Java 在Android Studio中,我在;“背景法”;
这里第一个getWeather方法execute,它执行DownloadTask方法,当用户传递一些空值,getWeather中的th链接不正确时,在doInBackground方法中,当获取输入流时,它显示致命错误Java 在Android Studio中,我在;“背景法”;,java,android,Java,Android,这里第一个getWeather方法execute,它执行DownloadTask方法,当用户传递一些空值,getWeather中的th链接不正确时,在doInBackground方法中,当获取输入流时,它显示致命错误 package com.ssd.weatherapp; import androidx.appcompat.app.AppCompatActivity; import android.content.Context; import android.os.AsyncTask; i
package com.ssd.weatherapp;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONObject;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
public class MainActivity extends AppCompatActivity {
EditText editText;
TextView resultTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = findViewById(R.id.editText);
resultTextView = findViewById(R.id.resultTextView);
}
public void getWeather (View view){
try {
DownloadTask task = new DownloadTask();
String encodedCityName = URLEncoder.encode(editText.getText().toString(), "UTF-8");
task.execute("https://openweathermap.org/data/2.5/weather?q=" + encodedCityName + "&appid=439d4b804bc8187953eb36d2a8c26a02\n");
InputMethodManager mgr = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
mgr.hideSoftInputFromWindow(editText.getWindowToken(), 0);
}catch(Exception e){
e.printStackTrace();
Log.i("info","1st one");
Toast.makeText(getApplicationContext(),"Could not find weather :(",Toast.LENGTH_SHORT).show();
}
}
public class DownloadTask extends AsyncTask<String,Void,String> {
@Override
protected String doInBackground(String... urls) {
String result = "";
URL url;
HttpURLConnection urlConnection = null;
try{
url = new URL(urls[0]);
urlConnection= (HttpURLConnection) url.openConnection();
System.out.println(urlConnection.getInputStream());
InputStream in = urlConnection.getInputStream();
InputStreamReader reader= new InputStreamReader(in);
int data = reader.read();
while(data != -1){
char current =(char) data;
result += current;
data = reader.read();
}
return result;
}catch(Exception e){
e.printStackTrace();
Toast.makeText(getApplicationContext(),"Could not find weather :(",Toast.LENGTH_SHORT).show();
return null;
}
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
try {
JSONObject jsonObject = new JSONObject(s);
String weatherInfo = jsonObject.getString("weather");
Log.i("info",weatherInfo);
JSONArray arr = new JSONArray(weatherInfo);
String msg ="";
for(int i=0; i < arr.length(); i++){
JSONObject jsonPart= arr. getJSONObject(i);
String main = jsonPart.getString("main");
String description =jsonPart.getString("description");
if(!main.equals("") && !description.equals("")){
msg += main + ": " + description + "\r\n";
}
}
if(!msg.equals("")){
resultTextView.setText(msg);
}else{
Log.i("info","3rd one");
Toast.makeText(getApplicationContext(),"Could not find weather :(",Toast.LENGTH_SHORT).show();
}
}catch(Exception e){
e.printStackTrace();
Log.i("info","4th one");
Toast.makeText(getApplicationContext(),"Could not find weather :(",Toast.LENGTH_SHORT).show();
}
}
}
}
package com.ssd.weatherapp;
导入androidx.appcompat.app.appcompat活动;
导入android.content.Context;
导入android.os.AsyncTask;
导入android.os.Bundle;
导入android.util.Log;
导入android.view.view;
导入android.view.inputmethod.InputMethodManager;
导入android.widget.EditText;
导入android.widget.TextView;
导入android.widget.Toast;
导入org.json.JSONArray;
导入org.json.JSONObject;
导入java.io.InputStream;
导入java.io.InputStreamReader;
导入java.net.HttpURLConnection;
导入java.net.URL;
导入java.net.urlcoder;
公共类MainActivity扩展了AppCompatActivity{
编辑文本编辑文本;
TextView结果TextView;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText=findViewById(R.id.editText);
resultTextView=findViewById(R.id.resultTextView);
}
公共天气(视图){
试一试{
DownloadTask任务=新建DownloadTask();
字符串encodedCityName=URLEncoder.encode(editText.getText().toString(),“UTF-8”);
任务。执行(“https://openweathermap.org/data/2.5/weather?q=“+encodedCityName+”&appid=439d4b804bc8187953eb36d2a8c26a02\n”);
InputMethodManager mgr=(InputMethodManager)getSystemService(Context.INPUT\u方法\u服务);
mgr.hideSoftInputFromWindow(editText.getWindowToken(),0);
}捕获(例外e){
e、 printStackTrace();
日志i(“信息”,“第一条”);
Toast.makeText(getApplicationContext(),“找不到天气:(”,Toast.LENGTH_SHORT).show();
}
}
公共类DownloadTask扩展了AsyncTask{
@凌驾
受保护的字符串doInBackground(字符串…URL){
字符串结果=”;
网址;
HttpURLConnection-urlConnection=null;
试一试{
url=新url(url[0]);
urlConnection=(HttpURLConnection)url.openConnection();
System.out.println(urlConnection.getInputStream());
InputStream in=urlConnection.getInputStream();
InputStreamReader reader=新的InputStreamReader(in);
int data=reader.read();
while(数据!=-1){
当前字符=(字符)数据;
结果+=电流;
data=reader.read();
}
返回结果;
}捕获(例外e){
e、 printStackTrace();
Toast.makeText(getApplicationContext(),“找不到天气:(”,Toast.LENGTH_SHORT).show();
返回null;
}
}
@凌驾
受保护的void onPostExecute(字符串s){
super.onPostExecute(s);
试一试{
JSONObject JSONObject=新的JSONObject;
字符串weatherInfo=jsonObject.getString(“天气”);
Log.i(“信息”,weatherInfo);
JSONArray arr=新JSONArray(天气信息);
字符串msg=“”;
对于(int i=0;i
当我未在textView中键入任何内容并将其发送到downloadTask类时发生的错误,应用程序崩溃并显示此错误,而不是显示异常并发出祝酒词:
2020-06-16 00:01:46.117 7948-7986/com.ssd.weatherapp D/NetworkSecurityConfig: No Network Security Config specified, using platform default
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: java.io.FileNotFoundException: https://openweathermap.org/data/2.5/weather?q=&appid=439d4b804bc8187953eb36d2a8c26a02
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:251)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:26)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:74)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:60)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:333)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:266)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
2020-06-16 00:01:47.530 7948-7986/com.ssd.weatherapp W/System.err: at java.lang.Thread.run(Thread.java:764)
--------- beginning of crash
2020-06-16 00:01:47.532 7948-7986/com.ssd.weatherapp E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.ssd.weatherapp, PID: 7948
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:354)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)
Caused by: java.lang.RuntimeException: Can't toast on a thread that has not called Looper.prepare()
at android.widget.Toast$TN.<init>(Toast.java:393)
at android.widget.Toast.<init>(Toast.java:117)
at android.widget.Toast.makeText(Toast.java:280)
at android.widget.Toast.makeText(Toast.java:270)
at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:94)
at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:60)
at android.os.AsyncTask$2.call(AsyncTask.java:333)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)
2020-06-16 00:01:47.919 7948-7976/com.ssd.weatherapp D/EGL_emulation: eglMakeCurrent: 0xe7740080: ver 2 0 (tinfo 0xdfb95320)
2020-06-16 00:01:46.117 7948-7986/com.ssd.weatherapp D/NetworkSecurityConfig:未指定网络安全配置,使用平台默认设置
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:java.io.FileNotFoundException:https://openweathermap.org/data/2.5/weather?q=&appid=439d4b804bc8187953eb36d2a8c26a02
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:251)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:26)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:74)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at com.ssd.weatherapp.MainActivity$DownloadTask.doInBackground(MainActivity.java:60)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at-android.os.AsyncTask$2.call(AsyncTask.java:333)
2020-06-16 00:01:47.529 7948-7986/com.ssd.weatherapp W/System.err:at ja