<style name="SplashTheme" parent="Theme.AppCompat.Light.NoActionBar"><item name="android:windowNoTitle">true</item><item name="android:windowFullscreen">true</item><item name="android:background">@drawable/splash_bg</item></style>

public class UpdateDialog extends DialogFragment {@Overridepublic Dialog onCreateDialog(Bundle savedInstanceState) {AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());builder.setTitle("检测到新版本啦！");builder.setMessage("1、优化了UI细节；n2、修复了一大波的bug");//立即更新按钮builder.setPositiveButton("立即更新", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {//这里执行更新操作Toast.makeText(getActivity(), "执行更新操作", Toast.LENGTH_SHORT).show();dialog.dismiss();}});//稍后再说按钮builder.setNegativeButton("稍后再说", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {//跳转到首页SplashActivity activity = (SplashActivity) getActivity();activity.toMainPage();dialog.dismiss();}});AlertDialog dialog = builder.create();dialog.show();//修改按钮颜色，必须在show方法之后调用dialog.getButton(AlertDialog.BUTTON_POSITIVE).setTextColor(Color.BLUE);dialog.getButton(DialogInterface.BUTTON_NEGATIVE).setTextColor(Color.RED);return dialog;}
}

new UpdateDialog().show(getFragmentManager(),"VersionUpdate");

<style name="UpdateDialogStyle" parent="@android:style/Theme.DeviceDefault.Light.Dialog.NoActionBar.MinWidth"><!--该行代码就是设置AlertDialog的背景--><item name="android:background">@android:color/white</item></style>

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.UpdateDialogStyle);