我正在制作一个天气应用程序，但每当我在EditText中没有输入或输入错误的城市名称时，该应用程序就会崩溃，尽管我使用了try-and-catch块来处理错误。下面是显示运行时错误的java、xml代码和日志。
Java
package com.atul.whatstheweather;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
EditText cityName;
TextView weatherInfo;
public class Content extends AsyncTask<String, Void ,String>
{
@Override
protected String doInBackground(String... urls) {
URL url;
HttpURLConnection urlConnection = null;
String result = "";
try {
url = new URL(urls[0]);
urlConnection = (HttpURLConnection)url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(inputStream);
int data = reader.read();
while(data != -1)
{
char current = (char)data;
result += current;
data = reader.read();
}
return result;
} catch (Exception e) {
Toast.makeText(MainActivity.this, "URL malfunctioned", Toast.LENGTH_SHORT).show();
}
return null;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
JSONObject jsonObject = new JSONObject(result);
String weatherData = jsonObject.getString("weather");
JSONArray array = new JSONArray(weatherData);
for(int i=0;i<array.length();i++)
{
JSONObject jsonPart = array.getJSONObject(i);
String main = jsonPart.getString("main");
String description = jsonPart.getString("description");
weatherInfo.setText("Weather: "+main+"nn"+"Description: "+description);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cityName = (EditText)findViewById(R.id.cityName);
weatherInfo = (TextView)findViewById(R.id.textView);
}
public void clicked(View view)
{
Content content = new Content();
content.execute("https://api.openweathermap.org/data/2.5/weather?q=" + cityName.getText().toString() + "&appid=c20cea76c84b519d67d4e6582064db92");
Log.i("clicked","is working");
}
}
在下面给出的日志中，它显示运行时错误
运行日志
05/03 17:35:25: Launching app
Cold swapped changes.
$ adb shell am start -n "com.atul.whatstheweather/com.atul.whatstheweather.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Connected to process 18757 on device xiaomi-redmi_note_3-9b51ac51
I/art: Late-enabling -Xcheck:jni
D/TidaProvider: TidaProvider()
W/ReflectionUtils: java.lang.NoSuchMethodException: android.os.MessageQueue#enableMonitor()#bestmatch
at miui.util.ReflectionUtils.findMethodBestMatch(ReflectionUtils.java:338)
at miui.util.ReflectionUtils.findMethodBestMatch(ReflectionUtils.java:375)
at miui.util.ReflectionUtils.callMethod(ReflectionUtils.java:800)
at miui.util.ReflectionUtils.tryCallMethod(ReflectionUtils.java:818)
at android.os.BaseLooper.enableMonitor(BaseLooper.java:47)
at android.os.Looper.prepareMainLooper(Looper.java:111)
at android.app.ActivityThread.main(ActivityThread.java:5586)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:774)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)
W/ResourceType: No package identifier when getting name for resource number 0x00000000
W/System: ClassLoader referenced unknown path: /data/app/com.atul.whatstheweather-1/lib/arm64
I/InstantRun: Instant Run Runtime started. Android package is com.atul.whatstheweather, real application class is null.
W/System: ClassLoader referenced unknown path: /data/app/com.atul.whatstheweather-1/lib/arm64
W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
D/AccessibilityManager: current package=com.atul.whatstheweather, accessibility manager mIsFinalEnabled=false, mOptimizeEnabled=false, mIsUiAutomationEnabled=false, mIsInterestedPackage=false
V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@9df51ef
V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@ce6e4fc
D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true
I/Adreno: QUALCOMM build : a7823f5, I59a6815413
Build Date : 09/23/16
OpenGL ES Shader Compiler Version: XE031.07.00.00
Local Branch : mybranch22028469
Remote Branch : quic/LA.BR.1.3.3_rb2.26
Remote Branch : NONE
Reconstruct Branch : NOTHING
I/OpenGLRenderer: Initialized EGL, version 1.4
E/HAL: hw_get_module_by_class: module name gralloc
E/HAL: hw_get_module_by_class: module name gralloc
I/clicked: is working
I/DpmTcmClient: RegisterTcmMonitor from: com.android.okhttp.TcmIdleTimerMonitor
E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.atul.whatstheweather, PID: 18757
java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:309)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:200)
at android.os.Handler.<init>(Handler.java:114)
at android.widget.Toast$TN.<init>(Toast.java:356)
at android.widget.Toast.<init>(Toast.java:101)
at android.widget.Toast.makeText(Toast.java:266)
at com.atul.whatstheweather.MainActivity$Content.doInBackground(MainActivity.java:60)
at com.atul.whatstheweather.MainActivity$Content.doInBackground(MainActivity.java:31)
at android.os.AsyncTask$2.call(AsyncTask.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
I/Process: Sending signal. PID: 18757 SIG: 9
Application terminated.
应用程序崩溃，因为您在后台线程中调用Toast。
将捕获块Toast.makeText(MainActivity.this, "URL malfunctioned", Toast.LENGTH_SHORT).show();中的Toast行替换为：
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, "URL malfunctioned", Toast.LENGTH_SHORT).show();
}
});
只需删除Toast.makeText