Categorylistview

Foursquare like map animation (sliding panel) with ListView

If you are wondering how to achieve map and listview behaviour like in Foursquare – this post is for you.
Here’s a short video what I’m talking about:

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Horizontal slide gallery with pages

Imagine you want to create interactive horizontal slide gallery with paging (scroll left/right not one-by-one but pages).
Like this one:

Hopefully you can easily implement this with HorizontalScrollView. Since API level 3 it has method smoothScrollBy.

Your code may looks like:

public class TestUIActivity extends Activity {

	private GestureDetector gestureDetector = null;
	private HorizontalScrollView hs;

	private int mWidth = 1160;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		gestureDetector = new GestureDetector(new MyGestureDetector());
		hs = (HorizontalScrollView) findViewById(R.id.hs);
		hs.setOnTouchListener(new OnTouchListener() {

			@Override
			public boolean onTouch(View v, MotionEvent event) {
				if (gestureDetector.onTouchEvent(event)) {
					return true;
				}
				if (event.getAction() == 1) {
					if (hs.getScrollX() > mWidth + mWidth / 2) {
						hs.smoothScrollBy(mWidth * 2 - hs.getScrollX(), 0);
					} else if (hs.getScrollX() > mWidth / 2) {
						hs.smoothScrollBy(mWidth - hs.getScrollX(), 0);
					} else {
						hs.smoothScrollBy(-hs.getScrollX(), 0);
					}
					return true;
				}
				return false;
			}
		});
	}

	class MyGestureDetector extends SimpleOnGestureListener {

		@Override
		public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
				float velocityY) {
			if (e1.getX() < e2.getX()) {
				moveLeft();
			} else {
				moveRight();
			}
			return true;
		}
	}

	private void moveRight() {
		if (hs.getScrollX() > 0 && hs.getScrollX() < mWidth) {
			hs.smoothScrollBy(mWidth - hs.getScrollX(), 0);
		} else if (hs.getScrollX() > mWidth && hs.getScrollX() < mWidth * 2) {
			hs.smoothScrollBy(mWidth * 2 - hs.getScrollX(), 0);
		}

	}

	private void moveLeft() {
		if (hs.getScrollX() > 0 && hs.getScrollX() < mWidth) {
			hs.smoothScrollBy(-hs.getScrollX(), 0);
		} else if (hs.getScrollX() > mWidth && hs.getScrollX() < mWidth * 2) {
			hs.smoothScrollBy(mWidth - hs.getScrollX(), 0);
		}

	}
}

and simple layout that you may construct from code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
	xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical"
	android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<com.dlukashev.test.HorizontalScrollView
		android:id="@+id/hs"
		android:scrollbars="none"
		android:layout_width="1160dp"
		android:layout_height="wrap_content">
		<LinearLayout
			android:layout_width="wrap_content"
			android:layout_height="fill_parent">
			<!-- page1 -->
			<TextView
				android:id="@+id/id1"
				android:background="#FFFFFF"
				android:layout_marginLeft="10dp"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFFFF"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFFFF"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFFFF"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFFFF"
				android:layout_marginRight="20dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<!-- page2 -->
			<TextView
				android:background="#FF0000"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FF0000"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FF0000"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FF0000"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FF0000"
				android:layout_marginRight="20dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<!-- page3 -->
			<TextView
				android:background="#FFFF00"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFF00"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFF00"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFF00"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
			<TextView
				android:background="#FFFF00"
				android:layout_marginRight="10dp"
				android:layout_width="220dp"
				android:layout_height="220dp" />
		</LinearLayout>
	</com.dlukashev.test.HorizontalScrollView>
</LinearLayout>

One sad detail that you cannot change view animation speed (DEFAULT_DURATION=250 in class OverScroller). But you can easily fix it by adding HorizontalScrollView, OverScroller, Scroller and EdgeGlow to your project.

You can find full sample with animation speed = 500 here. This sample is for tablet resolution – change layout and items sizes for the phone if you would like.

//DL

View recycling in Gallery

Did you know that view recycling in Gallery is not implemented?

https://groups.google.com/forum/#!topic/android-developers/mpvkI_za25g

“This is a known “bug” (it’s not a bug really, we just never had the
time to implement recycling in Gallery) but we have no ETA for a fix.” (c) Romain Guy

Custom solution can be found here http://pastebin.com/FWyYTt4D (http://goo.gl/lm6st)

//DL

Android tutorial slides

I would like to share some Android-related tutorial slides that we presented with Alexey in 2010 (http://habrahabr.ru/blogs/android/95250/) at St.Petersburg GTUG.

Some tips are still actual. So some of you could find it helpful;)

«Java and Android basics» (78 slides)

http://vk.amberfog.com/gtug/part1_Introduction2JavaAndroid_gtug.pdf

1.     Java and Android code style
2.     Java Collections
3.     Dalvik – Java Android VM
4.     Memory management in Java (GC + hard, soft, weak, phantom references)
5.     Java Exceptions handling
6.     Multithreading in Java
7.     Android Architecture
8.     Android entities: Activity, Service, Intent, BroadcastReceiver, ContentProvider
9.     Android Application, Context and Manifest
10.   Android System Services
11.   Android platform fragmentation and Java Reflection
12.   Saving state of application
13.   Android NDK
14.   Optimization for mobile: Design for better performance, responsiveness, seamlessness


«Android UI» (81 slides)

http://vk.amberfog.com/gtug/part2_WorkingWithAndroidUI_gtug.pdf

http://vk.amberfog.com/gtug/part2Examples.zip

1.     Activity lifecycle
2.     Activity, Layout, View, UI events, XML layouts
3.     XML layout’s types: FrameLayout, RelativeLayout, LinearLayout, TableLayout
4.     Layout tricks: merge, ViewStub, include
5.     Work with ListView and Adapters
6.     Menu & Dialogs
7.     UI thread! (and ANR)
8.     Developing custom UI-elements
9.     UI-development for difference screen resolutions and Android platform versions
10.   UI layout-tree analysis and optimization with special tools (hierarchyviewer, layoutopt)
11.   UI performance improvements
12.   UI guidelines
13.   Styles, Themes, Activity based dialogs
14.   Widgets, Live Folders, Live Wallpapers

«Android in Action» (69 slides).

http://vk.amberfog.com/gtug/part3_AndroidInAction_gtug.pdf

1.     Dealing with screen orientation change
2.     Possible causes of memory leaks: analysis and tools
3.     Data flow: Parcelable, Bundle, etc.
4.     android.app.Service
5.     Effective XML data parsing protocol
6.     Working with Databases
7.     Input Methods
8.     Search Providers
9.     Debugging hints & tools
10.   Battery life
11.   Usage statistics: Flurry
12.   Application signing and publishing

enjoy

//DL

HowTo: ListView, Adapter, getView and different list items’ layouts in one ListView

I was surprised that getViewTypeCount() is so rarely overrided (codesearch). If you are an expert in this – this post is not for you:-)

ListView and Adapter Basics

How it works:

  1. ListView asks adapter “give me a view” (getView) for each item of the list
  2. A new View is returned and displayed

Next question – what if we have one billion items? Create new view for each item? The answer is NO:-) Android caches views for you.

There’s a component in Android called “Recycler”. I drawed a picture based on Romain Guy presentation at Google IO ’09.

  1. If you have 1 billion items – there are only visible items in the memory + view in recycler.
  2. ListView asks for a view type1 first time (getView) x visible items. convertView is null in getView – you create new view of type1 and return it.
  3. ListView asks for a view type1 when one item1 is outside of the window and new item the same type is comming from the bottom. convertView is not null = item1. You should just set new data and return convertView back. No need to create view again.

Let’s write a simple code and put System.out to the getView:

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