下面的异常是什么意思;我该怎么解决呢?

这是代码:

Toast toast = Toast.makeText(mContext, "Something", Toast.LENGTH_SHORT);

这是例外:

java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
     at android.os.Handler.<init>(Handler.java:121)
     at android.widget.Toast.<init>(Toast.java:68)
     at android.widget.Toast.makeText(Toast.java:231)

当前回答

你需要在UI线程上创建吐司。请看下面的例子。

runOnUiThread(new Runnable() {
  public void run() {
    Toast.makeText(activity, "YOUR_MESSAGE", Toast.LENGTH_SHORT).show();
  }
});

要显示Toast消息,请参考这篇文章

其他回答

Rxjava和RxAndroid用户:

public static void shortToast(String msg) {
    Observable.just(msg)
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(message -> {
                Toast.makeText(App.getInstance(), message, Toast.LENGTH_SHORT).show();
            });
}

下面是Kotlin使用Coroutine的解决方案:

通过MainScope()使用CoroutineScope扩展类:

class BootstrapActivity :  CoroutineScope by MainScope() {}

然后简单地这样做:

launch {
        // whatever you want to do in the main thread
    }

不要忘记添加协程的依赖项:

org.jetbrains.kotlinx:kotlinx-coroutines-core:${Versions.kotlinCoroutines}
org.jetbrains.kotlinx:kotlinx-coroutines-android:${Versions.kotlinCoroutines}

你需要在UI线程上创建吐司。请看下面的例子。

runOnUiThread(new Runnable() {
  public void run() {
    Toast.makeText(activity, "YOUR_MESSAGE", Toast.LENGTH_SHORT).show();
  }
});

要显示Toast消息,请参考这篇文章

你需要从UI线程调用Toast.makeText(…):

activity.runOnUiThread(new Runnable() {
  public void run() {
    Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show();
  }
});

这是从另一个(复制)SO答案复制粘贴。

 runOnUiThread(new Runnable() {
            public void run() {
                Toast.makeText(mContext, "Message", Toast.LENGTH_SHORT).show();
            }
        });