Can't toast on a thread that has not called Looper.prepare()
2017-09-29 11:02
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前言
最近一段时间在忙着开发一款自己的APP,将自己常用的功能需求都加入进入,同时在GitHub上跟着大牛们学习新的技术,提升自己的技能,在开发的过程中不断的发现问题和解决问题。在开发过程遇到了这样一个问题:
Can't toast on a thread that has not called Looper.prepare(),如果在一个线程中没有调用Looper.prepare(),就不能在该线程中创建Toast。这个问题是因为在子线程中弹出Toast导致的。
Android是不能直接在子线程中弹出Toast的,可是如果我们非要这么做,那该怎么办呢?下面就为大家讲解如何在子线程中弹出Toast,以及一些其他类似的子线程中操作的错误。
本博客同步发布于 XueLong的博客
在子线程中调用Toast
在子线程中弹出Toast,会报错:java.lang.RuntimeException: Can’t toast on a thread that has not called Looper.prepare()。解决方式:先调用
Looper.prepare();再调用
Toast.makeText().show();最后再调用
Looper.loop();
public class ToastUtils { static Toast toast = null; public static void show(Context context, String text) { try { if(toast!=null){ toast.setText(text); }else{ toast= Toast.makeText(context, text, Toast.LENGTH_SHORT); } toast.show(); } catch (Exception e) { //解决在子线程中调用Toast的异常情况处理 Looper.prepare(); Toast.makeText(context, text, Toast.LENGTH_SHORT).show(); Looper.loop(); } } }
在子线程中更新UI
在子线程中更新UI,会报错:android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.解决方式:在子线程中更新UI,一般使用Handler或者runOnUiThread()或者AsyncTask。
在子线程中创建Handler
在子线程中创建Handler,会报错:java.lang.RuntimeException: Can’t create handler inside thread that has not called Looper.prepare()。解决方式:
new Thread() { public void run() { Looper.prepare(); new Handler().post(runnable);//在子线程中直接去new 一个handler Looper.loop(); //这种情况下,Runnable对象是运行在子线程中的,可以进行联网操作,但是不能更新UI } }.start();
写在最后
以上就是在子线程中更新UI、弹出Toast、创建Handler时会遇到的问题,及解决方式。如果你在参考过程中遇到问题,可以在我的联系方式中给我提问。
后面会继续介绍,Android的相关知识,欢迎继续关注我博客的更新。
参考资源
在子线程中new Handler报错Android – Looper.prepare()和Looper.loop() —深入版
Toast和Looper、Handler消息循环机制
转载请注明:XueLong的博客 » Can’t toast on a thread that has not called Looper.prepare()
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