我正在做一个电子邮件发送应用程序在Android上。当我通过单击按钮启动应用程序时，只有To字段可见。
为什么不显示“抄送”、“密件抄送”和“主题”字段？如何将这些字段添加到我的应用程序？以及如何在“收件人”字段中显示默认电子邮件地址？（现在默认情况下，“收件人”字段中不写入任何内容。）

super.onCreate(savedInstanceState);
setContentView(R.layout.main);
clickBtn = (Button) findViewById(R.id.sendemail);
clickBtn.setText("Send email");
clickBtn.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND);
        String aEmailList[] = { "user@fakehost.com","user2@fakehost.com" };
        String aEmailCCList[] = { "user3@fakehost.com","user4@fakehost.com"};
        String aEmailBCCList[] = { "user5@fakehost.com" };
        emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL, aEmailList);
        emailIntent.putExtra(android.content.Intent.EXTRA_CC, aEmailCCList);
        emailIntent.putExtra(android.content.Intent.EXTRA_BCC, aEmailBCCList);
        emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, "My subject");
        emailIntent.setType("text/plain");
        emailIntent.putExtra(android.content.Intent.EXTRA_TEXT, "My message body.");
        startActivity(emailIntent);
        //startActivity(Intent.createChooser(emailIntent, "Send mail..."));
        finish();
    }
});