<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="ru.hashmap.myapplol.MainActivity">

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:text="Your password should be here"
        android:ems="10"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="16dp"
        android:id="@+id/editText"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:singleLine="true" />

    <ProgressBar
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/editText"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:id="@+id/progressBar"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:indeterminate="true" />

    <Button
        android:text="generate!"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="62dp"
        android:id="@+id/button"
        android:layout_below="@+id/progressBar"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:onClick="genPass"/>

    <SeekBar
        style="@style/Widget.AppCompat.SeekBar.Discrete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:max="15"
        android:progress="6"
        android:layout_marginTop="27dp"
        android:id="@+id/seekBar"
        android:layout_below="@+id/progressBar"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />
</RelativeLayout>

package ru.hashmap.myapplol;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.SeekBar;
import android.widget.TextView;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void genPass(View view)
    {
        SeekBar seek = (SeekBar) findViewById(R.id.seekBar);
        int seekValue = seek.getProgress()+1;
        Log.d("seekValue", seekValue+"");
        String[] dict = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
        String[] pass = new String[seekValue];
        Random rnd = new Random();
        for(int i = 0; i < seekValue; i++) {
            pass[i] = dict[rnd.nextInt(dict.toString().length())];
        }
        ((TextView) findViewById(R.id.editText)).setText(pass.toString());
        Log.d("pass", pass+"");
    }
}