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多分あなたが私を助けることができます。私のアプリケーションでは、APIからmovieIDをSQLiteDatabaseに保存することができます。 movieIDとuserIDを正常に取得できました。ムービーのAPIリクエストが送信されると、ログにも正常に返されたことが表示されますが、次のエラーが表示され続け、アプリケーションが再起動またはクラッシュします。AsyncTask on doInBackground（）String.length（）nullオブジェクト参照
05-19 18:43:10.118 8103-8103/? W/PathParser: Points are too far apart 4.000000596046461
05-19 18:43:15.263 2407-2626/? I/ActivityManager: START u0 {flg=0x10000 cmp=com.example.asc.app/.MovieList} from uid 10058 on display 0
05-19 18:43:15.283 8103-8103/? W/PathParser: Points are too far apart 4.000000596046461
05-19 18:43:15.293 8103-8103/? D/MovieList:: movie_user_id1
05-19 18:43:17.222 8103-8651/? W/System.err: java.io.FileNotFoundException: https://api.themoviedb.org/3/movie/278?api_key=b5c3cfd30f424540a36db95684a067e0
05-19 18:43:17.222 8103-8651/? W/System.err: at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:238)
05-19 18:43:17.222 8103-8651/? W/System.err: at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210)
05-19 18:43:17.222 8103-8651/? W/System.err: at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java)
05-19 18:43:17.222 8103-8651/? W/System.err: at com.example.asc.app.MovieHttpClient.getMovieData(MovieHttpClient.java:43)
05-19 18:43:17.222 8103-8651/? W/System.err: at com.example.asc.app.MovieAsyncTask.doInBackground(MovieAsyncTask.java:21)
05-19 18:43:17.222 8103-8651/? W/System.err: at com.example.asc.app.MovieAsyncTask.doInBackground(MovieAsyncTask.java:13)
05-19 18:43:17.222 8103-8651/? W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:295)
05-19 18:43:17.222 8103-8651/? W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
05-19 18:43:17.222 8103-8651/? W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
05-19 18:43:17.222 8103-8651/? W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
05-19 18:43:17.222 8103-8651/? W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
05-19 18:43:17.222 8103-8651/? W/System.err: at java.lang.Thread.run(Thread.java:818)
05-19 18:43:17.223 8103-8103/? W/System.err: java.util.concurrent.ExecutionException: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
05-19 18:43:17.223 8103-8103/? W/System.err: at java.util.concurrent.FutureTask.report(FutureTask.java:94)
05-19 18:43:17.223 8103-8103/? W/System.err: at java.util.concurrent.FutureTask.get(FutureTask.java:164)
05-19 18:43:17.223 8103-8103/? W/System.err: at android.os.AsyncTask.get(AsyncTask.java:498)
05-19 18:43:17.223 8103-8103/? W/System.err: at com.example.asc.app.MovieList.populateList(MovieList.java:106)
05-19 18:43:17.223 8103-8651/? E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.example.asc.app, PID: 8103
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.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:156)
at org.json.JSONObject.<init>(JSONObject.java:173)
at com.example.asc.app.JSONMovieParser.getMovie(JSONMovieParser.java:19)
at com.example.asc.app.MovieAsyncTask.doInBackground(MovieAsyncTask.java:26)
at com.example.asc.app.MovieAsyncTask.doInBackground(MovieAsyncTask.java:13)
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)
MovieList.java - 私は
public class MovieList extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener{
dbOpenHelper helper = new dbOpenHelper(this);
int movieID = -1;
int userID = 1;
String title = "MLTitle";
String posterPath = "MLPosterPath";
private ArrayAdapter<String> listAdapter ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_movie_list);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
navigationView.setCheckedItem(R.id.nav_movielist);
populateList();
}
public void populateList() {
SQLiteDatabase database = helper.getWritableDatabase();
userID = ((ApplicationSession) getApplication()).getUserID();
String[] projection = {
helper.MOVIE_USER_ID,
helper.MOVIE_REF_ID,
helper.MOVIE_TITLE,
helper.MOVIE_POSTER_PATH
};
String selection = helper.MOVIE_USER_ID + " = ?";
String[] selectionArgs = {Integer.toString(userID)};
Log.d("MovieList: ", helper.MOVIE_USER_ID+userID); //Displays correct user id
Cursor cursor = database.query(
helper.TABLE_MOVIES, // The table to query
projection, // The columns to return
selection, // The columns for the WHERE clause
selectionArgs, // The values for the WHERE clause
null, // don't group the rows
null, // don't filter by row groups
null // The sort order
);
if (cursor.moveToFirst()){
do{
movieID = cursor.getInt(cursor.getColumnIndex("movie_ref_id"));
MovieAsyncTask task = new MovieAsyncTask();
try {
boolean search = false;
String searchString = Integer.toString(movieID);
JSONObject object = task.execute(searchString, search).get();
List<String> titlesList = new ArrayList<>();
List<String> posterpathList = new ArrayList<>();
ListView movieList = (ListView) findViewById(R.id.lstMovies);
final int numberOfItemsInResp = object.length();
for(int i = 0; i < numberOfItemsInResp; i++)
{
try{
title = object.get("title").toString();
posterPath = object.get("poster_path").toString();
}
catch (JSONException e) {
e.printStackTrace();
}
//FILL LIST HERE
titlesList.add(title);
posterpathList.add(posterPath);
}
movieList.setAdapter(listAdapter);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}while(cursor.moveToNext());
}
cursor.close();
}
MovieAsyncTask.java
public class MovieAsyncTask extends AsyncTask<Object, Void, JSONObject> {
@Override
protected JSONObject doInBackground(Object... params) {
String searchString = (String) params[0];
boolean search = (boolean) params[1];
String data = ((new MovieHttpClient()).getMovieData(searchString, search));
JSONObject jObj = new JSONObject();
try {
jObj = JSONMovieParser.getMovie(data);
} catch (JSONException e) {
e.printStackTrace();
}
return jObj;
}
}
MovieHTTPClient.java
public class MovieHttpClient {
private static final String API_KEY = "?api_key=b5c3cfd30f424540a36db95684a067e0";
private static final String BASE_URL = "https://api.themoviedb.org/3/";
private static final String SEARCH = "search/movie";
private static final String MOVIE = "movie/";
private static final String QUERY = "&query=";
public String getMovieData(String searchString, boolean search) {
HttpURLConnection con = null ;
InputStream is = null;
String url;
try {
if (search) {
url = BASE_URL + SEARCH + API_KEY + QUERY;
url += searchString;
}else{
url = BASE_URL + MOVIE + searchString + API_KEY;
}
con = (HttpURLConnection) (new URL(url)).openConnection();
con.setRequestMethod("GET");
con.setDoInput(true);
con.setDoOutput(true);
con.connect();
StringBuffer buffer = new StringBuffer();
is = con.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line = null;
while ((line = br.readLine()) != null)
buffer.append(line + "\r\n");
is.close();
con.disconnect();
return buffer.toString();
}
catch(Throwable t) {
t.printStackTrace();
}
finally {
try { is.close(); } catch(Throwable t) {}
try { con.disconnect(); } catch(Throwable t) {}
}
return null;
}
}
を表示したい場所を編集1：btnSearch
btnSearch.setOnClickListener(new android.view.View.OnClickListener() {
@Override
public void onClick(View arg0) {
String searchString = txtSearch.getText().toString();
TextView tvTitle = (TextView) findViewById(R.id.tvTitle);
TextView tvRating = (TextView) findViewById(R.id.tvRating);
TextView tvReleaseDate = (TextView) findViewById(R.id.tvReleaseDate);
TextView tvOverview = (TextView) findViewById(R.id.tvOverview);
ImageView imgVPoster = (ImageView) findViewById(R.id.imgVPoster);
boolean search = true;
MovieAsyncTask task = new MovieAsyncTask();
try {
JSONObject object = task.execute(searchString, search).get();
//String title = "title";
//String posterPath = "poster Path";
String rating = "rating";
String releaseDate = "release Date";
String overview = "overview";
final int numberOfItemsInResp = object.length();
for(int i = 0; i < numberOfItemsInResp; i++)
{
try{
title = object.get("title").toString();
movieID = (object.getInt("id"));
posterPath = object.get("poster_path").toString();
rating = object.get("vote_average").toString();
releaseDate = object.get("release_date").toString();
overview = object.get("overview").toString();
}
catch (JSONException e) {
e.printStackTrace();
}
}
String urlStr = BASE_URL + FILE_SIZE + posterPath;
tvTitle.setText(title);
tvRating.setText("Rating: " + rating + "/10");
tvReleaseDate.setText("Released: " + releaseDate);
tvOverview.setText("Plot \n" + overview);
new SetPosterTask((ImageView) findViewById(R.id.imgVPoster))
.execute(urlStr);
imgVPoster.setVisibility(View.VISIBLE);
ibtnOff.setVisibility(View.VISIBLE);
Log.d("MovieDetails", urlStr);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
}
});
[NullPointerExceptionとは何ですか？それを修正するにはどうすればいいですか？]（http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix -it） – Zoe
実行後にget（）を呼び出すと、Asynctaskの目的が無効になります。 –
別のアクティビティでは、オブジェクトを取得するために同じ構造を使用しました。 btnSearchで更新されました。このインスタンスでなぜそれが動作するのか、またはAsynctasksを行う適切な方法を詳しく説明できますか？ – Toxic