android按钮停止工作

Question

你好我的android应用程序有问题...应用程序正在android studio上工作，他们停止工作显示此错误..

 Error parsing data org.json.JSONException: End of input at character 0 of
03-29 17:38:39.180      890-890/com.example.cinema D/AndroidRuntime﹕ Shutting down VM
03-29 17:38:39.180      890-890/com.example.cinema W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb3b04ba8)
03-29 17:38:39.220      890-890/com.example.cinema E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.cinema, PID: 890
    java.lang.NullPointerException
            at com.example.cinema.MainActivity$1.onClick(MainActivity.java:63)
            at android.view.View.performClick(View.java:4438)
            at android.view.View$PerformClick.run(View.java:18422)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
03-29 17:38:44.320      890-890/com.example.cinema I/Process﹕ Sending signal. PID: 890 SIG: 9

主要活动代码如下

public class MainActivity extends Activity {

EditText etemail, etpass;
Button login, register;
TextView tError;



private static String KEY_SUCCESS = "success";

private static final String KEY_REFERRED_AS = "referred_as";
private static final String KEY_EMAIL = "email";
private static final String KEY_CARD = "Card";
private static final String KEY_ADDRESS = "address";
private static final String KEY_CONTACT_NO = "contact_no";
private static final String KEY_ID = "id";
private static final String KEY_DATEOFBIRTH = "DateOfBirth";


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // setting default screen to sign_in.xml
    setContentView(R.layout.activity_main);

    etemail = (EditText) findViewById(R.id.emailAddress);
    etpass = (EditText) findViewById(R.id.password);
    tError = (TextView) findViewById(R.id.error);
    login = (Button) findViewById(R.id.login);
    register = (Button) findViewById(R.id.reg);


    login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view){

            String email = etemail.getText().toString();
            String password = etpass.getText().toString();
            UserFunctions userFunction = new UserFunctions();
            Log.d("Button", "Login");
            JSONObject json = userFunction.loginUser(email, password);

            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    return;
                }
                tError.setText("login");
                String res = json.getString(KEY_SUCCESS);
                if(Integer.parseInt(res) == 1){
                    // user successfully logged in

                    // Store user details in SQLite Database
                    DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                    JSONObject json_user = json.getJSONObject("user");

                    // Clear all previous data in database
                    userFunction.logoutUser(getApplicationContext());
                    db.addUser(json_user.getString(KEY_REFERRED_AS),json_user.getString(KEY_EMAIL),json_user.getString(KEY_CARD),
                            json_user.getString(KEY_DATEOFBIRTH),json_user.getString(KEY_ADDRESS),
                            json_user.getString(KEY_CONTACT_NO),json_user.getString(KEY_ID));
                    // Launch Dashboard Screen
                    Intent intent = new Intent(getApplicationContext(), Home.class);

                    // Close all views before launching Dashboard
                    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    startActivity(intent);

                    // Close Login Screen
                    finish();
               }else{
                    // Error in login
                    tError.setText("Incorrect username/password");
               }
            } catch (JSONException e) {
                e.printStackTrace();
           }
        }
    });

    register.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            Intent i = new Intent(getApplicationContext(),Register.class);
            startActivity(i);

        }
    });


}   

}