强制关闭我的Android应用程序

Question

I have made an android application where there are a login form, an update details form, etc.

Whenever I enter a wrong detail, the app stops working and a force close dialog box appears.

This is my code:

Login.java

   public class AllProductsActivity extends ListActivity
   {
       private ProgressDialog pDialog;
       JSONParser jParser = new JSONParser();
       ArrayList<HashMap<String, String>> productsList;
       private static String url_all_products = "http://192.168.1.4/android_connect/get_all_products.php";

       // JSON Node names
       private static final String TAG_SUCCESS = "success";
       private static final String TAG_PRODUCTS = "products";
       private static final String TAG_PID = "pid";
       private static final String TAG_NAME = "name";

       // products JSONArray
       JSONArray products = null;

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

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

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

    // Get listview
    ListView lv = getListView();

    // on seleting single product
    // launching Edit Product Screen
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            // getting values from selected ListItem
            String pid = ((TextView) view.findViewById(R.id.pid)).getText()
                    .toString();

            // Starting new intent
            Intent in = new Intent(getApplicationContext(),
                    EditProductActivity.class);
            // sending pid to next activity
            in.putExtra(TAG_PID, pid);

            // starting new activity and expecting some response back
            startActivityForResult(in, 100);
        }
    });

}

// 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(AllProductsActivity.this);
        pDialog.setMessage("Loading products. 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
                products = json.getJSONArray(TAG_PRODUCTS);

                // looping through All Products
                for (int i = 0; i < products.length(); i++) {
                    JSONObject c = products.getJSONObject(i);

                    // Storing each json item in variable
                    String id = c.getString(TAG_PID);
                    String name = c.getString(TAG_NAME);

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

                    // adding each child node to HashMap key => value
                    map.put(TAG_PID, id);
                    map.put(TAG_NAME, name);

                    // adding HashList to ArrayList
                    productsList.add(map);
                }
            } else {
                // no products found
                // Launch Add New product Activity
                Intent i = new Intent(getApplicationContext(),
                        NewProductActivity.class);
                // Closing all previous activities
                i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(i);
            }
        } 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(
                        AllProductsActivity.this, productsList,
                        R.layout.list_item, new String[] { TAG_PID,
                                TAG_NAME},
                        new int[] { R.id.pid, R.id.name });
                // updating listview
                setListAdapter(adapter);
            }
        });
    }
}
}

UpdateDetails.java

   public class UpdateDetails extends Activity
   {

        EditText inputName;
        EditText inputAddress;
        EditText inputPassword;
        EditText confirmPassword;
        EditText inputEmailId, inputMobileno;

        // Progress Dialog
        private ProgressDialog pDialog;

    // JSON parser class
        JSONParser jsonParser = new JSONParser();

        // JSON Node names
        private static final String resp = "success";
        //private static final String Flag = "flag";

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.updatedetails);

        // Edit Text
        inputName = (EditText) findViewById(R.id.editName);
        inputAddress = (EditText) findViewById(R.id.editAddress);
        inputPassword = (EditText) findViewById(R.id.editPassword);
        confirmPassword=(EditText) findViewById(R.id.editConfirmPassword);
        inputEmailId=(EditText) findViewById(R.id.editText2_emailid);
        inputMobileno=(EditText) findViewById(R.id.editText1_mobile);

        // Create button
        Button update_details = (Button) findViewById(R.id.buttonUpdate);

        // button click event
        update_details.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                if (inputPassword == confirmPassword){
                // updating user in background thread
                new UpdateUserDetails().execute();
                }
                else {
                    //Some Sort Of Alert Box
                    Toast.makeText(getApplicationContext(), "Please Enter Valid Details", Toast.LENGTH_SHORT).show();
                    }
            }
        });
    }

    /**
     * Background Async Task to Create new product
     * */
    class UpdateUserDetails extends AsyncTask<String, String, String> {
        /**
         * Before starting background thread Show Progress Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(UpdateDetails.this);
            pDialog.setMessage("Updating User Details.. Please wait");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        /**
         * Updating User
         * */
        protected String doInBackground(String... args) {
            String name = inputName.getText().toString();
            String address = inputAddress.getText().toString();
            String password = inputPassword.getText().toString();
            String mobileno = inputMobileno.getText().toString();
            String emailid = inputEmailId.getText().toString();

            // Building Parameters
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("name", name));
            params.add(new BasicNameValuePair("address", address));
            params.add(new BasicNameValuePair("password", password));
            params.add(new BasicNameValuePair("mobile_no", mobileno));
            params.add(new BasicNameValuePair("email_id",emailid));

            final String url_user = "http://"+ Login.serve +"/catxam/android_update.php";

            // getting JSON Object
            JSONObject json = jsonParser.makeHttpRequest(url_user,"POST", params);

            // check log cat from response
            Log.d("Update Response", json.toString());

            // check for success tag
            try {
                int success = json.getInt(resp);

                if (success == 1) {
                    // successfully update user
                    Intent i = new Intent(getApplicationContext(), MainActivity.class);
                    startActivity(i);

                    // closing this screen
                    finish();
                } else {
                    Toast.makeText(getApplicationContext(), "Unsuccessful Updation", Toast.LENGTH_SHORT).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        /**
         * After completing background task Dismiss the progress dialog
         * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog once done
            pDialog.dismiss();
        }

    }
}

Can anyone help me in identifying my mistake and help me in rectifying mistakes in my project.

I appreciate your help. Thanks in advance

Here is the logCat window!

02-13 19:32:10.096: E/AndroidRuntime(7328): FATAL EXCEPTION: AsyncTask #2

02-13 19:32:10.096: E/AndroidRuntime(7328): java.lang.RuntimeException: An error occured while executing doInBackground()

02-13 19:32:10.096: E/AndroidRuntime(7328):     at android.os.AsyncTask$3.done(AsyncTask.java:299)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.FutureTask.setException(FutureTask.java:219)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.FutureTask.run(FutureTask.java:239)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.lang.Thread.run(Thread.java:838)

02-13 19:32:10.096: E/AndroidRuntime(7328): Caused by: java.lang.NullPointerException
02-13 19:32:10.096: E/AndroidRuntime(7328):     at 
com.example.catxam.Login$CreateNewUser.doInBackground(Login.java:146)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at com.example.catxam.Login$CreateNewUser.doInBackground(Login.java:1)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at android.os.AsyncTask$2.call(AsyncTask.java:287)

02-13 19:32:10.096: E/AndroidRuntime(7328):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)

02-13 19:32:10.096: E/AndroidRuntime(7328):     ... 4 more

Sorry not able to post images :(

Answer 1

Excecute this in postExecute. To display or pass to another activity, Use in postExecute. Only main operation to be performed in doInBackground.

        try {
            int success = json.getInt(resp);

            if (success == 1) {
                // successfully update user
                Intent i = new Intent(getApplicationContext(), MainActivity.class);
                startActivity(i);

                // closing this screen
                finish();
            } else {
                Toast.makeText(getApplicationContext(), "Unsuccessful Updation", Toast.LENGTH_SHORT).show();
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

Answer 2

You cannot make a call to Toast.makeText from the doInBackground method, as it needs to be done on the UI thread.

Do this at the end of doInBackground :

// check for success tag
try {
    int success = json.getInt(resp);
    String success = success == 1 ? "success" : null;
    return success;
} catch (JSONException e) {
    e.printStackTrace();
    return null;
}

and this in onPostExecute :

protected void onPostExecute(String result) {
    if (result!= null) {
        // successfully update user
        Intent i = new Intent(getApplicationContext(), MainActivity.class);
        startActivity(i);
        // closing this screen
        finish();
    } else {
        Toast.makeText(getApplicationContext(), "Unsuccessful Updation", Toast.LENGTH_SHORT).show();
    }
    pDialog.dismiss();
}

Additionally, you should not do this in LoadAllProducts :

// updating UI from Background Thread
runOnUiThread(new Runnable()

onPostExecute is designed for you to update the UI at the end of your background task, so you don't need to create an additional Thread to execute that code.

Answer 3

As in other answers, your error (althought without logcat....) is that you call:

Toast.makeText(getApplicationContext(), "Unsuccessful Updation", Toast.LENGTH_SHORT).show();

in doInBackground , UI operations are permitted only on UI thread. On the other hand you dont need:

runOnUiThread(new Runnable() {

in onPostExecute because it is already executed on UI thread, so you should use onPostExecute for your toast message.