Four components of Android-activation of Activity: StartActivity () and StartActivityForResult () (graphic explanation)

Four components of Android-activation of Activity: StartActivity () and StartActivityForResult () (graphic explanation)
[Four major Android component Learning Series Activity] 1. four components of Android-Activity (1) definition, status, and rollback (graphic explanation) 2. four components of Android-Activity lifecycle (graphic explanation) 3. the four main components of Android-the activation of StartActivity () and StartActivityForResult () (graphic explanation) of the Activity learned the basic concepts and lifecycle of the Activity for the first two times, today, let's take a look at Activity jump and value transfer. Start learning! There are two methods to enable a new Activity: startActivity (Intent) and startActivityForResult (Intent, int ). StartActivity (Intent): Used to start a new Activity, which is pushed to the top of the stack. The Intent parameter is used to describe the new Activity. StartActivityForResult (Intent, int): Used to start a new Activity. After the new Activity exits, the result is returned to the old Activity. StartActivity is easy to understand, and startActivityForResult () is a little troublesome. The following figure makes it easy for us to understand: Description: requestCode, request code, self-configured, but must be non-negative. This code is returned to onActivityResult () only when the Activity exits when it is not a negative number (). ResultCode, result code, used to identify the new Activity from which the returned data comes from. Its value is generally RESULT_CANCELED, RESULT_ OK, RESULT_FIRST_USER. I wrote a Demo about how to enable the Activity: a total of three activities: MainActivity Users enter the user name, phone number, city, CityActivity for the user to select the city, ShowActivity is used to display the user information. MainActivity: Copy code 1 package com. johntsai. startactivity; 2 3 import android. app. activity; 4 import android. content. intent; 5 import android. database. cursor; 6 import android.net. uri; 7 import android. OS. bundle; 8 import android. provider. contactsContract. commonDataKinds. phone; 9 import android. view. view; 10 import android. view. view. onClickListener; 11 import android. widget. button; 12 import android. widget. editText; 13 14 public class MainActivity extends Activity implements OnClickListener {15 16 private Button button_city, button_phone, button_save; 17 private EditText editText_city, editText_name, editText_phone; 18 private static final int Limit = 2; 19 private static final int SELECT_PHONE_REQUEST = 3; 20 21 @ Override22 protected void onCreate (Bundle savedInstanceState) {23 super. onCreate (savedInstanceState); 24 setContentView (R. layout. activity_main); 25 26 button_city = (Button) findViewById (R. id. button_city); 27 button_phone = (Button) findViewById (R. id. button_phone); 28 button_save = (Button) findViewById (R. id. button_save); 29 editText_city = (EditText) findViewById (R. id. editText_city); 30 editText_name = (EditText) findViewById (R. id. editText_name); 31 editText_phone = (EditText) findViewById (R. id. editText_Phone); 32 33 listener (this); 34 button_phone.setOnClickListener (this); 35 button_save.setOnClickListener (this); 36} 37 @ Override38 public void onClick (View v) {39 switch (v. getId () {40 case R. id. button_city: 41 Intent I = new Intent (); 42 I. setClass (MainActivity. this, CityActivity. class); 43 startActivityForResult (I, SELECT_CITY_REQUEST); 44 break; 45 case R. id. button_phone: 46 Intent pickContactIntent = new Intent (Intent. ACTION_PICK, Uri. parse ("content: // contacts"); 47 pickContactIntent. setType (Phone. CONTENT_TYPE); 48 startActivityForResult (pickContactIntent, SELECT_PHONE_REQUEST); 49 break; 50 case R. id. button_save: 51 String name = editText_name.getText (). toString (); 52 String city = editText_city.getText (). toString (); 53 String phone = editText_phone.getText (). toString (); 54 Intent saveIntent = new Intent (MainActivity. this, ShowActivity. class); 55 saveIntent. putExtra ("content", "NAME:" + name + "\ nCITY:" + city + "\ nPHONE" + phone); 56 startActivity (saveIntent); 57 break; 58 default: 59 break; 60} 61} 62 63 @ Override64 protected void onActivityResult (int requestCode, int resultCode, Intent data) {65 if (SELECT_CITY_REQUEST = requestCode) {66 if (resultCode = RESULT_ OK) {67 String city = data. getStringExtra ("city"); 68 editText_city.setText (city); 69} 70} 71 if (SELECT_PHONE_REQUEST = requestCode) {72 if (resultCode = RESULT_ OK) {73 Uri contactData = data. getData (); 74 String [] projection = {Phone. NUMBER}; 75 Cursor c = getContentResolver () 76. query (contactData, projection, null); 77 c. moveToFirst (); 78 int column = c. getColumnIndex (Phone. NUMBER); 79 String num = c. getString (column); 80 editText_phone.setText (num); 81} 82} 83 super. onActivityResult (requestCode, resultCode, data); 84} 85} 1 package com. johntsai. startactivity; 2 3 4 import android. app. activity; 5 import android. content. intent; 6 import android. OS. bundle; 7 import android. view. gravity; 8 import android. view. view; 9 import android. view. viewGroup; 10 import android. widget. absListView; 11 import android. widget. baseExpandableListAdapter; 12 import android. widget. expandableListAdapter; 13 import android. widget. expandableListView; 14 import android. widget. linearLayout; 15 import android. widget. textView; 16 import android. widget. toast; 17 18 public class CityActivity extends Activity {19 20 private ExpandableListView eListView; 21 @ Override 22 protected void onCreate (Bundle savedInstanceState) {23 24 super. onCreate (savedInstanceState); 25 setContentView (R. layout. layout_city); 26 initEListView (); 27} 28 29 // initialize 30 private void initEListView () {31 ExpandableListAdapter adapter = new BaseExpandableListAdapter () {32 33 34 private String [] countries = new String [] {35 "China", "USA", "UK" 36 }; 37 38 private String [] [] cities = new String [] [] {39 {"BeiJing", "ShangHai", "HongKong", "TaiBei "}, 40 {"Washington", "New York", "Los Angles", "San Fransico"}, 41 {"London", "Manchester", "birmheim ", "Liverpool"} 42}; 43 private TextView getTextView () {44 AbsListView. layoutParams lp = new AbsListView. layoutParams (ViewGroup. layoutParams. MATCH_PARENT, 45 ViewGroup. layoutParams. WRAP_CONTENT); 46 TextView textView = new TextView (CityActivity. this); 47 textView. setLayoutParams (lp); 48 textView. setGravity (Gravity. CENTER_HORIZONTAL); 49 textView. setPadding (0, 0, 0, 0); 50 textView. setTextSize (20); 51 return textView; 52 53} 54 @ Override 55 public boolean isChildSelectable (int groupPosition, int childPosition) {56 Toast. makeText (CityActivity. this, "you have clicked Group:" + groupPosition + "Child:" + childPosition + "\ n" + countries [groupPosition] + "" + cities [groupPosition] [childPosition], 57 Toast. LENGTH_SHORT ). show (); 58 Intent I = new Intent (); 59 I. putExtra ("city", cities [groupPosition] [childPosition]); 60 setResult (RESULT_ OK, I); 61 finish (); 62 return true; 63} 64 65 @ Override 66 public boolean hasStableIds () {67 return true; 68} 69 70 @ Override 71 public View getGroupView (int groupPosition, boolean isExpanded, 72 View convertView, viewGroup parent) {73 LinearLayout linearLayout = new LinearLayout (CityActivity. this); 74 linearLayout. setOrientation (0); 75 76 TextView textView = getTextView (); 77 textView. setText (getGroup (groupPosition ). toString (); 78 linearLayout. addView (textView); 79 return linearLayout; 80} 81 @ Override 82 public long getGroupId (int groupPosition) {83 return groupPosition; 84} 85 86 @ Override 87 public int getGroupCount () {88 return countries. length; 89} 90 91 @ Override 92 public Object getGroup (int groupPosition) {93 return countries [groupPosition]; 94} 95 96 @ Override 97 public int getChildrenCount (int groupPosition) {98 return cities [groupPosition]. length; 99} 100 101 @ Override102 public View getChildView (int groupPosition, int childPosition, 103 boolean isLastChild, View convertView, ViewGroup parent) {104 TextView textView = getTextView (); 105 textView. setText (getChild (groupPosition, childPosition ). toString (); 106 textView. setGravity (Gravity. CENTER_HORIZONTAL); 107 return textView; 108} 109 110 @ Override111 public long getChildId (int groupPosition, int childPosition) {112 return childPosition; 113} 114 115 @ Override116 public Object getChild (int groupPosition, int childPosition) {117 return cities [groupPosition] [childPosition]; 118} 119 eListView = (ExpandableListView) findViewById (R. id. expandableListView); 121 eListView. setAdapter (adapter); 122} 123} copy code 1 package com. johntsai. startactivity; 2 3 import android. app. activity; 4 import android. content. intent; 5 import android. OS. bundle; 6 import android. widget. textView; 7 8 public class ShowActivity extends Activity {9 private TextView showTextView; 10 @ Override11 protected void onCreate (Bundle savedInstanceState) {12 super. onCreate (savedInstanceState); 13 setContentView (R. layout. layout_show); 14 showTextView = (TextView) findViewById (R. id. textView_show); 15 16 Intent I = getIntent (); 17 String content = I. getStringExtra ("content"); 18 showTextView. setText (content); 19} 20}