new AlertDialog.Builder(loginregister.this)
            .setTitle("messege")
            .setPositiveButton("ok", null)
            .setMessage( "user name : " + username + "/n" +
                            "password :" + password + "/n"  )
    .show();

David Hedlund发布的代码给了我错误:

无法添加窗口-空令牌无效

如果你得到同样的错误，请使用下面的代码。它的工作原理!

runOnUiThread(new Runnable() {
    @Override
    public void run() {

        if (!isFinishing()){
            new AlertDialog.Builder(YourActivity.this)
              .setTitle("Your Alert")
              .setMessage("Your Message")
              .setCancelable(false)
              .setPositiveButton("ok", new OnClickListener() {
                  @Override
                  public void onClick(DialogInterface dialog, int which) {
                      // Whatever...
                  }
              }).show();
        }
    }
});

你也可以尝试这种方式，它将为你提供材料样式的对话框

private void showDialog()
{
    String text2 = "<font color=#212121>Medi Notification</font>";//for custom title color

    AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
    builder.setTitle(Html.fromHtml(text2));

    String text3 = "<font color=#A4A4A4>You can complete your profile now or start using the app and come back later</font>";//for custom message
    builder.setMessage(Html.fromHtml(text3));

    builder.setPositiveButton("DELETE", new DialogInterface.OnClickListener()
    {
        @Override
        public void onClick(DialogInterface dialog, int which)
        {
            toast = Toast.makeText(getApplicationContext(), "DELETE", Toast.LENGTH_SHORT);
            toast.setGravity(Gravity.CENTER, 0, 0);
            toast.show();              
        }
    });

    builder.setNegativeButton("CANCEL", new DialogInterface.OnClickListener()
    {
        @Override
        public void onClick(DialogInterface dialog, int which)
        {
            toast = Toast.makeText(getApplicationContext(), "CANCEL", Toast.LENGTH_SHORT);
            toast.setGravity(Gravity.CENTER, 0, 0);
            toast.show();
        }
    });
    builder.show();
}

这是一个创建Alert对话框的基本示例:

AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
dialog.setCancelable(false);
dialog.setTitle("Dialog on Android");
dialog.setMessage("Are you sure you want to delete this entry?" );
dialog.setPositiveButton("Delete", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int id) {
        //Action for "Delete".
    }
})
        .setNegativeButton("Cancel ", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
            //Action for "Cancel".
            }
        });

final AlertDialog alert = dialog.create();
alert.show();

new AlertDialog.Builder(context)
    .setTitle("title")
    .setMessage("message")
    .setPositiveButton(android.R.string.ok, null)
    .show();

您可以使用AlertDialog创建对话框。构建器

试试这个:

AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Are you sure you want to delete this entry?");

        builder.setPositiveButton("Yes, please", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //perform any action
                Toast.makeText(getApplicationContext(), "Yes clicked", Toast.LENGTH_SHORT).show();
            }
        });

        builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                //perform any action
                Toast.makeText(getApplicationContext(), "No clicked", Toast.LENGTH_SHORT).show();
            }
        });

        //creating alert dialog
        AlertDialog alertDialog = builder.create();
        alertDialog.show();

要改变Alert对话框的正反按钮的颜色，你可以在alertDialog.show()后面写下面两行;

alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setTextColor(getResources().getColor(R.color.colorPrimary));
alertDialog.getButton(AlertDialog.BUTTON_NEGATIVE).setTextColor(getResources().getColor(R.color.colorPrimaryDark));