Android Listview和Search视图不会在第一次加载/显示数据库

标题解释了我的问题所在。我的应用程序运行正常，我在列表视图和搜索视图中获得所有单词，并提供建议。问题是当我在eclipse运行应用程序后第一次启动应用程序时，例如，数据库没有加载。Listview没有显示任何内容。因此，当我切换到另一个活动并返回到主活动时，Listview会按原样显示所有数据。为什么？现在我将向您展示3个类的源代码：MyDatabase、provider和bancodictionary主活动

字典数据库

public class DictionaryDatabase {
private static final String TAG = "DictionaryDatabase";

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();

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

private static HashMap<String,String> buildColumnMap() {
    HashMap<String,String> map = new HashMap<String,String>();
    map.put(KEY_WORD, KEY_WORD);
    map.put(KEY_DEFINITION, KEY_DEFINITION);
    map.put(BaseColumns._ID, "rowid AS " +
            BaseColumns._ID);
    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;
}




public Cursor getWord(String rowId, String[] columns) {
    String selection = "rowid = ?";
    String[] selectionArgs = new String[] {rowId};

    return query(selection, selectionArgs, columns);

}

public Cursor getWordMatches(String query, String[] columns) {
    String selection = KEY_WORD + " MATCH ?";
    String[] selectionArgs = new String[] {query+"*"};

    return query(selection, selectionArgs, columns);

}

private Cursor query(String selection, String[] selectionArgs, String[] columns) {

    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;
}

private static class DictionaryOpenHelper extends SQLiteOpenHelper {

    private final Context mHelperContext;
    private SQLiteDatabase mDatabase;

    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();
    }



    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(input));

        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.");
    }


    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);
    }
}


 public ArrayList<WordDefinition> getAllWords() {
ArrayList<WordDefinition> arrayList=new ArrayList<WordDefinition>();
SQLiteDatabase database=mDatabaseOpenHelper.getReadableDatabase();

String selectAllQueryString="SELECT * FROM "+FTS_VIRTUAL_TABLE;
Cursor cursor=database.rawQuery(selectAllQueryString, null);

if (cursor.moveToFirst()) {
    do {            
        WordDefinition wordDefinition=new WordDefinition(cursor.getString(cursor.getColumnIndex(KEY_WORD)), cursor.getString(cursor.getColumnIndex(KEY_DEFINITION)));
        arrayList.add(wordDefinition);              
    } while (cursor.moveToNext());          
}   
return arrayList;
    }

public WordDefinition getWordDefinition(String word) {
SQLiteDatabase database=mDatabaseOpenHelper.getReadableDatabase();
WordDefinition wordDefinition=null;

String selectQueryString="SELECT * FROM "+FTS_VIRTUAL_TABLE+ " WHERE "+KEY_WORD+" = '"+word+ "'";
Cursor cursor=database.rawQuery(selectQueryString, null);

if (cursor.moveToFirst()) {
    wordDefinition=new WordDefinition(cursor.getString(cursor.getColumnIndex(KEY_WORD)), cursor.getString(cursor.getColumnIndex(KEY_DEFINITION)));

}   

return wordDefinition;

}

  public WordDefinition getWordDefinition(long id) {
SQLiteDatabase database=mDatabaseOpenHelper.getReadableDatabase();
WordDefinition wordDefinition=null;

String selectQueryString="SELECT * FROM "+FTS_VIRTUAL_TABLE+ " WHERE "+BaseColumns._ID+" = '"+id+ "'";
Cursor cursor=database.rawQuery(selectQueryString, null);

if (cursor.moveToFirst()) {
    wordDefinition=new WordDefinition(cursor.getString(cursor.getColumnIndex(KEY_WORD)), cursor.getString(cursor.getColumnIndex(KEY_DEFINITION)));

}   

return wordDefinition;

 }

   public void initializeDatabaseFortheFirstTime(ArrayList<WordDefinition> wordDefinitions) {
SQLiteDatabase database=mDatabaseOpenHelper.getWritableDatabase();
database.execSQL("BEGIN");

ContentValues contentValues=new ContentValues();

for (WordDefinition wordDefinition : wordDefinitions) {
    contentValues.put(KEY_WORD, wordDefinition.word);
    contentValues.put(KEY_DEFINITION, wordDefinition.definition);           
    database.insert(FTS_VIRTUAL_TABLE, null, contentValues);
}
database.execSQL("COMMIT");

}


}

班科词典

public class BancoDictionary extends Activity {

private TextView mTextView;
private ListView mListView;


ListView dictionaryListView;

String logTagString="DICTIONARY";
ArrayList<WordDefinition> allWordDefinitions=new ArrayList<WordDefinition>();


DictionaryDatabase DictionaryDatabase;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    setContentView(R.layout.main);

    Log.d("DICTIONARY", "second activity started");


    dictionaryListView=(ListView) findViewById(R.id.dictionaryListView);
    mTextView = (TextView) findViewById(R.id.text);
    mListView = (ListView) findViewById(R.id.list);


    mListView.setVisibility(View.INVISIBLE);
    DictionaryDatabase=new DictionaryDatabase(this);
    allWordDefinitions=DictionaryDatabase.getAllWords();

    dictionaryListView.setAdapter(new BaseAdapter() {

        @Override
        public View getView(int position, View view, ViewGroup arg2) {
            if (view==null) {
                view=getLayoutInflater().inflate(R.layout.list_item, arg2, false);
            }
            TextView textView=(TextView) view.findViewById(R.id.listItemTextView);
            textView.setText(allWordDefinitions.get(position).word);

            return view;
        }

        @Override
        public long getItemId(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return allWordDefinitions.size();
        }
    });

    dictionaryListView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View view, int position,
                long arg3) {
            Intent intent =new Intent(BancoDictionary.this, WordDefinitionDetailActivity.class);
            intent.putExtra("word", allWordDefinitions.get(position).word);
            intent.putExtra("definition", allWordDefinitions.get(position).definition);


            startActivity(intent);
        }
    });


    handleIntent(getIntent());
}

@Override
protected void onNewIntent(Intent intent) {
    handleIntent(intent);
}

private void handleIntent(Intent intent) {
    if (Intent.ACTION_VIEW.equals(intent.getAction())) {
        Intent wordIntent = new Intent(this, WordActivity.class);
        this.finish();
        wordIntent.setData(intent.getData());
        startActivity(wordIntent);
    } else if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
        String query = intent.getStringExtra(SearchManager.QUERY);
        showResults(query);

    }
}

private void showResults(String query) {

    Cursor cursor = managedQuery(DictionaryProvider.CONTENT_URI, null, null,
                            new String[] {query}, null);

    if (cursor == null) {
        mTextView.setText(getString(R.string.no_results, new Object[] {query}));
    } else {
        int count = cursor.getCount();
        String countString = getResources().getQuantityString(R.plurals.search_results,
                                count, new Object[] {count, query});
        mTextView.setText(countString);

        String[] from = new String[] { DictionaryDatabase.KEY_WORD,
                                       DictionaryDatabase.KEY_DEFINITION };

        int[] to = new int[] { R.id.word,
                               R.id.definition };

        SimpleCursorAdapter words = new SimpleCursorAdapter(this,
                                      R.layout.result, cursor, from, to);
        dictionaryListView.setVisibility(View.GONE);
        mListView.setVisibility(View.VISIBLE);
        mListView.setAdapter(words);

        mListView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent wordIntent = new Intent(getApplicationContext(), WordActivity.class);
                Uri data = Uri.withAppendedPath(DictionaryProvider.CONTENT_URI,
                                                String.valueOf(id));
                wordIntent.setData(data);
                startActivity(wordIntent);

            }
        });
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main, menu);

    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB){
        SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
        SearchView searchView = (SearchView) menu.findItem(R.id.search).getActionView();
        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
        searchView.setIconifiedByDefault(false);
        int searchPlateId = searchView.getContext().getResources().getIdentifier("android:id/search_plate", null, null);
        View searchPlate = searchView.findViewById(searchPlateId);
        if (searchPlate!=null) {
            searchPlate.setBackgroundColor(Color.RED);
            int searchTextId = searchPlate.getContext().getResources().getIdentifier("android:id/search_src_text", null, null);
            TextView searchText = (TextView) searchPlate.findViewById(searchTextId);
            if (searchText!=null) {
                searchText.setTextColor(Color.WHITE);
                searchText.setHintTextColor(Color.WHITE);
            }
        }
    }
        return true;
    }







@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.search:
            onSearchRequested();
            return true;
        default:
            return false;
    }
}

}

---

查看此简约代码段28行代码：在onCreate中设置适配器，并在每次更新listview显示的数据时调用notifyDatasetChanged。@Bhargav由于我是新手，请您详细演示一下，好吗？您看到我的代码段了吗？什么不清楚？它使用EditText作为过滤器，但与SearchView@pskink你好我试着用你的片段。但它不起作用。我认为这与我的代码不匹配。也许我做错了什么。我是新手。嗯，我需要一个我的问题的答案调整到我的代码。。。具体地说，正如我所说的，当涉及到与爪哇打交道时，我是一个新手。

public class BancoDictionary extends Activity {

private TextView mTextView;
private ListView mListView;


ListView dictionaryListView;

String logTagString="DICTIONARY";
ArrayList<WordDefinition> allWordDefinitions=new ArrayList<WordDefinition>();


DictionaryDatabase DictionaryDatabase;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    setContentView(R.layout.main);

    Log.d("DICTIONARY", "second activity started");


    dictionaryListView=(ListView) findViewById(R.id.dictionaryListView);
    mTextView = (TextView) findViewById(R.id.text);
    mListView = (ListView) findViewById(R.id.list);


    mListView.setVisibility(View.INVISIBLE);
    DictionaryDatabase=new DictionaryDatabase(this);
    allWordDefinitions=DictionaryDatabase.getAllWords();

    dictionaryListView.setAdapter(new BaseAdapter() {

        @Override
        public View getView(int position, View view, ViewGroup arg2) {
            if (view==null) {
                view=getLayoutInflater().inflate(R.layout.list_item, arg2, false);
            }
            TextView textView=(TextView) view.findViewById(R.id.listItemTextView);
            textView.setText(allWordDefinitions.get(position).word);

            return view;
        }

        @Override
        public long getItemId(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return allWordDefinitions.size();
        }
    });

    dictionaryListView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View view, int position,
                long arg3) {
            Intent intent =new Intent(BancoDictionary.this, WordDefinitionDetailActivity.class);
            intent.putExtra("word", allWordDefinitions.get(position).word);
            intent.putExtra("definition", allWordDefinitions.get(position).definition);


            startActivity(intent);
        }
    });


    handleIntent(getIntent());
}

@Override
protected void onNewIntent(Intent intent) {
    handleIntent(intent);
}

private void handleIntent(Intent intent) {
    if (Intent.ACTION_VIEW.equals(intent.getAction())) {
        Intent wordIntent = new Intent(this, WordActivity.class);
        this.finish();
        wordIntent.setData(intent.getData());
        startActivity(wordIntent);
    } else if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
        String query = intent.getStringExtra(SearchManager.QUERY);
        showResults(query);

    }
}

private void showResults(String query) {

    Cursor cursor = managedQuery(DictionaryProvider.CONTENT_URI, null, null,
                            new String[] {query}, null);

    if (cursor == null) {
        mTextView.setText(getString(R.string.no_results, new Object[] {query}));
    } else {
        int count = cursor.getCount();
        String countString = getResources().getQuantityString(R.plurals.search_results,
                                count, new Object[] {count, query});
        mTextView.setText(countString);

        String[] from = new String[] { DictionaryDatabase.KEY_WORD,
                                       DictionaryDatabase.KEY_DEFINITION };

        int[] to = new int[] { R.id.word,
                               R.id.definition };

        SimpleCursorAdapter words = new SimpleCursorAdapter(this,
                                      R.layout.result, cursor, from, to);
        dictionaryListView.setVisibility(View.GONE);
        mListView.setVisibility(View.VISIBLE);
        mListView.setAdapter(words);

        mListView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent wordIntent = new Intent(getApplicationContext(), WordActivity.class);
                Uri data = Uri.withAppendedPath(DictionaryProvider.CONTENT_URI,
                                                String.valueOf(id));
                wordIntent.setData(data);
                startActivity(wordIntent);

            }
        });
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main, menu);

    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB){
        SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
        SearchView searchView = (SearchView) menu.findItem(R.id.search).getActionView();
        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
        searchView.setIconifiedByDefault(false);
        int searchPlateId = searchView.getContext().getResources().getIdentifier("android:id/search_plate", null, null);
        View searchPlate = searchView.findViewById(searchPlateId);
        if (searchPlate!=null) {
            searchPlate.setBackgroundColor(Color.RED);
            int searchTextId = searchPlate.getContext().getResources().getIdentifier("android:id/search_src_text", null, null);
            TextView searchText = (TextView) searchPlate.findViewById(searchTextId);
            if (searchText!=null) {
                searchText.setTextColor(Color.WHITE);
                searchText.setHintTextColor(Color.WHITE);
            }
        }
    }
        return true;
    }







@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.search:
            onSearchRequested();
            return true;
        default:
            return false;
    }
}

}