Start activity to send email with multi images attached, with action of ACTION_SEND_MULTIPLE.

The post "Send email with Image by starting activity using Intent of ACTION_SEND" demonstrate how to send SINGLE image. It's modified to send multi images with action of Intent.ACTION_SEND_MULTIPLE. The Uris of the attached images are stored in a ArrayList, and pass to intent via putParcelableArrayListExtra() method.

package com.example.androidselectmultifiles;

import java.util.ArrayList;
import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends Activity {
 
 EditText edittextEmailAddress;
 EditText edittextEmailSubject;
    EditText edittextEmailText;
 Button btnAddFile, btnSend;
 ListView listViewFiles;
 
 ArrayList<Uri> arrayUri = new ArrayList<Uri>();
 ArrayAdapter<Uri> myFileListAdapter;
 
 final int RQS_LOADIMAGE = 0;
    final int RQS_SENDEMAIL = 1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        edittextEmailAddress = (EditText)findViewById(R.id.email_address);
        edittextEmailSubject = (EditText)findViewById(R.id.email_subject);
        edittextEmailText = (EditText)findViewById(R.id.email_text);
        
        btnAddFile = (Button)findViewById(R.id.addphoto);
        btnSend = (Button)findViewById(R.id.send);
        btnAddFile.setOnClickListener(btnAddFileOnClickListener);
        btnSend.setOnClickListener(btnSendOnClickListener);
        
        myFileListAdapter = new ArrayAdapter<Uri>(
          MainActivity.this,
          android.R.layout.simple_list_item_1,
          arrayUri);
        listViewFiles = (ListView)findViewById(R.id.filelist);
        listViewFiles.setAdapter(myFileListAdapter);
    }
    
    OnClickListener btnAddFileOnClickListener
    = new OnClickListener(){

  @Override
  public void onClick(View v) {
   Intent intent = new Intent(Intent.ACTION_PICK, 
     android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
   startActivityForResult(intent, RQS_LOADIMAGE);
   
  }};
  
 OnClickListener btnSendOnClickListener
 = new OnClickListener(){

  @Override
  public void onClick(View v) {
   String emailAddress = edittextEmailAddress.getText().toString();
   String emailSubject = edittextEmailSubject.getText().toString();
   String emailText = edittextEmailText.getText().toString();
   String emailAddressList[] = {emailAddress};
   
   Intent intent = new Intent();
   intent.putExtra(Intent.EXTRA_EMAIL, emailAddressList);  
   intent.putExtra(Intent.EXTRA_SUBJECT, emailSubject); 
   intent.putExtra(Intent.EXTRA_TEXT, emailText);
   
   if(arrayUri.isEmpty()){
    //Send email without photo attached
    intent.setAction(Intent.ACTION_SEND);
    intent.setType("plain/text"); 
   }else if(arrayUri.size() == 1){
    //Send email with ONE photo attached
    intent.setAction(Intent.ACTION_SEND); 
    intent.putExtra(Intent.EXTRA_STREAM, arrayUri.get(0));
       intent.setType("image/*");
   }else{
    //Send email with MULTI photo attached
    intent.setAction(Intent.ACTION_SEND_MULTIPLE);
    intent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, arrayUri);
       intent.setType("image/*");
   }
   
   startActivity(Intent.createChooser(intent, "Choice App to send email:"));
   
  }};

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  // TODO Auto-generated method stub
  super.onActivityResult(requestCode, resultCode, data);
  
  if (resultCode == RESULT_OK){
   switch(requestCode){
   case RQS_LOADIMAGE:
    Uri imageUri = data.getData();
    arrayUri.add(imageUri);
    myFileListAdapter.notifyDataSetChanged();
    break; 
   case RQS_SENDEMAIL:
    break; 
   }
  }
 }


}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world"
        tools:context=".MainActivity" />
    
    <TextView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Enter email address:"/>
    <EditText 
        android:id="@+id/email_address"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="textEmailAddress"/>
    <TextView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Enter email Subject:"/>
    <EditText 
        android:id="@+id/email_subject"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="textEmailSubject"/>
    <TextView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Enter Text:"/>
    <EditText 
        android:id="@+id/email_text"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"/>
    
    <Button
        android:id="@+id/addphoto"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add photo"/>
    <Button
        android:id="@+id/send"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Send"/>
    <ListView
        android:id="@+id/filelist"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

Download the files.

Next:
- Start activity to send email with multiple images attached, with build-in MediaStore.Images.Media selector.