How the settitle of the activity doesn t work

setTitle is the text that sets the actionbar, which is usually displayed.

You need to set the display actionbar first to be displayed.

There are a lot of ways to do this, first, tabhost can use getparent to call the method of the main interface. Second, in listener mode, write an interface to let the main interface be implemented, and then click on one of the items in the listview to go to the ** interface method.

Activity must inherit Activity, sqlitehelper is used to create, read, and write to the database, this is a relationship with activity similar to MVC, activity is responsible for display, database is responsible for storage, sqlitehelper is responsible for data logic, etc.

When you create a new class, you can choose to either extend the sqlitehelper class yourself.

To manage all the activities of Hail Larry need to be judged by the wisdom to use this instanceof activity class source macro slide name.

Static calls, if the component initializes these operations, will definitely report this error, because the activity method will not call its oncreate method and will not be able to load the XML layout. If you want to initialize the entire activity, its constructor will not be initialized, so it will also be a null pointer.

When there are many activities in an application, in order to better experience the user experience of the wheels or effects, it is necessary to do some artificial control over the display order of the activities, instead of using the history stack mechanism of Android's own activities, and it is often necessary to know which one the previous activity was. The specific idea is to pass the current activity information to the next activity when starting an activity through the intent, and when the next activity is started, you can know the information of the previous activity by obtaining the input parameters through the intent.

It's good to make an activity management queue, write the base class of an activity by yourself, call addactivity in the oncreate side of the base class activity, and call removeactivity in ondestroy. These methods all write letters to the custom application class, when they need to close, call the close method, and judge whether the activity is an instance of a in the close method, and do not close a when the activity is not, the general idea is this, public list activitylist = new linkedlist(); Add Activity to the container public void addactivity(baseactivityactivity) public void close() activitylist = new linkedlist(); public void removeactivity(activity activity) i++;