<receiver android:name=".MyAdmin">
  <meta-data android:name="android.app.device_admin"
    android:resource="@xml/my_admin" />
  <intent-filter>
    <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
  </intent-filter>
</receiver>

<?xml version="1.0" encoding="utf-8"?>
<device-admin xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-policies>
        <limit-password />
        <watch-login />
        <reset-password />
        <force-lock />
        <wipe-data />
    </uses-policies>
</device-admin>

public class LockActivity extends Activity {
  IDevicePolicyManager mService;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
  }
  //锁屏
  public void lock(View view){
    try {
      //通过反射获取到sdk隐藏的服务
      Method method = Class.forName("android.os.ServiceManager")
          .getMethod("getService", String.class);
      IBinder binder = (IBinder) method.invoke(null,//激活服务
          new Object[] { Context.DEVICE_POLICY_SERVICE });
       mService = IDevicePolicyManager.Stub.asInterface(binder);
       //定义组件的名字
       ComponentName mAdminName = new ComponentName(this, MyAdmin.class);
       //注册权限
       if (mService != null) {
          //判断自定义的广播接受者 是不是被注册成 deviceadmin的权限
          if (!mService.isAdminActive(mAdminName)) {
                Intent intent = new Intent(
                DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
                intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN,
                    mAdminName);
                startActivity(intent);
              }
          //调用服务实现锁屏
          mService.lockNow();
          //设置解锁密码
          mService.resetPassword("123", 0);
       }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

/*
**
** Copyright 2010, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
**   http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
package android.app.admin;
import android.content.ComponentName;
/**
 * Internal IPC interface to the device policy service.
 * {@hide}
 */
interface IDevicePolicyManager {
  void setPasswordQuality(in ComponentName who, int quality);
  int getPasswordQuality(in ComponentName who);
  void setPasswordMinimumLength(in ComponentName who, int length);
  int getPasswordMinimumLength(in ComponentName who);
  boolean isActivePasswordSufficient();
  int getCurrentFailedPasswordAttempts();
  void setMaximumFailedPasswordsForWipe(in ComponentName admin, int num);
  int getMaximumFailedPasswordsForWipe(in ComponentName admin);
  boolean resetPassword(String password, int flags);
  void setMaximumTimeToLock(in ComponentName who, long timeMs);
  long getMaximumTimeToLock(in ComponentName who);
  void lockNow();
  void wipeData(int flags);
  void setActiveAdmin(in ComponentName policyReceiver);
  boolean isAdminActive(in ComponentName policyReceiver);
  List<ComponentName> getActiveAdmins();
  boolean packageHasActiveAdmins(String packageName);
  void removeActiveAdmin(in ComponentName policyReceiver);
  void setActivePasswordState(int quality, int length);
  void reportFailedPasswordAttempt();
  void reportSuccessfulPasswordAttempt();
}