在Java（Android应用程序）中，在一个类中设置值并从另一个类中检索
当用户在应用程序启动时输入id时，我正在从我的主类设置id。考虑到这一点，我在一个名为GetSet.java的类中设置了它，该类也有一个方法在被调用时返回它。所以我需要一个名为MySQLitehelper.java的类中第一个类的id集，这样我就可以根据id集而不是硬编码来检索数据。这将使我的应用程序成为动态的，而不是静态的。这是我的密码： /----MainActivity.java-----/ /---MySQLitehelper.java---/在Java（Android应用程序）中，在一个类中设置值并从另一个类中检索,java,android,Java,Android,当用户在应用程序启动时输入id时，我正在从我的主类设置id。考虑到这一点，我在一个名为GetSet.java的类中设置了它，该类也有一个方法在被调用时返回它。所以我需要一个名为MySQLitehelper.java的类中第一个类的id集，这样我就可以根据id集而不是硬编码来检索数据。这将使我的应用程序成为动态的，而不是静态的。这是我的密码： /----MainActivity.java-----/ /---MySQLitehelper.java---/ 我在上面底部类的getRecord（）方法
我在上面底部类的getRecord（）方法中检索它，而不是
COLUMN_ID+”=47688507GetSetgetId47688507obj_getsetobj\u getset.setid（mCursor.COLUMN\u ID）getRecordobj_getset.getID（）obj_getsetobj\u getset.setid（mCursor.COLUMN\u ID）getRecordobj\u getset.getID（）- 使用全局单例存储和检索。执行此操作时，请确保该单例未包含对您的活动或上下文的引用
- 因为mysqlitehelper有一个对上下文的引用，所以您还可以从SharedReferences检索持久化数据 -
- 使用全局单例存储和检索。执行此操作时，请确保该单例未包含对您的活动或上下文的引用
- 因为mysqlitehelper有一个对上下文的引用，所以您还可以从SharedReferences检索持久化数据 -
/**
* This is a singleton class to hold preferences.
*/
public class Prefs {
private static volatile Prefs instance = null;
// The values held by this class
String identity = null;
String apiUrl = "http://example.com/cgi-bin/api";
int interval = 3600; // when there's no activity
/**
* Return the single instance of this class, creating it
* if necessary. This method is thread-safe.
*/
public static Prefs getPrefs(Context ctx) {
if (instance == null) {
synchronized(Prefs.class) {
if (instance == null) {
instance = new Prefs();
instance.readPrefs(ctx);
}
}
}
return instance;
}
/**
* Re-read all preferences (you never need to call this explicitly)
*/
private void readPrefs(Context ctx) {
try {
SharedPreferences sp =
PreferenceManager.getDefaultSharedPreferences(ctx);
identity = sp.getString("identity", identity);
apiUrl = sp.getString("apiUrl", apiUrl);
interval = sp.getInt("interval", interval);
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences; you can call this from onPause()
*/
public void savePrefs(Context ctx) {
try {
SharedPreferences.Editor sp =
PreferenceManager.getDefaultSharedPreferences(ctx).edit();
sp.putString("identity", identity);
sp.putString("apiUrl", apiUrl);
sp.putInt("interval", interval);
sp.commit();
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences to a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onSaveInstanceState()
*/
public void onSaveInstanceState(Bundle state) {
state.putString("identity", identity);
state.putString("apiUrl", apiUrl);
state.putInt("interval", interval);
}
/**
* Recall preferences from a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onCreate()
*/
public void restoreInstanceState(Bundle state) {
identity = state.getString("identity");
apiUrl = state.getString("apiUrl");
interval = state.getInt("interval");
}
}
/**
* This is a singleton class to hold preferences.
*/
public class Prefs {
private static volatile Prefs instance = null;
// The values held by this class
String identity = null;
String apiUrl = "http://example.com/cgi-bin/api";
int interval = 3600; // when there's no activity
/**
* Return the single instance of this class, creating it
* if necessary. This method is thread-safe.
*/
public static Prefs getPrefs(Context ctx) {
if (instance == null) {
synchronized(Prefs.class) {
if (instance == null) {
instance = new Prefs();
instance.readPrefs(ctx);
}
}
}
return instance;
}
/**
* Re-read all preferences (you never need to call this explicitly)
*/
private void readPrefs(Context ctx) {
try {
SharedPreferences sp =
PreferenceManager.getDefaultSharedPreferences(ctx);
identity = sp.getString("identity", identity);
apiUrl = sp.getString("apiUrl", apiUrl);
interval = sp.getInt("interval", interval);
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences; you can call this from onPause()
*/
public void savePrefs(Context ctx) {
try {
SharedPreferences.Editor sp =
PreferenceManager.getDefaultSharedPreferences(ctx).edit();
sp.putString("identity", identity);
sp.putString("apiUrl", apiUrl);
sp.putInt("interval", interval);
sp.commit();
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences to a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onSaveInstanceState()
*/
public void onSaveInstanceState(Bundle state) {
state.putString("identity", identity);
state.putString("apiUrl", apiUrl);
state.putInt("interval", interval);
}
/**
* Recall preferences from a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onCreate()
*/
public void restoreInstanceState(Bundle state) {
identity = state.getString("identity");
apiUrl = state.getString("apiUrl");
interval = state.getInt("interval");
}
}
setid和getID都在不同的类中。我在MainActivity中设置了它。但我需要在SelectOptions.java类中获取它。我可能缺少一些内容，但如果在调用intent（）的同一活动中设置它函数，为什么不能将id作为参数传递给该函数，并将其作为附加值发送给该函数？setid和getID都在不同的类中。我在MainActivity中设置了它。但我需要在SelectOptions.java类中获取它。我可能缺少一些内容，但如果在调用intent（）的同一活动中设置了它函数，为什么您不能将id作为参数传递给该函数，并将其作为附加值发送？我在应用程序中使用了类似的实现。很高兴知道我不是唯一得出此结论的人。我在应用程序中使用了类似的实现。很高兴知道我不是唯一得出此结论的人。
/**
* This is a singleton class to hold preferences.
*/
public class Prefs {
private static volatile Prefs instance = null;
// The values held by this class
String identity = null;
String apiUrl = "http://example.com/cgi-bin/api";
int interval = 3600; // when there's no activity
/**
* Return the single instance of this class, creating it
* if necessary. This method is thread-safe.
*/
public static Prefs getPrefs(Context ctx) {
if (instance == null) {
synchronized(Prefs.class) {
if (instance == null) {
instance = new Prefs();
instance.readPrefs(ctx);
}
}
}
return instance;
}
/**
* Re-read all preferences (you never need to call this explicitly)
*/
private void readPrefs(Context ctx) {
try {
SharedPreferences sp =
PreferenceManager.getDefaultSharedPreferences(ctx);
identity = sp.getString("identity", identity);
apiUrl = sp.getString("apiUrl", apiUrl);
interval = sp.getInt("interval", interval);
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences; you can call this from onPause()
*/
public void savePrefs(Context ctx) {
try {
SharedPreferences.Editor sp =
PreferenceManager.getDefaultSharedPreferences(ctx).edit();
sp.putString("identity", identity);
sp.putString("apiUrl", apiUrl);
sp.putInt("interval", interval);
sp.commit();
} catch (Exception e) {
Log.e(TAG, "exception reading preferences: " + e, e);
// TODO: report it
}
}
/**
* Save preferences to a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onSaveInstanceState()
*/
public void onSaveInstanceState(Bundle state) {
state.putString("identity", identity);
state.putString("apiUrl", apiUrl);
state.putInt("interval", interval);
}
/**
* Recall preferences from a bundle. You don't really need to implement
* this, but it can make start-up go faster.
* Call this from onCreate()
*/
public void restoreInstanceState(Bundle state) {
identity = state.getString("identity");
apiUrl = state.getString("apiUrl");
interval = state.getInt("interval");
}
}