android – Page 2 – A Computer Engineer

Display image grid in RecyclerView in Android

April 15, 2018May 24, 2019dakshbhattLeave a comment

Display image grid in Android is now very easy to do with this tutorial. We use RecyclerView for this tutorial using GridLayoutManager.

For Kotlin tutorial for image grid in recyclerview, go here. Display image grid in RecyclerView in Kotlin Android

For displaying image grid in RecyclerView in Kotlin, go here: https://acomputerengineer.wordpress.com/2019/05/09/display-image-grid-in-recyclerview-in-kotlin-android/

First of all we will create layout for this post.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
  xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  tools:context=".ImageGridActivity">

  <android.support.v7.widget.RecyclerView 
    android:id="@+id/rv" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent">

  </android.support.v7.widget.RecyclerView>

</RelativeLayout>

Now we create adapter which holds the ImageView which will go in the grid.

public class ImageGridAdapter extends RecyclerView.Adapter<ImageGridAdapter.GridItemViewHolder> {

  private List<String> imageList;

  private Context c;

  public class GridItemViewHolder extends RecyclerView.ViewHolder {
    SquareImageView siv;

    public GridItemViewHolder(View view) {
      super(view);
      siv = view.findViewById(R.id.siv);
    }
  }

  public ImageGridAdapter(Context c, List imageList) {
    this.c = c;
    this.imageList = imageList;
  }

  @Override
  public GridItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_grid, parent, false);

    return new GridItemViewHolder(itemView);
  }

  @Override
  public void onBindViewHolder(GridItemViewHolder holder, int position) {
    final String path = imageList.get(position);

    Picasso.get()
        .load(path)
        .resize(250, 250)
        .centerCrop()
        .into(holder.siv);

    holder.siv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //handle click event on image
        }
    });
  }

  @Override
  public int getItemCount() {
    return imageList.size();
  }

}

Here I used Picasso library to display image, if you want to integrate it in your project then please check their web page: http://square.github.io/picasso/

Now we will go for the layout we used in above adapter. It just hold single ImageView.

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

  <com.acomputerengineer.CustomView.SquareImageView 
    android:id="@+id/siv" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" />

</RelativeLayout>

In above code, you must be thinking what is SquareImageView, right? It is the custom view which keeps ImageView square in the grid. The code for it is given below.

public class SquareImageView extends AppCompatImageView {
  public SquareImageView(Context context) {
    super(context);
  }

  public SquareImageView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public SquareImageView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    int width = getMeasuredWidth();
    setMeasuredDimension(width, width);
  }
}

Now we set the above adapter to the RecyclerView so that our Images will be displayed in the grid manner. Here we use images from Flickr public domain. In RecyclerView, we used StaggeredGridLayoutManager which tell the RecyclerView to use the grid like layout with the number of columns provided.

RecyclerView rv = findViewById(R.id.rv);

StaggeredGridLayoutManager sglm = new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL);
rv.setLayoutManager(sglm);

List<String> imageList = new ArrayList<>();
imageList.add("https://farm5.staticflickr.com/4403/36538794702_83fd8b63b7_c.jpg");
imageList.add("https://farm5.staticflickr.com/4354/35684440714_434610d1d6_c.jpg");
imageList.add("https://farm5.staticflickr.com/4301/35690634410_f5d0e312cb_c.jpg");
imageList.add("https://farm4.staticflickr.com/3854/32890526884_7dc068fedd_c.jpg");
imageList.add("https://farm8.staticflickr.com/7787/18143831616_a239c78056_c.jpg");
imageList.add("https://farm9.staticflickr.com/8745/16657401480_57653ac8b0_c.jpg");
imageList.add("https://farm3.staticflickr.com/2917/14144166232_44613c53c7_c.jpg");
imageList.add("https://farm8.staticflickr.com/7453/13960410788_3dd02b7a02_c.jpg");
imageList.add("https://farm1.staticflickr.com/920/29297133218_de38a7e4c8_c.jpg");
imageList.add("https://farm2.staticflickr.com/1788/42989123072_6720c9608d_c.jpg");
imageList.add("https://farm1.staticflickr.com/888/29062858008_89851766c9_c.jpg");
imageList.add("https://farm2.staticflickr.com/1731/27940806257_8067196b41_c.jpg");
imageList.add("https://farm1.staticflickr.com/884/42745897912_ff65398e38_c.jpg");
imageList.add("https://farm2.staticflickr.com/1829/27971893037_1858467f9a_c.jpg");
imageList.add("https://farm2.staticflickr.com/1822/41996470025_414452d7a0_c.jpg");
imageList.add("https://farm2.staticflickr.com/1793/42937679651_3094ebb2b9_c.jpg");
imageList.add("https://farm1.staticflickr.com/892/42078661914_b940d96992_c.jpg");
ImageGridAdapter iga = new ImageGridAdapter(ImageGridActivity.this, imageList);
rv.setAdapter(iga);

You can find the source code for this on my github repo: https://github.com/dakshbhatt21/a-computer-engineer

Please let me know if you find any issue in the above code or have any difficulty in implementing that.

Draw circle shape in Canvas in Android

December 25, 2016December 25, 2016dakshbhattLeave a comment

Draw circle shape in canvas is very easy thing to do if you are familiar with Canvas in Android. Please checkout this tutorial if you don’t know about how to create basic Canvas, display it to ImageView and save it as Bitmap.

Here we draw one canvas of 500×500 resolution and draw circle shape in the middle of the canvas.

The below line will draw circle shape in canvas.

canvas.drawCircle(x, y, radius, paint);

Here we pass x and y as the center coordinats of the circle. radius represents the radius of the circle being drawn. And paint is the Paint for drawing circle.

Now we will write the full code to draw circle in canvas.

Paint pBackground = new Paint();
pBackground.setColor(Color.WHITE);
canvas.drawRect(0, 0, 512, 512, pBackground);
Paint pCircle = new Paint();
pCircle.setColor(Color.BLACK);
canvas.drawCircle(256, 256, 256, pCircle);

CRUD functions in SQLite in Android

August 31, 2016September 24, 2016dakshbhattLeave a comment

This article depicts the CRUD(create, read, update, delete) functions on a database table in SQLite. Here I take the example of ‘user’ class which has few properties.

Screenshot_2016-08-31-23-34-41 — CRUD in SQLite

First you need to create User class with its constructor and getter-setter methods.

public class User {
  private long id;
  private String firstName;
  private String lastName;
  private int age;

  public User() {
  }

  public long getId() {
    return id;
  }

  public void setId(long id) {
    this.id = id;
  }

  public String getFirstName() {
    return firstName;
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public void setLastName(String lastName) {
    this.lastName = lastName;
  }

  public int getAge() {
    return age;
  }

  public void setAge(int age) {
    this.age = age;
  }
}

Now we will initialize DataBaseHelper class which will perform all the database related operation.

First we initial DatabaseHelper class by extending SQLiteOpenHelper.

public class DatabaseHelperNew extends SQLiteOpenHelper {

  @Override
  public void onCreate(SQLiteDatabase db) {

  }

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

  }

  public DatabaseHelperNew(Context c) {
    super(context, &quot;db_name&quot;/*db name*/, null, 1/*version*/);
  }
}

Now we initialize onCreate and onUpgrade methods with appropriate queries.

public class DatabaseHelperNew extends SQLiteOpenHelper {

  static String TABLE_USER = "user";
  static String KEY_USER_ID = "user_id";
  static String KEY_USER_FIRSTNAME = "user_first_name";
  static String KEY_USER_LASTNAME = "user_last_name";
  static String KEY_USER_AGE = "user_age";

  String CREATE_TABLE_USER = "CREATE TABLE " + TABLE_USER + "(" + KEY_USER_ID + " INTEGER PRIMARY KEY," + KEY_USER_FIRSTNAME + " TEXT," + KEY_USER_LASTNAME + " TEXT," + KEY_USER_AGE + " INTEGER" + ")";

  @Override
  public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_TABLE_USER);
  }

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_USER);
    onCreate(db);
  }

  public DatabaseHelperNew(Context c) {
    super(context, "db_name"/*db name*/, null, 1/*version*/);
  }
}

Now we will see CRUD functions one by one.

Create

//create user
public long createUser(User u) {
  SQLiteDatabase db = this.getWritableDatabase();
  ContentValues values = new ContentValues();
  values.put(KEY_USER_FIRSTNAME, u.getFirstName());
  values.put(KEY_USER_LASTNAME, u.getLastName());
  values.put(KEY_USER_AGE, u.getAge());
  long id = db.insert(TABLE_USER, null, values);
  db.close();
  return id;
}

Update

//update user
public void updateUser(User u) {
  SQLiteDatabase db = this.getWritableDatabase();
  ContentValues values = new ContentValues();
  values.put(KEY_USER_FIRSTNAME, u.getFirstName());
  values.put(KEY_USER_LASTNAME, u.getLastName());
  values.put(KEY_USER_AGE, u.getAge());
  db.update(TABLE_USER, values, KEY_USER_ID + " = ?", new String[]{String.valueOf(u.getId())});
  db.close();
}

Delete

//delete user
public void deleteUser(User u){
  SQLiteDatabase db = this.getWritableDatabase();
  db.delete(TABLE_USER, KEY_USER_ID + " = ?", new String[]{String.valueOf(u.getId())});
  db.close();
}

Read

//read all users
public ArrayList<User> readUsers(){
  ArrayList<User> users = new ArrayList<>();
  String selectQuery = "SELECT * FROM " + TABLE_USER;
  SQLiteDatabase db = this.getReadableDatabase();
  Cursor c = db.rawQuery(selectQuery, null);

  if (c.moveToFirst()) {
    do {
      User u = new User();
      u.setId(c.getInt((c.getColumnIndex(KEY_USER_ID))));
      u.setFirstName(c.getString(c.getColumnIndex(KEY_USER_FIRSTNAME)));
      u.setLastName(c.getString(c.getColumnIndex(KEY_USER_LASTNAME)));
      u.setAge(c.getInt(c.getColumnIndex(KEY_USER_AGE)));
      users.add(u);
    } while (c.moveToNext());
  }
  db.close();
  return users;
}

//read single user
public User readUser(long id){
  ArrayList<User> users = new ArrayList<>();
  String selectQuery = "SELECT * FROM " + TABLE_USER + " WHERE " + KEY_USER_ID + " = ?";
  SQLiteDatabase db = this.getReadableDatabase();
  Cursor c = db.rawQuery(selectQuery, new String[]{String.valueOf(id)});

  if (c.moveToFirst()) {
    do {
      User u = new User();
      u.setId(c.getInt((c.getColumnIndex(KEY_USER_ID))));
      u.setFirstName(c.getString(c.getColumnIndex(KEY_USER_FIRSTNAME)));
      u.setLastName(c.getString(c.getColumnIndex(KEY_USER_LASTNAME)));
      u.setAge(c.getInt(c.getColumnIndex(KEY_USER_AGE)));
      users.add(u);
    } while (c.moveToNext());
  }
  db.close();
  return users.get(0);
}

Now the complete DatabaseHelper file looks like below.

public class DatabaseHelper extends SQLiteOpenHelper {

  static String TABLE_USER = "user";
  static String KEY_USER_ID = "user_id";
  static String KEY_USER_FIRSTNAME = "user_first_name";
  static String KEY_USER_LASTNAME = "user_last_name";
  static String KEY_USER_AGE = "user_age";

  String CREATE_TABLE_USER = "CREATE TABLE " + TABLE_USER + "(" + KEY_USER_ID + " INTEGER PRIMARY KEY," + KEY_USER_FIRSTNAME + " TEXT," + KEY_USER_LASTNAME + " TEXT," + KEY_USER_AGE + " INTEGER" + ")";

  @Override
  public void onCreate(SQLiteDatabase db) {
    db.execSQL(CREATE_TABLE_USER);
  }

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_USER);
    onCreate(db);
  }

  public DatabaseHelper(Context c) {
    super(c, "db_name"/*db name*/, null, 1/*version*/);
  }

  //create user
  public long createUser(User u) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(KEY_USER_FIRSTNAME, u.getFirstName());
    values.put(KEY_USER_LASTNAME, u.getLastName());
    values.put(KEY_USER_AGE, u.getAge());
    long id = db.insert(TABLE_USER, null, values);
    db.close();
    return id;
  }

  //update user
  public void updateUser(User u) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(KEY_USER_FIRSTNAME, u.getFirstName());
    values.put(KEY_USER_LASTNAME, u.getLastName());
    values.put(KEY_USER_AGE, u.getAge());
    db.update(TABLE_USER, values, KEY_USER_ID + " = ?", new String[]{String.valueOf(u.getId())});
    db.close();
  }

  //delete user
  public void deleteUser(User u){
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(TABLE_USER, KEY_USER_ID + " = ?", new String[]{String.valueOf(u.getId())});
    db.close();
  }

  //read all users
  public ArrayList<User> readUsers(){
    ArrayList<User> users = new ArrayList<>();
    String selectQuery = "SELECT * FROM " + TABLE_USER;
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor c = db.rawQuery(selectQuery, null);

    if (c.moveToFirst()) {
      do {
        User u = new User();
        u.setId(c.getInt((c.getColumnIndex(KEY_USER_ID))));
        u.setFirstName(c.getString(c.getColumnIndex(KEY_USER_FIRSTNAME)));
        u.setLastName(c.getString(c.getColumnIndex(KEY_USER_LASTNAME)));
        u.setAge(c.getInt(c.getColumnIndex(KEY_USER_AGE)));
        users.add(u);
      } while (c.moveToNext());
    }
    db.close();
    return users;
  }

  //read single user
  public User readUser(long id){
    ArrayList<User> users = new ArrayList<>();
    String selectQuery = "SELECT * FROM " + TABLE_USER + " WHERE " + KEY_USER_ID + " = ?";
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor c = db.rawQuery(selectQuery, new String[]{String.valueOf(id)});

    if (c.moveToFirst()) {
      do {
        User u = new User();
        u.setId(c.getInt((c.getColumnIndex(KEY_USER_ID))));
        u.setFirstName(c.getString(c.getColumnIndex(KEY_USER_FIRSTNAME)));
        u.setLastName(c.getString(c.getColumnIndex(KEY_USER_LASTNAME)));
        u.setAge(c.getInt(c.getColumnIndex(KEY_USER_AGE)));
        users.add(u);
      } while (c.moveToNext());
    }
    db.close();
    return users.get(0);
  }

  //user class
  public class User {
    private long id;
    private String firstName;
    private String lastName;
    private int age;

    public User() {
    }

    public long getId() {
      return id;
    }

    public void setId(long id) {
      this.id = id;
    }

    public String getFirstName() {
      return firstName;
    }

    public void setFirstName(String firstName) {
      this.firstName = firstName;
    }

    public String getLastName() {
      return lastName;
    }

    public void setLastName(String lastName) {
      this.lastName = lastName;
    }

    public int getAge() {
      return age;
    }

    public void setAge(int age) {
      this.age = age;
    }
  }
}

Now we will take a look at how to use above class to perform various database operation.

DatabaseHelper dh;
User u;

dh = new DatabaseHelper(MainActivity.this);
u = dh.new User();

u.setFirstName("John");
u.setLastName("Doe");
u.setAge(25);

//create user
long id = dh.createUser(u);

u.setId(id);
//update user
u.setAge(30);
dh.updateUser(u);

//read all users
ArrayList<User> alUser = dh.readUsers();

//read single user
User u1 = dh.readUser(u.getId());

//delete user
dh.deleteUser(u);

Download Source Code: https://github.com/dakshbhatt21/a-computer-engineer

Draw line on Canvas in Android

August 22, 2016August 22, 2016dakshbhattLeave a comment

You can draw different type of line on Canvas in Android. You can change it’s color, stroke, effect, etc. Here we will see the basics of drawing line on Canvas.

Checkout the basics of Canvas if you are new to Canvas: Draw Canvas on ImageView

Here is the example of different parameters you can apply to draw a line on Canvas in Android.

device-2016-08-23-003351 — Draw line on Canvas

//simple line
Paint p1 = new Paint();
p1.setAntiAlias(true);
p1.setColor(Color.BLACK);
p1.setStrokeWidth(10);
canvas.drawLine(10, 40, 400, 40, p1);

//line with color
Paint p2 = new Paint();
p2.setAntiAlias(true);
p2.setColor(Color.RED);
p2.setStrokeWidth(10);
canvas.drawLine(10, 80, 400, 80, p2);

//line with round ends
Paint p3 = new Paint();
p3.setAntiAlias(true);
p3.setColor(Color.BLUE);
p3.setStrokeWidth(10);
p3.setStrokeCap(Paint.Cap.ROUND);
canvas.drawLine(10, 120, 400, 120, p3);

//slanted line
Paint p4 = new Paint();
p4.setAntiAlias(true);
p4.setColor(Color.GREEN);
p4.setStrokeWidth(10);
canvas.drawLine(10, 160, 400, 200, p4);

Here we use AntiAlias flag to true to remove distortion in the lines.

Add border to RelativeLayout(or any view) in Android

August 18, 2016August 18, 2016dakshbhattLeave a comment

Screen Shot 2016-08-18 at 3.56.16 PM — relativelayout with border

To add border to your RelativeLayout, first you need to create a xml resource file in your drawable folder.

Then add the following code to that xml file.

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

  <stroke
    android:width="5dp"
    android:color="#757575” /> 
</shape>

The above code will create black border with 5dp thickness. You can change thickness using ‘width’ parameter and color using ‘color’ parameter in above code.

Sample code to apply above border to a RelativeLayout. Here we assume that the name of above file is border.xml in drawable folder.

<RelativeLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_margin="25dp"
  android:background="@drawable/border">
</RelativeLayout>

Extract colors from image(bitmap) using Palette in Android

July 15, 2016July 15, 2016dakshbhatt9 Comments

When open the profile page of any person or group in Whatsapp, you will find that the color of the toolbar at top uses the color from the DP of the user or group. It looks good when you use extracted colors from image in your layout. Your layout will blend with the image and other content.

So here we can extract different colors from any image(bitmap) used in our application and use those colors effectively in our app throughout.

Main Color Profiles

First of all there are main 6 type of color profiles in the image that we can extract.

Vibrant
Vibrant Dark
Vibrant Light
Muted
Muted Dark
Muted Light

Most used profile from above are Vibrant and Vibrant Dark. The reason is, vibrant colors are pure, bright, intense, saturated and high chroma color. They stand out in the image and easy to point out. Now if we use those colors in the layout along with the image, it will give a great look. Whatsapp is the best example of it as we discussed earlier.

Every profile(swatch) gives us following information that we can use in the application.

population of that color in image
hue, saturation, lightness
body text color with sufficient contrast with the main color
title text color with sufficient contrast with the main color

Now we look at the code to get the Palette from bitmap.

Bitmap b = null;
b = BitmapFactory.decodeResource(getResources(), R.drawable.img1);
Palette p = Palette.from(b).generate();

Here we get the Palette from image(bitmap). Now we extract main 6 different kind of color profile(swatch) from it.

Palette.Swatch psVibrant = p.getVibrantSwatch();
Palette.Swatch psVibrantLight = p.getLightVibrantSwatch();
Palette.Swatch psVibrantDark = p.getDarkVibrantSwatch();
Palette.Swatch psMuted = p.getMutedSwatch();
Palette.Swatch psMutedLight = p.getLightMutedSwatch();
Palette.Swatch psMutedDark = p.getDarkMutedSwatch();

Now we will extract 4 different values from these swatch as described earlier in the article. Here we will take psVibrant as an example.

int color = psVibrant.getRgb();
int population = psVibrant.getPopulation();
float[] hsl = psVibrant.getHsl();
int bodyTextColor = psVibrant.getBodyTextColor();
int titleTextColor = psVibrant.getTitleTextColor();

You can also get other colors from image other than above 6 by following code snippet.

List&lt;Palette.Swatch&gt; pss;
pss = p.getSwatches();
for(int j = 0; j &lt; pss.size(); j++) {
  Palette.Swatch ps = pss.get(j);
  int color = ps.getRgb();
  int population = ps.getPopulation();
  float[] hsl = ps.getHsl();
  int bodyTextColor = ps.getBodyTextColor();
  int titleTextColor = ps.getTitleTextColor();
}

Other Color Profiles

Various file operations(create, rename, delete, list files) in Android

June 30, 2016June 30, 2016dakshbhattLeave a comment

You can perform many file operation in Android. I described few of them here.

Create directory
Create directory and sub-directories in one instance
Rename directory
Delete directory
List the contain of that directory

The code for the first one, create a single directory at the root of your external storage directory.

File dirMain = new File(extdir + File.separator + "com.acomputerengineer");
if(!dirMain.exists())   {
  boolean mkdir = dirMain.mkdir();
  if(mkdir)   {
    Log.e("test", "Directory " + dirMain.getPath() + " created successfully");
  }
  else if(!mkdir) {
    Log.e("test", "Directory " + dirMain.getPath() + " not created");
  }
}

Result:

Screenshot of directory created — directory created

Now creating directory and sub-directories at the same time.

//example 1
File dirWithSubdir1 = new File(extdir + File.separator + "com.acomputerengineer" + File.separator + "testDir1" + File.separator + "testSubdir1");
if(!dirWithSubdir1.exists()) {
  dirWithSubdir1.mkdirs();
}

//example 2
File dirWithSubdir2 = new File(extdir + File.separator + "com.acomputerengineer" + File.separator + "testDir2" + File.separator + "testSubdir2" + File.separator + "testSubSubdir2");
if(!dirWithSubdir2.exists()) {
  dirWithSubdir2.mkdirs();
}

Result:

Screenshot of subdirectory created — subdirectory created

Now rename the directory ‘dirWithSubdir1’ from the above example.

File renameDir = new File(extdir + File.separator + "com.acomputerengineer" + File.separator + "newTestDir1");
dirWithSubdir1.renameTo(renameDir);

Result:

Screenshot of rename directory — rename directory

Now deleting the directory.

dirWithSubdir1.delete();

Result:

Screenshot of delete directory — delete directory

Now listing the content of the directory by logging them into logcat.

String[] dirMainFiles = dirMain.list();
for (int i = 0; i < dirMainFiles.length; i++)   {
  Log.e("test", "file " + i + " :" + dirMainFiles[i]);
}

Result:

Screenshot of list content of directory — list content of directory

Convert pixel to dp or dip and dp to pixel in Android

June 23, 2016dakshbhattLeave a comment

If we need to set dimension of any view from the java file, it will use pixel as default unit. Where as in XML file we use dp or dip(density independent pixel). So 100 dp is not equal to 100 pixel.

Screenshot_20160623-151106 — 200dp = 525pixel in this case

Android uses density factor to provide support to different devices with different screensize. So the conversion works as explained below.

First we will check the conversion of dp to pixel. Here dp is density independent and pixel is dependent on density. So if we need to find pixel from give dp, we need to multiply it with the density of the device.

So the equation will be like this

pixel = dp * (density of the device);

Here is the function to convert dp to pixel.

public static float dpTopixel(Context c, float dp) {
  float density = c.getResources().getDisplayMetrics().density;
  float pixel = dp * density;
  return pixel;
}

Now we will convert pixel to dp. Here we need to divide the pixel with the density of the device so the result will become independent of density(dp).

So the equation will be like this

dp = pixel / (density of the device);

Here is the function to convert pixel to dp.

public static float pixelTodp(Context c, float pixel) {
  float density = c.getResources().getDisplayMetrics().density;
  float dp = pixel / density;
  return dp;
}

Now if you want to use this value as width or height in any of your view’s LayoutParams, it will ask you for Integer(int) value and above functions will return you Float(float) value. So you have to do following thing to convert it to Integer(int).

int width = (int) dpTopixel(MainActivity.this, 200);

Please comment if you find any mistake or want to give feedback.

Rotate image(bitmap) to any angle in Android

June 19, 2016June 19, 2016dakshbhatt8 Comments

In many image related Android applications, we may need to rotate the bitmap(not ImageView). Here I added the code below to rotate the image at any possible angle using Matrix.

Screenshot_20160619-211636 — rotation of image resulted from below code

Bitmap bInput/*your input bitmap*/, bOutput;
float degrees = 45;//rotation degree
Matrix matrix = new Matrix();
matrix.setRotate(degrees);
bOutput = Bitmap.createBitmap(bInput, 0, 0, bInput.getWidth(), bInput.getHeight(), matrix, true);