Android – Can’t create handler inside thread that has not called Looper.prepare()

androidandroid-toastui-thread

What does the following exception mean; how can I fix it?

This is the code:

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

This is the exception:

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)

Best Answer

You need to call Toast.makeText(...) from the UI thread:

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

This is copy-pasted from another (duplicate) SO answer.

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