Android Studio Tips and Tools to Be Productive
Summary
The purpose of this article is to facilitate android development process with helpful tips and to give insights into handy android development tips regarding android API's to avoid common mistake.
let's get started with tips first
Data Structures With ArrayAdapter
Data structures are extremely significant and heavily used while creating adapters to display list of data to users. The parameterized constructors of ArrayAdapter either accepts array or ArrayList but if you look at the source code of ArrayAdapter then internally, it only use arrayList create from passed array by converting the array into an immutable ArrayList as
1public ArrayAdapter(@NonNull Context context, @LayoutRes int resource, @NonNull T[] objects) {
2 this(context, resource, 0, Arrays.asList(objects));
3}
4
5public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
6 @IdRes int textViewResourceId, @NonNull T[] objects) {
7 this(context, resource, textViewResourceId, Arrays.asList(objects));
8}The immutable list will not allow modification in the resultant so to level up your android development skills, you should consider to look at the source code of android APIs available on github.
Things to be considered while using DataStructures
- Ordering : Often, use of
HashMaporHashSetas data source with CursorAdapter or customize adapter cause issues while implementing search mechanism because they does not support ordering, instead useLinkedHashMaporHashSet. - Synchronization : HashSet, TreeSet, and LinkedHashSet are synchronized and should not be modified by concurrent thread, instead use
1Set dataSet = Collections.synchronizedSet(new HashSet(...));
2Set dataSet = Collections.synchronizedSet(new LinkedHashSet(...));
3Set dataSet = Collections.synchronizedSet(new TreeSet(...));- Performance : TreeSet is bit slower because it requires sorting with every modification to maintain the natural order of data.
Array
Arrays often used for being memory efficient but when the requirement is to store key-value pairs (for multi-selection list) then HashMap is considered as the first choice for being popular and effective but android also provides memory efficient family of SparseArray to store keys as int or long with values as Object, Boolean, Integer, Long as
| API | Key-Value pairs | HashMap |
|---|---|---|
| ArrayMap | <K,V> | HashMap< K, V> |
| SparseArray | <Integer, Object> | HashMap<Integer, Object> |
| SparseBooleanArray | <Integer, Boolean> | HashMap<Integer, Boolean> |
| SparseIntArray | <Integer, Integer> | HashMap<Integer, Integer> |
| SparseLongArray | <Integer, Long> | HashMap<Integer, Long> |
| LongSparseArray | <Long, Object> | HashMap<Long, Object> |
| LongSparseLongArray | <Long, Long> | HashMap<Long, Long> |
A SparseIntArray has only 3 data members to store key-value and size, on the other hand HashMap is quite heavy, compared to Sparse family though HashMaps are more suitable for large list.
- When to use SpareArray
- Size of data is in range of hundreds mean ideal when size < 1000
- To avoid auto boxing for performance
- Keys are obtained in ascending order
e.g
1SparseArray sparseArray = new SparseArray(); // API 1
2sparseArray.put(1, “Value_1”);
3
4SparseIntArray sparseIntArray = new SparseIntArray(); // API 1
5sparseIntArray.put(1, 12);
6
7SparseBooleanArray sparseBooleanArray = new SparseBooleanArray(); // API 1
8sparseBooleanArray.put(1, true);
9
10SparseLongArray sparseLongArray = new SparseLongArray(); // API 18
11sparseLongArray.put(1, 5L);ArrayMap can also be used as a replacement for
HashMapfor memory efficiency, but it's only available on API 19 and above.
Objects class
Objects is a utility class which contains many static helpful null-safe or null-tolerant methods for
- Computing the hash code
- Returning a string for an object
- Comparing two objects
Traditional approach of Generating hash code
1@Override
2 public int hashCode() {
3 int result = id != null ? id.hashCode() : 0;
4 result = 31 * result + (number != null ? number.hashCode() : 0);
5 result = 31 * result + (firstName != null ? firstName.hashCode() : 0);
6 result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
7 result = 31 * result + (externalCustomerId != null ? externalCustomerId.hashCode() : 0);
8 return result;
9 }- With Object.hash
1@Override
2public int hashCode() {
3 return Objects.hash(number,firstName,,lastName,externalCustomerId);
4}You can use other utility methods of Objects class though you have to be careful while using it because
- The
hashmethod acceptsObject...varargs as parameter so if you have too manyprimitivesfields and heavy use ofhashcodecalculations thenautoboxingcan cause more performance damage Objectsclass was introduced in API 19(kitkat) without any backward compatibility so cannot be used for older version.
Application and Context
The common pattern of inheritance in android is inheriting Application class or UI component classes. In android, a single Application instance represents the process for an applications mean the application objects is kept in the memory as long as the application is alive.The lifespan of a custom application's object is equivalent to static data members which can be used to provide a single source of data(like pojo instance) where the context of application class is accessible.
All activities receives their context from application object and can also retrieve the application object using (YourApplicationName)getApplicationContext() to access the data members and method of customize application class. A customize application class is an easy way to crate a singleton to
- Keep the heavy object like an image, accessible with context.
- To inject behavior in application life cycle via injection. e.g. dagger.
- To place boilerplate code for cloud services.
The customize application class needs to be registered in the manifest as
1<application ...
2 android:name = ".YourApplicaitonClassName">Context of an application and activity are different in terms of their lifespan so
- Use Activity's context to create objects which has short lifespan like adapter, dialogs etc.
- Every view in UI hierarchy has also access to context which can be fetched from view instance using
view.getContext(), where the context is of host activity.
Generic : Generic provides the type-safety often used with collection framework like ArrayList<T>.
1ArrayList list = new ArrayList(); // raw type list mean Object
2ArrayList<String> list2 = new ArrayList<>(); String type listThe wildcards can also be used to add more flexibility
1// To read objects from collection - use "extends"
2int addListValues(List<? extends Number> numList) {
3 int tot=0;
4 for (Number num : numList) {
5 tot = tot + num.intValue();
6 }
7 return tot;
8}
9
10// To add objects to collection - use "super"
11void addMoreValues(List<? super Number> numList) {
12 numList.add(11);
13 numList.add(1.1);
14}- Generic plays a crucial role during parsing and conversion of json or string response to POJO objects
- Network libraries like retrofit uses many 3rd party parsing libraries which uses reflection to retrieve the object type information.
- Generic are only compile time, the type info is not available at runtime.
Bonus
Access android developer site off-line : Yes, the official android developer site offline version comes along with the sdk which is available under your_SDK_Location/Android/sdk/docs/index.html.
By default the sdk location is C:\Users\<User_Name>\AppData\Local\Android\sdk\docs\index.html where AppData is a hidden directory.
Android Studio Tools
Java-8 features
Android studio 3.0 provides the inbuilt support for java 8 libraries and language features for API 24 without jack compiler support.
1// lambda expression
2button.setOnClickListener(
3 (v)-> Toast.makeText(context, "Click", Toast.LENGTH_SHORT).show()
4);To enable java-8 features, add following dependencies in build.gradle app module
1android {
2 //.. other dependencies
3
4 compileOptions {
5 targetCompatibility 1.8
6 sourceCompatibility 1.8
7 }
8}Android Studio 3.0 and later extends support for try-with-resources to all Android API levels
Profiler
Profile is a collection of tools to measure the app's cpu, memory and network usage in real-time. You can measure the method execution duration, capturing heap dump, memory consumption and network transmission.
Dalvik Debug Monitor Server also known as DDMS, has been deprecated so from android 3.0 and higher, Use Android Profiler to profile your app's CPU, memory, and network usage.
The native system processes can also be tracked using systrace command tool to track frame drops, CPU scheduling, disk activity and threads.
Profiler is available under "click View > Tool Windows > Android Profile" option
Device File Explorer
Device file explorer allow you to inspect the device's file system and file transmission between device and computer. The default DDMS has a quite popular bug with android nougat and above emulators where the file system is not completely accessible, hence it has been replaced with Device File Explorer.
To open, click "View > Tool Windows > Device File Explorer"
APK Analyzer
Often the build apk file can contain surprising behavior regarding the size, code shrinking and obfuscation. To analyze your apk, just drag and drop apk into editor screen of studio or
Select "Build > Analyze APK" in the menu bar and then select your APK
APK Analyzer can accomplish the followings
- View the absolute and relative size of files in the APK, such as the DEX and Android resource files.
- Understand the composition of DEX files.
- Quickly view the final versions of files in the APK, such as the AndroidManifest.xml file.
- Perform a side-by-side comparison of two APKs.
Layout-Inspector
A dynamically created hierarchy of views in layout is often time consuming and requires many attempts to set the desired layout positioning constraints. Layout inspector captures a snapshot and store it as .li and display it along with the attributes values of views on screen as shown below
- View Tree: The hierarchy of views in the layout
- Screenshot: The device screenshot with visible boundaries for each view
- Properties Table: The layout properties for the selected view
Android Asset Studio
Every android application requires basic drawable resources for icons, shape shifters for back press icon, an alpha channel background icon with white overlay, nine patch icons for flexible shapes for view etc, can simply be created with Android Asset Studio
Webp converter
Webp is an image file format which provides lossy and transparency with better compression.
Lossy WebP images are supported in Android 4.0 (API level 14) and higher, and lossless and transparent WebP images are supported in Android 4.3 (API level 18) and higher
To create Webp images
- Select image and right click then click Convert to WebP
- Select Lossy(offers preview as well) or lossless encoding
- Click OK to apply compression
3rd party tools
Image Loading Libraries
There are some awesome libraries to ease-up the task of loading images from network, resources or from storage.
- Picasso is fully featured and most simplified image loading library to support recycling and download cancellation.
- Glide is focused on smooth scrolling of image incentive list while supporting cache and Gifs.
- Fresco is a image loading library to support webp and gif while supporting two level cache, memory and internal storage.
Stetho
Stetho is a debug bridge for Android applications from Facebook that integrates with the Chrome desktop browser's Developer Tools. With Stetho you can easily inspect your application, most notably the network traffic. It also allows you to easily inspect and edit SQLite databases and the shared preferences in your app. You should, however, make sure that Stetho is only enabled in the debug build and not in the release build variant.
Another alternative is Chuck which, although offering slightly more simplified functionality, is still useful for testers as the logs are displayed on the device, rather than in the more complicated connected Chrome browser setup that Stetho requires.
EventBus
EventBus solves issues like communication between distant Activities, Fragments, Services, Threads etc.It is more suitable when you have the requirement to inform any component which resides deep in the hierarchy stack.
LeakCanary
LeakCanary helps to detect memory leaks mean the allocated space of memory which no longer referenced from scope and cannot be garbage collected. A common example is inner-class threads inside activities where user can go out of the app while the thread execution continues and expects to notify the activity with updated content at the end of its execution.
Timber
Timer is a logging library which is small, extensible and also provides utility on top of Android's normal Log class.
Json 2 Pojo
Writing POJO classes for json is time consuming and boring so there are couple of online tools like jsonschema2pojo which can write those POJO classes in seconds, all you need to do is paste json structure and select the options and finally press OK.