static method calls Toast.makeText

Question

I have a thread running in C++, it will call my UI thread's (Java) static method when some condition's satisfied. When the static method was called, I want a Toast to show on my UI. What I have tried are:

1

     static void myMethod(){
        Toast.makeText(context, "message", Toast.LENGTH_SHORT).show();
        (I have a static context reference in global scope)
     }

RESULT:

     E/AndroidRuntime( 1331): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

2

     static void myMethod(){
         runOnUiThread(new Runnable(){
             public void run(){
                Toast.makeText(Context, "message", Toast.LENGTH_SHORT).show();
             }
         });

RESULT:

   Can not compile: Cannot make a static reference to the non-static method runOnUiThread(Runnable) from the type Activity

Can anybody throw some light on this? Many thanks to you.

Answer 1

I think you are calling this method from a different thread than the UI thread and this causes an Exception. I have just tried declaring a static method in my Application class that would do the same as your first code. It worked - but of course only when called from main UI thread.

If you would like to be able to call the static method from a different thread, then you will need to create a handler on the UI thread to display the Toast. Something like this:

private static final int MSG_SHOW_TOAST = 1;

private static Handler messageHandler = new Handler() {
       public void handleMessage(android.os.Message msg) {
           if (msg.what == MSG_SHOW_TOAST) {
               String message = (String)msg.obj;
               Toast.makeText(App.this, message , Toast.LENGTH_SHORT).show();
           }
       }
};

private static void displayMessage() {
   Message msg = new Message();
   msg.what = MSG_SHOW_TOAST;
   msg.obj = "Message to show";
   messageHandler.sendMessage(msg);
}

The context in my sample is retrieved from App.this, which is the Application class. You can replace this with your Activity, or your static global context.

Answer 2

static Activity thisActivity = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    thisActivity = this;    
}

public static void showMsg()
{       
  Toast.makeText(thisActivity, "message" , Toast.LENGTH_SHORT).show();
}