final AlertController mAlert;

public Button getButton(int whichButton) {
 return mAlert.getButton(whichButton);
 }

Button btnPositive = (Button)AlertDialog.getButton(DialogInterface.BUTTON_POSITIVE);
btnPositive.setTextColor(color);

protected AlertDialog(@NonNull Context context, @StyleRes int themeResId) {
 super(context, resolveDialogTheme(context, themeResId));
 mAlert = new AlertController(getContext(), this, getWindow());
 }

#Dialog.getWindow()
 public @Nullable Window getWindow() {
 return mWindow;
 }

//标题
TextView tvTitle = (TextView)AlertDialog.getWindow().findViewById(R.id.alertTitle);
//按钮
Button btnPositive = (Button)AlertDialog.getWindow().findViewById(R.id.button1);

 Field mAlert = AlertDialog.class.getDeclaredField("mAlert");
 mAlert.setAccessible(true);
 Object controller = mAlert.get(dialog);

Button mButtonPositive;
Button mButtonNegative;
Button mButtonNeutral;
private TextView mTitleView;
private TextView mMessageView;

 Field mTitleView = controller.getClass().getDeclaredField("mTitleView");
 mTitleView.setAccessible(true);
 TextView tvTitle = (TextView) mTitleView.get(controller);
 tvTitle.setTextColor(Color.GREEN);//更改标题的颜色

Window window = dialog.getWindow();
 WindowManager.LayoutParams lp = window.getAttributes();
lp.gravity = Gravity.BOTTOM;
lp.x = 100;
lp.y = 100;
window.setAttributes(lp);

 /**
  * X position for this window. With the default gravity it is ignored.
  * When using {@link Gravity#LEFT} or {@link Gravity#START} or {@link Gravity#RIGHT} or
  * {@link Gravity#END} it provides an offset from the given edge.
  */
 @ViewDebug.ExportedProperty
 public int x;

 /**
  * Y position for this window. With the default gravity it is ignored.
  * When using {@link Gravity#TOP} or {@link Gravity#BOTTOM} it provides
  * an offset from the given edge.
  */
 @ViewDebug.ExportedProperty
 public int y;