//设置单例里面的数值，然后再将数值写入到SharedPreference里

 private String setCityName(String _cityName){
  City.getCity().setCityName(_cityName);
  
  Context ctx =MainActivity.this;
  SharedPreferences sp =ctx.getSharedPreferences("CITY", MODE_PRIVATE);
  Editor editor=sp.edit();
  editor.putString("CityName", City.getCity().getCityName());
  editor.commit();
  
  return City.getCity().getCityName();
 }

 //从单例里面找，如果不存在则在SharedPreferences里面读取

 private String getCityName(){
  String cityName = City.getCity().getCityName();
  if(cityName==null ||cityName==""){
   Context ctx =MainActivity.this;
   SharedPreferences sp =ctx.getSharedPreferences("CITY", MODE_PRIVATE);
   City.getCity().setCityName(sp.getString("CityName", "广州"));
  }
  return City.getCity().getCityName();
 }

ContentValues values=new ContentValues();
values.put("name", "liangjh");
values.put("password", "123456");
db.insert("t_user", "id", values);

// 方式1 直接将条件写入到条件里面（个人觉得容易被注入，但其实数据都在客户端，没啥安全性可言）
db.delete("t_user", "id=1", null);
// 方式2 条件分开写，感觉比较安全
db.delete("t_user", "name=? and password =?", new String[]{"weiyg","112233"});

// 使用rawQuery
// Cursor c = db.rawQuery("select * from t_user", null);
// db.rawQuery("select * from t_user where id=1", null);
// db.rawQuery("select * from t_user where id=?", new String[]{"1"});
 
// 使用query()
Cursor c = db.query("t_user", new String[]{"id","name"}, "name=?", new String[]{"weiyg"}, null, null, null);
c.moveToFirst();
while(!c.isAfterLast()){
 String msg="";
 for(int i=0,j=c.getColumnCount();i<j;i++){
  msg+="--"+c.getString(i);
 }
 Log.v("SQLite", "data:"+msg);
 c.moveToNext();
}

ContentValues values=new ContentValues();
values.put("password", "111111");
// 方式1 条件写在字符串内
db.update("t_user", values, "id=1", null);
// 方式2 条件和字符串分开
db.update("t_user", values, "name=? or password=?",new String[]{"weiyg","123456"});

public class MyProvider extends ContentProvider {

 @Override
 public int delete(Uri uri, String selection, String[] selectionArgs) {
  // TODO Auto-generated method stub
  return 0;
 }

 @Override
 public String getType(Uri uri) {
  // TODO Auto-generated method stub
  return null;
 }

 @Override
 public Uri insert(Uri uri, ContentValues values) {
  // TODO Auto-generated method stub
  return null;
 }

 @Override
 public boolean onCreate() {
  // 新建个数据库并插入一条数据
  SQLiteDatabase db=this.getContext().openOrCreateDatabase("test_db2.db", Context.MODE_PRIVATE, null);
  db.execSQL("CREATE TABLE t_user (id INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT NOT NULL)");
  ContentValues values=new ContentValues();
  values.put("name", "liangjh2");
  db.insert("t_user", "id", values);
  db.close();
  return false;
 }

 @Override
 public Cursor query(Uri uri, String[] projection, String selection,
   String[] selectionArgs, String sortOrder) {
  // 获取数据
  SQLiteDatabase db=this.getContext().openOrCreateDatabase("test_db2.db", Context.MODE_PRIVATE, null);
  Cursor c = db.query("t_user", null, null, null, null, null, null);
  db.close();
  return c;
 }

 @Override
 public int update(Uri uri, ContentValues values, String selection,
   String[] selectionArgs) {
  // TODO Auto-generated method stub
  return 0;
 }

}

<application ...>
 ...
 <provider android:name=".MyProvider" android:authorities="com.example.androidtestdemo" android:exported="true"/>
</application>

Context ctx=MainActivity.this;
ContentResolver resolver =ctx.getContentResolver();
Uri uri=Uri.parse("content://com.example.androidtestdemo");
Cursor c = resolver.query(uri, null, null, null, null);
c.moveToFirst();
while(!c.isAfterLast()){
 for(int i=0,j=c.getColumnCount();i<j;i++){
  Log.v("Android2",""+c.getString(i));
 }
 c.moveToNext();
}