My first exercise of using Data Binding + ObservableField

The Data Binding Library is a support library that allows you to bind UI components in your layouts to data sources in your app using a declarative format rather than programmatically. It's my first exercise of using Data Binding and ObservableField, in Java. Basically, it follow the steps in Android Developers document of Data Binding Library.


The TextViews myArchitecture, myRelease and myDensity are loaded in onCreate() once. The TextView myNumber is associated with ObservableField, and will be updated at run-time.

Prepare:

- To use the Data Binding Library in your app, you have to target devices running Android 4.0 (API level 14) or higher.

- It's recommended to use the latest Android Plugin for Gradle in your project. Currently it's 3.3.1.

Read this video how to:

- Make sure include Support Repository in the Android SDK manager.

-  Add the dataBinding element to your build.gradle file in the app module.

In Android Studio, select Project view, extend app view, select to edit build.gradle. Add the code:

    dataBinding {
        enabled = true
    }

- Enable the new data binding compiler.
Note: The new compiler in Android Plugin version 3.2 is enabled by default. (refer https://developer.android.com/topic/libraries/data-binding/start) So it's skipped here.

- layout:
layout/activity_main.xml

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

    <data>
        <variable name="user" type="com.blogspot.android_er.myandroidinfo.MainActivity.User"/>
    </data>

    <android.support.constraint.ConstraintLayout
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <TextView
            android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="My device info"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:textStyle="bold"/>
        <TextView
            android:id="@+id/mylink"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="android-er.blogspot.com"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/title" />
        <TextView
            android:id="@+id/myArchitecture"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text='@{user.bArchitecture, default="Architecture"}'
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/mylink"
            android:gravity="left"
            android:textSize="30dp"/>
        <TextView
            android:id="@+id/myRelease"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text='@{user.bRelease, default="Release"}'
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/myArchitecture"
            android:gravity="left"
            android:textSize="30dp"/>
        <TextView
            android:id="@+id/myDensity"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text='@{user.bDensity, default="Density"}'
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/myRelease"
            android:gravity="left"
            android:textSize="30dp"/>

        <TextView
            android:id="@+id/myNumber"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@{user.bNum}"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/myDensity"
            android:gravity="left"
            android:textSize="50dp"
            android:textStyle="italic|bold"
            android:textColor="#0000FF"/>

    </android.support.constraint.ConstraintLayout>
</layout>

- Java code
MainActivity.java

package com.blogspot.android_er.myandroidinfo;

import android.databinding.DataBindingUtil;
import android.databinding.ObservableField;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.DisplayMetrics;

import com.blogspot.android_er.myandroidinfo.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

    public class User {
        public final String bArchitecture;
        public final String bRelease;
        public final String bDensity;
        public final ObservableField<String> bNum = new ObservableField<>();
        public User(String arch, String rel, String den) {
            this.bArchitecture = arch;
            this.bRelease = rel;
            this.bDensity = den;
        }
    }

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

        @Override
        protected Void doInBackground(Void... voids) {

            for (int i = 0; i < 20; i++) {
                user.bNum.set(String.valueOf(i));
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            return null;
        }
    }

    User user;

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

        String arch = System.getProperty("os.arch");
        String release = Build.VERSION.RELEASE;

        DisplayMetrics metrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(metrics);
        int dpi = metrics.densityDpi;

        ActivityMainBinding binding =
                DataBindingUtil.setContentView(this, R.layout.activity_main);
        user = new User(arch, release, String.valueOf(dpi));
        binding.setUser(user);

        new MyTask().execute();

    }
}

Get Architecture, Version and Screen DPI programmatically

This code get Architecture, Version and Screen DPI of Android device programmatically, using Java.

package com.blogspot.android_er.myandroidinfo;

import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.DisplayMetrics;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView tvMyArch = findViewById(R.id.myArchitecture);
        TextView tvMyRelease = findViewById(R.id.myRelease);
        TextView tvMyDensity = findViewById(R.id.myDensity);

        String arch = System.getProperty("os.arch");
        tvMyArch.setText(arch);

        String release = Build.VERSION.RELEASE;
        tvMyRelease.setText(release);

        DisplayMetrics metrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(metrics);
        int dpi = metrics.densityDpi;
        tvMyDensity.setText(String.valueOf(dpi));

    }
}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="My device info"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:textStyle="bold"/>
    <TextView
        android:id="@+id/mylink"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-er.blogspot.com"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/title" />
    <TextView
        android:id="@+id/myArchitecture"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Architecture"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/mylink"
        android:gravity="left"
        android:textSize="30dp"/>
    <TextView
        android:id="@+id/myRelease"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Release"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/myArchitecture"
        android:gravity="left"
        android:textSize="30dp"/>
    <TextView
        android:id="@+id/myDensity"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Density"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/myRelease"
        android:gravity="left"
        android:textSize="30dp"/>

</android.support.constraint.ConstraintLayout>

Java code to listing Network Interface Addresses, run on Windows 10

One of the most useful pieces of information you can get from a network interface is the list of IP addresses that are assigned to it. You can obtain this information from a NetworkInterface instance by using one of two methods. The first method, getInetAddresses(), returns an Enumeration of InetAddress. The other method, getInterfaceAddresses(), returns a list of java.net.InterfaceAddress instances. This method is used when you need more information about an interface address beyond its IP address. For example, you might need additional information about the subnet mask and broadcast address when the address is an IPv4 address, and a network prefix length in the case of an IPv6 address. ~ https://docs.oracle.com/javase/tutorial/networking/nifs/listing.html

The following example program lists all the network interfaces and their addresses on a machine (tested on PC running Windows 10):

package javalistinetaddress;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Collections;
import java.util.Enumeration;

public class JavaListInetAddress {

    public static void main(String[] args) throws SocketException {
        Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
        for (NetworkInterface netint : Collections.list(nets))
            displayInterfaceInformation(netint);
    }
    
    static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
        System.out.printf("Display name: %s\n", netint.getDisplayName());
        System.out.printf("Name: %s\n", netint.getName());
        Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
        for (InetAddress inetAddress : Collections.list(inetAddresses)) {
            System.out.printf("InetAddress: %s\n", inetAddress);
        }
        System.out.printf("\n");
     }
    
}

Related:
- Java code to listing Network Interface Addresses, run on Raspberry Pi/Raspbian Jessie