从其他Activity中获取结果Result

1：使用startActivityForResult()而不是startActivity()启动另外一个Activity
方法的签名是：startActivityForResult(Intent intent, int requestCode)这个方法有几个重载的方法
注意：
传入的Intent可以是隐式Intent或者是显示Intent。但如果是启动一个你自己的Activity，则最好使用显示Intent
在调用 startActivityForResult()时传入一个请求码(这个请求码用来识别请求，即返回的结果是由那个Activity中返回的)，当返回结果时，这个请求码会被传回来
2：重写onActivityResult()这个方法接收返回的结果
方法的签名是：onActivityResult(int requestCode, int resultCode, Intent data)
第一个参数：startActivityForResult()方法执行时传入的请求码(请求码如果小于0，则和startActivity()方法一样，是不返回结果的)
第二个参数：返回操作的结果码，如果操作成功返回RESULT_OK，如果操作失败返回RESULT_CANCELED，例如用户自己回退(按BACK键)或其他原因失败
第三个参数：返回的结果，为了处理这个结果，你必须知道返回的Intent的格式。其中Android平台自带的Apps都有相应的API描述指定的结果数据
例子(摘自Android官网http://developer.android.com/training/basics/intents/result.html)：

    package com.example.androidgov;

    import android.app.Activity;
    import android.content.Intent;
    import android.database.Cursor;
    import android.net.Uri;
    import android.os.Bundle;
    import android.provider.ContactsContract.CommonDataKinds.Phone;
    import android.view.View;
    import android.widget.TextView;

    public class ReturnResultActivity extends Activity {

        static final int PICK_CONTACT_REQUEST = 1; // The request code
        private TextView rra_textview = null;
        
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_return_result);
            rra_textview = (TextView)findViewById(R.id.rra_textview1);
        }

        public void pickContact( View view ) {
         Intent pickContactIntent = new Intent(Intent.ACTION_PICK, Uri.parse("content://contacts"));
         pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers
         startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST);
        }
        
        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         // Check which request it is that we're responding to
         if (requestCode == PICK_CONTACT_REQUEST) {
         // Make sure the request was successful
         if (resultCode == RESULT_OK) {
         // Get the URI that points to the selected contact
         Uri contactUri = data.getData();
         // We only need the NUMBER column, because there will be only one row in the result
         String[] projection = {Phone.NUMBER};

         // Perform the query on the contact to get the NUMBER column
         // We don't need a selection or sort order (there's only one result for the given URI)
         // CAUTION: The query() method should be called from a separate thread to avoid blocking
         // your app's UI thread. (For simplicity of the sample, this code doesn't do that.)
         // Consider using CursorLoader to perform the query.
    //这个查询动作应该放到另外一个线程中，以防止阻塞UI线程,另外可以考虑使用CursorLoader来执行查询
         Cursor cursor = getContentResolver()
         .query(contactUri, projection, null, null, null);
         cursor.moveToFirst();

         // Retrieve the phone number from the NUMBER column
         int column = cursor.getColumnIndex(Phone.NUMBER);
         String number = cursor.getString(column);
         rra_textview.setText("You choose " + number);
         // Do something with the phone number...
         }
         }
        }
    }

布局文件为：

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="com.example.androidgov.ReturnResultActivity" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="pickContact"
            android:text="GetContact" /><!-- 最好放到strings.xml文件中定义 -->

        <TextView
            android:id="@+id/rra_textview1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </LinearLayout>

运行结果截图：

选择联系人后：