If app is new runs FirstPassword. Also added SplashActivity.

app/src/main/AndroidManifest.xml

@@ -5,21 +5,25 @@
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
     <application
-        android:requestLegacyExternalStorage="true"
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
+        android:requestLegacyExternalStorage="true"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/AppTheme">
-        <activity android:name=".Noto"></activity>
+
-        <activity android:name=".FormPassword" />
+        <activity android:name=".SplashActivity">
-        <activity android:name=".MainActivity">
         <intent-filter>
             <action android:name="android.intent.action.MAIN" />
+
             <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
         </activity>
+        <activity android:name=".FirstPassword" />
+        <activity android:name=".Noto" />
+        <activity android:name=".FormPassword" />
+        <activity android:name=".MainActivity"/>
     </application>
 
 </manifest>

app/src/main/java/com/zadanie1/mw/FirstPassword.java

@@ -0,0 +1,73 @@
+package com.zadanie1.mw;
+
+        import android.content.Intent;
+        import android.os.Bundle;
+        import android.app.Activity;
+        import android.view.View;
+        import android.widget.Button;
+        import android.widget.EditText;
+        import android.widget.TextView;
+        import android.widget.Toast;
+
+        import java.io.FileNotFoundException;
+        import java.io.FileOutputStream;
+        import java.io.IOException;
+        import java.io.PrintWriter;
+
+public class FirstPassword extends Activity {
+    private static final String FILE_NAME = "passwd.txt";
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_first_password);
+
+        final EditText newpassword;
+        final EditText renewpassword;
+        Button confirm;
+
+        newpassword = (EditText) findViewById(R.id.newpassword);
+        renewpassword = (EditText) findViewById(R.id.renewpassword);
+        confirm = (Button) findViewById(R.id.button);
+
+        confirm.setOnClickListener(new View.OnClickListener() {
+            public void onClick(View arg0) {
+                if (newpassword.getText().toString().equals(renewpassword.getText().toString())) {
+
+                    String text = newpassword.getText().toString();
+                    FileOutputStream fos = null;
+
+                    Toast toast = Toast.makeText(getApplicationContext(),
+                            "Password has been changed",
+                            Toast.LENGTH_SHORT);
+                    toast.show();
+
+                    try {
+                        fos = openFileOutput(FILE_NAME, MODE_PRIVATE);
+                        fos.write(text.getBytes());
+
+                    } catch (FileNotFoundException e) {
+                        e.printStackTrace();
+                    } catch (IOException e) {
+                        e.printStackTrace();
+                    } finally {
+                        if (fos != null) {
+                            try {
+                                fos.close();
+                            } catch (IOException e) {
+                                e.printStackTrace();
+                            }
+                        }
+                    }
+                    onBackPressed();
+                }
+                else
+                {
+                    Toast toast = Toast.makeText(getApplicationContext(),
+                            "Password has NOT been changed",
+                            Toast.LENGTH_SHORT);
+                    toast.show();
+                }
+            }
+        });
+    }
+}

app/src/main/java/com/zadanie1/mw/FormPassword.java

@@ -9,28 +9,60 @@ import android.widget.EditText;
 import android.widget.TextView;
 import android.widget.Toast;
 
+import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
+import java.io.FileReader;
 import java.io.IOException;
 import java.io.PrintWriter;
 
 public class FormPassword extends Activity {
     private static final String FILE_NAME = "passwd.txt";
+
+
+    public String readFile(String filename) throws IOException {
+        String content = null;
+        File file = new File(filename); // For example, foo.txt
+        FileReader reader = null;
+        try {
+            reader = new FileReader(file);
+            char[] chars = new char[(int) file.length()];
+            reader.read(chars);
+            content = new String(chars);
+            reader.close();
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            if (reader != null) {
+                reader.close();
+            }
+        }
+        return content;
+    }
+
     @Override
     public void onCreate(Bundle savedInstanceState) {
+
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_form_password);
 
+        final EditText currentpassword;
         final EditText newpassword;
         final EditText renewpassword;
         Button confirm;
 
+        currentpassword = (EditText) findViewById(R.id.currentpassword);
         newpassword = (EditText) findViewById(R.id.newpassword);
         renewpassword = (EditText) findViewById(R.id.renewpassword);
         confirm = (Button) findViewById(R.id.button);
 
         confirm.setOnClickListener(new View.OnClickListener() {
             public void onClick(View arg0) {
+                final String filename =  getFilesDir() + "/passwd.txt";
+                File file = new File(filename);
+
+                try {
+                    if (currentpassword.getText().toString().equals(readFile(filename).toString())) {
                         if (newpassword.getText().toString().equals(renewpassword.getText().toString())) {
 
                             String text = newpassword.getText().toString();
@@ -59,14 +91,24 @@ public class FormPassword extends Activity {
                                 }
                             }
                             onBackPressed();
-                }
+                        } else {
-                else
-                    {
                             Toast toast = Toast.makeText(getApplicationContext(),
-                                "Password has NOT been changed",
+                                    "Password has NOT been changed!",
                                     Toast.LENGTH_SHORT);
                             toast.show();
                         }
+                    } else {
+                        Toast toast = Toast.makeText(getApplicationContext(),
+                                "Current password is WRONG!",
+                                Toast.LENGTH_SHORT);
+                        toast.show();
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+                currentpassword.getText().clear();
+                newpassword.getText().clear();
+                renewpassword.getText().clear();
             }
         });
     }

app/src/main/java/com/zadanie1/mw/MainActivity.java

@@ -45,12 +45,25 @@ public class MainActivity extends AppCompatActivity {
         return content;
     }
 
+    private boolean isFileExists(File file) {
+        return file.exists() && !file.isDirectory();
+
+    }
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
 
+        final String filename =  getFilesDir() + "/passwd.txt";
+        File file = new File(filename);
+
+        if (!isFileExists(file)){
+            Intent myIntent3 = new Intent(MainActivity.this,
+                    FirstPassword.class);
+            startActivity(myIntent3);
+        }
+
         response = (TextView) findViewById(R.id.textView);
         button = (Button) findViewById(R.id.button);
         restartpassword = (Button) findViewById(R.id.restartpassword);
@@ -68,11 +81,6 @@ public class MainActivity extends AppCompatActivity {
         button.setOnClickListener(new OnClickListener() {
             private final String filename =  getFilesDir() + "/passwd.txt";
 
-            private boolean isFileExists(File file) {
-                return file.exists() && !file.isDirectory();
-
-            }
-
             @Override
             public void onClick(View view) {
                 /*response.setText(textPassword.getText());*/
@@ -90,22 +98,24 @@ public class MainActivity extends AppCompatActivity {
                                      Noto.class);
                              startActivity(myIntent2);
 
-                         }
-                     }  else if (textPassword.getText().toString().equals("FirstPassword!")) {
-                         Intent myIntent2 = new Intent(MainActivity.this,
-                                 Noto.class);
-                         startActivity(myIntent2);
                          } else {
                              Toast toast = Toast.makeText(getApplicationContext(),
                                      "Password is NOT correct",
                                      Toast.LENGTH_SHORT);
                              toast.show();
                             }
+                     } else {
+                         Intent myIntent3 = new Intent(MainActivity.this,
+                                 FirstPassword.class);
+                         startActivity(myIntent3);
+                     }
 
                  }  catch(IOException e){
                      e.printStackTrace();
                  }
+                textPassword.getText().clear();
             }
         });
+
     }
 }

app/src/main/java/com/zadanie1/mw/SplashActivity.java

@@ -0,0 +1,27 @@
+package com.zadanie1.mw;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.Handler;
+
+public class SplashActivity extends Activity {
+
+    Handler handler;
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.splashfile);
+
+        handler=new Handler();
+        handler.postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                Intent intent=new Intent(SplashActivity.this,MainActivity.class);
+                startActivity(intent);
+                finish();
+            }
+        },3000);
+
+    }
+}

app/src/main/res/layout/activity_first_password.xml

@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<androidx.appcompat.widget.LinearLayoutCompat 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=".FirstPassword"
+    android:orientation="vertical"
+    android:padding="20px">
+
+    <EditText
+        android:id="@+id/newpassword"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword"
+        android:hint="New Password"
+        tools:layout_editor_absoluteX="97dp"
+        tools:layout_editor_absoluteY="409dp" />
+
+    <EditText
+        android:id="@+id/renewpassword"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword"
+        android:hint="New Password again"
+        tools:layout_editor_absoluteX="97dp"
+        tools:layout_editor_absoluteY="409dp" />
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="CONFIRM NEW PASSWORD"
+        tools:layout_editor_absoluteX="260dp"
+        tools:layout_editor_absoluteY="492dp" />
+
+</androidx.appcompat.widget.LinearLayoutCompat>

app/src/main/res/layout/activity_form_password.xml

@@ -9,12 +9,23 @@ tools:context=".MainActivity"
     android:orientation="vertical"
     android:padding="20px">
 
+    <EditText
+        android:id="@+id/currentpassword"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:ems="10"
+        android:inputType="textPassword"
+        android:hint="Current Password"
+        tools:layout_editor_absoluteX="97dp"
+        tools:layout_editor_absoluteY="409dp" />
+
     <EditText
         android:id="@+id/newpassword"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:ems="10"
         android:inputType="textPassword"
+        android:hint="New Password"
         tools:layout_editor_absoluteX="97dp"
         tools:layout_editor_absoluteY="409dp" />
 
@@ -24,6 +35,7 @@ android:padding="20px">
         android:layout_height="wrap_content"
         android:ems="10"
         android:inputType="textPassword"
+        android:hint="New Password again"
         tools:layout_editor_absoluteX="97dp"
         tools:layout_editor_absoluteY="409dp" />
 

app/src/main/res/layout/splashfile.xml

@@ -0,0 +1,35 @@
+<?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"
+    android:gravity="center">
+
+    <ImageView
+
+        android:id="@+id/logo_id"
+        android:layout_width="250dp"
+        android:layout_height="250dp"
+        android:layout_centerInParent="true"
+        android:src="@drawable/img"/>
+
+    <TextView
+        android:id="@+id/textView"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_below="@+id/logo_id"
+        android:layout_centerHorizontal="true"
+        android:layout_marginTop="16dp"
+        android:text="Encrypted Noto"
+        android:textSize="30dp" />
+
+    <TextView
+        android:id="@+id/textView2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_below="@+id/textView"
+        android:layout_centerHorizontal="true"
+        android:layout_marginTop="18dp"
+        android:text="by Marcin Wozniak"
+        android:textSize="15dp" />
+
+</RelativeLayout>

app/src/main/res/values/strings.xml

@@ -1,3 +1,3 @@
 <resources>
-    <string name="app_name">My Application</string>
+    <string name="app_name">Encrypted Noto</string>
 </resources>