startActivityForResult用于啟動其他指定的Activity，而且期望擷取該指定Activity傳回的結果。
啟動其他Activity并傳回結果過程：
目前ActivityA需要調用startActivityForResult(int requestCode,Intent intent)請求調用參數intent對應的ActivityB，請求碼是requestCode，同時需要重寫onActivityResult(int requestCode,int resultCode,Intent intent),當被啟動的ActivityB傳回結果時，必須使用setResult(int resultCode,Intent intent)将攜帶資料的intent傳回到ActivityA，這個傳回動作響應的結果碼是resultCode，此時會觸發onActivityResult，然後請求碼和結果碼就唯一确定一個過程，然後就可以接下來處理了
請求碼和結果碼
一個Activity中可能包含多個按鈕，并調用多個startActivityForResult方法來打開不同的Activity處理業務，當這些新Activity關閉後，系統會調用前面的Activity的onActivityResult方法。為了知道該方法是由哪個請求結果所觸發的，可利用requestCode辨別，為了知道傳回的資料來自于那個新的Activity，可利用resultCode辨別
例，第二個Activity讓使用者選擇資訊然後把結果傳回給第一個Activity
MainActivity.java
package com.hust.activityforresult;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
Button bn;
EditText edit;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bn=(Button) findViewById(R.id.button1);
edit=(EditText) findViewById(R.id.editText1);
bn.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//建立需要對應目标Activity的intent
Intent intent=new Intent(MainActivity.this,CityActivity.class);
//啟動指定Activity并等待傳回的結果，0是請求碼。用于表示該請求
startActivityForResult(intent ,0);
}
});
}
//重寫該方法，以回調的形式來擷取Activity傳回的結果
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
//當請求碼和結果碼都是0時，也就是處理的特定結果
if(requestCode==0&&resultCode==0){
//擷取Bundle中的資料
Bundle bundle=data.getExtras();
String city=bundle.getString("city");
//修改編輯框的内容
edit.setText(city);
}
}
CityActivity.java
package com.hust.activityforresult;
import android.app.ExpandableListActivity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Gravity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.TextView;
public class CityActivity extends ExpandableListActivity {
//定義省份
private String[] provinces={
"廣東","湖北","河南"
};
//定義城市
private String[][] cities={
{"廣州","深圳","珠海","惠州"},
{"武漢","襄陽","随州","十堰"},
{"鄭州","平頂山","信陽","駐馬店"}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_city);
ExpandableListAdapter ad=new BaseExpandableListAdapter(){
private TextView getTextView(){
AbsListView.LayoutParams lp=new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,64);
TextView textview =new TextView(CityActivity.this);
textview.setLayoutParams(lp);
textview.setTextSize(16);
textview.setGravity(Gravity.CENTER_VERTICAL|Gravity.LEFT);
textview.setPadding(30, 5, 0, 5);
return textview;
}
@Override
public int getGroupCount() {
// TODO Auto-generated method stub
return provinces.length;
}
@Override
public int getChildrenCount(int groupPosition) {
// TODO Auto-generated method stub
return cities[groupPosition].length;
}
@Override
public Object getGroup(int groupPosition) {
// TODO Auto-generated method stub
return provinces[groupPosition];
}
@Override
public Object getChild(int groupPosition, int childPosition) {
// TODO Auto-generated method stub
return cities[groupPosition][childPosition];
}
@Override
public long getGroupId(int groupPosition) {
// TODO Auto-generated method stub
return groupPosition;
}
@Override
public long getChildId(int groupPosition, int childPosition) {
// TODO Auto-generated method stub
return childPosition;
}
@Override
public boolean hasStableIds() {
// TODO Auto-generated method stub
return false;
}
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
TextView text=getTextView();
text.setTextColor(Color.RED);
text.setText(getGroup(groupPosition).toString());
return text;
}
@Override
public View getChildView(int groupPosition, int childPosition,
boolean isLastChild, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
TextView text=getTextView();
text.setText(getChild(groupPosition, childPosition)
.toString());
return text;
}
//主要在給子選項設定監聽器時，這個函數一定要傳回true，否則監聽器沒有用
@Override
public boolean isChildSelectable(int groupPosition,
int childPosition) {
// TODO Auto-generated method stub
return true;
}
};
//設定adapter
setListAdapter(ad);
//為每個子選項添加監聽器
getExpandableListView().setOnChildClickListener(new OnChildClickListener(){
@Override
public boolean onChildClick(ExpandableListView parent, View v,
int groupPosition, int childPosition, long id) {
// TODO Auto-generated method stub
//擷取啟動該Activity之前的Activity對應的Intent
Intent intent=getIntent();
intent.putExtra("city", cities[groupPosition][childPosition]);
//設定該Activity的結果碼，并設定結束之後退回的Activity
CityActivity.this.setResult(0, intent);
//結束本Activity
CityActivity.this.finish();
return false;
}
});
}
