A blank screen appears when starting another activity from inside onCreate()

Question

I am working on an android application. I have just started coding it. I want to have an initial activity which would check if a user is already logged in. If yes, then it will redirect it to the user's home page, otherwise it'll redirect the user to a login/signup page.

For now, I have created a simple main activity, which should show a progress bar. I've added a 5sec delay and then this activity should direct the user to a login page (I've not kept any button on this page). This activity creates an intent and start the other activity using this after the 5 sec delay. I'll store the user's login state in shared preference later.

The problem is that when I run the app on my device, it just shows a blank screen (not the progress bar that I had put) for 5 sec and then redirects to the login page. What I'm doing wrong?

Here's my activity_main.xml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@id/main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ProgressBar
        android:id="@id/firstProgress"
        style="@android:style/Widget.ProgressBar"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="40dp">
    </ProgressBar>
</LinearLayout>

and here's my MainActivity.java file

package com.example.neeraj.myapplication;

import android.app.Activity;
import android.app.Notification;
import android.content.Intent;
import android.os.Bundle;
import android.os.SystemClock;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.RadioGroup;
import android.widget.Toast;

import com.facebook.AccessToken;
import com.facebook.AccessTokenTracker;
import com.facebook.CallbackManager;
import com.facebook.FacebookActivity;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.FacebookSdk;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SystemClock.sleep(5000);
        Intent i = new Intent(MainActivity.this, LoginActivity.class);
        startActivity(i);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}

Answer 1

By using Thread.sleep() or SystemClock.sleep() you are blocking the main thread of the app, which is responsible for almost everything like displaying your UI. Use Handler.postDelayed() instead.