错误尝试在空对象引用上调用虚拟方法“android.text.Editable android.widget.EditText.getText()”

Question

我一直在尝试在应用程序中创建一个模块。这个模块就像创建一个新的用户配置文件。当用户点击工具栏中的图标时，它会显示具有表单的对话框。

表单有 5 个主要输入

1. 名称 –> 使用的 EditText
2. 性别 –> 使用 RadioGroup
3. 高度 –> 使用的 EditText
4. 权重 –> 使用的 EditText
5. 年龄 –> 使用的 EditText

当我点击对话框 完成 按钮时，它应该将信息保存在 SQLite 数据库中，同时在手机中创建一个 用户卡。用户可以在应用程序中创建 N 个配置文件，为此用户必须填写信息并点击完成，但每当用户点击完成按钮时，它就会使整个应用程序崩溃。到目前为止，我已经走了这么多，遇到了一个问题——

添加表格.xml

 <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <TextView
        android:id="@+id/form_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#3498DB"
        android:textColor="#FFF"
        android:textSize="21sp"
        android:padding="16dp"
        android:text="ADD PERSON"/>
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="16dp"
        android:layout_below="@+id/form_title">
        <EditText
            android:id="@+id/person_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingTop="16dp"
            android:paddingBottom="16dp"
            android:textSize="14sp"
            android:hint="PERSON NAME"
            android:inputType="text" />

        <RadioGroup
            android:id="@+id/gender_selection"
            android:layout_below="@+id/person_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:orientation="horizontal">
            <RadioButton
                android:id="@+id/male"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="MALE"
                android:onClick="RadioButtonClicked"
                />
            <RadioButton
                android:id="@+id/female"
                android:layout_marginLeft="16dp"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="FEMALE"
                android:onClick="RadioButtonClicked"/>
        </RadioGroup>

        <LinearLayout
            android:id="@+id/person_metrics"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:layout_below="@+id/gender_selection">
            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                android:layout_weight="1">
                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:text="WEIGHT"/>
                <EditText
                    android:id="@+id/person_weight"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:padding="16dp"
                    android:textSize="21sp"
                    android:hint="KG"
                    android:inputType="text" />
            </LinearLayout>
            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                android:layout_weight="1">
                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:text="HEIGHT"/>
                <EditText
                    android:id="@+id/person_height"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:padding="16dp"
                    android:textSize="21sp"
                    android:hint="M"
                    android:inputType="text" />
            </LinearLayout>
            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                android:layout_weight="1">
                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:text="AGE"/>
                <EditText
                    android:id="@+id/person_age"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAlignment="center"
                    android:padding="16dp"
                    android:textSize="21sp"
                    android:hint="Y"
                    android:inputType="text" />
            </LinearLayout>

        </LinearLayout>
    </RelativeLayout>

</RelativeLayout>

PersonDBHelper.java

 package com.example.kuro.bloodpressure;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.text.Editable;

/**
 * Created by Kuro on 4/18/2016.
 */
public class PersonDBHelper extends SQLiteOpenHelper{

    public static final String DATABASE_NAME = "person_profile.db";
    public static final String TABLE_NAME = "person_info_table";
    public static final String id = "ID";
    public static final String name = "NAME";
    public static final String gender = "GENDER";
    public static final String weight = "WEIGHT";
    public static final String height = "HEIGHT";
    public static final String age = "AGE";
//    public static final String blood_pressure_upper = "BPU";
//    public static final String blood_pressure_lowser = "BPL";
//    public static final String heart_beat = "HB";

    public PersonDBHelper(Context context) {
        super(context, DATABASE_NAME,null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table " + TABLE_NAME +
                "(ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
                " NAME STRING, " +
                " GENDER STRING," +
                " WEIGHT INTEGER," +
                " HEIGHT INTEGER, " +
                " AGE INTEGER)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXSITS"+TABLE_NAME);
        onCreate(db);
    }

    public boolean insertData(String name, String gender, String weight, String height, String age){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();

        contentValues.put(name,name);
        contentValues.put(gender,gender);
        contentValues.put(weight,weight);
        contentValues.put(height,height);
        contentValues.put(age, age);

        long result = db.insert(TABLE_NAME,null,contentValues);
        if (result==-1) return false;
        else return true;
    }

    public Cursor getAllData(){
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("select * from"+TABLE_NAME,null);
        return res;
    }
}

主活动.java

 package com.example.kuro.bloodpressure;

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Build;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.ImageView;
import android.app.Fragment;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {
    public Toolbar mtoolbar;
    public TabLayout mtabLayout;
    public ViewPager mviewPager;
    public ViewPagerAdapter viewPagerAdapter;
    PersonDBHelper mydb;

    EditText name, weight, height, age;
    RadioGroup mradioGroup;
    RadioButton male,female;
    TextView selectedGender;
    private String gender_value;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mtoolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mtoolbar);

        mtabLayout = (TabLayout) findViewById(R.id.tablayout);
        mviewPager = (ViewPager) findViewById(R.id.viewpager);
        viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
        viewPagerAdapter.addFragments(new Measure(), "MEASURE");
        viewPagerAdapter.addFragments(new People(), "PEOPLE");
        mviewPager.setAdapter(viewPagerAdapter);
        mtabLayout.setupWithViewPager(mviewPager);

        mydb = new PersonDBHelper(this);

    }

    public void RadioButtonClicked(View view) {
        boolean checked = ((RadioButton) view).isChecked();
        switch (view.getId()) {
            case R.id.male:
                if (checked)gender_value = "male";
                else male.setChecked(false);
                break;
            case R.id.female:
                if (checked) gender_value = "female";
                else female.setChecked(false);
                break;
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    public void viewAll(){

    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.add_person:
                AlertDialog.Builder add_people_form = new AlertDialog.Builder(MainActivity.this);
                add_people_form.setView(R.layout.add_form)
                        .setCancelable(false)
                        .setPositiveButton("DONE", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {

                                name = (EditText) findViewById(R.id.person_name);
                                mradioGroup = (RadioGroup)findViewById(R.id.gender_selection);
                                male = (RadioButton)findViewById(R.id.male);
                                female = (RadioButton)findViewById(R.id.female);
                                weight = (EditText) findViewById(R.id.person_weight);
                                height = (EditText) findViewById(R.id.person_height);
                                age = (EditText) findViewById(R.id.person_age);

                                String user_name = (String) name.getText().toString();
                                String user_gender = (String) gender_value;
                                String user_weight = (String) weight.getText().toString();
                                String user_height = (String) height.getText().toString();
                                String user_age = (String) age.getText().toString();

                                boolean isInserted = mydb.insertData(user_name,user_gender,user_weight,user_height,user_age);
                                if(isInserted==true)
                                    Toast.makeText(MainActivity.this,"ADDED",Toast.LENGTH_LONG).show();
                                else
                                    Toast.makeText(MainActivity.this,"NOT ADDED",Toast.LENGTH_LONG).show();
                            }
                        })
                        .setNegativeButton("CANCLE", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                            }
                        });
                AlertDialog alert = add_people_form.create();
                alert.show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

}

日志猫

04-18 23:22:44.207 28079-28079/com.example.kuro.bloodpressure E/AndroidRuntime: FATAL EXCEPTION: main
                                                                            Process: com.example.kuro.bloodpressure, PID: 28079
                                                                            java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
                                                                                at com.example.kuro.bloodpressure.MainActivity$2.onClick(MainActivity.java:111)
                                                                                at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:162)
                                                                                at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                at android.os.Looper.loop(Looper.java:135)
                                                                                at android.app.ActivityThread.main(ActivityThread.java:5343)
                                                                                at java.lang.reflect.Method.invoke(Native Method)
                                                                                at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
                                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)

原文由 B L Λ C K 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您正在将对话和活动视图混合在一起。 findViewById 是 Activity 的一种方法，但您尝试使用的视图不是活动的一部分。

 @Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.add_person: {
            createAddPersonDialog().show();
        }
        default: {
            return super.onOptionsItemSelected(item);
        }
    }
}

private Dialog createAddPersonDialog() {
    final AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);

    // Inflate using dialog themed context.
    final Context context = builder.getContext();
    final LayoutInflater inflater = LayoutInflater.from(context);
    final View view = inflater.inflate(R.layout.add_form, null, false);

    // Find widgets inside "view".
    final EditText name = (EditText) view.findViewById(R.id.person_name);
    final RadioGroup mradioGroup = (RadioGroup) view.findViewById(R.id.gender_selection);
    final RadioButton male = (RadioButton) view.findViewById(R.id.male);
    final RadioButton female = (RadioButton) view.findViewById(R.id.female);
    final EditText weight = (EditText) view.findViewById(R.id.person_weight);
    final EditText height = (EditText) view.findViewById(R.id.person_height);
    final EditText age = (EditText) view.findViewById(R.id.person_age);

    final View.OnClickListener listener = new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            if (which == DialogInterface.BUTTON_NEGATIVE) {
                dialog.cancel();
                return;
            }

            String user_name = (String) name.getText().toString();
            String user_gender = (String) gender_value;
            String user_weight = (String) weight.getText().toString();
            String user_height = (String) height.getText().toString();
            String user_age = (String) age.getText().toString();

            boolean isInserted = mydb.insertData(user_name, user_gender, user_weight, user_height, user_age);
            if (isInserted == true)
                Toast.makeText(MainActivity.this, "ADDED", Toast.LENGTH_LONG).show();
            else
                Toast.makeText(MainActivity.this, "NOT ADDED", Toast.LENGTH_LONG).show();
        }
     };

     builder
         .setView(view)
         .setCancelable(false)
         .setPositiveButton(android.R.string.ok, listener)
         .setNegativeButton(android.R.string.cancel, listener);
     return builder.create();
}

您可能还想动态地为单选按钮分配点击侦听器。 android:onClick XML 中的属性是通往地狱的道路。

原文由 Eugen Pechanec 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

利用

name = (EditText)alert.findViewById(R.id.person_name);

代替

name = (EditText) findViewById(R.id.person_name);

因为您正在访问的视图是 AlertDialog 的一部分，而不是您的 Activity。对 AlertDialog 的所有其他视图执行相同的操作。

 AlertDialog.Builder add_people_form = new AlertDialog.Builder(MainActivity.this);

                add_people_form.setView(getLayoutInflater().inflate(R.layout.add_form,null));
 final AlertDialog alert = add_people_form.create();
                        add_people_form.setCancelable(false)
                        .setPositiveButton("DONE", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {

                                name = (EditText) alert.findViewById(R.id.person_name);
                        })
                        .setNegativeButton("CANCLE", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.cancel();
                            }
                        });

                alert.show();

原文由 Shadab Ansari 发布，翻译遵循 CC BY-SA 3.0 许可协议