java.lang.RuntimeException: Unable to instantiate activity… java.lang.InstantiationException: class has no zero argument constructor

Question

Here is my code.. USING ANDROID STUDIO for Searchable Dict ionary Sample code by google. I tried to follow hell lot of posts on stackoverflow but no success.. pls help

package com.example.android.searchabledict;

import android.app.SearchManager;
import android.content.ContentValues;
import android.content.Context;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.provider.BaseColumns;
import android.text.TextUtils;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;

/**
 * Contains logic to return specific words from the dictionary, and
 * load the dictionary table when it needs to be created.
 */
public class DictionaryDatabase {
private static final String TAG = "DictionaryDatabase";

//The columns we'll include in the dictionary table
public static final String KEY_WORD = SearchManager.SUGGEST_COLUMN_TEXT_1;
public static final String KEY_DEFINITION = SearchManager.SUGGEST_COLUMN_TEXT_2;

private static final String DATABASE_NAME = "dictionary";
private static final String FTS_VIRTUAL_TABLE = "FTSdictionary";
private static final int DATABASE_VERSION = 2;

private final DictionaryOpenHelper mDatabaseOpenHelper;
private static final HashMap<String,String> mColumnMap = buildColumnMap();

/**
 * Constructor
 * @param context The Context within which to work, used to create the DB
 */

public DictionaryDatabase(Context context) {
    mDatabaseOpenHelper = new DictionaryOpenHelper(context);
}

/**
 * Builds a map for all columns that may be requested, which will be given to the 
 * SQLiteQueryBuilder. This is a good way to define aliases for column names, but must include 
 * all columns, even if the value is the key. This allows the ContentProvider to request
 * columns w/o the need to know real column names and create the alias itself.
 */
private static HashMap<String,String> buildColumnMap() {
    HashMap<String,String> map = new HashMap<>();
    map.put(KEY_WORD, KEY_WORD);
    map.put(KEY_DEFINITION, KEY_DEFINITION);
    map.put(BaseColumns._ID, "rowid AS " +
            BaseColumns._ID);`enter code here`
    map.put(SearchManager.SUGGEST_COLUMN_INTENT_DATA_ID, "rowid AS " +
            SearchManager.SUGGEST_COLUMN_INTENT_DATA_ID);
    map.put(SearchManager.SUGGEST_COLUMN_SHORTCUT_ID, "rowid AS " +
            SearchManager.SUGGEST_COLUMN_SHORTCUT_ID);
    return map;
}

/**
 * Returns a Cursor positioned at the word specified by rowId
 *
 * @param rowId id of word to retrieve
 * @param columns The columns to include, if null then all are included
 * @return Cursor positioned to matching word, or null if not found.
 */
public Cursor getWord(String rowId, String[] columns) {
    String selection = "rowid = ?";
    String[] selectionArgs = new String[] {rowId};

    return query(selection, selectionArgs, columns);

    /* This builds a query that looks like:
     *     SELECT <columns> FROM <table> WHERE rowid = <rowId>
     */
}

/**
 * Returns a Cursor over all words that match the given query
 *
 * @param query The string to search for
 * @param columns The columns to include, if null then all are included
 * @return Cursor over all words that match, or null if none found.
 */
public Cursor getWordMatches(String query, String[] columns) {
    String selection = KEY_WORD + " MATCH ?";
    String[] selectionArgs = new String[] {query+"*"};

    return query(selection, selectionArgs, columns);

    /* This builds a query that looks like:
     *     SELECT <columns> FROM <table> WHERE <KEY_WORD> MATCH 'query*'
     * which is an FTS3 search for the query text (plus a wildcard) inside the word column.
     *
     * - "rowid" is the unique id for all rows but we need this value for the "_id" column in
     *    order for the Adapters to work, so the columns need to make "_id" an alias for "rowid"
     * - "rowid" also needs to be used by the SUGGEST_COLUMN_INTENT_DATA alias in order
     *   for suggestions to carry the proper intent data.
     *   These aliases are defined in the DictionaryProvider when queries are made.
     * - This can be revised to also search the definition text with FTS3 by changing
     *   the selection clause to use FTS_VIRTUAL_TABLE instead of KEY_WORD (to search across
     *   the entire table, but sorting the relevance could be difficult.
     */
}

/**
 * Performs a database query.
 * @param selection The selection clause
 * @param selectionArgs Selection arguments for "?" components in the selection
 * @param columns The columns to return
 * @return A Cursor over all rows matching the query
 */
private Cursor query(String selection, String[] selectionArgs, String[] columns) {
    /* The SQLiteBuilder provides a map for all possible columns requested to
     * actual columns in the database, creating a simple column alias mechanism
     * by which the ContentProvider does not need to know the real column names
     */
    SQLiteQueryBuilder builder = new SQLiteQueryBuilder();
    builder.setTables(FTS_VIRTUAL_TABLE);
    builder.setProjectionMap(mColumnMap);

    Cursor cursor = builder.query(mDatabaseOpenHelper.getReadableDatabase(),
            columns, selection, selectionArgs, null, null, null);

    if (cursor == null) {
        return null;
    } else if (!cursor.moveToFirst()) {
        cursor.close();
        return null;
    }
    return cursor;
}


/**
 * This creates/opens the database.
 */
private static class DictionaryOpenHelper extends SQLiteOpenHelper {

    private final Context mHelperContext;
    private SQLiteDatabase mDatabase;

    /* Note that FTS3 does not support column constraints and thus, you cannot
     * declare a primary key. However, "rowid" is automatically used as a unique
     * identifier, so when making requests, we will use "_id" as an alias for "rowid"
     */
    private static final String FTS_TABLE_CREATE =
            "CREATE VIRTUAL TABLE " + FTS_VIRTUAL_TABLE +
                    " USING fts3 (" +
                    KEY_WORD + ", " +
                    KEY_DEFINITION + ");";

    DictionaryOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        mHelperContext = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        mDatabase = db;
        mDatabase.execSQL(FTS_TABLE_CREATE);
        loadDictionary();
    }

    /**
     * Starts a thread to load the database table with words
     */
    private void loadDictionary() {
        new Thread(new Runnable() {
            public void run() {
                try {
                    loadWords();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }).start();
    }

    private void loadWords() throws IOException {
        Log.d(TAG, "Loading words...");
        final Resources resources = mHelperContext.getResources();
        InputStream inputStream = resources.openRawResource(R.raw.definitions);
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

        try {
            String line;
            while ((line = reader.readLine()) != null) {
                String[] strings = TextUtils.split(line, "-");
                if (strings.length < 2) continue;
                long id = addWord(strings[0].trim(), strings[1].trim());
                if (id < 0) {
                    Log.e(TAG, "unable to add word: " + strings[0].trim());
                }
            }
        } finally {
            reader.close();
        }
        Log.d(TAG, "DONE loading words.");
    }

    /**
     * Add a word to the dictionary.
     * @return rowId or -1 if failed
     */
    public long addWord(String word, String definition) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_WORD, word);
        initialValues.put(KEY_DEFINITION, definition);

        return mDatabase.insert(FTS_VIRTUAL_TABLE, null, initialValues);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                + newVersion + ", which will destroy all old data");
        db.execSQL("DROP TABLE IF EXISTS " + FTS_VIRTUAL_TABLE);
        onCreate(db);
    }
}
}

and i'm getting the following error

03-28 23:07:38.553 7282-7282/? E/AndroidRuntime: FATAL EXCEPTION: main
                                             Process: com.example.android.searchabledict, PID: 7282
                                             java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.searchabledict/com.example.android.searchabledict.DictionaryDatabase}: java.lang.InstantiationException: class com.example.android.searchabledict.DictionaryDatabase has no zero argument constructor
                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2246)
                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397)
                                                 at android.app.ActivityThread.access$800(ActivityThread.java:153)
                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1309)
                                                 at android.os.Handler.dispatchMessage(Handler.java:102)
                                                 at android.os.Looper.loop(Looper.java:139)
                                                 at android.app.ActivityThread.main(ActivityThread.java:5267)
                                                 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:927)
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:722)
                                              Caused by: java.lang.InstantiationException: class com.example.android.searchabledict.DictionaryDatabase has no zero argument constructor
                                                 at java.lang.Class.newInstance(Class.java:1597)
                                                 at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397) 
                                                 at android.app.ActivityThread.access$800(ActivityThread.java:153) 
                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1309) 
                                                 at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                 at android.os.Looper.loop(Looper.java:139) 
                                                 at android.app.ActivityThread.main(ActivityThread.java:5267) 
                                                 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:927) 
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:722) 
                                              Caused by: java.lang.NoSuchMethodException: <init> []
                                                 at java.lang.Class.getConstructor(Class.java:531)
                                                 at java.lang.Class.getDeclaredConstructor(Class.java:510)
                                                 at java.lang.Class.newInstance(Class.java:1595)
                                                 at android.app.Instrumentation.newActivity(Instrumentation.java:1066) 
                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236) 
                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397) 
                                                 at android.app.ActivityThread.access$800(ActivityThread.java:153) 
                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1309) 
                                                 at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                 at android.os.Looper.loop(Looper.java:139) 
                                                 at android.app.ActivityThread.main(ActivityThread.java:5267) 
                                                 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:927) 
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:722) 

What i'm I doing wrong.. Sorry i'm new to programming..

Answer 1

DictionaryDatabase is not an Activity . Your AndroidManifest.xml file has an <activity> element, pointing to DictionaryDatabase . This will not work.

Implement an Activity . Change your manifest so the <activity> element points to that activity, not to DictionaryDatabase .