PhoneGap, "Building cross-platform APP:PHONEGAP mobile Applications" serial Three (experience life week through examples)

4.1.2 Experience the life cycle of an activity by example

The previous section describes the processes in the activity life cycle, and this section takes a simple example to give the reader a firsthand experience of each event in the activity life cycle.

Create a new Android project in Eclipse, named Example4_1, and modify the contents of its Mainactivity class as shown in example 4-1.

"Example 4-1activity life cycle Demo"

01     //A number of import files are omitted here, automatically generated by Eclipse   02     public  classMainActivity extends Activity {                                              // Class Mainactivity inheriting class activity  03               string tag= "Activity life cycle Events";  04                @Override   05               protected voidoncreate (bundle savedinstancestate)  {   06                      &nbSp;  super.oncreate (savedinstancestate);  07                          Setcontentview (R.layout.activity_main);  08                         LOG.E (TAG, " Start OnCreate event ");  09               }  10              @ override  11               Protected voidondestroy ()  {                                                               //overriding OnDestroy Events   12                         // TODO  auto-generatedmethod stub  13                         super.ondestroy ();   14                          LOG.E (TAG, "Start OnDestroy event");                                          //Show records in Logcat    15              }  16                @Override   17               protected void onpause () {  18                          // TODO Auto-generatedmethod stub  19                          super.onpause ();  20                         LOG.E (TAG, " Start OnPause event ");  21               }  22               @Override   23               protected voidonrestart ()  {   24                         // TODO Auto-generatedmethod stub  25                          super.onrestart ();  26                         LOG.E (TAG, " Start Onrestart event ");  27               }  28              @ Override  29              protected void  Onresume () {  30                         // todo auto-generatedmethod stub   31                         super.onresume ();  32                          LOG.E (TAG, "Start Onresume event");  33               }  34                @Override   35               protected&nbsP;void onstart () {  36                         // todo auto-generatedmethod  stub  37                         super.onstart ();  38                          LOG.E (TAG, "Start OnStart event");  39               }  40                @Override   41               protected void onstop ()  {  42                         // todo  auto-generatedmethod stub  43                         super.onstop ();   44                          LOG.E (TAG, "Start OnStop event");  45               }  46     }

After running, you can see the contents shown in the Logcat window in 4-2.

Tip: You can filter the information in the Logcat by setting a filter so that it displays only records related to that activity, as shown in 4-3. The filtered contents are shown in 4-4.

Look back and look at the description of the start activity in a section, to start an activity you need to go through OnCreate, OnStart, Onresume 3 events, you can confirm this in Figure 4-4. You can verify the contents of the previous section by further manipulating your phone, such as clicking the Home button or the Back button to see the log records in the Logcat.

Figure 4-2 events that were experienced when activity was started

Figure 4-3 Filtering the information in the LOGCAT using tag tags

Figure 4-4 Filtered Logcat window

Right-click in the code editing area of Eclipse and select source| The Overridemethods command can see some other events, as shown in 4-5.

Figure 4-5 Some of the other events in activity

Most of these events correspond to a particular operation or error of the application. For example, event ontitlechanged is the event that is emitted by the system when the title of the app is modified, such as listening to music, music playing to 1 minutes 50 seconds when suddenly call in a phone, the system will use the player's activity OnPause method, At the same time start a call activity, when the user after the call will be returned through the Onrestar method and the OnStar method to return to the music interface, and adjust the music playback progress of 1 minutes 50 seconds.

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PhoneGap, "Building cross-platform APP:PHONEGAP mobile Applications" serial Three (experience life week through examples)