camera works on foreground

Signed-off-by: Jerry Chen <jerryc05@qq.com>

app/build.gradle

@@ -5,7 +5,7 @@ android {
     buildToolsVersion "29.0.0"
     defaultConfig {
         applicationId "jerryc05.unlockme"
-        minSdkVersion 19
+        minSdkVersion 21
         targetSdkVersion 29
         versionCode 1
         versionName "1.0"

app/src/androidTest/java/jerryc05/unlockme/ExampleInstrumentedTest.java

@@ -17,11 +17,4 @@
  */
 @RunWith(AndroidJUnit4.class)
 public class ExampleInstrumentedTest {
-  @Test
-  public void useAppContext() {
-    // Context of the app under test.
-    Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
-
-    assertEquals("jerryc05.unlockme", appContext.getPackageName());
-  }
 }

app/src/main/AndroidManifest.xml

@@ -4,9 +4,14 @@
     package="jerryc05.unlockme"
     tools:ignore="GoogleAppIndexingWarning">
 
+    <uses-permission android:name="android.permission.CAMERA" />
+    <uses-feature
+        android:name="android.hardware.camera2"
+        android:required="true" />
+
     <application
-        android:hardwareAccelerated="false"
         android:allowBackup="true"
+        android:hardwareAccelerated="false"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:theme="@style/AppTheme"
@@ -19,6 +24,18 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
-    </application>
 
+        <receiver
+            android:name=".receivers.MyDAReceiver"
+            android:permission="android.permission.BIND_DEVICE_ADMIN">
+            <meta-data
+                android:name="android.app.device_admin"
+                android:resource="@xml/device_policy" />
+            <intent-filter>
+                <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
+                <action android:name="android.app.action.DEVICE_ADMIN_DISABLE_REQUESTED" />
+                <action android:name="android.app.action.DEVICE_ADMIN_DISABLED" />
+            </intent-filter>
+        </receiver>
+    </application>
 </manifest>

app/src/main/java/jerryc05/unlockme/MainActivity.java

@@ -1,14 +1,154 @@
 package jerryc05.unlockme;
 
-
+import android.Manifest;
 import android.app.Activity;
+import android.app.AlertDialog;
+import android.app.admin.DevicePolicyManager;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.DialogInterface;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.os.Build;
 import android.os.Bundle;
+import android.provider.MediaStore;
+import android.util.Log;
+import android.view.View;
+import android.widget.Toast;
+
+import jerryc05.unlockme.receivers.MyDAReceiver;
 
+@SuppressWarnings("NullableProblems")
 public class MainActivity extends Activity {
 
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setContentView(R.layout.activity_main);
+  private final static String              TAG                 =
+          MainActivity.class.getName();
+  private              DevicePolicyManager devicePolicyManager;
+  private              ComponentName       componentName;
+  private final static int                 REQUEST_CODE_CAMERA = 0;
+
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    setContentView(R.layout.activity_main);
+
+    new Thread(new Runnable() {
+      @Override
+      public void run() {
+        handleDeviceAdmin();
+        findViewById(R.id.activity_main_button_takePhoto)
+                .setOnClickListener(new View.OnClickListener() {
+                  @Override
+                  public void onClick(View view) {
+                    takePhoto();
+                  }
+                });
+      }
+    }).start();
+  }
+
+  @Override
+  protected void onResume() {
+    super.onResume();
+
+    if (isDeviceAdminDisabled())
+      requireDeviceAdmin();
+  }
+
+  @Override
+  public void onRequestPermissionsResult(int requestCode,
+                                         String[] permissions,
+                                         int[] grantResults) {
+    if (requestCode == REQUEST_CODE_CAMERA) {
+      final String granted = grantResults.length > 0 &&
+              grantResults[0] == PackageManager.PERMISSION_GRANTED
+              ? "Camera Permission Granted √"
+              : "Camera Permission Denied ×";
+      if (BuildConfig.DEBUG)
+        Log.d(TAG, "onRequestPermissionsResult: " + granted);
+      Toast.makeText(this,
+              granted, Toast.LENGTH_SHORT)
+              .show();
+      takePhoto();
+    }
+  }
+
+  void takePhoto() {
+    if (BuildConfig.DEBUG)
+      Log.d(TAG, "takePhoto: ");
+
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&
+            checkSelfPermission(Manifest.permission.CAMERA)
+                    != PackageManager.PERMISSION_GRANTED) {
+      if (shouldShowRequestPermissionRationale(
+              Manifest.permission.CAMERA))
+        new AlertDialog.Builder(this)
+                .setTitle("Permission Required")
+                .setMessage(getResources().getString(R.string.permission_camera_explanation))
+                .setCancelable(false)
+                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
+                  @Override
+                  public void onClick(DialogInterface dialogInterface, int i) {
+                    requestPermissions(
+                            new String[]{Manifest.permission.CAMERA},
+                            REQUEST_CODE_CAMERA);
+                  }
+                })
+                .show();
+      else
+        requestPermissions(
+                new String[]{Manifest.permission.CAMERA},
+                REQUEST_CODE_CAMERA);
+
+    } else {
+      final int REQUEST_IMAGE_CAPTURE = 1;
+
+      Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
+      if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
+        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
+      }
     }
+  }
+
+  void handleDeviceAdmin() {
+    devicePolicyManager = (DevicePolicyManager)
+            getSystemService(Context.DEVICE_POLICY_SERVICE);
+    componentName = new ComponentName(
+            getApplicationContext(), MyDAReceiver.class);
+
+    if (isDeviceAdminDisabled())
+      requireDeviceAdmin();
+  }
+
+  private boolean isDeviceAdminDisabled() {
+    final boolean disabled = devicePolicyManager == null ||
+            !devicePolicyManager.isAdminActive(componentName);
+
+    runOnUiThread(new Runnable() {
+      @Override
+      public void run() {
+        Toast.makeText(MainActivity.this,
+                disabled ? "Device Admin Disabled ×"
+                        : "Device Admin Enabled √", Toast.LENGTH_SHORT)
+                .show();
+      }
+    });
+    return disabled;
+  }
+
+  private void requireDeviceAdmin() {
+    Intent intent = new Intent(
+            DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
+    intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN,
+            componentName);
+    intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,
+            getResources().getString(R.string.device_admin_explanation));
+
+    runOnUiThread(new Runnable() {
+      @Override
+      public void run() {
+        startActivity(intent);
+      }
+    });
+  }
 }

app/src/main/java/jerryc05/unlockme/receivers/MyDAReceiver.java

@@ -0,0 +1,34 @@
+package jerryc05.unlockme.receivers;
+
+import android.app.admin.DeviceAdminReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.os.UserHandle;
+import android.util.Log;
+
+import jerryc05.unlockme.BuildConfig;
+
+@SuppressWarnings("NullableProblems")
+public class MyDAReceiver extends DeviceAdminReceiver {
+
+  private final static String TAG = MyDAReceiver.class.getName();
+  private static       int    failedAttempt;
+
+  @Override
+  public void onPasswordFailed(Context context, Intent intent, UserHandle user) {
+    super.onPasswordFailed(context, intent, user);
+
+    if (BuildConfig.DEBUG)
+      Log.d(TAG, "onPasswordFailed: " + ++failedAttempt);
+  }
+
+  @Override
+  public void onPasswordSucceeded(Context context, Intent intent, UserHandle user) {
+    super.onPasswordSucceeded(context, intent, user);
+
+    if (failedAttempt > 0) {
+
+    }
+    failedAttempt = 0;
+  }
+}

app/src/main/res/layout/activity_main.xml

@@ -5,13 +5,10 @@
     android:layout_height="match_parent"
     tools:context=".MainActivity">
 
-    <TextView
+    <Button
+        android:id="@+id/activity_main_button_takePhoto"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_alignParentStart="true"
-        android:layout_alignParentTop="true"
-        android:layout_alignParentEnd="true"
-        android:layout_alignParentBottom="true"
         android:gravity="center"
-        android:text="Hello World!" />
+        android:text="Take Photo!" />
 </RelativeLayout>

app/src/main/res/values/strings.xml

@@ -1,3 +1,5 @@
 <resources>
     <string name="app_name">UnlockMe</string>
+    <string name="device_admin_explanation">This app needs Device Admin to work properly.</string>
+    <string name="permission_camera_explanation">This app needs Camera permission to work properly.</string>
 </resources>

app/src/main/res/xml/device_policy.xml

@@ -0,0 +1,5 @@
+<device-admin>
+    <uses-policies>
+        <watch-login />
+    </uses-policies>
+</device-admin>

app/src/test/java/jerryc05/unlockme/ExampleUnitTest.java

@@ -10,8 +10,4 @@
  * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
  */
 public class ExampleUnitTest {
-  @Test
-  public void addition_isCorrect() {
-    assertEquals(4, 2 + 2);
-  }
 }