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我有这样的代码：Android应用程序异常
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_log_reg);
pw=(ProgressBar) findViewById(R.id.wait);
pw.setVisibility(View.GONE);
SharedPreferences settings = getSharedPreferences(info.PREFS_NAME, 0);
boolean current_status = settings.getBoolean("status",false);
String saved_phone;
String saved_password;
if(current_status){
saved_phone = settings.getString("phone","");
saved_password = settings.getString("password","");
SyncTask syncTask = new SyncTask(this,"L");
syncTask.execute("LOGIN", "", "", "", "", saved_phone,saved_password);
}
应用程序总是crushs，当我删除
SharedPreferences settings = getSharedPreferences(info.PREFS_NAME, 0);
boolean current_status = settings.getBoolean("status",false);
String saved_phone;
String saved_password;
if(current_status){
saved_phone = settings.getString("phone","");
saved_password = settings.getString("password","");
SyncTask syncTask = new SyncTask(this,"L");
syncTask.execute("LOGIN", "", "", "", "", saved_phone,saved_password);
我可以理解为什么它crushs，因为SyncTask类的工作，当我把它称为来自其他类。我试图解决debuger的问题，但它不能帮助我。 这是我的日志：
06-24 10:28:13.226 8479-8479/com.myapp E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.LogReg}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.myapp.SyncTask.onPreExecute(SyncTask.java:38)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at com.myapp.LogReg.onCreate(LogReg.java:41)
at android.app.Activity.performCreate(Activity.java:5008)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
at android.app.ActivityThread.access$600(ActivityThread.java:130)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
这是我SyncTask：
public class SyncTask extends AsyncTask<String,Void,String> {
Context ctx;
String type;
AlertDialog alertDialog;
static String info="",name="",surname="";
private static final String TAG = "myLogs";
SyncTask(Context ctx, String type) {
this.ctx = ctx;
this.type = type;
}
@Override
protected void onPreExecute() {
if (type.equals("L")) {
Login.pw.setVisibility(View.VISIBLE);
Login.ent.setClickable(false);
}
}
@Override
protected String doInBackground(String... params) {
String URL_REG = "http://androidsqltest.netau.net/reg.php";
String URL_LOGIN = "http://androidsqltest.netau.net/login.php";
if (params[0].equals("REGISTRATION")) {
try {
URL url = new URL(URL_REG);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
OutputStream OS = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
String data = URLEncoder.encode("name", "UTF-8") + "=" + URLEncoder.encode(params[1], "UTF-8") + "&" +
URLEncoder.encode("surname", "UTF-8") + "=" + URLEncoder.encode(params[2], "UTF-8") + "&" +
URLEncoder.encode("phone", "UTF-8") + "=" + URLEncoder.encode(params[3], "UTF-8") + "&" +
URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode(params[4], "UTF-8");
bufferedWriter.write(data);
bufferedWriter.flush();
bufferedWriter.close();
OS.close();
InputStream IS = httpURLConnection.getInputStream();
IS.close();
return "Գրանցումը հաջողությամբ ավարտվել է";
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
if (params[0].equals("LOGIN")) {
try {
URL url = new URL(URL_LOGIN);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoInput(true);
httpURLConnection.setDoOutput(true);
OutputStream OS = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
String data = URLEncoder.encode("cphone", "UTF-8") + "=" + URLEncoder.encode(params[5], "UTF-8") + "&" +
URLEncoder.encode("cpassword", "UTF-8") + "=" + URLEncoder.encode(params[6], "UTF-8");
bufferedWriter.write(data);
bufferedWriter.flush();
bufferedWriter.close();
OS.close();
InputStream IS = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(IS, "UTF-8"));
String response = "";
String line = "";
while ((line = bufferedReader.readLine()) != null) {
response += line;
}
bufferedReader.close();
IS.close();
info = response;
return info;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return "Ստուգեք ինտերնետ կապի առկայությունը";
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
@Override
protected void onPostExecute(String result) {
if (result.equals("Գրանցումը հաջողությամբ ավարտվել է")) {
Toast.makeText(ctx, result, Toast.LENGTH_LONG).show();
LogReg.pw.setVisibility(View.GONE);
} else {
Login.ent.setClickable(true);
if (info.equals("Համակարգում այդպիսի տվյալներով գրանցում չկա, փորձեք կրկին ")) {
alertDialog = new AlertDialog.Builder(ctx).create();
alertDialog.setTitle("Մուտք համակարգ");
Login.pw.setVisibility(View.GONE);
alertDialog.setMessage(info);
alertDialog.show();
} else {
String temp = info;
int s;
for(int i =0;;i++){
if (temp.charAt(i)==' '){
s=i;
break;
}
name+=temp.charAt(i);
}
for(int i = s+1;i<(temp.length()-1);i++)
{
surname+=temp.charAt(i);
}
Log.d(TAG, info);
ctx.startActivity(new Intent(ctx, info.class));
}
}
}
}
但是，什么是NullPointerException异常 –
的原因，尝试使用deguger追查为什么你得到的NullPointerException –
它在你的'SyncTask' ..行数38 ..'onPreExecute（）'方法 – SripadRaj