堆栈内存溢出
  繁体   English   中英

片段崩溃的应用程序

[英]Fragment crashing application [duplicate]

 原文  2019-11-29 08:23:06  0   3    java/ android/ android-fragments/ nullpointerexception

问题描述

该问题与以下内容完全相同：

我正在尝试通过使用片段创建登录\\注册屏幕。

我的问题是，当我按“登录”按钮时，应用程序崩溃了。

我发现问题出在（应用程序或片段在此行崩溃） 

return view;

当我替换为 

return inflater.inflate(R.layout.fragment_login, container, false);

应用程序不会崩溃，但按钮不会执行任何操作，就像根本没有单击一样。

首先，我只是尝试从我的两个“ EditText”字段中检索数据： 

public class LoginFragment extends Fragment {

    public LoginFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        //Database creation
        DatabaseCreator db = Room.databaseBuilder(getActivity().getApplicationContext(),
                DatabaseCreator.class, "Database").allowMainThreadQueries().build();
        //View rootView = inflater.inflate(R.layout.fragment_login, container, false);
        View view = inflater.inflate(R.layout.fragment_login, container, false);
        final TextView mail = view.findViewById(R.id.et_email);
        final TextView password = view.findViewById(R.id.et_name);

        OnClick(mail, password, view);

        // Inflate the layout for this fragment
        return view;
        //return inflater.inflate(R.layout.fragment_login, container, false);
    }

    private void OnClick(final TextView mail, final TextView password, final View rootView){

        Button login = rootView.findViewById(R.id.btn_login);

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String Mail = mail.getText().toString().trim();
                String Password = password.getText().toString().trim();
                mail.setText("Test");
                //closeKeyboard(getActivity());

                if(Mail.equals(null) || Mail.equals("") || Password.equals(null) || Password.equals("")){
                    showToast("Type correct data!");
                }else{
                    Database();
                }
            }
        });
    }

    private void Database(){
        showToast("Dosao!");
    }

    private void showToast(String msg){
        Toast.makeText(getActivity(),msg.trim(),Toast.LENGTH_SHORT).show();
    }

编辑

我试图像下面的代码那样做，但是应用程序仍然崩溃：

包com.example.loginapp; 

import android.app.Activity;
import android.arch.persistence.room.Room;
import android.content.Context;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.inputmethod.InputMethodManager;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;


/**
 * A simple {@link Fragment} subclass.
 */
public class LoginFragment extends Fragment {

    public LoginFragment() {
        // Required empty public constructor
    }

    View view;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        view = inflater.inflate(R.layout.fragment_login, container, false);
        return view;
    }

    private void OnClick(final TextView mail, final TextView password, final View rootView) {

        Button login = rootView.findViewById(R.id.btn_login);

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String Mail = mail.getText().toString().trim();
                String Password = password.getText().toString().trim();
                mail.setText("Test");
                //closeKeyboard(getActivity());

                if (Mail.equals(null) || Mail.equals("") || Password.equals(null) || Password.equals("")) {
                    showToast("Type correct data!");
                } else {
                    Database();
                }
            }
        });
    }

    private void Database(){
        showToast("Dosao!");
    }

    private void showToast(String msg){
        Toast.makeText(getActivity(),msg.trim(),Toast.LENGTH_SHORT).show();
    }

    public void closeKeyboard(Activity activity) {
        View view = activity.getCurrentFocus();
        if (view != null) {
            InputMethodManager inputManager = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
            inputManager.hideSoftInputFromWindow(view.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
        }
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        //Database creation
        DatabaseCreator db = Room.databaseBuilder(getActivity().getApplicationContext(),
                DatabaseCreator.class, "Database").allowMainThreadQueries().build();
        final TextView mail = view.findViewById(R.id.et_email);
        final TextView password = view.findViewById(R.id.et_name);


        OnClick(mail, password, view);
    }
}

更新2

LOGCAT： 

    --------- beginning of crash
2019-11-29 10:05:15.269 20167-20167/com.example.loginapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.loginapp, PID: 20167
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.widget.TextView.getText()' on a null object reference
        at com.example.loginapp.LoginFragment$1.onClick(LoginFragment.java:47)
        at android.view.View.performClick(View.java:6597)
        at android.view.View.performClickInternal(View.java:6574)
        at android.view.View.access$3100(View.java:778)
        at android.view.View$PerformClick.run(View.java:25885)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
2019-11-29 10:05:15.282 20167-20167/com.example.loginapp I/Process: Sending signal. PID: 20167 SIG: 9

更新3 -fragment_login.xml 

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorBlue"
    tools:context=".LoginFragment">

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@id/tv_subtitle"
        android:layout_marginStart="25dp"
        android:layout_marginBottom="13dp"
        android:fontFamily="@font/indigo_daisy"
        android:text="@string/CryptoExplorer"
        android:textColor="@color/colorWhite"
        android:textSize="60sp" />

    <TextView
        android:id="@+id/tv_subtitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@id/et_email"
        android:layout_marginStart="25dp"
        android:layout_marginBottom="50dp"
        android:fontFamily="@font/roboto_regular"
        android:text="@string/tag"
        android:textColor="@color/colorWhite"
        android:textSize="17sp" />

    <EditText
        android:id="@+id/et_email"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:hint="@string/e_mail"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:padding="15dp"
        android:inputType="textEmailAddress"
        android:fontFamily="@font/roboto_regular"
        android:layout_above="@id/et_password"
        android:background="@drawable/et_custom"
        android:textSize="15sp" />

    <EditText
        android:id="@+id/et_password"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:hint="@string/password"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="10dp"
        android:padding="15dp"
        android:fontFamily="@font/roboto_regular"
        android:inputType="textPassword"
        android:layout_centerInParent="true"
        android:background="@drawable/et_custom"
        android:textSize="15sp" />

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/et_password"
        android:background="@color/colorBlueDark"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="15dp"
        android:fontFamily="@font/roboto_regular"
        android:textColor="@color/colorWhite"
        android:text="@string/login"/>

    <ImageView
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:src="@drawable/ic_arrow_right"
        android:layout_above="@id/swipeRight"
        android:layout_centerHorizontal="true"/>

    <TextView
        android:id="@+id/swipeRight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/swipe_left_for_register"
        android:textSize="15sp"
        android:fontFamily="@font/roboto_regular"
        android:layout_centerHorizontal="true"
        android:layout_alignParentBottom="true"
        android:textColor="@color/colorWhite"
        android:layout_marginBottom="20dp"/>

</RelativeLayout>

3 个解决方案

解决方案1
 0  2019-11-29 08:29:48

您不应在onCreateView中拥有此功能，而应尝试使用此功能 

    public class LoginFragment extends Fragment {

        public LoginFragment() {
            // Required empty public constructor
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {

            //Database creation
            DatabaseCreator db = Room.databaseBuilder(getActivity().getApplicationContext(),
                    DatabaseCreator.class, "Database").allowMainThreadQueries().build();
            //View rootView = inflater.inflate(R.layout.fragment_login, container, false);
            View view = inflater.inflate(R.layout.fragment_login, container, false);
            final TextView mail = view.findViewById(R.id.et_email);
            final TextView password = view.findViewById(R.id.et_name);



            // Inflate the layout for this fragment
            return view;
            //return inflater.inflate(R.layout.fragment_login, container, false);
        }



 @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
OnClick(mail, password, view);
}
        private void OnClick(final TextView mail, final TextView password, final View rootView){

            Button login = rootView.findViewById(R.id.btn_login);

            login.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String Mail = mail.getText().toString().trim();
                    String Password = password.getText().toString().trim();
                    mail.setText("Test");
                    //closeKeyboard(getActivity());

                    if(Mail.equals(null) || Mail.equals("") || Password.equals(null) || Password.equals("")){
                        showToast("Type correct data!");
                    }else{
                        Database();
                    }
                }
            });
        }

        private void Database(){
            showToast("Dosao!");
        }

        private void showToast(String msg){
            Toast.makeText(getActivity(),msg.trim(),Toast.LENGTH_SHORT).show();
        }

解决方案2
 0 已采纳  2019-11-29 08:33:42

您只需要从onCreateView返回视图，并在onViewCreated执行其他操作 

public class LoginFragment extends Fragment {

        public LoginFragment() {
            // Required empty public constructor
        }

        View view;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            view = inflater.inflate(R.layout.fragment_login, container, false);
            return view;
        }


        private void OnClick(final TextView mail, final TextView password, final View rootView) {

            Button login = rootView.findViewById(R.id.btn_login);

            login.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String Mail = mail.getText().toString().trim();
                    String Password = password.getText().toString().trim();
                    mail.setText("Test");
                    //closeKeyboard(getActivity());

                    if (Mail.equals(null) || Mail.equals("") || Password.equals(null) || Password.equals("")) {
                        showToast("Type correct data!");
                    } else {
                        Database();
                    }
                }
            });
        }

        private void Database() {
            showToast("Dosao!");
        }

        private void showToast(String msg) {
            Toast.makeText(getActivity(), msg.trim(), Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);

            //Database creation
            DatabaseCreator db = Room.databaseBuilder(getActivity().getApplicationContext(),
                    DatabaseCreator.class, "Database").allowMainThreadQueries().build();
            final TextView mail = view.findViewById(R.id.et_email);
            final TextView password = view.findViewById(R.id.et_name);


            OnClick(mail, password, view);
        }

    }

解决方案3
 -2  2019-11-29 08:29:32

最好用一种方法制作所有的findViewById() 。 在这里，您可以在onCreateView扩展视图，并尝试在第一个方法中调用的onClick找到一个视图（注意：最好不要大写方法名称）。 但是，您的视图整个视图尚未初始化，因此您无法在rootView找到登录按钮。

所以，我的建议是onCreateView()两种方法合并到onCreateView()

暂无
暂无

声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.

相关问题 片段在屏幕旋转时崩溃 片段中的OnClickListener导致Android应用崩溃 Fragment中的按钮正在崩溃应用程序 Android片段getChildAt（）有时会崩溃 ListView在片段中崩溃-onClick方法 Android Intent应用程序崩溃 引导后应用程序崩溃 setBackgroundColor 使 Android 应用程序崩溃 Java应用程序崩溃 应用程序在启动时立即崩溃
相关标签
 
粤ICP备18138465号  © 2020-2024 STACKOOM.COM