 s4=s1-s3;
368             }
369             if(s2==3)
370             {
371                 s4=s1*s3;
372             }
373             if(s2==4&&s3!=0)
374             {
375                 s4=s1/s3;
376             }
377             if (s2==4&&s3==0)
378             {
379                 s1=0;
380                 s2=0;
381                 s3=0;
382                 s4=0;
383                 s5=0;
384             }
385             String str2=s4+"";
386             tv_1.setText(str2);
387             s5=1;
388             s2=0;
389             s6=0;
390         }
391     }
392     class bt_c_onClick implements View.OnClickListener {
393         public void onClick(View v) {
394             s1=0;
395             s2=0;
396             s3=0;
397             s5=0;
398             s4=0;
399             s6=0;
400             tv_1.setText(null);
401         }
402     }
403     class bt_tui_onClick implements View.OnClickListener {
404         public void onClick(View v) {
405 
406             String str = tv_1.getText().toString();
407             if (str.length() == 0) {
408                 return;
409             }
410             String str2 = str.substring(0, str.length() - 1);
411             tv_1.setText(str2);
412             if (s5 == 1) {
413                 s5 = 0;
414             }
415         }
416     }
417 }

可实现计算器的基本运算功能

感谢@storm47给予我的帮助