File extensions are strings of characters that follow the last dot (.) in a file name and indicate the type of the file. They are used by the operating system to determine how to handle the file, what application to use to open it, and what icon to display for the file. Let’s see the implementation:
Step by Step Implementation
Step 1: Create a New Project
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.
Step 2:
Here is build.gradle file.
XML
plugins { id 'com.android.application'} android { namespace 'com.example.fileextensionchekergfg' compileSdk 33 defaultConfig { applicationId "com.example.fileextensionchekergfg" minSdk 24 targetSdk 33 versionCode 1 versionName "1.0" testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" } viewBinding{ enabled = true } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro' } } compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 }} dependencies { implementation 'androidx.appcompat:appcompat:1.4.1' implementation 'com.google.android.material:material:1.5.0' implementation 'androidx.constraintlayout:constraintlayout:2.1.3' testImplementation 'junit:junit:4.13.2' androidTestImplementation 'androidx.test.ext:junit:1.1.3' androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'} |
Step 3: Make a design to show the device type in the resource layout file
Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file.
XML
<?xml version="1.0" encoding="utf-8"?><androidx.constraintlayout.widget.ConstraintLayout android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Pick a file" android:backgroundTint="#81E30F" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" android:onClick="picker"/> <TextView android:id="@+id/extensionTV" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="69dp" android:text="No file found" android:textStyle="bold" android:textColor="@color/black" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toBottomOf="@+id/button" app:layout_constraintVertical_bias="0.0" /> </androidx.constraintlayout.widget.ConstraintLayout> |
Step 4: Working with the MainActivity.java file
Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file.
Java
package com.example.fileextensionchekergfg; import android.app.Activity;import android.content.Intent;import android.database.Cursor;import android.net.Uri;import android.os.Bundle;import android.provider.OpenableColumns;import android.view.View;import android.widget.Button;import android.widget.TextView;import android.widget.Toast; import androidx.activity.result.ActivityResult;import androidx.activity.result.ActivityResultCallback;import androidx.activity.result.ActivityResultLauncher;import androidx.activity.result.contract.ActivityResultContracts;import androidx.appcompat.app.AppCompatActivity; public class MainActivity extends AppCompatActivity { Button btn; TextView text; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn = findViewById(R.id.button); btn.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v) { Intent data = new Intent(Intent.ACTION_GET_CONTENT); data.setType("*/*"); data = Intent.createChooser(data, "Choose a file"); startActivityResultLauncher.launch(data); } }); } ActivityResultLauncher<Intent> startActivityResultLauncher = registerForActivityResult( new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() { @Override public void onActivityResult(ActivityResult result) { if(result.getResultCode() == Activity.RESULT_OK){ Intent data = result.getData(); Uri uri = data.getData(); String fileName = null; if (uri.getScheme().equals("content")) { Cursor cursor = getContentResolver().query(uri, null, null, null, null); try { if (cursor != null && cursor.moveToFirst()) { fileName = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME)); } } finally { cursor.close(); } } if (fileName == null){ fileName = uri.getPath(); int mark = fileName.lastIndexOf("/"); if (mark != -1){ fileName = fileName.substring(mark + 1); } } String extension = fileName.substring(fileName.lastIndexOf(".") + 1); text = findViewById(R.id.extensionTV); text.setText(String.format("File extension is: %s", extension)); }else{ Toast.makeText(MainActivity.this, "No file chosen", Toast.LENGTH_SHORT).show(); } } } );} |
Now all are set, just run your app and you will be able to see the extension of files you select from your device.
