RuntimeException的：无法启动活动ComponentInfo {}：显示java.lang.NullPointerException。 Android版 [英] RuntimeException: Unable to start activity ComponentInfo{}: java.lang.NullPointerException. Android

问题描述

我试图到一个列表视图中读取从SQLlite数据库值。我也做了code，它有没有错误，但在运行时我得到的错误说......

i am trying to read values from a SQLlite database in to a list view. i have done the code, it has no error, but during the run time i get the error saying....

FATAL EXCEPTION: main
02-01 15:40:31.397: E/AndroidRuntime(10663): java.lang.RuntimeException: Unable to start activity ComponentInfo{lk.adspace.jaffnadb/lk.adspace.jaffnadb.MainActivity}: java.lang.NullPointerException

谁能帮我解决这个错误吧。

can anyone help me to fix this error please.

Dbhandler.java文件

    package lk.adspace.jaffnadb;

    import java.util.ArrayList;


    import android.content.ContentValues;
    import android.content.Context;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;

    import android.database.sqlite.SQLiteOpenHelper;
    import android.util.Log;

    public class Dbhandler extends SQLiteOpenHelper  {


        private static final int DATABASE_VERSION = 1;

        // Database Name
        private static final String DATABASE_NAME = "jaffnatempletest";

        // Temple table name
        private static final String TABLE_TEMPLE = "templ";


        // Contacts Table Columns names
        private static final String KEY_ID = "id";
        private static final String KEY_TMPNAME = "temple_name";
        private static final String KEY_TMPTYPE = "temple_type";
        private static final String KEY_LATITUDE = "latitude";
        private static final String KEY_LONGITUDE = "longitude";
        private static final String KEY_IMGNAME = "image_name";
        private static final String KEY_YEARBUILD = "year_build";
        private static final String KEY_ADDRESS = "address";
        private static final String KEY_CITY = "city";
        private static final String KEY_EMAIL = "email";
        private static final String KEY_WEB = "website";
        private static final String KEY_TEL1 = "telephone1";
        private static final String KEY_TEL2 = "telephone2";
        private static final String KEY_DESCRI = "Description";
        private final ArrayList<kovil> temple_list = new ArrayList<kovil>();


        public Dbhandler (Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }



        // Creating Tables
        @Override
        public void onCreate(SQLiteDatabase db) {
        String CREATE_TEMPLE_TABLE = "CREATE TABLE " + TABLE_TEMPLE + "("
            + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL," + KEY_TMPNAME + " TEXT," + KEY_TMPTYPE + " TEXT," + KEY_LATITUDE + " TEXT," + KEY_LONGITUDE + " TEXT," + KEY_IMGNAME + " TEXT,"
            + KEY_YEARBUILD + " TEXT," + KEY_ADDRESS + " TEXT," + KEY_CITY + " TEXT," + KEY_EMAIL + " TEXT," + KEY_WEB + " TEXT," + KEY_TEL1 + " TEXT," + KEY_TEL2 + " TEXT,"
            + KEY_DESCRI + " TEXT" + ")";
        db.execSQL(CREATE_TEMPLE_TABLE);
        }


        // Upgrading database
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_TEMPLE);

        // Create tables again
        onCreate(db);
        }



        // Adding new temple
        public void Add_Temple(kovil Kovil) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();

        values.put(KEY_TMPNAME, Kovil.gettemplename()); 
        values.put(KEY_TMPTYPE, Kovil.gettempletype()); 
        values.put(KEY_LATITUDE, Kovil.getlatitude()); 
        values.put(KEY_LONGITUDE, Kovil.getlongitude()); 
        values.put(KEY_IMGNAME, Kovil.getimage_name()); 
        values.put(KEY_YEARBUILD, Kovil.getyear_build()); 
        values.put(KEY_ADDRESS, Kovil.getaddress()); 
        values.put(KEY_CITY, Kovil.getcity()); 
        values.put(KEY_EMAIL, Kovil.getemail()); 
        values.put(KEY_WEB, Kovil.getwebsite()); 
        values.put(KEY_TEL1, Kovil.gettelephone1()); 
        values.put(KEY_TEL2, Kovil.gettelephone2());
        values.put(KEY_DESCRI, Kovil.getDescription());

        // Inserting Row
        db.insert(TABLE_TEMPLE, null, values);
        db.close(); // Closing database connection
        }






        // Getting single contact
        kovil Get_Temple(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_TEMPLE, new String[] { KEY_ID,
                KEY_TMPNAME, KEY_TMPTYPE, KEY_LATITUDE, KEY_LONGITUDE, KEY_IMGNAME, KEY_YEARBUILD, KEY_ADDRESS, KEY_CITY, KEY_EMAIL, KEY_EMAIL, KEY_WEB, KEY_TEL1, KEY_TEL2, KEY_DESCRI }, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        kovil Kovil = new kovil(Integer.parseInt(cursor.getString(0)),
            cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4), cursor.getString(5), cursor.getString(6), cursor.getString(7), cursor.getString(8), cursor.getString(9), cursor.getString(10), cursor.getString(11), cursor.getString(12), cursor.getString(13));
        // return contact
        cursor.close();
        db.close();

        return Kovil;
        }





        // Getting All Contacts
        public ArrayList<kovil> Get_Temple() {
        try {
            temple_list.clear();

            // Select All Query
            String selectQuery = "SELECT  * FROM " + TABLE_TEMPLE;

            SQLiteDatabase db = this.getWritableDatabase();
            Cursor cursor = db.rawQuery(selectQuery, null);

            // looping through all rows and adding to list
            if (cursor.moveToFirst()) {
            do {
                kovil Kovil = new kovil();
                Kovil.setID(Integer.parseInt(cursor.getString(0)));
                Kovil.settemplename(cursor.getString(1)); 
                Kovil.settempletype(cursor.getString(2)); 
                Kovil.setlatitude(cursor.getString(3)); 
                Kovil.setlongitude(cursor.getString(4)); 
                Kovil.setimage_name(cursor.getString(5)); 
                Kovil.setyear_build(cursor.getString(6)); 
                Kovil.setaddress(cursor.getString(7)); 
                Kovil.setcity(cursor.getString(8)); 
                Kovil.setemail(cursor.getString(9)); 
                Kovil.setwebsite(cursor.getString(10)); 
                Kovil.settelephone1(cursor.getString(11)); 
                Kovil.settelephone2(cursor.getString(12));
                Kovil.setDescription(cursor.getString(13));



                // Adding contact to list
                temple_list.add(Kovil);
            } while (cursor.moveToNext());
            }

            // return contact list
            cursor.close();
            db.close();
            return temple_list;
        } catch (Exception e) {
            // TODO: handle exception
            Log.e("all_temples", "" + e);
        }

        return temple_list;
        }




        // Getting contacts Count
        public int Get_Total_Temple() {
            String countQuery = "SELECT * FROM " + TABLE_TEMPLE;
            SQLiteDatabase db = this.getReadableDatabase();
            Cursor cursor = db.rawQuery(countQuery, null);
            int count = cursor.getCount();
            cursor.close();
            db.close();
            return count;
        }


    }

MainActivity.java文件

    package lk.adspace.jaffnadb;

    import java.util.ArrayList;




    import android.os.Bundle;
    import android.app.Activity;
    import android.content.Context;
    import android.view.Menu;
    import android.widget.ArrayAdapter;
    import android.widget.ListView;
    import android.widget.TextView;

    public class MainActivity extends Activity {



        Temple_Adapter tAdapter;

        ArrayList<kovil> temple_data = new ArrayList<kovil>();
        ListView temple_listview;
        Dbhandler dbhand = new Dbhandler(this); 



                    @Override
                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);


                        kovil insertData = new kovil("temple_name", "temple_type", "latitude",  "longitude", "image_name", "year_build", "address", 
                                "city", "email", "website", "telephone1", "telephone2",  "Description");
                            Dbhandler dbhand = new Dbhandler(this); 
                            dbhand .Add_Temple(insertData );


                            kovil insertData2 = new kovil("temple_name", "temple_type", "latitude",  "longitude", "image_name", "year_build", "address", 
                                    "city", "email", "website", "telephone1", "telephone2",  "Description");

                                dbhand .Add_Temple(insertData2 );

                                int count =dbhand .Get_Total_Temple();

                             TextView textView = (TextView) findViewById(R.id.count);
                             textView.setText(Integer.toString(count));


                             // i want to display all the values in a list over here.

                        View_all_temples();


                    }



                    public void View_all_temples(){


                        temple_data.clear();
                        ArrayList<kovil> temple_array_from_db = dbhand.Get_Temple();

                        for (int i = 0; i < temple_array_from_db.size(); i++) {

                            int tidno = temple_array_from_db.get(i).getID();
                            String tempname = temple_array_from_db.get(i).gettemplename();
                            String city = temple_array_from_db.get(i).getcity();
                            String telphon = temple_array_from_db.get(i).gettelephone1();
                            kovil kov = new kovil();
                            kov.setID(tidno);
                            kov.settemplename(tempname);
                            kov.setcity(city);
                            kov.settelephone1(telphon);

                            temple_data.add(kov);
                        }
                        dbhand.close();
                        tAdapter = new Temple_Adapter(MainActivity.this, R.layout.activity_main);
                        temple_listview.setAdapter(tAdapter);
                        tAdapter.notifyDataSetChanged();


                    }



                    public class Temple_Adapter extends ArrayAdapter<kovil> {
                        public Temple_Adapter(Context context,
                                int textViewResourceId) {
                            super(context, textViewResourceId);
                            // TODO Auto-generated constructor stub
                        }



                        Activity activity;
                        int layoutResourceId;
                        kovil user;
                        ArrayList<kovil> data = new ArrayList<kovil>();

                        public void Temple_Adapter_Adapter(Activity act, int layoutResourceId,
                            ArrayList<kovil> data) {
                            this.layoutResourceId = layoutResourceId;
                            this.activity = act;
                            this.data = data;
                            notifyDataSetChanged();
                        }

                    }

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

                }

Kovil.java文件

    package lk.adspace.jaffnadb;

    public class kovil {

        //public variables
        public int _id;
        public String _temple_name;
        public String _temple_type;
        public String _latitude;
        public String _longitude;
        public String _image_name;
        public String _year_build;
        public String _address;
        public String _city;
        public String _email;
        public String _website;
        public String _telephone1;
        public String _telephone2;
        public String _Description;

        //empty constructor
        public kovil (){

        }


        // int id, String temple_name, String temple_type, String latitude,  String longitude, String image_name, String year_build, String address, String city, String email, String website, String telephone1, String telephone2,  String Description


        public kovil(int id, String temple_name, String temple_type, String latitude,  String longitude, String image_name, String year_build, String address, 
                String city, String email, String website, String telephone1, String telephone2,  String Description) {
            // TODO Auto-generated constructor stub



              this._id= id;
              this._temple_name=temple_name;
              this._temple_type=temple_type;
              this._latitude=latitude;
              this._longitude=longitude;
              this._image_name=image_name;
              this._year_build=year_build;
              this._address=address;
              this._city=city;
              this._email=email;
              this._website=website;
              this._telephone1=telephone1;
              this._telephone2=telephone2;
              this._Description=Description;

        }



        public kovil(String temple_name, String temple_type, String latitude,  String longitude, String image_name, String year_build, String address, 
                String city, String email, String website, String telephone1, String telephone2,  String Description) {
            // TODO Auto-generated constructor stub

              this._temple_name=temple_name;
              this._temple_type=temple_type;
              this._latitude=latitude;
              this._longitude=longitude;
              this._image_name=image_name;
              this._year_build=year_build;
              this._address=address;
              this._city=city;
              this._email=email;
              this._website=website;
              this._telephone1=telephone1;
              this._telephone2=telephone2;
              this._Description=Description;

        }


                public int getID() {
                return this._id;
                }


                public void setID(int id) {
                this._id = id;
                }


                public String gettemplename() {
                return this._temple_name;
                }


                public void settemplename(String temple_name) {
                this._temple_name=temple_name;
                }

                public String gettempletype() {
                return this._temple_type;
                }


                public void settempletype(String temple_type) {
                this._temple_type=temple_type;
                }

                public String getlatitude() {
                return this._latitude;
                }


                public void setlatitude(String latitude) {
                    this._latitude=latitude;
                }

                public String getlongitude() {
                return this._longitude;
                }


                public void setlongitude(String longitude) {
                    this._longitude=longitude;
                }


                public String getimage_name() {
                return this._image_name;
                }


                public void setimage_name(String image_name) {
                    this._image_name=image_name;
                }

                public String getyear_build() {
                return this._year_build;
                }


                public void setyear_build(String year_build) {
                    this._year_build=year_build;
                }


                public String getaddress() {
                return this._address;
                }


                public void setaddress(String address) {
                    this._address=address;
                }

                public String getcity() {
                return this._city;
                }


                public void setcity(String city) {
                    this._city=city;
                }


                public String getemail() {
                return this._email;
                }


                public void setemail(String email) {
                    this._email=email;
                }


                public String getwebsite() {
                return this._website;
                }


                public void setwebsite(String website) {
                    this._website=website;
                }


                public String gettelephone1() {
                return this._telephone1;
                }


                public void settelephone1(String telephone1) {
                    this._telephone1=telephone1;
                }

                public String gettelephone2() {
                return this._telephone2;
                }


                public void settelephone2(String telephone2) {
                    this._telephone2=telephone2;
                }


                public String getDescription() {
                return this._Description;
                }


                public void setDescription(String Description) {
                    this._Description=Description;
                }


    }

Activitymain.xml文件

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




        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <ListView
                android:id="@+id/list"
                android:layout_width="fill_parent"
                android:layout_height="388dp"
                android:focusable="false"
                android:focusableInTouchMode="false" />
        </LinearLayout>

        <TextView
            android:id="@+id/count"
            android:layout_width="212dp"
            android:layout_height="62dp"
            android:text="TextView" />

    </LinearLayout>

完整的错误

02-01 16:05:14.265: D/jdwp(11214): sendBufferedRequest : len=0x41
02-01 16:05:14.268: W/asset(11214): AssetManager-->addDefaultAssets CIP path not exsit!
02-01 16:05:14.532: D/AbsListView(11214): checkAbsListViewlLogProperty get invalid command
02-01 16:05:14.997: D/AndroidRuntime(11214): Shutting down VM
02-01 16:05:14.997: W/dalvikvm(11214): threadid=1: thread exiting with uncaught exception (group=0x416969a8)
02-01 16:05:15.014: E/AndroidRuntime(11214): FATAL EXCEPTION: main
02-01 16:05:15.014: E/AndroidRuntime(11214): java.lang.RuntimeException: Unable to start activity ComponentInfo{lk.adspace.jaffnadb/lk.adspace.jaffnadb.MainActivity}: java.lang.NullPointerException
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread.access$600(ActivityThread.java:162)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.os.Handler.dispatchMessage(Handler.java:107)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.os.Looper.loop(Looper.java:194)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread.main(ActivityThread.java:5371)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at java.lang.reflect.Method.invokeNative(Native Method)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at java.lang.reflect.Method.invoke(Method.java:525)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at dalvik.system.NativeStart.main(Native Method)
02-01 16:05:15.014: E/AndroidRuntime(11214): Caused by: java.lang.NullPointerException
02-01 16:05:15.014: E/AndroidRuntime(11214):    at lk.adspace.jaffnadb.MainActivity.View_all_temples(MainActivity.java:66)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at lk.adspace.jaffnadb.MainActivity.onCreate(MainActivity.java:55)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.Activity.performCreate(Activity.java:5122)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
02-01 16:05:15.014: E/AndroidRuntime(11214):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)

16 02-01：05：15.014：E / AndroidRuntime（11214）：... 11个

02-01 16:05:15.014: E/AndroidRuntime(11214): ... 11 more

推荐答案

请全局变量为你的数据库类

Make global variable for your Database class

  Dbhandler dbhand;

和初始化这个在onCreate（）方法

and initialize this on oncreate() method

  dbhand = new Dbhandler(this); 

还找到在onCreate（）方法的ListView的ID。

also find the id for listView on oncreate() method.

 temple_listview = (ListView)findViewById(R.id.list);

没有找到ID为ListView的元素已在其设置的适配器。所以，在那一刻，你一定会得到空指针异常。

Without finding Id for ListView element you have set adapter in it. So at that moment you will be sure got Null Pointer exception.

您应该改变这种..

    kovil insertData;
    TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.activity_main);

                    textView = (TextView) findViewById(R.id.count);


                    insertData = new kovil("temple_name", "temple_type", "latitude",  "longitude", "image_name", "year_build", "address", 
                            "city", "email", "website", "telephone1", "telephone2",  "Description");


                        dbhand.open():
                        dbhand .Add_Temple(insertData );
                        dbhand.close():


                        kovil insertData2 = new kovil("temple_name", "temple_type", "latitude",  "longitude", "image_name", "year_build", "address", 
                                "city", "email", "website", "telephone1", "telephone2",  "Description");
                        dbhand.open():
                        dbhand .Add_Temple(insertData2 );
                        dbhand.close():

                        int count = dbhand .Get_Total_Temple();


                         textView.setText(Integer.toString(count));


                         // i want to display all the values in a list over here.

                        View_all_temples();


                }

编辑：

尝试改变：

            public ArrayList<kovil> Get_Temple() {
    try {
        temple_list.clear();

        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_TEMPLE;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.getCount()>0)) {
           cursor.moveToFirst(
        do {
            kovil Kovil = new kovil();
            Kovil.setID(Integer.parseInt(cursor.getString(0)));
            Kovil.settemplename(cursor.getString(1)); 
            Kovil.settempletype(cursor.getString(2)); 
            Kovil.setlatitude(cursor.getString(3)); 
            Kovil.setlongitude(cursor.getString(4)); 
            Kovil.setimage_name(cursor.getString(5)); 
            Kovil.setyear_build(cursor.getString(6)); 
            Kovil.setaddress(cursor.getString(7)); 
            Kovil.setcity(cursor.getString(8)); 
            Kovil.setemail(cursor.getString(9)); 
            Kovil.setwebsite(cursor.getString(10)); 
            Kovil.settelephone1(cursor.getString(11)); 
            Kovil.settelephone2(cursor.getString(12));
            Kovil.setDescription(cursor.getString(13));



            // Adding contact to list
            temple_list.add(Kovil);
        } while (cursor.moveToNext());
        }

        // return contact list
        cursor.close();
        db.close();

    } catch (Exception e) {
        // TODO: handle exception
        Log.e("all_temples", "" + e);
    }

    return temple_list;
    }

这篇关于RuntimeException的：无法启动活动ComponentInfo {}：显示java.lang.NullPointerException。 Android版的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！