我是Android的新手。我看过一个教程，将我的数据库中的一些元素放到我的列表视图中，但是我遇到了一些问题。当我打开下面的页面时，应用程序崩溃：ListBooks.java。 下面我把我的代码。我错了什么？
public class customAdapter{
public List<HashMap<String, Object>> parse(JSONObject JObject) {
JSONArray infoBooks = null;
try {
infoBooks = JObject.getJSONArray("infoBooks");
} catch (JSONException e) {
e.printStackTrace();
}
return getBooks(infoBooks);
}
private List<HashMap<String, Object>> getBooks(JSONArray infoBooks){
int booksCount = infoBooks.length();
List<HashMap<String, Object>> bookList = new ArrayList<HashMap<String, Object>>();
HashMap<String, Object> book;
for(int i = 0; i < booksCount; i++) {
try {
book = getBook((JSONObject) infoBooks.get(i));
bookList.add(book);
} catch (JSONException e) {
e.printStackTrace();
}
}
return bookList;
}
private HashMap<String, Object> getBook(JSONObject jBook){
HashMap<String, Object> book = new HashMap<String, Object>();
String user_name = "";
String title = "";
String author = "";
String urlImage = "";
try {
user_name = jBook.getString("user_name");
title = jBook.getString("title");
author = jBook.getString("author");
urlImage = jBook.getString("urlImage");
String details = "Title: " + title + "\n" +
"Author/s: " + author;
book.put("user_name", user_name);
book.put("details", details);
book.put("launcherImage", R.mipmap.ic_launcher);
book.put("urlImage", urlImage);
} catch (JSONException e) {
e.printStackTrace();
}
return book;
}
}
ListView mListView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search_books);
String strUrl = "http://192.168.1.118:8888/webappdb/listViewBooks.php";
DownloadTask downloadTask = new DownloadTask();
downloadTask.execute(strUrl);
mListView = (ListView) findViewById(R.id.listView);
}
private String downloadUrl (String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
try {
URL url = new URL(strUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}
data = sb.toString();
br.close();
}catch (Exception e){
Log.d("Exception while downloading url", e.toString());
}finally {
iStream.close();
}
return data;
}
private class DownloadTask extends AsyncTask<String, Integer, String>{
String data = null;
@Override
protected String doInBackground(String... url) {
try {
data = downloadUrl(url[0]);
} catch (IOException e) {
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
listViewLoaderTask.execute(result);
}
}
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
@Override
protected SimpleAdapter doInBackground(String... strJson) {
try {
jObject = new JSONObject(strJson[0]);
customAdapter customAdapter = new customAdapter();
customAdapter.parse(jObject);
} catch (JSONException e) {
Log.d("JSON Exception1", e.toString());
}
customAdapter customAdapter = new customAdapter();
List<HashMap<String, Object>> books = null;
try {
books = customAdapter.parse(jObject);
} catch (Exception e){
Log.d("Exception", e.toString());
}
String infoFrom[] = {"user_name", "details"};
int infoTo[] = {R.id.user_name_search, R.id.bookDescriptionSearch};
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), books, R.layout.row_list_books, infoFrom, infoTo);
return adapter;
}
@Override
protected void onPostExecute(SimpleAdapter adapter) {
mListView.setAdapter(adapter);
for (int i = 0; i < adapter.getCount(); i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
String imgUrl = (String) hm.get("urlImage");
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
HashMap<String, Object> hmDownload = new HashMap<String, Object>();
hm.put("urlImage", imgUrl);
hm.put("position", i);
imageLoaderTask.execute();
}
}
}
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream = null;
String imgUrl = (String) hm[0].get("urlImage");
int position = (Integer) hm[0].get("position");
URL url;
try {
url = new URL(imgUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
iStream = urlConnection.getInputStream();
File cacheDirectory = getBaseContext().getCacheDir();
File tmpFile = new File (cacheDirectory.getPath() + "/wpta_" + position + ".png");
FileOutputStream fOutputStream = new FileOutputStream(tmpFile);
Bitmap b = BitmapFactory.decodeStream(iStream);
b.compress(Bitmap.CompressFormat.PNG, 100, fOutputStream);
fOutputStream.flush();
fOutputStream.close();
HashMap<String, Object> hmBitmap = new HashMap<String, Object>();
hmBitmap.put("launcherImage", tmpFile.getPath());
hmBitmap.put("position", position);
return hmBitmap;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
String path = (String) result.get("launcherImage");
int position = (Integer) result.get("position");
SimpleAdapter simpleAdapter = (SimpleAdapter) mListView.getAdapter();
HashMap<String, Object> hm = (HashMap<String, Object>) simpleAdapter.getItem(position);
hm.put("launcherImage", path);
simpleAdapter.notifyDataSetChanged();
}
}
03-09 23:12:36.876 9938-9938/? E/Zygote: v2
03-09 23:12:36.886 9938-9938/? E/SELinux: [DEBUG] get_category: variable seinfo: default sensitivity: NULL, cateogry: NULL
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:124)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:124)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:124)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:135)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:135)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: org.json.JSONException: No value for title
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.get(JSONObject.java:389)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at org.json.JSONObject.getString(JSONObject.java:550)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBook(customAdapter.java:58)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.getBooks(customAdapter.java:37)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.customAdapter.parse(customAdapter.java:24)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:135)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at gamingproject.sellmybooks.SearchBooks$ListViewLoaderTask.doInBackground(SearchBooks.java:114)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$2.call(AsyncTask.java:288)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.FutureTask.run(FutureTask.java:237)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
03-09 23:12:39.476 9938-10019/gamingproject.sellmybooks W/System.err: at java.lang.Thread.run(Thread.java:818)
提前致谢。