適配器不填充回收器

Question

我有一個回收站的問題，問題是：我有AsyncTask從我的數據庫查詢數據，然後通過CursorLoader更新回收站，但適配器不填充回收站，日誌說數據從數據庫正在成功讀取，然後適配器構造函數成功地將ArrayList與數據，但這就是所有，日誌說適配器的方法不會調用。

MainActivity：

public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor> { 


private SQLiteDatabase db; 
private SimpleCursorLoader loader; 
private MySimpleAdapter adapter; 
private RecyclerView recycler; 

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

    recycler = (RecyclerView) findViewById(R.id.recycler); 

    new SimpleTask(SimpleTask.OPEN, null).execute(); 
} 

private class SimpleTask extends AsyncTask<Void, Void, Void> { 

    public static final int INSERT = 0; 
    public static final int DELETE = 1; 
    public static final int OPEN = 2; 
    private int task; 
    private String name; 

    public SimpleTask(int task, String name) { 
     this.task = task; 
     this.name = name; 
    } 

    @Override 
    protected Void doInBackground(Void... params) { 
     switch (task) { 
      case INSERT : 
       ContentValues values = new ContentValues(); 
       values.put(SimpleHelper.KEY_NAME, name); 
       db.insert(SimpleHelper.TABLE_NAME, null, values); 
       break; 
      case DELETE : 
       db.delete(SimpleHelper.TABLE_NAME, SimpleHelper.KEY_NAME + " = ? ", new String[]{name}); 
       break; 
      case OPEN : 
       if (db == null) { 
        try { 
         db = new SimpleHelper(MainActivity.this).getWritableDatabase(); 
        } catch (SQLiteException e) { 
         e.printStackTrace(); 
        } 
       } 
       break; 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Void aVoid) { 
     if (loader == null) { 
      loader = new SimpleCursorLoader(MainActivity.this, db); 
      loader.setQueryParams(SimpleHelper.TABLE_NAME, new String[]{SimpleHelper.KEY_NAME}, 
        null, null); 
      getSupportLoaderManager().initLoader(0, null, MainActivity.this); 
     } 
     getSupportLoaderManager().getLoader(0).forceLoad(); 
    } 
} 

@Override 
public Loader<Cursor> onCreateLoader(int id, Bundle args) { 
    return loader; 
} 

@Override 
public void onLoadFinished(Loader<Cursor> loader, Cursor data) { 
    Log.i("MyLog", "onLoadFinished cursor size is " + data.getCount()); 
    List<String> items = new ArrayList<>(); 
    data.moveToFirst(); 
    do { 
     items.add(data.getString(0)); 
     Log.i("MyLog", data.getString(0)); 
    } while (data.moveToNext()); 

    Log.i("MyLog", "onLoadFinished items size is " + items.size()); 

    if (adapter == null) { 
     adapter = new MySimpleAdapter(items); 
     recycler.setAdapter(adapter); 
    } else { 
     adapter.updateAdapter(items); 
    } 
} 

@Override 
public void onLoaderReset(Loader<Cursor> loader) { 

} 

private class MySimpleAdapter extends RecyclerView.Adapter<MySimpleAdapter.MyHolder> { 

    private List<String> items; 

    public MySimpleAdapter(List<String> items) { 
     Log.i("MyLog", "Constructor called with items size " + items.size()); 
     this.items = items; 
    } 

    public class MyHolder extends RecyclerView.ViewHolder implements View.OnClickListener { 

     TextView tvText; 

     public MyHolder(View itemView) { 
      super(itemView); 
      tvText = (TextView) itemView.findViewById(android.R.id.text1); 
      itemView.setOnClickListener(this); 
     } 

     @Override 
     public void onClick(View v) { 
      new SimpleTask(SimpleTask.DELETE, tvText.getText().toString()); 
     } 
    } 

    public void updateAdapter(List<String> items) { 
     this.items = items; 
     notifyDataSetChanged(); 
    } 

    @Override 
    public MyHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     Log.i("MyLog", "onCreateViewHolder"); 
     View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, null, false); 
     return new MyHolder(view); 
    } 

    @Override 
    public void onBindViewHolder(MyHolder holder, int position) { 
     holder.tvText.setText(items.get(position)); 
     Log.i("MyLog", "onBindViewHolder setText : " + items.get(position)); 
    } 

    @Override 
    public int getItemCount() { 
     Log.d("MyLog", "getItemCount called with size : " + items.size()); 
     return items.size(); 
    } 
} 

SimpleCursorLoader：

public class SimpleCursorLoader extends CursorLoader { 

private SQLiteDatabase db; 
private String tableName; 
private String[] columns; 

public SimpleCursorLoader(Context context, SQLiteDatabase db) { 
    super(context); 
    this.db = db; 
} 

public void setQueryParams(String tableName, String[] columns, String selection, String[] selectionArgs) { 
    this.tableName = tableName; 
    this.columns = columns; 
    setSelection(selection); 
    setSelectionArgs(selectionArgs); 
} 

@Override 
public Cursor loadInBackground() { 
    Cursor cursor = db.query(tableName, columns, getSelection(), getSelectionArgs(), 
      null, null, null); 
    return cursor; 
} 

DBHelper：

public class SimpleHelper extends SQLiteOpenHelper{ 

public static final String TABLE_NAME = "users"; 
public static final String KEY_NAME = "name"; 
public static final String KEY_ID = "_id"; 
private static final int DB_VERSION = 1; 
private static final String DB_NAME = "SimpleDB"; 

public SimpleHelper(Context context) { 
    super(context, DB_NAME, null, DB_VERSION); 
} 


@Override 
public void onCreate(SQLiteDatabase db) { 
    db.execSQL("create table " + TABLE_NAME + "(" 
    + KEY_ID + " integer primary key autoincrement, " 
    + KEY_NAME + " text)"); 
    for (int i = 0; i < 5; i ++) { 
     ContentValues values = new ContentValues(); 
     values.put(KEY_NAME, "name" + i+1); 
     db.insert(TABLE_NAME, null, values); 
     Log.i("MyLog", "inserted"); 
    } 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

} 

activity_main.xml中：

<?xml version="1.0" encoding="utf-8"?> 
<android.support.v7.widget.RecyclerView 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/recycler" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" /> 

Answer 1

使用此。

recycler.setLayoutManager(new LinearLayoutManager(this)); 
recycler.setHasFixedSize(true); 
recycler.setNestedScrollingEnabled(false);