Java、ios、android開發總結(二) Android中全局變量和靜態變量的使用

1.盡量不要使用靜態變量,靜態常量除外(static final).

http://blog.csdn.net/zhangyue0503/article/details/7614944

2.自定義一個MyApplication繼承android.app.Application,在其中定義全局變量。
啟動Application時，系統會創建一個PID，即進程ID，所有的Activity就會在此進程上運行。那麼我們在Application創建的 時候初始化全局變量，同一個應用的所有Activity都可以取到這些全局變量的值

import android.app.Application;
import android.util.Log;

public class MyApplication extends Application {
	
	public static final String TAG = MyApplication.class.getSimpleName();
	
	private User user;
	
	@Override
	public void onCreate() {
		
		Log.i(TAG, "onCreate ::");
		super.onCreate();
	}

	public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

}

AndroidManifest.xml中

Activity、Service中

MyApplication app = (MyApplication)getApplication().
MyApplication app = (MyApplication)getApplicationContext();
app.getUser();
app.setUser(xxx);

BroadcastReceiver中onReceive()方法

MyApplication app = (MyApplication)context.getApplicationContext();
app.getUser();
app.setUser(xxx);

ContentProvider中

MyApplication app = (MyApplication)getContext().getApplicationContext();
app.getUser();
app.setUser(xxx);

其他類中，可以通過傳遞context,通過如下方式調用

MyApplication app = (MyApplication)context.getApplicationContext();
app.getUser();
app.setUser(xxx);