HB Blog 128: Android Jack And Jill Toolchain.

Jack is a new Android toolchain that compiles Java source into Android dex bytecode. It replaces the previous Android toolchain, which consists of multiple tools, such as javac, ProGuard, jarjar, and dx.
For information related to Android Build System visit post HB Blog 51: Android Build System - How Android Apk Is Built.

The Jack toolchain provides the following advantages:

• Completely open source
  Available in AOSP; partners are welcome to contribute. 
• Speeds compilation time
  Jack has specific supports to reduce compilation time: pre-dexing, incremental compilation and a Jack compilation server. 
• Handles shrinking, obfuscation, repackaging and multidex
  Using a separate package such as ProGuard is no longer necessary.

Jack has its own .jack file format, which contains the pre-compiled dex code for the library, allowing for faster compilation (pre-dex).

The Jill tool translates the existing .jar libraries into the new library format, as shown below.

How to use Jack in Android build?
You don’t have to do anything differently to use Jack — just use your standard makefile commands to compile the tree or your project. Jack is the default Android build toolchain for M.
The first time Jack is used, it launches a local Jack compilation server on your computer:

•     This server brings an intrinsic speedup, because it avoids launching a new host JRE JVM, loading Jack code, initializing Jack and warming up the JIT at each compilation. It also provides very good compilation times during small compilations (e.g. in incremental mode).
•     The server is also a short-term solution to control the number of parallel Jack compilations, and so to avoid overloading your computer (memory or disk issue), because it limits the number of parallel compilations.

The Jack server shuts itself down after an idle time without any compilation. It uses two TCP ports on the localhost interface, and so is not available externally. All these parameters (number of parallel compilations, timeout, ports number, etc) can be modified by editing the $HOME/.jack file.

Jack and Jill are available in Build Tools version 21.1.1, and greater, via the SDK Manager. Complementary Gradle and Android Studio support is also already available in the Android 1.0.0+ Gradle plugin.'
Using Gradle, add the following to your module-level build config file:

1 2 3 4 5 6 7 8 9 10 11

android { ... buildToolsVersion '21.1.2' defaultConfig { // Enable the experimental Jack build tools. jackOptions { enabled true } } ... }

Jack limitations:

• The Jack server is mono-user by default, so can be only used by one user on a computer. If it is not the case, please, choose different port numbers for each user and adjust SERVER_NB_COMPILE accordingly. You can also disable the Jack server by setting SERVER=false in your $HOME/.jack.  
•  CTS compilation is slow due to current vm-tests-tf integration. 
•  Bytecode manipulation tools, like JaCoCo, are not supported. 

HB Blog 85: Creating Material Design Listing Using RecyclerView And CardView.

In this post, I will show how to use card view and recyclerview for listing data items. To create complex lists and cards with material design styles in your apps, you can use the RecyclerView and CardView widgets.

RecyclerView:- A flexible view for providing a limited window into a large data set. 
The RecyclerView widget is a more advanced and flexible version of ListView. This widget is a container for displaying large data sets that can be scrolled very efficiently by maintaining a limited number of views. To use the RecyclerView widget, you have to specify an adapter and a layout manager. To create an adapter, extend the RecyclerView.Adapter class. The details of the implementation depend on the specifics of your dataset and the type of views. A layout manager positions item views inside a RecyclerView and determines when to reuse item views that are no longer visible to the user. To reuse (or recycle) a view, a layout manager may ask the adapter to replace the contents of the view with a different element from the dataset.

CardView:- A FrameLayout with a rounded corner background and shadow. 
The CardView uses elevation property in lollipop version for shadows and falls back to a custom shadow implementation on older platforms. To create a card with a shadow, use the card_view:cardElevation attribute. CardView uses real elevation and dynamic shadows on Android 5.0 (API level 21) and above and falls back to a programmatic shadow implementation on earlier versions.

The RecyclerView and CardView widgets are part of the v7 Support Libraries. To use these widgets in your project, add these Gradle dependencies to your app's module:
dependencies {
    compile 'com.android.support:cardview-v7:21.0.+'
    compile 'com.android.support:recyclerview-v7:21.0.+'
}

Refer the below link for complete sample code:-
Download Sample Code

Download Apk File

Have a look on few code snippets,

RecycleViewActivity.java

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91

import android.app.Activity; import android.os.Bundle; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; /** * Created by harshalbenake on 02/06/15. */ public class RecycleViewActivity extends Activity { RecyclerView mRecyclerView; RecyclerView.Adapter mAdapter; RecyclerView.LayoutManager mLayoutManager; String[] myDataset; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main_recycle_view); mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view); // use this setting to improve performance if you know that changes // in content do not change the layout size of the RecyclerView mRecyclerView.setHasFixedSize(true); // use a linear layout manager mLayoutManager = new LinearLayoutManager(RecycleViewActivity.this); mRecyclerView.setLayoutManager(mLayoutManager); myDataset = new String[101]; for (int i = 0; i < 101; i++) { myDataset[i] = String.format("Harshal Benake: "+i, i); } // specify an adapter mAdapter = new MyAdapter(myDataset); mRecyclerView.setAdapter(mAdapter); } public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { private String[] mDataset; // Provide a reference to the views for each data item // Complex data items may need more than one view per item, and // you provide access to all the views for a data item in a view holder public class ViewHolder extends RecyclerView.ViewHolder { // each data item is just a string in this case public TextView mTextView; public ViewHolder(View v) { super(v); mTextView=(TextView)v.findViewById(R.id.row_textView); } } // Provide a suitable constructor (depends on the kind of dataset) public MyAdapter(String[] myDataset) { mDataset = myDataset; } // Create new views (invoked by the layout manager) @Override public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // create a new view View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_item, parent, false); // set the view's size, margins, paddings and layout parameters ViewHolder viewHolder = new ViewHolder(view); return viewHolder; } // Replace the contents of a view (invoked by the layout manager) @Override public void onBindViewHolder(ViewHolder holder, int position) { // - get element from your dataset at this position // - replace the contents of the view with that element holder.mTextView.setText(mDataset[position]); } // Return the size of your dataset (invoked by the layout manager) @Override public int getItemCount() { return mDataset.length; } } }

main_recycle_view.xml

1 2 3 4 5 6 7 8 9 10 11

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <!-- A RecyclerView with some commonly used attributes --> <android.support.v7.widget.RecyclerView android:id="@+id/my_recycler_view" android:scrollbars="none" android:layout_width="match_parent" android:layout_height="match_parent"/> </LinearLayout>

row_item.xml

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:card_view="http://schemas.android.com/apk/res-auto" android:id="@+id/card_view" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_margin="10dp" card_view:cardCornerRadius="4dp"> <TextView android:id="@+id/row_textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_margin="10dp" android:elevation="2dp" android:text="New Text" /> </android.support.v7.widget.CardView>

build.gradle

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

apply plugin: 'com.android.application' android { compileSdkVersion 21 buildToolsVersion "22.0.1" defaultConfig { applicationId "com.lollipopsupport_as" minSdkVersion 15 targetSdkVersion 21 versionCode 1 versionName "1.0" } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' } } } dependencies { compile fileTree(dir: 'libs', include: ['*.jar']) compile 'com.android.support:appcompat-v7:21.0.+' compile 'com.android.support:cardview-v7:21.0.+' compile 'com.android.support:recyclerview-v7:21.0.+' }

HB Blog 76: Android M With Fingerprint Authentication.

Authentication is the act of confirming the truth of an attribute of a single piece of data (datum) or entity. Fingerprint recognition or fingerprint authentication refers to the automated method of verifying a match between two human fingerprints. Fingerprints are one of many forms of biometrics used to identify individuals and verify their identity.

Authentication
Android M Developer Preview offers new APIs to let you authenticate users by using their fingerprint scans on supported devices, and check how recently the user was last authenticated using a device unlocking mechanism (such as a lockscreen password). Use these APIs in conjunction with the Android Keystore system. The Android Keystore system lets you store private keys in a container to make it more difficult to extract from the device. Once keys are in the keystore, they can be used for cryptographic operations with the private key material remaining non-exportable.

Fingerprint Authentication
To authenticate users via fingerprint scan, get an instance of the new android.hardware.fingerprint. FingerprintManager class and call the FingerprintManager.authenticate() method. Your app must be running on a compatible device with a fingerprint sensor. You must implement the user interface for the fingerprint authentication flow on your app, and use the standard Android fingerprint icon in your UI. If you are developing multiple apps that use fingerprint authentication, note that each app must authenticate the user’s fingerprint independently.

Use KeyGenerator to create a symmetric key in the Android Key Store which can be only be used after the user has authenticated with fingerprint and pass a KeyGeneratorSpec.

Use KeyGeneratorSpec.Builder.setUserAuthenticationRequired to permit the use of the key only after the user authenticate it including when authenticated with the user's fingerprint.

Use FingerprintManager.authenticate to tart listening to a fingerprint on the fingerprint sensor with a Cipher initialized with the symmetric key created.

Use FingerprintManager.AuthenticationCallback#onAuthenticationSucceeded() callback after the fingerprint (or password) is verified.

To use this feature in your app, add the USE_FINGERPRINT permission in your manifest.

1 2	<uses-permission android:name="android.permission.USE_FINGERPRINT" />

If you are testing this feature, follow these steps:

1. Install Android SDK Tools Revision 24.3, if you have not done so.
2. Enroll a new fingerprint in the emulator by going to Settings > Security > Fingerprint, then follow the enrollment instructions.
3. Use an emulator to emulate fingerprint touch events with the following command. Use the same command to emulate fingerprint touch events on the lockscreen or in your app. 

adb -e emu finger touch <finger_id>

Confirm Credential
Your app can authenticate users based on how recently they last unlocked their device. This feature frees users from having to remember additional app-specific passwords, and avoids the need for you to implement your own authentication user interface. Your app should use this feature in conjunction with a public or secret key implementation for user authentication.
To set the timeout duration for which the same key can be re-used after a user is successfully authenticated, call the new android.security.keystore.KeyGenParameterSpec.setUserAuthenticationValidityDurationSeconds() method when you set up a KeyGenerator or KeyPairGenerator. This feature currently works for symmetric cryptographic operations.
Avoid showing the re-authentication dialog excessively -- your apps should try using the cryptographic object first and if the the timeout expires, use the createConfirmDeviceCredentialIntent() method to re-authenticate the user within your app.