工具类ToastUtil 避免在子线程中使用抛异常 "Can't create handler inside thread that has not called Looper.prepare()"

package com.example.kbr.utils;

import android.view.Gravity;
import android.widget.Toast;

import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;

/**
 * Created by keranbin on 2017/12/19.
 */

public class ToastUtil {
    private static Toast toast;


    /**
     * 短时间显示Toast【居上】
     *
     * @param msg 显示的内容-字符串
     */
    public static void showShortToastTop(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            Observable.create(emit -> {

            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_SHORT);
                            toast.setGravity(Gravity.TOP, 0, 0);
                        } else {
                            toast.setText(msg);
                        }
                        toast.show();
                    });
        }
    }


    /**
     * 短时间显示Toast【居中】
     *
     * @param msg 显示的内容-字符串
     */
    public static void showShortToastCenter(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            io.reactivex.Observable.create(emit -> {
                emit.onNext(msg);
                emit.onComplete();
            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_SHORT);
                        } else {
                            toast.setText(msg);
                        }
//                        toast.setGravity(Gravity.CENTER,0,0); 默认居中显示
                        toast.show();
                    });

        }
    }


    /**
     * 短时间显示Toast【居下】
     *
     * @param msg
     */
    public static void showShortToast(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            Observable.create(emit -> {
                emit.onNext(msg);
                emit.onComplete();
            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_SHORT);
                        } else {
                            toast.setText(msg);
                        }
                        toast.setGravity(Gravity.BOTTOM, 0, 0);
                        toast.show();
                    });


        }
    }


    /**
     * 长时间显示Toast【居上】
     *
     * @param msg 显示的内容-字符串
     */
    public static void showLongToastTop(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            Observable.create(emit -> {
                emit.onNext(msg);
                emit.onComplete();
            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_LONG);
                        } else {
                            toast.setText(msg);
                        }
                        toast.setGravity(Gravity.TOP, 0, 0);
                        toast.show();
                    });
        }

    }


    /**
     * 长时间显示Toast【居中】
     *
     * @param msg 显示的内容-字符串
     */
    public static void showLongToastCenter(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            Observable.create(emit -> {
                emit.onNext(msg);
                emit.onComplete();
            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_LONG);
                        } else {
                            toast.setText(msg);
                        }
//                        toast.setGravity(Gravity.CENTER, 0, 0);  //默认居中显示
                        toast.show();
                    });
        }

    }

    /**
     * 长时间显示Toast【居下】
     *
     * @param msg 显示的内容-字符串
     */
    public static void showLongToast(String msg) {
        if (EmptyUtil.isNotEmpty(msg) && EmptyUtil.isNotEmpty(App.getContext())) {
            Observable.create(emit -> {
                emit.onNext(msg);
                emit.onComplete();
            }).observeOn(AndroidSchedulers.mainThread())
                    .subscribe(re -> {
                        if (toast == null) {
                            toast = Toast.makeText(App.getContext(), msg, Toast.LENGTH_LONG);
                        } else {
                            toast.setText(msg);
                        }
                        toast.setGravity(Gravity.BOTTOM, 0, 0);  //默认居中显示
                        toast.show();
                    });
        }
    }
}