我正在尝试构建一个Android登录应用程序，它将用户引导到具有滑动视图的页面 但是在登录似乎是什么问题之后总会崩溃
每个活动都在清单文件中声明
在我无法理解错误之前它是有效的
这是logcat报告
09-15 01:45:16.578: E/AndroidRuntime(1398): FATAL EXCEPTION: main
09-15 01:45:16.578: E/AndroidRuntime(1398): Process: com.learn2crack.tab, PID: 1398
09-15 01:45:16.578: E/AndroidRuntime(1398): java.lang.NullPointerException
09-15 01:45:16.578: E/AndroidRuntime(1398): at com.learn2crack.tab.Login$ProcessLogin.onPostExecute(Login.java:206)
09-15 01:45:16.578: E/AndroidRuntime(1398): at com.learn2crack.tab.Login$ProcessLogin.onPostExecute(Login.java:1)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.os.AsyncTask.finish(AsyncTask.java:632)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.os.AsyncTask.access$600(AsyncTask.java:177)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.os.Handler.dispatchMessage(Handler.java:102)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.os.Looper.loop(Looper.java:136)
09-15 01:45:16.578: E/AndroidRuntime(1398): at android.app.ActivityThread.main(ActivityThread.java:5017)
09-15 01:45:16.578: E/AndroidRuntime(1398): at java.lang.reflect.Method.invokeNative(Native Method)
09-15 01:45:16.578: E/AndroidRuntime(1398): at java.lang.reflect.Method.invoke(Method.java:515)
09-15 01:45:16.578: E/AndroidRuntime(1398): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-15 01:45:16.578: E/AndroidRuntime(1398): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-15 01:45:16.578: E/AndroidRuntime(1398): at dalvik.system.NativeStart.main(Native Method)
这是我的滑动视图代码
import android.os.Bundle;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
public class MainActivity extends FragmentActivity {
ViewPager Tab;
TabPagerAdapter TabAdapter;
ActionBar actionBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TabAdapter = new TabPagerAdapter(getSupportFragmentManager());
Tab = (ViewPager)findViewById(R.id.pager);
Tab.setOnPageChangeListener(
new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar = getActionBar();
actionBar.setSelectedNavigationItem(position); }
});
Tab.setAdapter(TabAdapter);
actionBar = getActionBar();
//Enable Tabs on Action Bar
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.TabListener tabListener = new ActionBar.TabListener(){
@Override
public void onTabReselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
Tab.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(android.app.ActionBar.Tab tab,
FragmentTransaction ft) {
// TODO Auto-generated method stub
}};
//Add New Tab
actionBar.addTab(actionBar.newTab().setText("Android").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("iOS").setTabListener(tabListener));
actionBar.addTab(actionBar.newTab().setText("Windows").setTabListener(tabListener));
}
}
我的登录页面代码
import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.learn2crack.library.DatabaseHandler;
import com.learn2crack.library.UserFunctions;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class Login extends Activity {
Button btnLogin;
Button Btnregister;
Button passreset;
EditText inputEmail;
EditText inputPassword;
private TextView loginErrorMsg;
/**
* Called when the activity is first created.
*/
private static String KEY_SUCCESS = "success";
private static String KEY_UID = "uid";
private static String KEY_USERNAME = "uname";
private static String KEY_FIRSTNAME = "fname";
private static String KEY_LASTNAME = "lname";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
inputEmail = (EditText) findViewById(R.id.email);
inputPassword = (EditText) findViewById(R.id.pword);
Btnregister = (Button) findViewById(R.id.registerbtn);
btnLogin = (Button) findViewById(R.id.login);
loginErrorMsg = (TextView) findViewById(R.id.loginErrorMsg);
Btnregister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent myIntent = new Intent(view.getContext(), Register.class);
startActivityForResult(myIntent, 0);
finish();
}});
/**
* Login button click event
* A Toast is set to alert when the Email and Password field is empty
**/
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
if ( ( !inputEmail.getText().toString().equals("")) && ( !inputPassword.getText().toString().equals("")) )
{
NetAsync(view);
}
else if ( ( !inputEmail.getText().toString().equals("")) )
{
Toast.makeText(getApplicationContext(),
"Password field empty", Toast.LENGTH_SHORT).show();
}
else if ( ( !inputPassword.getText().toString().equals("")) )
{
Toast.makeText(getApplicationContext(),
"Email field empty", Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(getApplicationContext(),
"Email and Password field are empty", Toast.LENGTH_SHORT).show();
}
}
});
}
/**
* Async Task to check whether internet connection is working.
**/
private class NetCheck extends AsyncTask<String,String,Boolean>
{
private ProgressDialog nDialog;
@Override
protected void onPreExecute(){
super.onPreExecute();
nDialog = new ProgressDialog(Login.this);
nDialog.setTitle("Checking Network");
nDialog.setMessage("Loading..");
nDialog.setIndeterminate(false);
nDialog.setCancelable(true);
nDialog.show();
}
/**
* Gets current device state and checks for working internet connection by trying Google.
**/
@Override
protected Boolean doInBackground(String... args){
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnected()) {
try {
URL url = new URL("http://www.google.com");
HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
urlc.setConnectTimeout(3000);
urlc.connect();
if (urlc.getResponseCode() == 200) {
return true;
}
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return false;
}
@Override
protected void onPostExecute(Boolean th){
if(th == true){
nDialog.dismiss();
new ProcessLogin().execute();
}
else{
nDialog.dismiss();
loginErrorMsg.setText("Error in Network Connection");
}
}
}
/**
* Async Task to get and send data to My Sql database through JSON respone.
**/
private class ProcessLogin extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
String email,password;
@Override
protected void onPreExecute() {
super.onPreExecute();
inputEmail = (EditText) findViewById(R.id.email);
inputPassword = (EditText) findViewById(R.id.pword);
email = inputEmail.getText().toString();
password = inputPassword.getText().toString();
pDialog = new ProgressDialog(Login.this);
pDialog.setTitle("Contacting Servers");
pDialog.setMessage("Logging in ...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected JSONObject doInBackground(String... args) {
UserFunctions userFunction = new UserFunctions();
JSONObject json = userFunction.loginUser(email, password);
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
try {
if (json.getString(KEY_SUCCESS) != null) {
String res = json.getString(KEY_SUCCESS);
if(Integer.parseInt(res) == 1){
pDialog.setMessage("Loading User Space");
pDialog.setTitle("Getting Data");
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
JSONObject json_user = json.getJSONObject("user");
/**
* Clear all previous data in SQlite database.
**/
UserFunctions logout = new UserFunctions();
logout.logoutUser(getApplicationContext());
db.addUser(json_user.getString(KEY_FIRSTNAME),json_user.getString(KEY_LASTNAME),json_user.getString(KEY_EMAIL),json_user.getString(KEY_USERNAME),json_user.getString(KEY_UID),json_user.getString(KEY_CREATED_AT));
/**
*If JSON array details are stored in SQlite it launches the User Panel.
**/
Intent upanel = new Intent(getApplicationContext(), MainActivity.class);
upanel.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
pDialog.dismiss();
startActivity(upanel);
/**
* Close Login Screen
**/
finish();
}else{
pDialog.dismiss();
loginErrorMsg.setText("Incorrect username/password");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public void NetAsync(View view){
new NetCheck().execute();
}
}
答案 0 :(得分：0)
ProcessLogin doInBackground。你在行
中得到json == null JSONObject json = userFunction.loginUser(email, password);
可能userName与密码不匹配。 json的这个空值传递给onPostExecute，它在行中产生错误：
JSONObject json_user = json.getJSONObject("user");
导致应用程序崩溃。
检查LogCat以查看loginUser失败。