帮助jsonObject NPE。我可以解析并显示我想从我的数据库中获得的结果。我尝试了jsonlint.com中的php代码。我的问题是在android studio中，当我解析并显示它的工作结果时。但是当我在应用程序崩溃的地方运行活动时。
分析器
public class Send extends Activity {
EditText et1, et2, et3, et4, et5;
String team1, score1, team2, score2, Type;
Button logout;
String json_string, JSON_STRING;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.send);
et1 = (EditText) findViewById(R.id.et1);
et2 = (EditText) findViewById(R.id.et2);
et3 = (EditText) findViewById(R.id.et3);
et4 = (EditText) findViewById(R.id.et4);
et5 = (EditText) findViewById(R.id.et5);
logout = (Button) findViewById(R.id.logout);
logout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(v.getContext(), login.class));
finish();
}
});
}
public void send(View view) {
Type = et1.getText().toString();
team1 = et2.getText().toString();
score1 = et3.getText().toString();
team2 = et4.getText().toString();
score2 = et5.getText().toString();
String method = "send";
BackgroundTask backgroundTask = new BackgroundTask(this);
backgroundTask.execute(method, Type, team1, score1, team2, score2);
}
public void get(View view) {
new BgTask().execute();
}
class BgTask extends AsyncTask<Void, Void, String> {
String json_url;
@Override
protected void onPreExecute() {
json_url = "http://10.0.2.2/result/hehe.php";
}
@Override
protected String doInBackground(Void... params) {
try {
URL url = new URL(json_url);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
InputStream inputstream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputstream));
StringBuilder stringBuilder = new StringBuilder();
while ((JSON_STRING = bufferedReader.readLine()) != null) {
stringBuilder.append(JSON_STRING + "\n");
}
bufferedReader.close();
inputstream.close();
httpURLConnection.disconnect();
return stringBuilder.toString().trim();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
json_string = result;
}
}
public void publishGame(View view)
{
if(json_string == null)
{
Toast.makeText(getApplicationContext(), "Get Data First",Toast.LENGTH_SHORT).show();
}
else
{
Intent intent = new Intent(this, Games.class);
intent.putExtra("json_data", json_string);
startActivity(intent);
}
}
}
这是应用程序显示json结果的位置
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.games);
final Spinner sports;
final String[] str = {"Sports", "Basketball", "Football", "Futsal", "Softball", "Badminton", "Track and Field", "Chess", "Table Tennis", "Swimming", "Volleyball", "Sepak Takraw", "Taekwondo", "Judo", "Frisbee"};
sports = (Spinner) findViewById(R.id.sp1);
nonsports = (Spinner) findViewById(R.id.sp2);
games = (Button) findViewById(R.id.games);
news = (Button) findViewById(R.id.news);
sched = (Button) findViewById(R.id.sched);
stand = (Button) findViewById(R.id.stand);
listview = (ListView) findViewById(R.id.listView);
gamesAdapter = new GamesAdapter(this,R.layout.gamesadapterlayout);
listview.setAdapter(gamesAdapter);
Bundle intent=getIntent().getExtras();
if(intent !=null) {
json_string = getIntent().getExtras().getString("json_data");
}
ArrayAdapter<String> sp1 = new ArrayAdapter<String>(this, R.layout.support_simple_spinner_dropdown_item, str);
sports.setAdapter(sp1);
games.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(v.getContext(), Games.class); startActivity(getIntent());
}
});
news.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(v.getContext(), MainActivity.class);
startActivity(intent);
}
});
stand.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(v.getContext(), Standings.class);
startActivity(intent);
}
});
sched.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(v.getContext(), Schedule.class);
startActivity(intent);
}
});
sports.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long row_id) {
Intent intent = null;
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
try {
jsonObject = new JSONObject(json_string);
jsonArray = jsonObject.getJSONArray("server_response");
int count = 0;
String team1, score1, team2, score2, Type;
while (count < jsonArray.length()) {
JSONObject JO = jsonArray.getJSONObject(count);
team1 = JO.getString("team1");
score1 = JO.getString("score1");
team2 = JO.getString("team2");
score2 = JO.getString("score2");
Type = JO.getString("Type");
Downloader downloader = new Downloader(team1, score1, team2, score2, Type);
gamesAdapter.add(downloader);
count++;
}
} catch (JSONException e) {
e.printStackTrace();
}
}
错误指向
try {
jsonObject = new JSONObject(json_string);
它告诉我它是NPE
Here is an image where i will dispaly the result in Games.class
The result of the display in the Games.class
现在问题是在显示之后。当我点击其他菜单并再次单击“游戏”菜单时，它会崩溃。因为jsonObject NPE。感谢
logcat的
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.abe.ateneofiesta, PID: 6392
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.abe.ateneofiesta/com.example.abe.ateneofiesta.Games}: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
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.abe.ateneofiesta.Games.onCreate(Games.java:111)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)