java - 机器人:强制关闭

Question

我是 Android 应用程序开发的新手，我正在尝试开发一个可用的应用程序。但是我创建的这个页面自创建以来就出现了问题，我真的希望有人能帮助我解决这个问题。每次我运行这个程序时，应用程序都会关闭。

这是源代码:

public class Latest extends ListActivity {

// Progress Dialog
private ProgressDialog pDialog;

// Creating JSON Parser object
JSONParser jParser = new JSONParser();

ArrayList<HashMap<String, String>> eventsList;

// url to get all products list
private static String url_all_products = "http://";

// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_BOOKS = "books";
private static final String TAG_TITLE = "title";
private static final String TAG_AUTHOR = "author";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_PRICE = "price";
private static final String TAG_DISCOUNT = "discount";
private static final String TAG_CATEGORY = "category";
private static final String TAG_PID = "pid";

// products JSONArray
JSONArray events = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_latest);

    // Hashmap for ListView
    eventsList = new ArrayList<HashMap<String, String>>();

    // Loading products in Background Thread
    new LoadAllProducts().execute();

    // Get listview
//  ListView lv = getListView();



}

// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    // if result code 100
    if (resultCode == 100) {
        // if result code 100 is received 
        // means user edited/deleted product
        // reload this screen again
        Intent intent = getIntent();
        finish();
        startActivity(intent);
    }

}

/**
 * Background Async Task to Load all product by making HTTP Request
 * */
class LoadAllProducts extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(Latest.this);
        pDialog.setMessage("Loading Books. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    /**
     * getting All products from url
     * */
    protected String doInBackground(String... args) {
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        // getting JSON string from URL
        JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);

        // Check your log cat for JSON reponse
        Log.d("All Products: ", json.toString());

        try {
            // Checking for SUCCESS TAG
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // products found
                // Getting Array of Products
                events = json.getJSONArray(TAG_BOOKS);

                // looping through All Products
                for (int i = events.length()-1; i > events.length()-4; i--) {
                    JSONObject c = events.getJSONObject(i);

                    // Storing each json item in variable
                    String pid = c.getString(TAG_PID);
                    String title = c.getString(TAG_TITLE);
                    String author = "Author :" +c.getString(TAG_AUTHOR);
                    String description = c.getString(TAG_DESCRIPTION);
                    String price = "Price :" +c.getString(TAG_PRICE);
                    String discount = "Discount : " +c.getString(TAG_DISCOUNT);
                    String category = "Category :" +c.getString(TAG_CATEGORY);


                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    map.put(TAG_PID, pid);
                    map.put(TAG_TITLE, title);
                    map.put(TAG_AUTHOR, author);
                    map.put(TAG_DESCRIPTION, description);
                    map.put(TAG_PRICE, price);
                    map.put(TAG_DISCOUNT, discount);
                    map.put(TAG_CATEGORY, category);
                    // adding HashList to ArrayList
                    eventsList.add(map);
                }
            } 


        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
        pDialog.dismiss();
        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                /**
                 * Updating parsed JSON data into ListView
                 * */
                ListAdapter adapter = new SimpleAdapter(
                        Latest.this, eventsList,
                        R.layout.list_item2, new String[] { TAG_PID, TAG_TITLE, TAG_AUTHOR, TAG_DESCRIPTION, TAG_PRICE, TAG_DISCOUNT, TAG_DESCRIPTION},
                        new int[] { R.id.pid, R.id.title, R.id.author,R.id.description, R.id.price, R.id.discount,R.id.category });
                // updating listview
                setListAdapter(adapter);
            }
        });

    }

}
}

这是 LogCat(错误):

Buffer Error(1024): Error converting result java.lang.NullPointerException: lock == null
JSON Parser(1024): Error parsing data org.json.JSONException: End of input at character 0 of 
AndroidRuntime(1024): FATAL EXCEPTION: AsyncTask #1
AndroidRuntime(1024): java.lang.RuntimeException: An error occured while executing  doInBackground()
AndroidRuntime(1024):   at android.os.AsyncTask$3.done(AsyncTask.java:299)
AndroidRuntime(1024):   at  java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
AndroidRuntime(1024):   at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
AndroidRuntime(1024):   at java.util.concurrent.FutureTask.run(FutureTask.java:239)
AndroidRuntime(1024):   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
AndroidRuntime(1024):   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
AndroidRuntime(1024):   at java.lang.Thread.run(Thread.java:856)
AndroidRuntime(1024): Caused by: java.lang.NullPointerException
AndroidRuntime(1024):   at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:113)
AndroidRuntime(1024):   at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:1)
AndroidRuntime(1024):   at android.os.AsyncTask$2.call(AsyncTask.java:287)
AndroidRuntime(1024):   at java.util.concurrent.FutureTask.run(FutureTask.java:234)
AndroidRuntime(1024):   ... 3 more

这是 JSONParser 类:

public class JSONParser {
    private static final String TAG = "JSONParser";

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
        List<NameValuePair> params) {

    // Making HTTP request
    try{
        // check for request method
        if(method == "POST"){
            Log.d(TAG, "method=POST");
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            Log.d(TAG, "url=" + url);
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            Log.d(TAG, "method=GET");
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            Log.d(TAG, "url=" + url);
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }           

        Log.d(TAG, "HTTP request done");
    } catch (UnsupportedEncodingException e) {
        Log.d(TAG, "UNSUPPORTED ENCODING: ", e);
    } catch (ClientProtocolException e) {
        Log.d(TAG, "CLIENT PROTOCOL: ", e);
    } catch (IOException e) {
        Log.d(TAG, "IO EXCEPTION: ", e);
    }

    try {
        Log.d(TAG, "Extract response");
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            Log.d(TAG, "line=" + line);
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
        Log.d(TAG, "json=" + json);
    } catch (Exception e) {
        Log.d(TAG, "Exception: ", e);
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        Log.d(TAG, "Parse JSON");
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.d(TAG, "JSONException: ", e);
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
}

这是最近的日志:

03-19 12:44:55.985: D/dalvikvm(919): GC_CONCURRENT freed 338K, 15% free 2791K/3268K, paused 111ms+119ms, total 437ms
03-19 12:45:10.246: D/dalvikvm(919): GC_CONCURRENT freed 373K, 16% free 2815K/3324K, paused 110ms+100ms, total 551ms
03-19 12:45:11.366: D/JSONParser(919): IO EXCEPTION: 
03-19 12:45:11.366: D/JSONParser(919): org.apache.http.conn.HttpHostConnectException: Connection to http:// refused
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:183)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
03-19 12:45:11.366: D/JSONParser(919):  at com.spyraa.bookstore.JSONParser.makeHttpRequest(JSONParser.java:66)
03-19 12:45:11.366: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:105)
03-19 12:45:11.366: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:1)
03-19 12:45:11.366: D/JSONParser(919):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-19 12:45:11.366: D/JSONParser(919):  at java.util.concurrent.FutureTask.run(FutureTask.java:234)
03-19 12:45:11.366: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
03-19 12:45:11.366: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
03-19 12:45:11.366: D/JSONParser(919):  at java.lang.Thread.run(Thread.java:856)
03-19 12:45:11.366: D/JSONParser(919): Caused by: java.net.ConnectException: failed to connect to http/1 (port 80): connect failed: ECONNREFUSED (Connection refused)
03-19 12:45:11.366: D/JSONParser(919):  at libcore.io.IoBridge.connect(IoBridge.java:114)
03-19 12:45:11.366: D/JSONParser(919):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
03-19 12:45:11.366: D/JSONParser(919):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
03-19 12:45:11.366: D/JSONParser(919):  at java.net.Socket.connect(Socket.java:842)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
03-19 12:45:11.366: D/JSONParser(919):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
03-19 12:45:11.366: D/JSONParser(919):  ... 14 more
03-19 12:45:11.366: D/JSONParser(919): Caused by: libcore.io.ErrnoException: connect failed: ECONNREFUSED (Connection refused)
03-19 12:45:11.366: D/JSONParser(919):  at libcore.io.Posix.connect(Native Method)
03-19 12:45:11.366: D/JSONParser(919):  at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:85)
03-19 12:45:11.366: D/JSONParser(919):  at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
03-19 12:45:11.366: D/JSONParser(919):  at libcore.io.IoBridge.connect(IoBridge.java:112)
03-19 12:45:11.366: D/JSONParser(919):  ... 19 more
03-19 12:45:11.499: D/JSONParser(919): Extract response
03-19 12:45:12.838: D/JSONParser(919): Exception: 
03-19 12:45:12.838: D/JSONParser(919): java.lang.NullPointerException: lock == null
03-19 12:45:12.838: D/JSONParser(919):  at java.io.Reader.<init>(Reader.java:64)
03-19 12:45:12.838: D/JSONParser(919):  at java.io.InputStreamReader.<init>(InputStreamReader.java:79)
03-19 12:45:12.838: D/JSONParser(919):  at com.spyraa.bookstore.JSONParser.makeHttpRequest(JSONParser.java:83)
03-19 12:45:12.838: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:105)
03-19 12:45:12.838: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:1)
03-19 12:45:12.838: D/JSONParser(919):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-19 12:45:12.838: D/JSONParser(919):  at java.util.concurrent.FutureTask.run(FutureTask.java:234)
03-19 12:45:12.838: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
03-19 12:45:12.838: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
03-19 12:45:12.838: D/JSONParser(919):  at java.lang.Thread.run(Thread.java:856)
03-19 12:45:12.985: D/JSONParser(919): Parse JSON
03-19 12:45:31.570: D/JSONParser(919): JSONException: 
03-19 12:45:31.570: D/JSONParser(919): org.json.JSONException: End of input at character 0 of 
03-19 12:45:31.570: D/JSONParser(919):  at org.json.JSONTokener.syntaxError(JSONTokener.java:450)
03-19 12:45:31.570: D/JSONParser(919):  at org.json.JSONTokener.nextValue(JSONTokener.java:97)
03-19 12:45:31.570: D/JSONParser(919):  at org.json.JSONObject.<init>(JSONObject.java:154)
03-19 12:45:31.570: D/JSONParser(919):  at org.json.JSONObject.<init>(JSONObject.java:171)
03-19 12:45:31.570: D/JSONParser(919):  at com.spyraa.bookstore.JSONParser.makeHttpRequest(JSONParser.java:101)
03-19 12:45:31.570: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:105)
03-19 12:45:31.570: D/JSONParser(919):  at com.spyraa.bookstore.Latest$LoadAllProducts.doInBackground(Latest.java:1)
03-19 12:45:31.570: D/JSONParser(919):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-19 12:45:31.570: D/JSONParser(919):  at java.util.concurrent.FutureTask.run(FutureTask.java:234)
03-19 12:45:31.570: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
03-19 12:45:31.570: D/JSONParser(919):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
03-19 12:45:31.570: D/JSONParser(919):  at java.lang.Thread.run(Thread.java:856)
03-19 12:45:32.365: D/dalvikvm(919): GC_CONCURRENT freed 412K, 17% free 2798K/3352K, paused 55ms+31ms, total 671ms

除上述之外，大多数 logcat 都包含这两个:

03-19 12:45:44.466: I/Choreographer(919): Skipped 289 frames!  The application may be doing too much work on its main thread.
03-19 12:45:44.706: W/Trace(919): Unexpected value from nativeGetEnabledTags: 0

Answer 1

由于您没有提供行号，我只能猜测。

Error parsing data org.json.JSONException: End of input at character 0 of

提示无效的 JSON 字符串。您应该将接收到的 JSON 字符串打印到 logcat 以进行调试。

更新:

JSONParser 的问题(到目前为止我所看到的)主要是它捕获异常、转储一些消息然后继续。结果是您通常会收到多条消息，并且不知道它最初在哪里失败。

这就是为什么您必须将跟踪语句添加到 makeHttpRequest() 中以查看失败的原因。另一种(附加)方法是删除所有 try/catch 语句并让异常传播到外部。然后您将获得第一个失败所在的堆栈跟踪，并且可以查看问题的真正原因。

但即便如此，适当的跟踪和调试日志也是必不可少的。