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我是學生，我正在學習android，我得到以下錯誤，我無法找到該錯誤的解決方案，請幫助我解決該錯誤。謝謝...JSON在運行時解析錯誤
java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.sumit.json1/com.sumit.json1.ParseJSON}:
java.lang.NullPointerException: Attempt to invoke virtual method
'org.json.JSONObject org.json.JSONArray.getJSONObject(int)' on a null object
reference.
沒有連接到數據庫的問題。我PHP代碼是這是對hostinger.in
<?
//these are the server details
//the username is root by default in case of xampp
//password is nothing by default
//and lastly we have the database named android. if your database name is
different you have to change it
$servername = "mysql.hostinger.in";
$username = "username";
$password = "*********";
$database = "database_name";
//creating a new connection object using mysqli
$conn = new mysqli($servername, $username, $password, $database);
//if there is some error connecting to the database
//with die we will stop the further execution by displaying a message
causing the error
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
//if everything is fine
//creating an array for storing the data
$heroes = array();
//this is our sql query
$sql = "SELECT id, name, email, username, password, gender, lat, lon FROM
appusers;";
//creating an statment with the query
$stmt = $conn->prepare($sql);
//executing that statment
$stmt->execute();
//binding results for that statment
$stmt->bind_result($id, $name, $email, $username, $password, $gender, $lat,
$lon);
//looping through all the records
while($stmt->fetch()){
//pushing fetched data in an array
$temp = [
'id'=>$id,
'name'=>$name,
'email'=>$email,
'username'=>$username,
'password'=>$password,
'gender'=>$gender,
'lat'=>$lat,
'lon'=>$lon
];
//pushing the array inside the hero array
array_push($heroes, $temp);
}
//displaying the data in json format
echo json_encode($heroes);
主辦瞭解析JSON我的Android代碼即ParseJSON.java
public class ParseJSON extends ActionBarActivity implements
View.OnClickListener{
private String myJSONString;
private static final String JSON_ARRAY ="heroes";
private static final String ID = "id";
private static final String NAME= "name";
private static final String EMAIL = "email";
private static final String USERNAME= "username";
private static final String PASSWORD = "password";
private static final String GENDER = "gender";
private static final String LAT = "lat";
private static final String LON = "lon";
private JSONArray users = null;
private int TRACK = 0;
private EditText editTextId;
private EditText editTextName;
private EditText editTextEmail;
private EditText editTextUserName;
private EditText editTextPassword;
private EditText editTextGender;
private EditText editTextLat;
private EditText editTextLon;
Button btnPrev;
Button btnNext;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_parse_json);
Intent intent = getIntent();
myJSONString = intent.getStringExtra(MainActivity.MY_JSON);
editTextId = (EditText) findViewById(R.id.editTextID);
editTextName = (EditText) findViewById(R.id.editTextName);
editTextEmail = (EditText) findViewById(R.id.editTextEmail);
editTextUserName = (EditText) findViewById(R.id.editTextUsername);
editTextPassword = (EditText) findViewById(R.id.editTextPassword);
editTextGender = (EditText) findViewById(R.id.editTextGender);
editTextLat = (EditText) findViewById(R.id.editTextLat);
editTextLon = (EditText) findViewById(R.id.editTextLon);
btnPrev = (Button) findViewById(R.id.buttonPrev);
btnNext = (Button) findViewById(R.id.buttonNext);
btnPrev.setOnClickListener(this);
btnNext.setOnClickListener(this);
extractJSON();
showData();
}
private void extractJSON(){
try {
JSONObject jsonObject = new JSONObject(myJSONString);
users = jsonObject.getJSONArray(JSON_ARRAY);
} catch (JSONException e) {
e.printStackTrace();
}
}
private void moveNext(){
if(TRACK<users.length()){
TRACK++;
}
showData();
}
private void movePrev(){
if(TRACK>0){
TRACK--;
}
showData();
}
private void showData(){
try {
JSONObject jsonObject = users.getJSONObject(TRACK);
editTextId.setText(jsonObject.getString(ID));
editTextName.setText(jsonObject.getString(NAME));
editTextEmail.setText(jsonObject.getString(EMAIL));
editTextUserName.setText(jsonObject.getString(USERNAME));
editTextPassword.setText(jsonObject.getString(PASSWORD));
editTextGender.setText(jsonObject.getString(GENDER));
editTextLat.setText(jsonObject.getString(LAT));
editTextLon.setText(jsonObject.getString(LON));
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_parse_json, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onClick(View v) {
if(v == btnNext){
moveNext();
}
if(v == btnPrev){
movePrev();
}
}
}
在我的Android項目MainActivity.java被賦予波紋管如果有任何錯誤發現plz幫我解僱
public class MainActivity extends ActionBarActivity implements View.OnClickListener {
private TextView textViewJSON;
private Button buttonGet;
private Button buttonParse;
public static final String MY_JSON ="MY_JSON";
private static final String JSON_URL = "http://mydatabasedb.16mb.com/JSON1/send-data1.php";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textViewJSON = (TextView) findViewById(R.id.textViewJSON);
textViewJSON.setMovementMethod(new ScrollingMovementMethod());
buttonGet = (Button) findViewById(R.id.buttonGet);
buttonParse = (Button) findViewById(R.id.buttonParse);
buttonGet.setOnClickListener(this);
buttonParse.setOnClickListener(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onClick(View v) {
if(v==buttonGet){
getJSON(JSON_URL);
}
if(v==buttonParse){
showParseActivity();
}
}
private void showParseActivity() {
Intent intent = new Intent(this, ParseJSON.class);
intent.putExtra(MY_JSON,textViewJSON.getText().toString());
startActivity(intent);
}
private void getJSON(String url) {
class GetJSON extends AsyncTask<String, Void, String>{
ProgressDialog loading;
@Override
protected void onPreExecute() {
super.onPreExecute();
loading = ProgressDialog.show(MainActivity.this, "Please Wait...",null,true,true);
}
@Override
protected String doInBackground(String... params) {
String uri = params[0];
BufferedReader bufferedReader = null;
try {
URL url = new URL(uri);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String json;
while((json = bufferedReader.readLine())!= null){
sb.append(json+"\n");
}
return sb.toString().trim();
}catch(Exception e){
return null;
}
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
loading.dismiss();
textViewJSON.setText(s);
}
}
GetJSON gj = new GetJSON();
gj.execute(url);
}
}
'users = jsonObject.getJSONArray（JSON_ARRAY）;' – Sumit
在上面的行我得到了錯誤 – Sumit