Создать простой File Finder Dialog в Android

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1- Цель примера

В данной статье я покажу вам как создать простое приложение, поиск файлов в Android и отобразить результат на  Dialog.
Данное приложение будет находить файлы на SD Card (SD Карта), поэтому если вы тестируете данное приложение на Android Emulator, вам нужно настроить для него  SD Card.
Используйте  Device File Explorer чтобы скопировать файл в  Android Emulator, это нужно для того, чтобы вы протестировали приложение.

2- Пример File Finder Dialog

На  Android Studio создайте новый project:
  • File > New > New Project > Empty Activity
    • Name: FileFinderDialogExample
    • Package name: org.o7planning.filefinderdialogexample
    • Language: Java
После того, как пользователь нажал на кнопку поиска, список найденных файлов отобразится на  RecyclerView. Это неготовый компонент интерфейса на  Android SDK, поэтому вам нужно установить его в project.
После успешной установки вы увидите, как он будет объявлен в build.gradle (Module App):
dependencies {
    ...
    implementation 'androidx.recyclerview:recyclerview:1.0.0'
}
Далее, зарегистрируйте с системой, чтобы ваше приложение могло получить доступ в файлы.
<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>
Интерфейс приложения:
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>
Класс  FileFinder включает методы поиска файлов в системе. Примечание: С  Android 6.0+ (API Level 23+) вашему приложению нужно спросить пользователя разрешение получить доступ в файлы, при отказе в разрешении пользователя, данный метод всегда вернет пустой список.
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;
            }
        }
    }


}

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