Initialize the app

public class MainActivity extends AppCompatActivity {

    private final String TAG = "MainActivity";
    static final int DEVICE_ADMIN_ADD_RESULT_ENABLE = 1;

    private Button mToggleAdminBtn;
    private ComponentName mDeviceAdmin;
    private DevicePolicyManager mDevicePolicyManager;
    private Utils mUtils;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //...called when the activity is starting. This is where most initialization should go.
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView logView = findViewById(R.id.logview_id);
        logView.setMovementMethod(new ScrollingMovementMethod());
        mToggleAdminBtn = findViewById(R.id.toggleAdminBtn);
        Button activateLicenseBtn = findViewById(R.id.activateLicenseBtn);
        Button deactivateLicenseBtn = findViewById(R.id.deactivateLicenseBtn);
        Button showEnabledPackagesBtn = findViewById(R.id.showEnabledPackagesBtn);
        Button showDisabledPackagesBtn = findViewById(R.id.showDisabledPackagesBtn);
        Button enableAllDisabledPackagesBtn = findViewById(R.id.enableAllDisabledPackagesBtn);
        Button enablePackageBtn = findViewById(R.id.enablePackageBtn);
        Button disablePackageBtn = findViewById(R.id.disablePackageBtn);
        Button activateBackwardsCompatibleKeyBtn = findViewById(R.id.activateBackwardsCompatibleKeyBtn);
        Button toggleBatteryOptimizationWhitelistBtn = findViewById(R.id.toggleBatteryOptimizationWhitelistBtn);
        Button toggleForceStopBlacklistBtn = findViewById(R.id.toggleForceStopBlacklistBtn);

        mDeviceAdmin = new ComponentName(MainActivity.this, SampleAdminReceiver.class);
        mDevicePolicyManager = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE);
        mUtils = new Utils(logView, TAG);

        mToggleAdminBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {toggleAdmin();
            }
        });
        activateLicenseBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activateLicense();
            }
        });
        deactivateLicenseBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                deactivateLicense();
            }
        });
        activateBackwardsCompatibleKeyBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activateBackwardsCompatibleKey();
            }
        });

        // Backwards Compatibility button is only visible if the device is
        // on at least Knox version 2.5 AND lower than Knox version 2.8 (Knox API 17 to 21)
        if(EnterpriseDeviceManager.getAPILevel() < EnterpriseDeviceManager.KNOX_VERSION_CODES.KNOX_2_8 &&
                EnterpriseDeviceManager.getAPILevel() >= EnterpriseDeviceManager.KNOX_VERSION_CODES.KNOX_2_5) {
            activateBackwardsCompatibleKeyBtn.setVisibility(View.VISIBLE);
        }

        showEnabledPackagesBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPackageState(true);
            }
        });
        showDisabledPackagesBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showPackageState(false);
            }
        });
        enableAllDisabledPackagesBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                enableAllDisabledPackages();
            }
        });
        enablePackageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                promptUserForPackageToEnableOrDisable(true);
            }
        });
        disablePackageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                promptUserForPackageToEnableOrDisable(false);
            }
        });
        toggleBatteryOptimizationWhitelistBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                promptUserPackageForBatteryWhitelist();
            }
        });
        toggleForceStopBlacklistBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                promptUserPackageForForceStopBlacklist();
            }
        });
    }

    //the logic for onClickListener functions are done here
}