Create Project
Create new project in Android Studio with steps as below:
Step 1: Input Project Name and Select Project Location
Step 2: Select SDK for Android App
Step 3: Select Default Activity for App
Step 4: Finish create project
Add Strings
Open res\values\strings.xml file and add new string as below:
<resources>
<string name="app_name">Learn Android with Real Apps</string>
<string name="folder_name">Folder Name</string>
<string name="file_name">File Name</string>
<string name="content">Content</string>
<string name="write_file">Write File</string>
<string name="read_file">Read File</string>
<string name="delete_file">Delete File</string>
<string name="done">Done</string>
<string name="unavailable">External Storage is Unavailable</string>
</resources>
Manifest Permissions
Open AndroidManifest.xml file in manifest folder and add permissions as below:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="android.demo.learnandroidwithrealapps">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_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>
Main Activity Layout
Open res\layout\activity_main.xml file and create layout as below:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ffffff"
android:orientation="vertical"
tools:ignore="HardcodedText">
<EditText
android:id="@+id/editTextFolderName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="@string/folder_name"
android:inputType="textPersonName" />
<EditText
android:id="@+id/editTextFileName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="@string/file_name"
android:inputType="textPersonName" />
<EditText
android:id="@+id/editTextContent"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:hint="@string/content"
android:inputType="textMultiLine" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<Button
android:id="@+id/buttonWriteFile"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/write_file" />
<Button
android:id="@+id/buttonReadFile"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/read_file" />
<Button
android:id="@+id/buttonDeleteFile"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/delete_file" />
</LinearLayout>
</LinearLayout>
Main Activity Class
Add code to MainActivity.java file in android.demo.learnandroidwithrealapps package as below:
package android.demo.learnandroidwithrealapps;
import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
public class MainActivity extends AppCompatActivity {
private EditText editTextFileName, editTextFolderName, editTextContent;
private Button buttonDeleteFile, buttonWriteFile, buttonReadFile;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
assignPermission();
}
private void assignPermission() {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_DENIED) {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
}
}
private void initView() {
editTextFileName = findViewById(R.id.editTextFileName);
editTextFolderName = findViewById(R.id.editTextFolderName);
editTextContent = findViewById(R.id.editTextContent);
buttonReadFile = findViewById(R.id.buttonReadFile);
buttonReadFile.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
buttonReadFile_onClick(view);
}
});
buttonWriteFile = findViewById(R.id.buttonWriteFile);
buttonWriteFile.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
buttonWriteFile_onClick(view);
}
});
buttonDeleteFile = findViewById(R.id.buttonDeleteFile);
buttonDeleteFile.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
buttonDeleteFile_onClick(view);
}
});
}
private void buttonReadFile_onClick(View view) {
try {
if (checkExternalMedia()) {
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File(sdCard.getAbsolutePath() + File.separator + editTextFolderName.getText().toString() + File.separator);
File file = new File(dir, editTextFileName.getText().toString());
StringBuilder result = new StringBuilder();
String line = "";
BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
while ((line = bufferedReader.readLine()) != null) {
result.append(line);
}
editTextContent.setText(result.toString());
} else {
Toast.makeText(getApplicationContext(), getString(R.string.unavailable), Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
}
private void buttonWriteFile_onClick(View view) {
try {
if (checkExternalMedia()) {
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File(sdCard.getAbsolutePath() + File.separator + editTextFolderName.getText().toString() + File.separator);
dir.mkdirs();
File file = new File(dir, editTextFileName.getText().toString());
FileOutputStream fileOutputStream = new FileOutputStream(file);
fileOutputStream.write(editTextContent.getText().toString().getBytes());
fileOutputStream.close();
Toast.makeText(getApplicationContext(), getString(R.string.done), Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), getString(R.string.unavailable), Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
}
private void buttonDeleteFile_onClick(View view) {
try {
if (checkExternalMedia()) {
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File(sdCard.getAbsolutePath() + File.separator + editTextFolderName.getText().toString() + File.separator);
File file = new File(dir, editTextFileName.getText().toString());
if(file.exists()) {
file.delete();
}
Toast.makeText(getApplicationContext(), getString(R.string.done), Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(), getString(R.string.unavailable), Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();
}
}
private boolean checkExternalMedia() {
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
mExternalStorageAvailable = mExternalStorageWriteable = true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
mExternalStorageAvailable = true;
mExternalStorageWriteable = false;
} else {
mExternalStorageAvailable = mExternalStorageWriteable = false;
}
return mExternalStorageAvailable && mExternalStorageWriteable;
}
}
Structure of Project
Run App
Write A File To A Folder
File and Folder in Emulator
Read A File To A Folder
Delete A File To A Folder
Folder After Delete in Emulator
