最好的(也是最简单的)方法是使用Intent:

Intent i = new Intent(Intent.ACTION_SEND);
i.setType("message/rfc822");
i.putExtra(Intent.EXTRA_EMAIL  , new String[]{"recipient@example.com"});
i.putExtra(Intent.EXTRA_SUBJECT, "subject of email");
i.putExtra(Intent.EXTRA_TEXT   , "body of email");
try {
    startActivity(Intent.createChooser(i, "Send mail..."));
} catch (android.content.ActivityNotFoundException ex) {
    Toast.makeText(MyActivity.this, "There are no email clients installed.", Toast.LENGTH_SHORT).show();
}

否则你就得自己写客户端了。

/**
 * Will start the chosen Email app
 *
 * @param context    current component context.
 * @param emails     Emails you would like to send to.
 * @param subject    The subject that will be used in the Email app.
 * @param forceGmail True - if you want to open Gmail app, False otherwise. If the Gmail
 *                   app is not installed on this device a chooser will be shown.
 */
public static void sendEmail(Context context, String[] emails, String subject, boolean forceGmail) {

    Intent i = new Intent(Intent.ACTION_SENDTO);
    i.setData(Uri.parse("mailto:"));
    i.putExtra(Intent.EXTRA_EMAIL, emails);
    i.putExtra(Intent.EXTRA_SUBJECT, subject);
    if (forceGmail && isPackageInstalled(context, "com.google.android.gm")) {
        i.setPackage("com.google.android.gm");
        i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(i);
    } else {
        try {
            context.startActivity(Intent.createChooser(i, "Send mail..."));
        } catch (ActivityNotFoundException e) {
            Toast.makeText(context, "No email app is installed on your device...", Toast.LENGTH_SHORT).show();
        }
    }
}

/**
 * Check if the given app is installed on this devuice.
 *
 * @param context     current component context.
 * @param packageName The package name you would like to check.
 * @return True if this package exist, otherwise False.
 */
public static boolean isPackageInstalled(@NonNull Context context, @NonNull String packageName) {
    PackageManager pm = context.getPackageManager();
    if (pm != null) {
        try {
            pm.getPackageInfo(packageName, 0);
            return true;
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
    }
    return false;
}

为了让电子邮件应用程序来解决你的意图，你需要指定ACTION_SENDTO作为动作和mailto作为数据。

private void sendEmail(){

    Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
    emailIntent.setData(Uri.parse("mailto:" + "recipient@example.com")); // You can use "mailto:" if you don't know the address beforehand.
    emailIntent.putExtra(Intent.EXTRA_SUBJECT, "My email's subject");
    emailIntent.putExtra(Intent.EXTRA_TEXT, "My email's body");
    
    try {
        startActivity(Intent.createChooser(emailIntent, "Send email using..."));
    } catch (android.content.ActivityNotFoundException ex) {
        Toast.makeText(Activity.this, "No email clients installed.", Toast.LENGTH_SHORT).show();
    }

}

下面的代码可以在Android 10及更高的设备上运行。它还设置了主题、正文和收件人(To)。

val uri = Uri.parse("mailto:$EMAIL")
                .buildUpon()
                .appendQueryParameter("subject", "App Feedback")
                .appendQueryParameter("body", "Body Text")
                .appendQueryParameter("to", EMAIL)
                .build()

            val emailIntent = Intent(Intent.ACTION_SENDTO, uri)

            startActivity(Intent.createChooser(emailIntent, "Select app"))

使用. settype ("message/rfc822")或ACTION_SEND的策略似乎也适用于非电子邮件客户端的应用程序，如Android Beam和蓝牙。

使用ACTION_SENDTO和mailto: URI似乎工作得很好，并且在开发人员文档中推荐使用。但是，如果你在官方模拟器上这样做，并且没有设置任何电子邮件帐户(或者没有任何邮件客户端)，你会得到以下错误:

不支持的操作 目前不支持该操作。

如下图所示:

结果是模拟器将意图解析为一个名为com.android.fallback的活动。Fallback，它显示上面的消息。显然这是故意的。

如果你想让你的应用在官方模拟器上也能正常运行，你可以在发送邮件之前检查一下:

private void sendEmail() {
    Intent intent = new Intent(Intent.ACTION_SENDTO)
        .setData(new Uri.Builder().scheme("mailto").build())
        .putExtra(Intent.EXTRA_EMAIL, new String[]{ "John Smith <johnsmith@yourdomain.com>" })
        .putExtra(Intent.EXTRA_SUBJECT, "Email subject")
        .putExtra(Intent.EXTRA_TEXT, "Email body")
    ;

    ComponentName emailApp = intent.resolveActivity(getPackageManager());
    ComponentName unsupportedAction = ComponentName.unflattenFromString("com.android.fallback/.Fallback");
    if (emailApp != null && !emailApp.equals(unsupportedAction))
        try {
            // Needed to customise the chooser dialog title since it might default to "Share with"
            // Note that the chooser will still be skipped if only one app is matched
            Intent chooser = Intent.createChooser(intent, "Send email with");
            startActivity(chooser);
            return;
        }
        catch (ActivityNotFoundException ignored) {
        }

    Toast
        .makeText(this, "Couldn't find an email app and account", Toast.LENGTH_LONG)
        .show();
}

在开发人员文档中找到更多信息。

我是这么做的。很好很简单。

String emailUrl = "mailto:email@example.com?subject=Subject Text&body=Body Text";
        Intent request = new Intent(Intent.ACTION_VIEW);
        request.setData(Uri.parse(emailUrl));
        startActivity(request);