Display a loading overlay on Android screen

I have ProgressBar in Relative Layout and I hide or show it respectively. And yes activity can be transparent.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <LinearLayout
        android:id="@+id/hsvBackgroundContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
    </LinearLayout>


    <ProgressBar
        android:id="@+id/pbProgess"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true" />

</RelativeLayout>

Maybe too late, but I guess somebody might find it useful.

Activity:

public class MainActivity extends Activity implements View.OnClickListener {

    String myLog = "myLog";

    AlphaAnimation inAnimation;
    AlphaAnimation outAnimation;

    FrameLayout progressBarHolder;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);
        progressBarHolder = (FrameLayout) findViewById(R.id.progressBarHolder);

        button.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button:
                new MyTask().execute();
                break;
        }

    }

    private class MyTask extends AsyncTask <Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            button.setEnabled(false);
            inAnimation = new AlphaAnimation(0f, 1f);
            inAnimation.setDuration(200);
            progressBarHolder.setAnimation(inAnimation);
            progressBarHolder.setVisibility(View.VISIBLE);
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            outAnimation = new AlphaAnimation(1f, 0f);
            outAnimation.setDuration(200);
            progressBarHolder.setAnimation(outAnimation);
            progressBarHolder.setVisibility(View.GONE);
            button.setEnabled(true);
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                for (int i = 0; i < 5; i++) {
                    Log.d(myLog, "Emulating some task.. Step " + i);
                    TimeUnit.SECONDS.sleep(1);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return null;
        }
    }

}

Layout xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start doing stuff"
        android:id="@+id/button"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Do Some Stuff"
        android:id="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <FrameLayout
        android:id="@+id/progressBarHolder"
        android:animateLayoutChanges="true"
        android:visibility="gone"
        android:alpha="0.4"
        android:background="#000000"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ProgressBar
            style="?android:attr/progressBarStyleLarge"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:indeterminate="true"
            android:layout_gravity="center" />
    </FrameLayout>
</RelativeLayout>

I like the approach in Kostya But's answer.

Building on that, here's a couple of ideas to make the same overlay easily reusable across your app:

Consider putting the overlay FrameLayout in a separate layout file, e.g. res/layout/include_progress_overlay:

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/progress_overlay"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:alpha="0.4"
    android:animateLayoutChanges="true"
    android:background="@android:color/black"
    android:clickable="true"
    android:visibility="gone">

    <ProgressBar
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:indeterminate="true"/>

</FrameLayout>

(One thing I added in the overlay FrameLayout is android:clickable="true". So while the overlay is shown, it prevents clicks going through to UI elements underneath it. At least in my typical use cases this is what I want.)

Then include it where needed:

<!-- Progress bar overlay; shown while login is in progress -->
<include layout="@layout/include_progress_overlay"/>

And in code:

View progressOverlay;
[...]

progressOverlay = findViewById(R.id.progress_overlay);
[...]

// Show progress overlay (with animation): 
AndroidUtils.animateView(progressOverlay, View.VISIBLE, 0.4f, 200);
[...]

// Hide it (with animation): 
AndroidUtils.animateView(progressOverlay, View.GONE, 0, 200); 

With animation code extracted into a util method:

/**
 * @param view         View to animate
 * @param toVisibility Visibility at the end of animation
 * @param toAlpha      Alpha at the end of animation
 * @param duration     Animation duration in ms
 */
public static void animateView(final View view, final int toVisibility, float toAlpha, int duration) {
    boolean show = toVisibility == View.VISIBLE;
    if (show) {
        view.setAlpha(0);
    }
    view.setVisibility(View.VISIBLE);
    view.animate()
            .setDuration(duration)
            .alpha(show ? toAlpha : 0)
            .setListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationEnd(Animator animation) {
            view.setVisibility(toVisibility);
        }
    });
}

(Here using view.animate(), added in API 12, instead of AlphaAnimation.)

A spinner with a message over the application can be created using a ProgressDialog. Whilst it doesn't achieve the exact effect as in the picture, it's a good way to show that the app is working.