实现一键锁屏的功能

    参照谷歌官方文档：

Creating the manifest
To use the Device Administration API, the application's manifest must include the following:
A subclass of DeviceAdminReceiver
that includes the following:The BIND_DEVICE_ADMIN
permission.
The ability to respond to the ACTION_DEVICE_ADMIN_ENABLED
intent, expressed in the manifest as an intent filter.
A decl aration of security policies used in metadata.

  直接给出我的总结：

1.要创建一个类继承 DeviceAdminReceiver
然后，在清单文件中增加

<receiver android:name=".app.DeviceAdminSample$DeviceAdminSampleReceiver"
        android:label="@string/sample_device_admin"
        android:description="@string/sample_device_admin_description"
        android:permission="android.permission.BIND_DEVICE_ADMIN">
    <meta-data android:name="android.app.device_admin"
            android:resource="@xml/device_admin_sample" />
    <intent-filter>
        <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
    </intent-filter>
</receiver>

里面的字符串创建就好了，具体什么意思，等你运行起来就一目了然，注意android:resource="@xml/device_admin_sample" 着xml 是一个文件夹，然后里面的文件具体写的如下，就是一些功能，比如锁屏等

<device-admin xmlns:android="http://schemas.android.com/apk/res/android">
  <uses-policies>
    <limit-password />
    <watch-login />
    <reset-password />
    <force-lock />
    <wipe-data />
    <expire-password />
    <encrypted-storage />
    <disable-camera />
  </uses-policies>
</device-admin>

4.启动代码如下，这里要传入步骤1创建的 .class 文件

 ComponentName  name = new ComponentName(this,LockScrrrrrr.class);
        Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
        intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, name);
        intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,
                getString(R.string.add_admin_extra_app_text));
        startActivityForResult(intent, REQUEST_CODE_ENABLE_ADMIN);

这个时候运行项目就可以看到管理员页面了，但是点击效果还要代码实现：

 @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        switch (requestCode){
            case  10:
                if (requestCode== RESULT_OK){
                    dpm.lockNow();
                    finish();
                }else {
//                    反激活  ，要先判断是否激活才能反激活
mDPM.removeActiveAdmin(mDeviceAdminSample);
 enableDeviceCapabilitiesArea(false);
                }
                break;
        }
    }

其中的 dpm 是 dpm = (DevicePolicyManager) getSystemService(DEVICE_POLICY_SERVICE);

然后激活了设备管理员的程序卸载比较麻烦，要进入设置里面的设备管理卸载。