Main Activity for the Lock Screen Device App on the SSaurel's Channel

MainActivity.java

package com.ssaurel.lockdevice;

import android.app.Activity;
import android.app.admin.DevicePolicyManager;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

  private Button lock, disable, enable;
  public static final int RESULT_ENABLE = 11;
  private DevicePolicyManager devicePolicyManager;
  private ComponentName compName;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    devicePolicyManager = (DevicePolicyManager) getSystemService(DEVICE_POLICY_SERVICE);
    compName = new ComponentName(this, MyAdmin.class);

    lock = (Button) findViewById(R.id.lock);
    enable = (Button) findViewById(R.id.enableBtn);
    disable = (Button) findViewById(R.id.disableBtn);
    lock.setOnClickListener(this);
    enable.setOnClickListener(this);
    disable.setOnClickListener(this);
  }

  @Override
  protected void onResume() {
    super.onResume();
    boolean isActive = devicePolicyManager.isAdminActive(compName);
    disable.setVisibility(isActive ? View.VISIBLE : View.GONE);
    enable.setVisibility(isActive ? View.GONE : View.VISIBLE);
  }

  @Override
  public void onClick(View view) {
    if (view == lock) {
      boolean active = devicePolicyManager.isAdminActive(compName);

      if (active) {
        devicePolicyManager.lockNow();
      } else {
        Toast.makeText(this, "You need to enable the Admin Device Features", Toast.LENGTH_SHORT).show();
      }

    } else if (view == enable) {
      Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
      intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, compName);
      intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "Additional text explaining why we need this permission");
      startActivityForResult(intent, RESULT_ENABLE);

    } else if (view == disable) {
      devicePolicyManager.removeActiveAdmin(compName);
      disable.setVisibility(View.GONE);
      enable.setVisibility(View.VISIBLE);
    }
  }

  @Override
  protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch(requestCode) {
      case RESULT_ENABLE :
        if (resultCode == Activity.RESULT_OK) {
          Toast.makeText(MainActivity.this, "You have enabled the Admin Device features", Toast.LENGTH_SHORT).show();
        } else {
          Toast.makeText(MainActivity.this, "Problem to enable the Admin Device features", Toast.LENGTH_SHORT).show();
        }
      break;
    }
    
	super.onActivityResult(requestCode, resultCode, data);
  }
}