Create a simple File Finder Dialog in Android
View more Tutorials:
In this article I'm going to guide you to create a simple application, search for files in Android and display the results on a Dialog.

This application will search for files on the SD Card, so if you test this application on Android Emulator, you need to set up SD Card for it.
Use Device File Explorer to copy some files into Android Emulator which is necessary for you to test the application.

First, create a new project on Android Studio:
- File > New > New Project > Empty Activity
- Name: FileFinderDialogExample
- Package name: org.o7planning.filefinderdialogexample
- Language: Java

After the user clicks the search button, a list of found files will be displayed on a RecyclerView. It is an interface component which is not available on the Android SDK, so you have to install it into the project.

After the library was successfully installed, you will see it be declared in build.gradle (Module App):
dependencies { ... implementation 'androidx.recyclerview:recyclerview:1.0.0' }

Next, register with the system so that your application is allowed to get access to the files.
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="org.o7planning.filefinderdialogexample"> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
And this is the application interface:

activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.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"> <EditText android:id="@+id/editText_search" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="16dp" android:layout_marginLeft="16dp" android:layout_marginTop="32dp" android:layout_marginEnd="16dp" android:layout_marginRight="16dp" android:ems="10" android:hint="File Name" android:inputType="textPersonName" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" /> <CheckBox android:id="@+id/checkBox_isRegex" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="16dp" android:layout_marginLeft="16dp" android:layout_marginTop="16dp" android:layout_marginEnd="16dp" android:layout_marginRight="16dp" android:text="Regex?" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toBottomOf="@+id/editText_search" /> <Button android:id="@+id/button_search" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="24dp" android:text="Search" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.498" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toBottomOf="@+id/checkBox_isRegex" /> </androidx.constraintlayout.widget.ConstraintLayout>
The FileFinder class includes methods for searching files in the system. Noting that with Android 6.0+ (API Level 23+), the application needs to ask the user for permission in order to get access to the files. But if it is not allowed by the user, these methods will always return an empty list.
FileFinder.java
package org.o7planning.filefinderdialogexample; import android.os.Environment; import android.util.Log; import java.io.File; import java.util.ArrayList; import java.util.List; import java.util.regex.Pattern; public class FileFinder { private static final String LOG_TAG_FILE_FINDER = "FileSelector"; private boolean enableLog; public FileFinder(boolean enableLog) { this.enableLog = enableLog; } public List<File> findByKeyword(File rootDir, String keywordFileName) { if(keywordFileName==null || keywordFileName.isEmpty()) { return new ArrayList<File>(); } String regexFileName = keywordFileName.replace("*", ".*?"); List<File> resultList = this.listOfFile(rootDir, regexFileName); return resultList; } public List<File> findByRegex(File rootDir, String regexFileName) { List<File> resultList = this.listOfFile(rootDir, regexFileName); return resultList; } public List<File> findInSDCardByKeyword(String keywordFileName) { // (Example): /storage/emulated/0 String sdCardPath = Environment.getExternalStorageDirectory().getAbsolutePath(); this.log("External Storage Directory: " + sdCardPath); File sdCardDir = new File(sdCardPath); return this.findByKeyword(sdCardDir, keywordFileName); } public List<File> findInSDCardByRegex(String regexFileName) { // (Example): /storage/emulated/0 String sdCardPath = Environment.getExternalStorageDirectory().getAbsolutePath(); this.log("External Storage Directory: " + sdCardPath); File sdCardDir = new File(sdCardPath); return this.findByRegex(sdCardDir, regexFileName); } private List<File> listOfFile(File dir, String regexFileName) { Pattern patternFileName = Pattern.compile(regexFileName); List<File> resultList = new ArrayList<File>(); this.listOfFile(dir, patternFileName, resultList); return resultList; } private void listOfFile(File dir, Pattern patternFileName, List<File> resultList) { this.log("LIST OF DIR " + dir.getAbsolutePath()); File[] list = dir.listFiles(); if(list == null) { this.log("Directory" + dir.getAbsolutePath()+ " has no files"); return; } this.log("Directory" + dir.getAbsolutePath()+ " has " + list.length +" direct files"); for (File file : list) { if (file.isDirectory()) { if (!new File(file, ".nomedia").exists() && !file.getName().startsWith(".")) { this.log( "IS DIR " + file); listOfFile(file, patternFileName, resultList); } } else { String path = file.getAbsolutePath(); this.log( "FILE PATH: " + path); String fileName = file.getName(); if(patternFileName.matcher(fileName).find()) { resultList.add(file); this.log( "ADD " + path); } } } } private void log(String message) { if(enableLog) { Log.i(LOG_TAG_FILE_FINDER, message); } } }
OnFileSelectListener.java
package org.o7planning.filefinderdialogexample; import java.io.File; public interface OnFileSelectListener { void onSelect(File file); }
ResultDialog.java
package org.o7planning.filefinderdialogexample; import android.app.Dialog; import android.content.Context; import android.graphics.Typeface; import android.util.TypedValue; import android.view.Gravity; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.widget.LinearLayout; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.recyclerview.widget.LinearLayoutManager; import androidx.recyclerview.widget.RecyclerView; import java.io.File; import java.util.List; public class ResultDialog extends Dialog { public ResultDialog(@NonNull Context context, List<File> resultList, OnFileSelectListener listener) { super(context); this.requestWindowFeature(Window.FEATURE_NO_TITLE); // LinearLayout linearLayout = new LinearLayout(this.getContext()); linearLayout.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT)); linearLayout.setOrientation(LinearLayout.VERTICAL); int p = convertToPixels(12); linearLayout.setPadding(p, p, p, p); linearLayout.setGravity(Gravity.CENTER); TextView textView = new TextView(this.getContext()); textView.setLayoutParams(new LinearLayout.LayoutParams(screenWidth(), ViewGroup.LayoutParams.WRAP_CONTENT)); textView.setGravity(Gravity.CENTER); textView.setText("~ Search Result ~"); RecyclerView recyclerView = new RecyclerView(this.getContext()); linearLayout.addView(textView); linearLayout.addView(recyclerView); RecyclerViewAdapter adapter = new RecyclerViewAdapter(this.getContext(), this, listener, resultList); recyclerView.setAdapter(adapter); LinearLayoutManager layoutManager = new LinearLayoutManager(this.getContext()); layoutManager.setOrientation(LinearLayoutManager.VERTICAL); recyclerView.setLayoutManager(layoutManager); // // this.getWindow().setBackgroundDrawable(new ColorDrawable(android.graphics.Color.TRANSPARENT)); // this.setContentView(linearLayout); this.setCancelable(true); } private int convertToPixels(int dp) { float scale = this.getContext().getResources().getDisplayMetrics().density; return (int) (dp * scale + 0.5f); } private int screenWidth() { return this.getContext().getResources().getDisplayMetrics().widthPixels; } // RecyclerViewAdapter private class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> { private Context context; private List<File> files; private OnFileSelectListener listener; private Dialog dialog; public RecyclerViewAdapter(Context context, Dialog dialog, OnFileSelectListener listener, List<File> files) { this.context = context; this.files = files; this.listener = listener; this.dialog = dialog; } // Create new views (invoked by the layout manager) @Override public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { LinearLayout linearLayout = new LinearLayout(context); linearLayout.setOrientation(LinearLayout.VERTICAL); TextView txtName = new TextView(context); TextView txtPath = new TextView(context); txtPath.setTypeface(txtPath.getTypeface(), Typeface.ITALIC); txtPath.setTextSize(TypedValue.COMPLEX_UNIT_SP, 11); linearLayout.addView(txtName); linearLayout.addView(txtPath); RecyclerViewAdapter.ViewHolder viewHolder = new RecyclerViewAdapter.ViewHolder(linearLayout); return viewHolder; } // Inner class to hold a reference to each item of RecyclerView public class ViewHolder extends RecyclerView.ViewHolder { public LinearLayout linearLayout; public TextView textViewFileName; public TextView textViewPath; public ViewHolder(View itemLayoutView) { super(itemLayoutView); this.linearLayout = (LinearLayout) itemLayoutView; this.textViewFileName = (TextView) linearLayout.getChildAt(0); this.textViewPath = (TextView) linearLayout.getChildAt(1); } } @Override public int getItemCount() { return files.size(); } @Override public void onBindViewHolder(RecyclerViewAdapter.ViewHolder viewHolder, final int position) { final File selectedFile = files.get(position); final String path = selectedFile.getAbsolutePath(); String[] split = path.split("/"); final String name = split[split.length - 1]; viewHolder.textViewFileName.setText(name); viewHolder.textViewPath.setText(path); viewHolder.linearLayout.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { dialog.dismiss(); listener.onSelect(selectedFile); } }); } } }
MainActivity.java
package org.o7planning.filefinderdialogexample; import androidx.appcompat.app.AppCompatActivity; import androidx.core.app.ActivityCompat; import android.Manifest; import android.content.pm.PackageManager; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.CheckBox; import android.widget.EditText; import android.widget.Toast; import java.io.File; import java.util.List; public class MainActivity extends AppCompatActivity { private static final int MY_REQUEST_CODE_PERMISSION = 1000; private static final String LOG_TAG = "AndroidExample"; private Button buttonSearch; private EditText editTextSearch; private CheckBox checkBoxIsRegex; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); this.editTextSearch = (EditText) this.findViewById(R.id.editText_search); this.checkBoxIsRegex = (CheckBox) this.findViewById(R.id.checkBox_isRegex); this.buttonSearch = (Button) this.findViewById(R.id.button_search); this.buttonSearch.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v) { askPermissionAndSearchFile(); } }); } private void askPermissionAndSearchFile() { // With Android Level >= 23, you have to ask the user // for permission to access External Storage. if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) { // Level 23 // Check if we have Call permission int permisson = ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE); if (permisson != PackageManager.PERMISSION_GRANTED) { // If don't have permission so prompt the user. this.requestPermissions( new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, MY_REQUEST_CODE_PERMISSION ); return; } } this.doSearchFile(); } private void doSearchFile() { FileFinder fileSelector = new FileFinder(true); String searchText = this.editTextSearch.getText().toString(); boolean isRegex = this.checkBoxIsRegex.isChecked(); List<File> resultList = null; if(isRegex) { resultList = fileSelector.findInSDCardByRegex(searchText); } else { resultList = fileSelector.findInSDCardByKeyword(searchText); } ResultDialog dialog = new ResultDialog(this, resultList, new OnFileSelectListener() { @Override public void onSelect(File file) { Toast.makeText(MainActivity.this, "Path: " + file.getAbsolutePath(), Toast.LENGTH_LONG).show(); } }); dialog.show(); } // When you have the request results @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { super.onRequestPermissionsResult(requestCode, permissions, grantResults); // switch (requestCode) { case MY_REQUEST_CODE_PERMISSION: { // Note: If request is cancelled, the result arrays are empty. // Permissions granted (CALL_PHONE). if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { Log.i( LOG_TAG,"Permission granted!"); Toast.makeText(this, "Permission granted!", Toast.LENGTH_SHORT).show(); this.doSearchFile(); } // Cancelled or denied. else { Log.i(LOG_TAG,"Permission denied!"); Toast.makeText(this, "Permission denied!", Toast.LENGTH_SHORT).show(); } break; } } } }