私はまだJavaに慣れていないので、髪の毛を引き抜こうとしているクラスプロジェクトに取り組んでいます。iTunes API から JSON 情報を取得しようとしています。引っ張ってきた情報はとあるアルバムから。WebClass.java クラスの getURLStringResponse() メソッドで try/catch を使用していますが、組み込みの例外がスローされており、その理由がわかりません。先生からの助けもまったく得られません。だから私は脳に手を差し伸べています！
それが役立つ場合は、ここに私のgithubリンクがあります
https://github.com/agvinsant/Java1/tree/master/week3
ここに私の主な活動があります
package com.agvinsant.java1application;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import com.agvinsant.lib.BasicLayout;
import com.agvinsant.lib.WebClass;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.res.Resources;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
Context context;
String[] songName;
Resources res;
TextView results;
Spinner viewSpinner;
TextView jsonView;
TextView connectedView;
String trackName;
String artistName;
String albumName;
String trackSite;
ArrayList<String> trackNameList = new ArrayList<String>();
ArrayList<String> artistNameList = new ArrayList<String>();
ArrayList<String> albumNameList = new ArrayList<String>();
ArrayList<String> trackSiteList = new ArrayList<String>();
Boolean connected = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = this;
res = getResources();
// setting the linear layout
LinearLayout ll = new LinearLayout(this);
LinearLayout ml = BasicLayout.layoutWithButton(this, "Show Info");
ll.setOrientation(LinearLayout.VERTICAL);
LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT);
ll.setLayoutParams(lp);
// Creating button from BasicLayout class
Button mb = (Button) ml.findViewById(1);
mb.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// Get selected song info
int pos = viewSpinner.getSelectedItemPosition();
String tName = trackNameList.get(pos).toString();
String arName = artistNameList.get(pos).toString();
String alName = albumNameList.get(pos).toString();
String tSite = trackSiteList.get(pos).toString();
jsonView.setText("Song Name: " +tName+ "\r\n" + "Artist Name: " +arName+ "\r\n" +"Album Name: "+alName+ "\r\n" + "Song Website: " +tSite);
}
});
connectedView = new TextView(context);
//Detecting network settings
connected = WebClass.getConnectionStatus(context);
if(connected){
Log.i("Network Connection", WebClass.getConnectionType(context));
connectedView.setText("Network Connection: " + WebClass.getConnectionType(context)+"\n");
}
else{
connectedView.setText(""+WebClass.getConnectionType(context)+"\n");
}
// calling the getSongInfo function
getSongInfo();
// song length display
int songNum = res.getStringArray(R.array.songArray).length;
TextView tv = new TextView(context);
tv.setText("Check out one of the "+songNum+" songs on the album");
//spinner adapter
ArrayAdapter<String> spinnerAdapter = new ArrayAdapter<String>(context, android.R.layout.simple_spinner_item, songName);
spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//creating the spinner
viewSpinner = new Spinner(context);
viewSpinner.setAdapter(spinnerAdapter);
lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
viewSpinner.setLayoutParams(lp);
//spinner onClick function
viewSpinner.setOnItemSelectedListener(new OnItemSelectedListener(){
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(context, "You selected " + songName[position], Toast.LENGTH_LONG).show();
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
});
// setting different layout parts to the main layout
ll.addView(ml);
ll.addView(tv);
ll.addView(viewSpinner);
//ll.addView(connectedView);
ll.addView(jsonView);
// setting the content view
setContentView(ll);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
//get URL
private void getSongInfo(){
String baseURL = "https://itunes.apple.com/search?term=groove+logic+logical+thinking";
URL finalURL;
try{
finalURL = new URL(baseURL);
songRequest sr = new songRequest();
sr.execute(finalURL);
} catch (MalformedURLException e){
Log.e("BAD URL", "MALFORMED URL");
finalURL = null;
}
}
//get data from URL
private class songRequest extends AsyncTask<URL, Void, String>{
@Override
protected String doInBackground(URL... urls){
String response = "";
for(URL url: urls){
response = WebClass.getURLStringResponse(url);
}
return response;
}
//get data and add to arrays.
@Override
protected void onPostExecute(String result){
try {
Log.i("URL Response", result);
JSONArray jsonArray = new JSONArray(result);
int n = jsonArray.length();
for(int i = 0;i<n; i++){
JSONObject jsonObject = jsonArray.getJSONObject(i);
trackName = jsonObject.getString("trackName");
artistName= jsonObject.getString("artistName");
albumName = jsonObject.getString("collectionName");
trackSite= jsonObject.getString("trackViewUrl");
trackNameList.add(trackName);
artistNameList.add(artistName);
albumNameList.add(albumName);
trackSiteList.add(trackSite);
}
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
}
ここにウェブクラスがあります
package com.agvinsant.lib;
import java.io.BufferedInputStream;
import java.net.URL;
import java.net.URLConnection;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;
public class WebClass {
static Boolean connection = false;
static String connectionType = "Unavailable";
public static String getConnectionType(Context context){
webInfo(context);
return connectionType;
}
public static Boolean getConnectionStatus(Context context){
webInfo(context);
return connection;
}
private static void webInfo(Context context){
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo ni = cm.getActiveNetworkInfo();
if(ni != null){
if(ni.isConnected()){
connectionType = ni.getTypeName();
connection = true;
}
}
}
public static String getURLStringResponse(URL url){
String response = "";
try{
URLConnection conn = url.openConnection();
BufferedInputStream bin = new BufferedInputStream(conn.getInputStream());
byte[] contentBytes = new byte[1024];
int bytesRead = 0;
StringBuffer responseBuffer = new StringBuffer();
while((bytesRead = bin.read(contentBytes)) != -1){
response = new String(contentBytes,0,bytesRead);
responseBuffer.append(response);
}
return responseBuffer.toString();
}
catch(Exception e){
// This is the exception that is being thrown
Log.e("URL RESPONSE ERROR", "getURLStringResponse");
}
return response;
}
}
これは、ファイル応答の一部を処理する FileClass でもあります。
package com.agvinsant.lib;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import android.content.Context;
import android.util.Log;
// TODO: Auto-generated Javadoc
/**
* The Class FileClass.
*/
public class FileClass {
/**
* Store string file.
*
* @param context the context
* @param filename the filename
* @param content the content
* @param external the external
* @return the boolean
*/
@SuppressWarnings("resource")
public static Boolean storeStringFile(Context context, String filename, String content, Boolean external){
try{
File file;
FileOutputStream fos;
if(external){
file = new File(context.getExternalFilesDir(null), filename);
fos = new FileOutputStream(file);
}else{
fos = context.openFileOutput(filename, Context.MODE_PRIVATE);
}
fos.write(content.getBytes());
fos.close();
} catch (IOException e){
Log.e("WRITE ERROR", filename);
}
return true;
}
/**
* Store object file.
*
* @param context the context
* @param filename the filename
* @param external the external
* @return the boolean
*/
public static Boolean storeObjectFile(Context context, String filename, Boolean external){
return true;
}
/**
* Store object file.
*
* @param context the context
* @param filename the filename
* @param content the content
* @param external the external
* @return the boolean
*/
@SuppressWarnings("resource")
public static Boolean storeObjectFile(Context context, String filename, Object content, Boolean external){
try{
File file;
FileOutputStream fos;
ObjectOutputStream oos;
if(external){
file = new File(context.getExternalFilesDir(null), filename);
fos = new FileOutputStream(file);
} else {
fos = context.openFileOutput(filename, Context.MODE_PRIVATE);
}
oos = new ObjectOutputStream(fos);
oos.writeObject(content);
oos.close();
fos.close();
} catch (IOException e){
Log.e("WRITE ERROR", filename);
}
return true;
}
/**
* Read string file.
*
* @param context the context
* @param filename the filename
* @param external the external
* @return the string
*/
@SuppressWarnings("resource")
public static String readStringFile(Context context, String filename, Boolean external){
String content = "";
try{
File file;
FileInputStream fin;
if(external){
file = new File(context.getExternalFilesDir(null), filename);
fin = new FileInputStream(file);
} else {
file = new File(filename);
fin = context.openFileInput(filename);
}
BufferedInputStream bin = new BufferedInputStream(fin);
byte[] contentBytes = new byte[1024];
int bytesRead = 0;
StringBuffer contentBuffer = new StringBuffer();
while((bytesRead = bin.read(contentBytes)) != -1){
content = new String(contentBytes,0,bytesRead);
contentBuffer.append(content);
}
content = contentBuffer.toString();
fin.close();
} catch (FileNotFoundException e) {
Log.e("READ ERROR", "FILE NOT FOUND " + filename);
} catch (IOException e){
Log.e("READ ERROR", "I/O ERROR");
}
return content;
}
/**
* Read object file.
*
* @param context the context
* @param filename the filename
* @param external the external
* @return the object
*/
@SuppressWarnings("resource")
public static Object readObjectFile(Context context, String filename, Boolean external){
Object content = new Object();
try{
File file;
FileInputStream fin;
if(external){
file = new File(context.getExternalFilesDir(null), filename);
fin = new FileInputStream(file);
} else {
file = new File(filename);
fin = context.openFileInput(filename);
}
ObjectInputStream ois = new ObjectInputStream(fin);
try{
content = (Object) ois.readObject();
} catch (ClassNotFoundException e){
Log.e("READ ERROR", "INVALID JAVA OBJECT FILE");
}
ois.close();
fin.close();
} catch (FileNotFoundException e) {
Log.e("READ ERROR", "FILE NOT FOUND " + filename);
return null;
} catch (IOException e){
Log.e("READ ERROR", "I/O ERROR");
}
return content;
}
}
これは、実行時に LogCat が表示するものです
09-11 21:11:25.496: E/Trace(2500): error opening trace file: No such file or directory (2)
09-11 21:11:25.676: I/Network Connection(2500): mobile
09-11 21:11:25.707: D/AndroidRuntime(2500): Shutting down VM
09-11 21:11:25.707: W/dalvikvm(2500): threadid=1: thread exiting with uncaught exception (group=0xb2f55288)
09-11 21:11:25.756: E/AndroidRuntime(2500): FATAL EXCEPTION: main
09-11 21:11:25.756: E/AndroidRuntime(2500): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.agvinsant.java1application/com.agvinsant.java1application.MainActivity}: java.lang.NullPointerException
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.os.Handler.dispatchMessage(Handler.java:99)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.os.Looper.loop(Looper.java:137)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-11 21:11:25.756: E/AndroidRuntime(2500): at java.lang.reflect.Method.invokeNative(Native Method)
09-11 21:11:25.756: E/AndroidRuntime(2500): at java.lang.reflect.Method.invoke(Method.java:511)
09-11 21:11:25.756: E/AndroidRuntime(2500): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-11 21:11:25.756: E/AndroidRuntime(2500): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-11 21:11:25.756: E/AndroidRuntime(2500): at dalvik.system.NativeStart.main(Native Method)
09-11 21:11:25.756: E/AndroidRuntime(2500): Caused by: java.lang.NullPointerException
09-11 21:11:25.756: E/AndroidRuntime(2500): at java.util.Arrays$ArrayList.<init>(Arrays.java:38)
09-11 21:11:25.756: E/AndroidRuntime(2500): at java.util.Arrays.asList(Arrays.java:154)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:128)
09-11 21:11:25.756: E/AndroidRuntime(2500): at com.agvinsant.java1application.MainActivity.onCreate(MainActivity.java:121)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.Activity.performCreate(Activity.java:5008)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-11 21:11:25.756: E/AndroidRuntime(2500): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-11 21:11:25.756: E/AndroidRuntime(2500): ... 11 more
09-11 21:11:25.766: E/URL RESPONSE ERROR(2500): getURLStringResponse