Android四大组件之——Activity的开启:StartActivity()和StartActivityForResult()(图文详解)...
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[Android四大组件学习系列Activity篇]
1.Android四大组件之——Activity(一)定义、状态和后退栈(图文详解)
2.Android四大组件之——Activity的生命周期(图文详解)
3.Android四大组件之——Activity的开启StartActivity()和StartActivityForResult()(图文详解)
前两次学习了Activity的基本概念和生命周期,今天学习一下Activity的跳转和值传递。
废话不多说,开始学习!
- Activity的开启
开启一个新的Activity有两种方法:
startActivity(Intent)和startActivityForResult(Intent,int)。
startActivity(Intent):
用于开启一个新的Activity,新Activity压入栈顶。参数Intent用于描述新Activity。
startActivityForResult(Intent,int):
用于开启新Activity,新Activity退出后,返回结果给旧Activity。
startActivity好理解,startActivityForResult()就麻烦一点,下面这张图方便我们的理解:
说明一下:
requestCode,请求码,自己随意设置,但必须是非负数。只有是非负数时,Activity退出时,这个码会返回到onActivityResult()。
resultCode,结果码,用于标识返回数据来自于哪个新Activity,它的值一般是
RESULT_CANCELED, RESULT_OK, RESULT_FIRST_USER。
写了一个关于开启Activity的Demo:
共三个Activity:MainActivity用户填写用户姓名电话城市、CityActivity用于用户选择城市,ShowActivity用于展示用户信息。
MainActivity:
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 SELECT_CITY_REQUEST =2; 19 private static final int SELECT_PHONE_REQUEST =3; 20 21 @Override 22 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 button_city.setOnClickListener(this); 34 button_phone.setOnClickListener(this); 35 button_save.setOnClickListener(this); 36 } 37 @Override 38 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 @Override 64 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, null, 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 //初始化 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","Birmingham","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 @Override 102 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 @Override 111 public long getChildId(int groupPosition, int childPosition) { 112 return childPosition; 113 } 114 115 @Override 116 public Object getChild(int groupPosition, int childPosition) { 117 return cities[groupPosition][childPosition]; 118 } 119 }; 120 eListView = (ExpandableListView)findViewById(R.id.expandableListView); 121 eListView.setAdapter(adapter); 122 } 123 }
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 @Override 11 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 }
Demo运行效果图
如果喜欢,请推荐!谢谢~