Animation codes
This time, we implement ActionBar animation using AppCompatActivity in the support library.
Apply layout to the activity
At first, let Activity extend the AppCompatActivity and set the layout we wrote to it.
import android.support.v7.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Initialize ObservableListView
Add some initialization codes to onCreate():
@Override
protected void onCreate(Bundle savedInstanceState) {
ObservableListView listView = (ObservableListView) findViewById(R.id.list);
listView.setScrollViewCallbacks(this);
}
You will see an error around setScrollViewCallbacks(this) because the Activity does not implement the required interface yet.
So add implements ObservableScrollViewCallbacks to the Activity definition:
public class MainActivity extends AppCompatActivity
implements ObservableScrollViewCallbacks {
Then implement required methods:
@Override
public void onScrollChanged(int scrollY, boolean firstScroll,
boolean dragging) {
}
@Override
public void onDownMotionEvent() {
}
@Override
public void onUpOrCancelMotionEvent(ScrollState scrollState) {
}
}
Now we can handle the scroll events.
Populate list data
Before write codes to animate views, set data to ListView.
// Add these codes after ListView initialization
ArrayList<String> items = new ArrayList<String>();
for (int i = 1; i <= 100; i++) {
items.add("Item " + i);
}
listView.setAdapter(new ArrayAdapter<String>(
this, android.R.layout.simple_list_item_1, items));
Animate with scroll events
Finally, we can write the main code now.
Add some code to show/hide the ActionBar in onUpOrCancelMotionEvent method for example.
@Override
public void onUpOrCancelMotionEvent(ScrollState scrollState) {
ActionBar ab = getSupportActionBar();
if (scrollState == ScrollState.UP) {
if (ab.isShowing()) {
ab.hide();
}
} else if (scrollState == ScrollState.DOWN) {
if (!ab.isShowing()) {
ab.show();
}
}
}
ScrollState parameter indicates the direction of swiping, and this event will occur when you touch up (or cancel) the ListView.
This is just an introduction so we don't use other events like onScrollChanged.
Now let's build and launch the app.
You can see the ActionBar gets hidden or shown when you swipe the ListView.
As you can see, the most important codes are the animation codes in the callbacks. You can learn how to write these code in this tutorial.
In the next section, we'll check the existing examples to see what we can do with this library.
Program list
Following codes are the entire Activity, just for your reference.
import android.support.v7.app.AppCompatActivity;
// other imports and package statement are omitted
public class MainActivity extends AppCompatActivity
implements ObservableScrollViewCallbacks {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ObservableListView listView = (ObservableListView) findViewById(R.id.list);
listView.setScrollViewCallbacks(this);
// TODO These are dummy. Populate your data here.
ArrayList<String> items = new ArrayList<String>();
for (int i = 1; i <= 100; i++) {
items.add("Item " + i);
}
listView.setAdapter(new ArrayAdapter<String>(
this, android.R.layout.simple_list_item_1, items));
}
@Override
public void onScrollChanged(int scrollY, boolean firstScroll,
boolean dragging) {
}
@Override
public void onDownMotionEvent() {
}
@Override
public void onUpOrCancelMotionEvent(ScrollState scrollState) {
ActionBar ab = getSupportActionBar();
if (scrollState == ScrollState.UP) {
if (ab.isShowing()) {
ab.hide();
}
} else if (scrollState == ScrollState.DOWN) {
if (!ab.isShowing()) {
ab.show();
}
}
}
}