尝试登录时，我的 AsyncTask 代码返回 null。我很困惑，为什么在设备上它可以抛出吐司“return null ...”但在模拟器上它强制关闭，任何人请帮我解决这个问题。非常感谢您
登录.java
public class Login extends Activity {
public Koneksi linkurl;
String SERVER_URL;
private Button login, register, setting;
private EditText username, password;
public ProgressDialog progressDialog;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
setting = (Button)findViewById(R.id.bsetting);
login = (Button) findViewById(R.id.login);
register = (Button) findViewById(R.id.reg);
username = (EditText) findViewById(R.id.uname);
password = (EditText) findViewById(R.id.pass);
setting.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intentSet = new Intent(Login.this, UrlSetting.class);
startActivity(intentSet);
}
});
register.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intentReg = new Intent(Login.this, Register.class);
startActivity(intentReg);
}
});
login.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
new LoginTask().execute();
}
});
}
protected String tryLogin(String mUsername, String mPassword)
{
Log.d(" TryLoginCheck ","Here");
HttpURLConnection connection;
OutputStreamWriter request = null;
URL url = null;
String response = null;
String temp=null;
String parameters = "username="+mUsername+"&password="+mPassword;
System.out.println("UserName"+mUsername+"\n"+"password"+mPassword);
Log.d("Parameters",parameters);
try
{
;
linkurl = new Koneksi(this);
SERVER_URL = linkurl.getUrl();
SERVER_URL += "/mobile/Login.php";
url = new URL(SERVER_URL);
connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setRequestMethod("POST");
request = new OutputStreamWriter(connection.getOutputStream());
request.write(parameters);
request.flush();
request.close();
String line = "";
InputStreamReader isr = new InputStreamReader(connection.getInputStream());
BufferedReader reader = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
while ((line = reader.readLine()) != null)
{
sb.append(line + "\n");
}
temp=sb.toString();
Log.d("Temp",temp);
response = sb.toString();
Log.d("Response",response);
Log.d("Sb Value",sb.toString());
isr.close();
reader.close();
}
catch(IOException e)
{
e.printStackTrace();
Log.d("Error",e.getMessage());
return null;
}
return response;
}
public class LoginTask extends AsyncTask<String, String, String> {
String response = null;
@Override
protected void onPreExecute()
{
}
@Override
protected String doInBackground(String... arg0)
{
String mUsername = username.getText().toString();
String mPassword = password.getText().toString();
return tryLogin(mUsername, mPassword);
}
protected void onPostExecute(String result){
super.onPostExecute(result);
if(result==null)
{
Toast.makeText(Login.this,"result is null- an error occured",Toast.LENGTH_SHORT).show();
}
else{
result = result.trim();
Log.d("Check","Here");
Log.d("Response",response);
if(response.toLowerCase().contains("berhasil"))
{
String nama = username.getText().toString();
Intent newIntent = new Intent(Login.this, MainPage.class);
Bundle bundle = new Bundle();
bundle.putString("nama", nama);
newIntent.putExtras(bundle);
startActivityForResult(newIntent, 0);
}
else
{
//Optional
//Kalau bisa dibuat constant untuk menghindari salah penulisan
String RoleError = "ROLE SALAH";
String UserError = "USER SALAH";
createDialog("Maaf", response.equals(RoleError) ? "Role Anda bukan Student!" : "Username Atau Password Salah!");
}
}
}
}
private void createDialog(String title, String text) {
AlertDialog ad = new AlertDialog.Builder(this)
.setPositiveButton("Ok", null)
.setTitle(title)
.setMessage(text)
.create();
ad.show();
}
}
Logcat - 当我在设备中测试时
06-10 17:34:43.715: D/TextLayoutCache(13251): Using debug level: 0 - Debug Enabled: 0
06-10 17:34:43.786: D/libEGL(13251): loaded /vendor/lib/egl/libEGL_POWERVR_SGX540_120.so
06-10 17:34:43.793: D/libEGL(13251): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX540_120.so
06-10 17:34:43.801: D/libEGL(13251): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX540_120.so
06-10 17:34:43.918: D/OpenGLRenderer(13251): Enabling debug mode 0
06-10 17:34:45.090: D/TryLoginCheck(13251): Here
06-10 17:34:45.098: I/System.out(13251): UserName
06-10 17:34:45.098: I/System.out(13251): password
06-10 17:34:45.098: D/Parameters(13251): username=&password=
logcat-wen 我在模拟器上测试
06-10 17:37:34.375: I/Process(451): Sending signal. PID: 451 SIG: 9
06-10 17:43:06.032: W/KeyCharacterMap(488): No keyboard for id 0
06-10 17:43:06.032: W/KeyCharacterMap(488): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
06-10 17:43:19.961: D/TryLoginCheck(488): Here
06-10 17:43:19.963: I/System.out(488): UserNametes
06-10 17:43:19.963: I/System.out(488): passwordTes12345*
06-10 17:43:19.963: D/Parameters(488): username=tes&password=Tes12345*
06-10 17:43:20.343: D/Temp(488): Login Berhasil dengan userid='3'
06-10 17:43:20.343: D/Response(488): Login Berhasil dengan userid='3'
06-10 17:43:20.343: D/Sb Value(488): Login Berhasil dengan userid='3'
06-10 17:43:20.343: D/Check(488): Here
06-10 17:43:20.343: D/AndroidRuntime(488): Shutting down VM
06-10 17:43:20.343: W/dalvikvm(488): threadid=1: thread exiting with uncaught exception (group=0x40015560)
06-10 17:43:20.363: E/AndroidRuntime(488): FATAL EXCEPTION: main
06-10 17:43:20.363: E/AndroidRuntime(488): java.lang.NullPointerException: println needs a message
06-10 17:43:20.363: E/AndroidRuntime(488): at android.util.Log.println_native(Native Method)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.util.Log.d(Log.java:137)
06-10 17:43:20.363: E/AndroidRuntime(488): at com.karismaelearning.Login$LoginTask.onPostExecute(Login.java:163)
06-10 17:43:20.363: E/AndroidRuntime(488): at com.karismaelearning.Login$LoginTask.onPostExecute(Login.java:1)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.os.AsyncTask.finish(AsyncTask.java:417)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.os.AsyncTask.access$300(AsyncTask.java:127)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.os.Handler.dispatchMessage(Handler.java:99)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.os.Looper.loop(Looper.java:123)
06-10 17:43:20.363: E/AndroidRuntime(488): at android.app.ActivityThread.main(ActivityThread.java:3683)
06-10 17:43:20.363: E/AndroidRuntime(488): at java.lang.reflect.Method.invokeNative(Native Method)
06-10 17:43:20.363: E/AndroidRuntime(488): at java.lang.reflect.Method.invoke(Method.java:507)
06-10 17:43:20.363: E/AndroidRuntime(488): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-10 17:43:20.363: E/AndroidRuntime(488): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-10 17:43:20.363: E/AndroidRuntime(488): at dalvik.system.NativeStart.main(Native Method)