我已经点击此链接并成功在 Android 中创建了单例类。http://www.devahead.com/blog/2011/06/extending-the-android-application-class-and-dealing-with-singleton/
问题是我想要一个对象。就像我有活动 A 和活动 B 一样。在活动 A 中,我从 Singleton 访问该对象class
。我使用该对象并对其进行了一些更改。
当我移动到 Activity B 并从 Singleton 类访问该对象时,它给了我初始化的对象,并且不保留我在 Activity A 中所做的更改。
还有其他方法可以保存更改吗?
请专家帮帮我。
这是MainActivity
public class MainActivity extends Activity {
protected MyApplication app;
private OnClickListener btn2=new OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent=new Intent(MainActivity.this,NextActivity.class);
startActivity(intent);
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Get the application instance
app = (MyApplication)getApplication();
// Call a custom application method
app.customAppMethod();
// Call a custom method in MySingleton
Singleton.getInstance().customSingletonMethod();
Singleton.getInstance();
// Read the value of a variable in MySingleton
String singletonVar = Singleton.customVar;
Log.d("Test",singletonVar);
singletonVar="World";
Log.d("Test",singletonVar);
Button btn=(Button)findViewById(R.id.button1);
btn.setOnClickListener(btn2);
}
}
This is NextActivity
public class NextActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_next);
String singletonVar = Singleton.customVar;
Log.d("Test",singletonVar);
}
}
Singleton
Class
public class Singleton
{
private static Singleton instance;
public static String customVar="Hello";
public static void initInstance()
{
if (instance == null)
{
// Create the instance
instance = new Singleton();
}
}
public static Singleton getInstance()
{
// Return the instance
return instance;
}
private Singleton()
{
// Constructor hidden because this is a singleton
}
public void customSingletonMethod()
{
// Custom method
}
}
and MyApplication
public class MyApplication extends Application
{
@Override
public void onCreate()
{
super.onCreate();
// Initialize the singletons so their instances
// are bound to the application process.
initSingletons();
}
protected void initSingletons()
{
// Initialize the instance of MySingleton
Singleton.initInstance();
}
public void customAppMethod()
{
// Custom application method
}
}
当我运行这段代码时,我得到了我已经初始化的HelloSingleton
我给予它的世界MainActivity
并再次显示 HelloNextActivity
在 logcat 中。
我希望它再次向世界展示NextActivity
。
请帮我纠正这个问题。