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這是我的代碼..使用ANDROID STUDIO的可搜索的Dict ionary示例代碼由谷歌。我試圖按照地獄很多計算器上，但沒有成功帖子..請幫助java.lang.RuntimeException：無法實例化活動.... java.lang.InstantiationException：類沒有零參數構造函數
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);
}
}
}
，我發現了以下錯誤
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)
我是我做錯了..對不起，我是新來的編程..
'引起：java.lang.NoSuchMethodException： []' –