import android.os.AsyncTask;什么意思
时间: 2024-02-22 10:01:38 浏览: 21
这段代码是导入了Android系统中的`AsyncTask`类,它是一个抽象类,可以用于在后台线程中执行异步任务,以避免在主线程中执行耗时操作而导致应用程序无响应。
`AsyncTask`类的工作原理是:在主线程中创建一个`AsyncTask`对象,并通过调用`execute()`方法启动异步任务。`AsyncTask`将在后台线程中执行`doInBackground()`方法,该方法是必须要实现的,用于执行耗时的任务。`doInBackground()`方法执行完毕后,将返回执行结果,并调用`onPostExecute()`方法,在主线程中更新UI界面。
`AsyncTask`类还提供了一些其他的方法,如`onPreExecute()`方法,在主线程中执行,用于在异步任务执行前执行一些准备工作,以及`onProgressUpdate()`方法和`onCancelled()`方法,用于在异步任务的执行过程中进行进度更新和任务取消等操作。
相关问题
package com.hmongsoft.merchant.Module.dataSource.onLine.V20230707; import android.os.AsyncTask; import com.hmongsoft.merchant.Base.Interface.ActionCallbackValue; import com.hmongsoft.merchant.Base.config.SysConfig; import java.io.IOException; import okhttp3.MultipartBody; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.RequestBody; /** * 校验商铺名称是否存在 */ public class JudgeMerchantIsExist { public JudgeMerchantIsExist(String merchantName, ActionCallbackValue<String,Boolean> actionCallback) { SignInTask signInTask=new SignInTask(merchantName,actionCallback); signInTask.execute(); } private static class SignInTask extends AsyncTask<String,Integer,Boolean>{ private String merchantName; private ActionCallbackValue<String,Boolean> actionCallback; private String requestResult; public SignInTask(String merchantName, ActionCallbackValue<String,Boolean> actionCallback) { this.merchantName =merchantName; this.actionCallback=actionCallback; } //异步前(UI) @Override protected void onPreExecute() { super.onPreExecute(); } //异步中(非UI) @Override protected Boolean doInBackground(String... strings) { OkHttpClient client = new OkHttpClient().newBuilder().build(); RequestBody body = new MultipartBody.Builder().setType(MultipartBody.FORM) .addFormDataPart("merchantName",merchantName) .build(); Request request = new Request.Builder() .url(SysConfig.MerchantPORT+"/MerchantController/judgeMerchantNameIsExist") .method("POST", body) .build(); try { requestResult = client.newCall(request).execute().body().string(); if (requestResult.equals("true")){ return true; }else { return false; } } catch (IOException e) { e.printStackTrace(); return false; } } //异步后(UI) @Override protected void onPostExecute(Boolean aBoolean) { super.onPostExecute(aBoolean); actionCallback.callback("result",aBoolean); } } } 这段代码的SignInTask已经被弃用,请帮换一个写法
package com.hmongsoft.merchant.Module.dataSource.onLine.V20230707;
import android.os.AsyncTask;
import com.hmongsoft.merchant.Base.Interface.ActionCallbackValue;
import com.hmongsoft.merchant.Base.config.SysConfig;
import java.io.IOException;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
/**
* 校验商铺名称是否存在
*/
public class JudgeMerchantIsExist {
public JudgeMerchantIsExist(String merchantName, ActionCallbackValue<String, Boolean> actionCallback) {
new SignInTask(merchantName, actionCallback).execute();
}
private static class SignInTask extends AsyncTask<Void, Void, Boolean> {
private String merchantName;
private ActionCallbackValue<String, Boolean> actionCallback;
public SignInTask(String merchantName, ActionCallbackValue<String, Boolean> actionCallback) {
this.merchantName = merchantName;
this.actionCallback = actionCallback;
}
@Override
protected Boolean doInBackground(Void... voids) {
OkHttpClient client = new OkHttpClient();
MediaType mediaType = MediaType.parse("application/json");
String json = "{\"merchantName\":\"" + merchantName + "\"}";
RequestBody body = RequestBody.create(json, mediaType);
Request request = new Request.Builder()
.url(SysConfig.MerchantPORT + "/MerchantController/judgeMerchantNameIsExist")
.post(body)
.build();
try {
String response = client.newCall(request).execute().body().string();
return response.equals("true");
} catch (IOException e) {
e.printStackTrace();
return false;
}
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
actionCallback.callback("result", result);
}
}
}
android studio天气预报代码
以下是一个简单的 Android Studio 天气预报应用的代码示例:
```java
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private EditText cityEditText;
private Button getWeatherButton;
private TextView weatherTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cityEditText = findViewById(R.id.cityEditText);
getWeatherButton = findViewById(R.id.getWeatherButton);
weatherTextView = findViewById(R.id.weatherTextView);
getWeatherButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String city = cityEditText.getText().toString();
if (!city.isEmpty()) {
String url = "http://api.openweathermap.org/data/2.5/weather?q=" + city + "&appid=YOUR_API_KEY";
new GetWeatherTask().execute(url);
}
}
});
}
private class GetWeatherTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
String result = "";
try {
URL url = new URL(params[0]);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
StringBuilder response = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
response.append(line);
}
reader.close();
result = response.toString();
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
JSONObject jsonObject = new JSONObject(result);
JSONObject main = jsonObject.getJSONObject("main");
double temp = main.getDouble("temp");
int humidity = main.getInt("humidity");
weatherTextView.setText("Temperature: " + temp + "°C\nHumidity: " + humidity + "%");
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
```
请注意替换代码中的 `YOUR_API_KEY` 为你自己的 OpenWeatherMap API 密钥。此代码使用 OpenWeatherMap 的 API 来获取天气数据,并在界面上显示温度和湿度信息。
这只是一个简单的示例,你可以根据需要进行修改和扩展。希望对你有所帮助!