Intent、Bundle——实现Activity之间的通信

http://blog.sina.com.cn/s/blog_62dea93001015847.html

一个应用程序会有多个Activity，但是只有一个Activity作为程序的入口，应用中的其他的Activity只能通过入口Activity来启动，或者由入口Activity启动的Activity启动。（在这里不要晕，可以理解成是一个树结构，入口Activity是根节点）

要用到的两个方法：

• startActivty(Intent intent)
• startActivtyForResult(Intent intent,int requestCode)：启动其他Activity，从新启动的Activity中取回结果返回到启动新Activity的Activity。

启动其他Activity需要用到Intent类，在Activity之间传递数据还需要用到Bundle类。下面按Activity的两种启动方法来学习他们的用法。

（1）使用startActivity（）
例子：

public class StartActivity extends Activity
{
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  //获取应用程序中的bn按钮
  Button bn = (Button)findViewById(R.id.bn);
  //为bn按钮绑定事件监听器
  bn.setOnClickListener(new OnClickListener()
  {
   @Override
   public void onClick(View source)
   {
    //创建需要启动的Activity对应的Intent
    Intent intent = new Intent(StartActivity.this
     , SecondActivity.class);
    //启动intent对应的Activity
    startActivity(intent);    
   }  
  });
 }
}

===================================================================

public class SecondActivity extends Activity
{
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.second);
  //获取应用程序中的previous按钮
  Button previous = (Button)findViewById(R.id.previous);
  //获取应用程序中的close按钮
  Button close = (Button)findViewById(R.id.close);
  //为previous按钮绑定事件监听器
  previous.setOnClickListener(new OnClickListener()
  {
   @Override
   public void onClick(View source)
   {
    //获取启动当前Activity的上一个Intent
    Intent intent = new Intent(SecondActivity.this
     , StartActivity.class);
    //启动intent对应的Activity
    startActivity(intent);    
   }
  });
  //为close按钮绑定事件监听器 
  close.setOnClickListener(new OnClickListener()
  {
   @Override
   public void onClick(View source)
   {
    //获取启动当前Activity的上一个Intent
    Intent intent = new Intent(SecondActivity.this
     , StartActivity.class);
    //启动intent对应的Activity
    startActivity(intent);
    //结束当前Activity
    finish();
   }
  }); 
 }
}

（2）使用Bundle在Activity之间传递数据

例子如下：

public class BundleTest extends Activity
{
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  Button bn = (Button)findViewById(R.id.bn);
  bn.setOnClickListener(new OnClickListener()
  {
   @Override
   public void onClick(View v)
   {
    EditText name = (EditText)findViewById(R.id.name);
    EditText passwd = (EditText)findViewById(R.id.passwd);
    RadioButton male = (RadioButton)findViewById(R.id.male);
    String gender = male.isChecked() ? "男 " : "女";
    Person p = new Person(name.getText().toString()
     , passwd.getText().toString() , gender);
    //创建一个Bundle对象
    Bundle data = new Bundle();
    data.putSerializable("person", p);
    //创建一个Intent
    Intent intent = new Intent(BundleTest.this
     , ResultActivity.class);
    intent.putExtras(data);
    //启动intent对应的Activity
    startActivity(intent);
    
   }
  });  
 }
}

=====================================================================

public class ResultActivity extends Activity
{
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.result);
  TextView name = (TextView)findViewById(R.id.name);
  TextView passwd = (TextView)findViewById(R.id.passwd);
  TextView gender = (TextView)findViewById(R.id.gender);
  //获取启动该Result的Intent
  Intent intent = getIntent();
  //获取该intent所携带的数据
  Bundle data = intent.getExtras();
  //从Bundle数据包中取出数据
  Person p = (Person)data.getSerializable("person");
  name.setText("您的用户名为：" + p.getName());
  passwd.setText("您的密码为：" + p.getPass());
  gender.setText("您的性别为：" + p.getGender());
 }
}
======================================================================

public class Person implements Serializable
{
 
 private static final long serialVersionUID = 1L;
 
 private Integer id;
 private String name;
 private String pass;
 private String gender;

public Person()
 {
 } 
 
 
 public Person(String name, String pass, String gender)
 {
  this.name = name;
  this.pass = pass;
  this.gender = gender;
 }
 public Integer getId()
 {
  return id;
 }
 public void setId(Integer id)
 {
  this.id = id;
 }
 public String getName()
 {
  return name;
 }
 public void setName(String name)
 {
  this.name = name;
 }
 public String getPass()
 {
  return pass;
 }
 public void setPass(String pass)
 {
  this.pass = pass;
 }
 public String getGender()
 {
  return gender;
 }
 public void setGender(String gender)
 {
  this.gender = gender;
 }

}

（3）通过startActivityForResult(Intent intent,int requestCode)启动Activity并返回结果

例子如下：
public class ActivityForResult extends Activity
{
 Button bn;
 EditText city; 
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  //获取界面上的组件
  bn = (Button)findViewById(R.id.bn);
  city = (EditText)findViewById(R.id.city);
  //为按钮绑定事件监听器
  bn.setOnClickListener(new OnClickListener()
  {
   @Override
   public void onClick(View source)
   {
    //创建需要对应于目标Activity的Intent
    Intent intent = new Intent(ActivityForResult.this
     , SelectCityActivity.class);
    //启动指定Activity并等待返回的结果，其中0是请求码，用于标识该请求
    startActivityForResult(intent , 0);
   }
  });
 }
 //重写该方法，该方法以回调的方式来获取指定Activity返回的结果
 @Override
 public void onActivityResult(int requestCode , int resultCode
  , Intent intent)
 {
  //当requestCode、resultCode同时为0，也就是处理特定的结果
  if (requestCode == 0
   && resultCode == 0)
  {
   //取出Intent里的Extras数据
   Bundle data = intent.getExtras();
   //取出Bundle中的数据
   String resultCity = data.getString("city");
   //修改city文本框的内容
   city.setText(resultCity);
  }
 }
}
——————————————————————————————————

public class SelectCityActivity extends ExpandableListActivity
{
 //定义省份数组
 private String[] provinces = new String[]
 { "广东", "广西", "湖南"};
 private String[][] cities = new String[][]
 {
  { "广州", "深圳", "珠海", "中山" },
  { "桂林", "柳州", "南宁", "北海" },
  { "长沙", "岳阳" , "衡阳" , "株洲" }
 }; 
 public void onCreate(Bundle savedInstanceState)
 {
  super.onCreate(savedInstanceState);
  ExpandableListAdapter adapter = new BaseExpandableListAdapter()
  {
   //获取指定组位置、指定子列表项处的子列表项数据
   @Override
   public Object getChild(int groupPosition, int childPosition)
   {
    return cities[groupPosition][childPosition];
   }
   @Override
   public long getChildId(int groupPosition, int childPosition)
   {
    return childPosition;
   }
   @Override
   public int getChildrenCount(int groupPosition)
   {
    return cities[groupPosition].length;
   }
   private TextView getTextView()
   {
    AbsListView.LayoutParams lp = new AbsListView.LayoutParams(
      ViewGroup.LayoutParams.FILL_PARENT, 64);
    TextView textView = new TextView(SelectCityActivity.this);
    textView.setLayoutParams(lp);
    textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
    textView.setPadding(36, 0, 0, 0);
    textView.setTextSize(20);
    return textView;
   }
   //该方法决定每个子选项的外观
   @Override
   public View getChildView(int groupPosition, int childPosition,
     boolean isLastChild, View convertView, ViewGroup parent)
   {
    TextView textView = getTextView();   
    textView.setText(getChild(groupPosition, childPosition).toString());
    return textView;
   }
   //获取指定组位置处的组数据
   @Override
   public Object getGroup(int groupPosition)
   {
    return provinces[groupPosition];
   }
   @Override
   public int getGroupCount()
   {
    return provinces.length;
   }
   @Override
   public long getGroupId(int groupPosition)
   {
    return groupPosition;
   }
   //该方法决定每个组选项的外观
   @Override
   public View getGroupView(int groupPosition, boolean isExpanded,
     View convertView, ViewGroup parent)
   {
    LinearLayout ll = new LinearLayout(SelectCityActivity.this);
    ll.setOrientation(0);
    ImageView logo = new ImageView(SelectCityActivity.this);
    ll.addView(logo);
    TextView textView = getTextView();
    textView.setText(getGroup(groupPosition).toString());    
    ll.addView(textView);   
    return ll;
   }
   @Override
   public boolean isChildSelectable(int groupPosition, int childPosition)
   {
    return true;
   }
   @Override
   public boolean hasStableIds()
   {
    return true;
   }
  };
  // 设置该窗口显示列表
  setListAdapter(adapter);
  getExpandableListView().setOnChildClickListener(
   new OnChildClickListener()
  {
   @Override
   public boolean onChildClick(ExpandableListView parent, View source,
    int groupPosition, int childPosition, long id)
   {
    //获取启动该Activity之前的Activity对应的Intent
    Intent intent = getIntent();
    Bundle data = new Bundle();
    data.putString("city" ,cities[groupPosition][childPosition]);
    intent.putExtras(data);
    // 设置该SelectActivity的结果码，并设置结束之后退回的Activity
    SelectCityActivity.this.setResult(0 , intent);
    //结束SelectCityActivity。
    SelectCityActivity.this.finish();
    return false;
   }
  });
 }
}