Android系统是目前世界上最受欢迎的移动操作系统之一，它的应用程序数量众多，包括了各种小应用，这些小应用不仅能够提高我们的生活质量，还能够帮助我们更好地理解Android系统的工作原理。在本文中，我将介绍几个必看的小程序，并附上其代码。
1.计算器
计算器是最基本的小程序之一，它可以帮助我们进行简单的数学运算。以下是一个简单的计算器程序：
```
public class Calculator {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("请输入第一个数字：");
double num1 = scanner.nextDouble();
System.out.print("请输入第二个数字：");
double num2 = scanner.nextDouble();
System.out.println("请输入需要进行的运算：+、-、*、/ ");
char operator = scanner.next().charAt(0);
double result = 0.0;
switch (operator) {
case '+':
result = num1 + num2;
break;
case '-':
result = num1 - num2;
break;
case '*':
result = num1 * num2;
break;
case '/':
result = num1 / num2;
break;
default:
System.out.println("输入的运算符有误！");
return;
}
System.out.println(num1 + " " + operator + " " + num2 + " = " + result);
}
}
```
2.天气预报
天气预报是一个非常实用的小程序，它可以帮助我们了解当地的天气情况。以下是一个基于Android Studio的天气预报程序：
```
public class WeatherActivity extends AppCompatActivity {
private TextView tvCity;
private TextView tvTemperature;
private TextView tvWeather;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_weather);
tvCity = findViewById(R.id.tv_city);
tvTemperature = findViewById(R.id.tv_temperature);
tvWeather = findViewById(R.id.tv_weather);
String city = "北京";
String url = "http://wthrcdn.etouch.cn/weather_mini?city=" + city;
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(url)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
String responseData = response.body().string();
parseJsonWithGson(responseData);
}
});
}
private void parseJsonWithGson(String jsonData) {
Gson gson = new Gson();
Weather weather = gson.fromJson(jsonData, Weather.class);
runOnUiThread(new Runnable() {
@Override
public void run() {
tvCity.setText(weather.getData().getCity());
tvTemperature.setText(weather.getData().getWendu());
tvWeather.setText(weather.getData().getForecast().get(0).getType());
}
});
}
}
```
3.翻译工具
翻译工具是一个非常实用的小程序，它可以帮助我们进行多种语言之间的翻译。以下是一个基于有道翻译API的翻译工具程序：
```
public class Translator {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("请输入需要翻译的内容：");
String text = scanner.nextLine();
System.out.println("请输入需要翻译的语言：1.英文 2.中文");
int type = scanner.nextInt();
String from = "";
String to = "";
if (type == 1) {
from = "EN";
to = "zh-CHS";
} else if (type == 2) {
from = "zh-CHS";
to = "EN";
}
String url = "http://fanyi.youdao.com/translate?&doctype=json&type=" + from + "2" + to + "&i=" + text;
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(url)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
String responseData = response.body().string();
parseJsonWithGson(responseData);
}
});
}
private static void parseJsonWithGson(String jsonData) {
Gson gson = new Gson();
Translation translation = gson.fromJson(jsonData, Translation.class);
System.out.println(translation.getTranslateResult().get(0).get(0).getTgt());
}
}
```
以上就是几个必看的小程序，它们不仅能够帮助我们更好地理解Android系统的工作原理，同时也能够提高我们的生活质量。
