我有一个函数，通过检查用户的标志来检查用户是否是高级用户：
package com.example.waheed.library;
import java.util.Calendar;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.SearchView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;
public class SearchViewActivity extends Activity implements
SearchView.OnQueryTextListener,
SearchView.OnCloseListener {
private ListView mListView;
private SearchView searchView;
private LibraryDbAdapter mDbHelper;
private TextView inspectionDate;
private TextView bookName;
private TextView bookAuthor;
private TextView storeName;
private TextView storeAddress;
private TextView storeLat;
private TextView storeLong;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
searchView = (SearchView) findViewById(R.id.search);
searchView.setIconifiedByDefault(false);
searchView.setOnQueryTextListener(this);
searchView.setOnCloseListener(this);
mListView = (ListView) findViewById(R.id.list);
inspectionDate = (TextView) findViewById(R.id.inspectionDate);
displayDate();
mDbHelper = new LibraryDbAdapter(this);
mDbHelper.open();
//Clean all Customers
mDbHelper.deleteAllLibrary();
//Add some Customer data as a sample
mDbHelper.createLibrary("How to Win Friends and Influence People", "Dale Carnegie", "Book Centre", " Haider Rd, Rawalpindi 46000", "33.596651", "73.049094");
mDbHelper.createLibrary("The 7 Habits of Highly Effective People", "Stephen Covey", "Idris Book Bank", "Bank Rd, Rawalpindi 46000", "33.595789", "73.052405");
mDbHelper.createLibrary("Think and Grow Rich", "Napoleon Hill", "Students Book Company", "Bank Rd, Rawalpindi 44000", "33.596524", "73.051051");
mDbHelper.createLibrary("Psycho-Cybernetics", "Maxwell Maltz", "Old Book Bank", "Green Super Market, Kashmir Rd, Saddar, Rawalpindi, Punjab", "33.595810", "73.051530");
mDbHelper.createLibrary("How to stop worrying and start living", "Dale Carnegie", "Saeed Book Bank", "F-, Street 7, Islamabad 44000", "33.722446", "73.058763");
mDbHelper.createLibrary("A New Earth", " Eckhart Tolle", "Variety Books", "41-BC, Bank Rd, Saddar, Rawalpindi 46000", "33.597497", "73.049917");
mDbHelper.createLibrary("Blink: The Power of Thinking Without Thinking", "Malcolm Gladwell", "Rehan Book Shop", "Islamabad", "33.689734", "73.031652");
mDbHelper.createLibrary("First Things First", "Stephen Covey", "Idris Book Bank", "Bank Rd, Rawalpindi 46000", "33.595789", "73.052405");
mDbHelper.createLibrary("Emotional Intelligence", "Daniel Goleman", "Book Centre", " Haider Rd, Rawalpindi 46000", "33.596651", "73.049094");
mDbHelper.createLibrary("Anatomy of the Spirit", "Caroline Myss", "Students Book Company", "Bank Rd, Rawalpindi 44000", "33.596524", "73.051051");
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mDbHelper != null) {
mDbHelper.close();
}
}
public boolean onQueryTextChange(String newText) {
showResults(newText + "*");
return false;
}
public boolean onQueryTextSubmit(String query) {
showResults(query + "*");
return false;
}
public boolean onClose() {
showResults("");
return false;
}
private void showResults(String query) {
Cursor cursor = mDbHelper.searchBook((query != null ? query.toString() : "@@@@"));
if (cursor == null) {
//
} else {
// Specify the columns we want to display in the result
String[] from = new String[]{
LibraryDbAdapter.KEY_BOOKNAME,
LibraryDbAdapter.KEY_BOOKAUTHOR,
LibraryDbAdapter.KEY_STORENAME,
LibraryDbAdapter.KEY_STOREADDRESS,
LibraryDbAdapter.KEY_STORELAT,
LibraryDbAdapter.KEY_STORELONG
};
// Specify the Corresponding layout elements where we want the columns to go
int[] to = new int[] { R.id.sbook,
R.id.sauthor,
R.id.sstore,
R.id.sstoreaddress,
R.id.slat,
R.id.slong};
// Create a simple cursor adapter for the definitions and apply them to the ListView
SimpleCursorAdapter books = new SimpleCursorAdapter(this,R.layout.bookresult, cursor, from, to);
mListView.setAdapter(books);
// Define the on-click listener for the list items
mListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// Get the cursor, positioned to the corresponding row in the result set
Cursor cursor = (Cursor) mListView.getItemAtPosition(position);
// Get the state's capital from this row in the database.
String Book = cursor.getString(cursor.getColumnIndexOrThrow("Book"));
String Author = cursor.getString(cursor.getColumnIndexOrThrow("Author"));
String Store = cursor.getString(cursor.getColumnIndexOrThrow("Store"));
String storeaddress = cursor.getString(cursor.getColumnIndexOrThrow("storeaddress"));
String lat = cursor.getString(cursor.getColumnIndexOrThrow("lat"));
String lon = cursor.getString(cursor.getColumnIndexOrThrow("lon"));
//Check if the Layout already exists
LinearLayout bookLayout = (LinearLayout)findViewById(R.id.booklayout);
if(bookLayout == null){
//Inflate the Customer Information View
LinearLayout leftLayout = (LinearLayout)findViewById(R.id.rightLayout);
View bookInfo = getLayoutInflater().inflate(R.layout.bookinfo, leftLayout, false);
leftLayout.addView(bookInfo);
}
//Get References to the TextViews
bookName = (TextView) findViewById(R.id.book);
bookAuthor = (TextView) findViewById(R.id.author);
storeName = (TextView) findViewById(R.id.store);
storeAddress = (TextView) findViewById(R.id.storeaddress);
storeLat = (TextView) findViewById(R.id.latitude);
storeLong = (TextView) findViewById(R.id.longitude);
// Update the parent class's TextView
bookName.setText(Book);
bookAuthor.setText(Author);
storeName.setText(Store);
storeAddress.setText(storeaddress);
storeLat.setText(lat);
storeLong.setText(lon);
searchView.setQuery("",true);
}
});
}
}
private void displayDate() {
final Calendar c = Calendar.getInstance();
inspectionDate.setText(
new StringBuilder()
// Month is 0 based so add 1
.append(c.get(Calendar.MONTH) + 1).append("/")
.append(c.get(Calendar.DAY_OF_MONTH)).append("/")
.append(c.get(Calendar.YEAR)).append(" "));
}
}
现在让我们说我想要另一个功能，但这一次要检查用户是否空闲，但是使用相同的标志。我试图否定返回的值，但我想知道是否有更好的方法来执行此操作。
isUserPremium() {
return this.flags & Flags.PREMIUM; // returns true
}
答案 0 :(得分：2)
无法检查是否未使用单个运算符设置标志。我建议稍后在代码中使用!isUserPremium()而不是isUserFree() - 不要创建反转从另一个函数返回的值的函数。但是，请确保您不依赖于此以确保安全性。浏览器中执行的所有操作都可以轻松操作。