Update Ui From Another Thread In Android

i want to change UI in android. my main class make a second class then second class call a method of main class.method in main class should update UI but program crash in runtime.

Solution 1:

You can't call UI methods from threads other than the main thread. You should use Activity#runOnUiThread() method.

publicclassFileObserverActivityextendsActivity 
{
    /** Called when the activity is first created. */@OverridepublicvoidonCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        tv = (TextView) findViewById(R.id.textView1);
        tv.setText("new world");
        MyFileObserver myFileObserver = newMyFileObserver("/sdcard/", this);
        myFileObserver.startWatching();
    }

    String mySTR = "";
    TextView tv ;

    publicvoidevent(String absolutePath,String path,int event)
    {
        runOnUiThread(action);
    }

    privateRunnable action = newRunnable() {
        @Overridepublicvoidrun() {
            mySTR = absolutePath+path+"\t"+event;
            tv.setText(mySTR);
        }
    };
}

publicclassMyFileObserverextendsFileObserver 
{
    publicString absolutePath;
    FileObserverActivity fileobserveractivity;

    publicMyFileObserver(String path,FileObserverActivity foa) 
    {
        super(path, FileObserver.ALL_EVENTS);
        absolutePath = path;
        fileobserveractivity = foa;
    }

    @OverridepublicvoidonEvent(int event, String path) 
    {
        if (path == null) 
        {
            return;
        }
        elseif(event!=0)
        {
            fileobserveractivity.event(absolutePath, path, event);
        }
        else
        {
            return;
        }
    }
}

Solution 2:

Try as follows

publicclassFileObserverActivityextendsActivity 
{
    /** Called when the activity is first created. */@OverridepublicvoidonCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        tv = (TextView) findViewById(R.id.textView1);
        tv.setText("new world");
        MyFileObserver myFileObserver = newMyFileObserver("/sdcard/", this);
        myFileObserver.startWatching();
        registerReceiver(onBroadcast,newIntentFilter("abcd"));

    }

    String mySTR = "";
    TextView tv ;

    publicvoidevent(String absolutePath,String path,int event)
    {
        mySTR = absolutePath+path+"\t"+event;
            tv.setText(mySTR);  // program crash here!
    }
    @OverrideprotectedvoidonDestroy() {

        super.onDestroy();
        unregisterReceiver(onBroadcast);
    }

      private final BroadcastReceiver onBroadcast = newBroadcastReceiver() {


        @OverridepublicvoidonReceive(Context ctxt, Intent i) {
            // do stuff to the UIevent(absolutePath, path, event);
        }
    };
}


publicclassMyFileObserverextendsFileObserver 
{
    publicString absolutePath;
    FileObserverActivity fileobserveractivity;

    publicMyFileObserver(String path,FileObserverActivity foa) 
    {
        super(path, FileObserver.ALL_EVENTS);
        absolutePath = path;
        fileobserveractivity = foa;
    }

    @OverridepublicvoidonEvent(int event, String path) 
    {
        if (path == null) 
        {
            return;
        }
        elseif(event!=0)
        {
             context.sendBroadcast(newIntent("abcd"));
            //fileobserveractivity.event(absolutePath, path, event);
        }
        else
        {
            return;
        }
    }
}