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如何使用Google的Cloud Anchors API-(Ko

如何使用Google的Cloud Anchors API-(Ko

作者: 橙果子 | 来源:发表于2019-08-14 20:06 被阅读0次

这篇文章将分为以下几个部分：

1.启用Cloud Anchors API。
2.添加API密钥和清单权限。
3.导入Sceneform资产。
4.编写Cloud Anchors应用程序。

启用Cloud Anchors API

要从云托管和检索锚点，我们需要使用Cloud Anchors API。按照以下简单步骤启用API。

  1. 请访问：谷歌云服务官网并使用您的Google帐户登录或创建一个。
  2. 在Cloud Platform上创建项目并将其命名为您想要的任何名称。
  3. 创建项目后，单击屏幕左上角的三条水平线。
  4. 选择API和Serivces，然后单击“启用API和服务”。
  5. 搜索“Cloud Anchor”并显示ARCore Cloud Anchor API。您需要单击它并单击启用按钮。
  6. 然后从左侧的菜单中单击凭据。在这里，您将创建API凭据。
  7. 单击“创建凭据”，然后按照出现的简单步骤操作。最后，您将获得API密钥！

添加API密钥和清单权限

现在启用API密钥后，就可以启动Android Studio了。使用空活动创建新的Android Studio项目。

打开AndroidManifest.xml并在<application>标记之外添加以下权限：

<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-feature android:name="android.hardware.camera.ar" android:required="true"/>

现在，在<application>标记下直接添加以下元数据：

<meta-data
        android:name="com.google.ar.core"
        android:value="required"/>
<meta-data
        android:name="com.google.android.ar.API_KEY"
        android:value="YOUR API KEY"/>

不要忘记将API密钥添加到上面的标记中。

要使用ARCore开发增强现实应用程序，您需要使用Sceneform插件和Sceneform SDK。下面的文章将向您展示如何为Android Studio启用Sceneform插件：

检查如何启用Sceneform插件

https://developers.google.com/ar/develop/java/sceneform/

启用插件后，将以下依赖项添加到应用程序级build.gradle文件中：

implementation 'com.google.ar:core:1.10.0' 
implementation 'com.google.ar.sceneform.ux:sceneform-ux:1.10.0' 
implementation 'com.google.android.material:material:1.0.0'

现在我们准备将3D模型导入我们的Android应用程序。

导入Sceneform资产

我们将从poly.google.com下载3D资源，它是下载sceneform的.obj文件的绝佳工具。选择任何3D模型并以.obj格式下载。您将获得一个已下载到您的计算机上的zip文件。

右键单击Android Studio中的应用程序包，然后单击新建→包并将其命名为“ sampledata ”。解压缩此文件夹中的.zip文件。

解压缩文件后，找到.obj文件并右键单击它。选择“导入场景资源”并按照步骤完成在应用程序中导入3D模型。

编写Cloud Anchors应用程序

我们现在准备使用Sceneform SDK对增强现实应用程序进行编码。创建一个新类并从ArFragment扩展它。然后覆盖getSessionConfiguration（）方法并添加以下代码：

class CloudAnchorFragment : ArFragment() {
    override fun getSessionConfiguration(session: Session?): Config {
        planeDiscoveryController.setInstructionView(null)
        val config: Config = super.getSessionConfiguration(session)
        config.cloudAnchorMode = Config.CloudAnchorMode.ENABLED
        return config
    }
}

使用planeDiscoveryController我们将instructionView设置为null。这将阻止任何教程阻止我们的视图。然后我们启用CloudAnchorsMode。为此，我们获取会话配置并将cloudAnchorsMode设置为Enabled。最后，我们返回自定义配置。

创建布局

我们需要将这个自定义ArFragment添加到Activity的布局文件中。我们还将添加两个额外的按钮。一个用于清除屏幕上的任何对象，另一个用于解析锚点。除此之外，我们将自定义ArFragment覆盖整个屏幕。
将以下代码添加到布局文件中：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <fragment
        android:id="@+id/ar_fragment"
        android:name="com.example.cloudanchors.CloudAnchorFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <Button
            android:id="@+id/btn_clear"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Clear" />
        <Button
            android:id="@+id/btn_resolve"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Resolve" />
    </LinearLayout>


</RelativeLayout>

有了这个，我们已经完成了我们的布局文件。我们准备在屏幕上渲染增强现实场景。

将3D模型添加到场景的方法

如果您已准备好以前的文章，您将知道我们使用2种方法将3D对象添加到增强现实场景中。第一种方法将.obj文件中的3D模型从Sceneform SDK加载到Renderable对象中。另一种方法实际上可以渲染到我们的场景。
因此，请将以下方法添加到MainAcitivity.java文件中

private fun cloudAnchor(newAnchor: Anchor?) {
    cloudAnchor?.detach()
    cloudAnchor = newAnchor
    appAnchorState = AppAnchorState.NONE
    snackbarHelper.hide(this)
}
private fun placeObject(fragment: ArFragment, anchor: Anchor, model: Uri) {
    ModelRenderable.Builder()
        .setSource(fragment.context, model)
        .build()
        .thenAccept { renderable ->
            addNodeToScene(fragment, anchor, renderable)
        }
        .exceptionally {
            val builder = AlertDialog.Builder(this)
            builder.setMessage(it.message).setTitle("Error!")
            val dialog = builder.create()
            dialog.show()
            return@exceptionally null
        }
}
private fun addNodeToScene(fragment: ArFragment, anchor: Anchor, renderable: ModelRenderable) {
    val node = AnchorNode(anchor)
    val transformableNode = TransformableNode(fragment.transformationSystem)
    transformableNode.renderable = renderable
    transformableNode.setParent(node)
    fragment.arSceneView.scene.addChild(node)
    transformableNode.select()
}

托管云锚

我们现在准备好将我们的锚点托管到云端。首先，我们将添加一个侦听器来检测平面上的触摸并将锚点+ 3D模型放置到场景中。

arFragment.setOnTapArPlaneListener { hitResult, plane, _ ->
    if (plane.type != Plane.Type.HORIZONTAL_UPWARD_FACING || appAnchorState != AppAnchorState.NONE) {
        return@setOnTapArPlaneListener
    }
    val anchor = arFragment.arSceneView.session?.hostCloudAnchor(hitResult.createAnchor())


    placeObject(arFragment, cloudAnchor!!, Uri.parse("model.sfb"))
}

该hostCloudAnchors方法开始举办锚定到云的过程。它返回一个状态为TASK_IN_PROGRESS的Anchor。接下来，我们添加一个方法来设置全局锚点以引用托管锚点。它还将锚点的状态设置为NONE。

private fun cloudAnchor(newAnchor: Anchor?) {
    cloudAnchor?.detach()
    cloudAnchor = newAnchor
    appAnchorState = AppAnchorState.NONE
    snackbarHelper.hide(this)
}

为了保持Anchor的状态，我们需要创建一个Enum和一个全局变量来跟踪锚的当前状态。

class MainActivity : AppCompatActivity() {
    lateinit var arFragment: CloudAnchorFragment
    var cloudAnchor: Anchor? = null
    enum class AppAnchorState {
        NONE,
        HOSTING,
        HOSTED,
        RESOLVING,
        RESOLVED
    }
     ...

现在每当我们触摸场景时，我们都会开始主持锚点。因此，我们需要更新当前锚点，以及它的状态。在setOnTapArPlaneListener中添加以下代码

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    arFragment.setOnTapArPlaneListener { hitResult, plane, _ ->
        if (plane.type != Plane.Type.HORIZONTAL_UPWARD_FACING || appAnchorState != AppAnchorState.NONE) {
            return@setOnTapArPlaneListener
        }
        val anchor = arFragment.arSceneView.session?.hostCloudAnchor(hitResult.createAnchor())
        cloudAnchor(anchor)
        appAnchorState = AppAnchorState.HOSTING
        snackbarHelper.showMessage(this, "Hosting anchor")
        placeObject(arFragment, cloudAnchor!!, Uri.parse("model.sfb"))
    }
}

接下来，我们需要定期检查锚是否已成功托管到云端。如果没有，那么我们需要通知用户失败。为此，我们将onUpdateListener添加到场景中。对于每个相机帧，此方法将检查是否托管锚。

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    arFragment = supportFragmentManager.findFragmentById(R.id.ar_fragment) as CloudAnchorFragment
    arFragment.arSceneView.scene.addOnUpdateListener(this::onUpdateFrame)
    
    ....
}
fun onUpdateFrame(frameTime: FrameTime) {
    checkUpdatedAnchor()
}
@Synchronized
private fun checkUpdatedAnchor() {
    if (appAnchorState != AppAnchorState.HOSTING && appAnchorState != AppAnchorState.RESOLVING)
        return
    val cloudState: CloudAnchorState = cloudAnchor?.cloudAnchorState!!
    if (appAnchorState == AppAnchorState.HOSTING) {
        if (cloudState.isError) {
            snackbarHelper.showMessageWithDismiss(this, "Error hosting anchor...")
            appAnchorState = AppAnchorState.NONE
        } else if (cloudState == CloudAnchorState.SUCCESS) {
            val shortCode = storageManager.nextShortCode(this)
            storageManager.storeUsingShortCode(this, shortCode, cloudAnchor?.cloudAnchorId)
            snackbarHelper.showMessageWithDismiss(this, "Anchor hosted: $shortCode")
            appAnchorState = AppAnchorState.HOSTED
        }
    } else if (appAnchorState == AppAnchorState.RESOLVING) {
        if (cloudState.isError) {
            snackbarHelper.showMessageWithDismiss(this, "Error resolving anchor...")
            appAnchorState = AppAnchorState.NONE
        } else if (cloudState == CloudAnchorState.SUCCESS) {
            snackbarHelper.showMessageWithDismiss(this, "Anchor resolved...")
            appAnchorState = AppAnchorState.RESOLVED
        }
    }
}

这种方法可能看起来很长，但唯一的工作就是检查云锚HOSTING / RESOLVING的当前状态，并检查托管是成功还是失败。然后它相应地设置当前状态。
我们使用了一个StorageHelper类来在sharedPreferences中存储锚ID。您可以使用其他存储方法，例如Firebase，FireStore或您的自定义解决方案。但本文的目的是展示如何在云上存储增强现实锚点。因此，对于本地存储，我们将使用共享首选项。

/** Helper class for managing on-device storage of cloud anchor IDs. */
public class StorageManager {
    private static final String NEXT_SHORT_CODE = "next_short_code";
    private static final String KEY_PREFIX = "anchor;";
    private static final int INITIAL_SHORT_CODE = 142;
    /** Gets a new short code that can be used to store the anchor ID. */
    int nextShortCode(Activity activity) {
        SharedPreferences sharedPrefs = activity.getPreferences(Context.MODE_PRIVATE);
        int shortCode = sharedPrefs.getInt(NEXT_SHORT_CODE, INITIAL_SHORT_CODE);
        // Increment and update the value in sharedPrefs, so the next code retrieved will be unused.
        sharedPrefs.edit().putInt(NEXT_SHORT_CODE, shortCode + 1)
                .apply();
        return shortCode;
    }
    /** Stores the cloud anchor ID in the activity's SharedPrefernces. */
    void storeUsingShortCode(Activity activity, int shortCode, String cloudAnchorId) {
        SharedPreferences sharedPrefs = activity.getPreferences(Context.MODE_PRIVATE);
        sharedPrefs.edit().putString(KEY_PREFIX + shortCode, cloudAnchorId).apply();
    }
    /**
     * Retrieves the cloud anchor ID using a short code. Returns an empty string if a cloud anchor ID
     * was not stored for this short code.
     */
    String getCloudAnchorID(Activity activity, int shortCode) {
        SharedPreferences sharedPrefs = activity.getPreferences(Context.MODE_PRIVATE);
        return sharedPrefs.getString(KEY_PREFIX + shortCode, "");
    }
}

解析锚点

我们需要做的最后一件事是解决托管锚点。为此，我们将onClickListeners添加到两个按钮：Clear和Resolve。
对于clear按钮，我们只需调用cloudAnchors方法并将null传递给它。

btn_clear.setOnClickListener {
    cloudAnchor(null)
}

对于解析按钮，我们将在单击时显示一个对话框。它将有一个EditText用于输入锚的短代码。当用户提交短代码时，我们将解析锚并显示对象！
首先，我们需要一个dialogFragment。我为你创造了一个：

public class ResolveDialogFragment extends DialogFragment {
    interface OkListener {
        void onOkPressed(String dialogValue);
    }
    private OkListener okListener;
    private EditText shortCodeField;
    /** Sets a listener that is invoked when the OK button on this dialog is pressed. */
    void setOkListener(OkListener okListener) {
        this.okListener = okListener;
    }
    /**
     * Creates a simple layout for the dialog. This contains a single user-editable text field whose
     * input type is retricted to numbers only, for simplicity.
     */
    private LinearLayout getDialogLayout() {
        Context context = getContext();
        LinearLayout layout = new LinearLayout(context);
        shortCodeField = new EditText(context);
        shortCodeField.setInputType(InputType.TYPE_CLASS_NUMBER);
        shortCodeField.setLayoutParams(
                new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
        shortCodeField.setFilters(new InputFilter[]{new InputFilter.LengthFilter(8)});
        layout.addView(shortCodeField);
        layout.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
        return layout;
    }

 @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder
                .setView(getDialogLayout())
                .setTitle("Resolve Anchor")
                .setPositiveButton(
                        "OK",
                        (dialog, which) -> {
                            Editable shortCodeText = shortCodeField.getText();
                            if (okListener != null && shortCodeText != null && shortCodeText.length() > 0) {
                                // Invoke the callback with the current checked item.
                                okListener.onOkPressed(shortCodeText.toString());
                            }
                        })
                .setNegativeButton("Cancel", (dialog, which) -> {});
        return builder.create();
    }
}

将其添加到项目中，并在用户单击“解析”按钮时调用它，如下所示：

btn_resolve.setOnClickListener {
    if (cloudAnchor != null) {
        snackbarHelper.showMessageWithDismiss(this, "Please clear the anchor")
        return@setOnClickListener
    }
    val dialog = ResolveDialogFragment()
    dialog.setOkListener(this::onResolveOkPressed)
    dialog.show(supportFragmentManager, "Resolve")
}

这是onResolveOkMethod：

fun onResolveOkPressed(dialogVal: String) {
    val shortCode = dialogVal.toInt()
    val cloudAnchorId = storageManager.getCloudAnchorID(this, shortCode)
    val resolvedAnchor = arFragment.arSceneView.session?.resolveCloudAnchor(cloudAnchorId)
    cloudAnchor(resolvedAnchor)
    placeObject(arFragment, cloudAnchor!!, Uri.parse("model.sfb"))
    snackbarHelper.showMessage(this, "Now resolving anchor...")
    appAnchorState = AppAnchorState.RESOLVING
}

它得到了短代码并将对象解析为我们的增强现实场景。

请注意，我们也经常使用SnackBarHelper类。这是谷歌管理Android中零食栏的另一个类别。这是它的链接：SnackbarHelper

我们完成了！

这是您最终的MainActivity.kt类的样子：

class MainActivity : AppCompatActivity() {
    lateinit var arFragment: CloudAnchorFragment
    var cloudAnchor: Anchor? = null
    enum class AppAnchorState {
        NONE,
        HOSTING,
        HOSTED,
        RESOLVING,
        RESOLVED
    }
    var appAnchorState = AppAnchorState.NONE
    var snackbarHelper = SnackbarHelper()
    var storageManager = StorageManager()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        arFragment = supportFragmentManager.findFragmentById(R.id.ar_fragment) as CloudAnchorFragment
        arFragment.arSceneView.scene.addOnUpdateListener(this::onUpdateFrame)
        arFragment.planeDiscoveryController.hide()
        arFragment.planeDiscoveryController.setInstructionView(null)
        btn_clear.setOnClickListener {
            cloudAnchor(null)
        }
        btn_resolve.setOnClickListener {
            if (cloudAnchor != null) {
                snackbarHelper.showMessageWithDismiss(this, "Please clear the anchor")
                return@setOnClickListener
            }
            val dialog = ResolveDialogFragment()
            dialog.setOkListener(this::onResolveOkPressed)
            dialog.show(supportFragmentManager, "Resolve")
        }

 arFragment.setOnTapArPlaneListener { hitResult, plane, _ ->
            if (plane.type != Plane.Type.HORIZONTAL_UPWARD_FACING || appAnchorState != AppAnchorState.NONE) {
                return@setOnTapArPlaneListener
            }
            val anchor = arFragment.arSceneView.session?.hostCloudAnchor(hitResult.createAnchor())
            cloudAnchor(anchor)
            appAnchorState = AppAnchorState.HOSTING
            snackbarHelper.showMessage(this, "Hosting anchor")
            placeObject(arFragment, cloudAnchor!!, Uri.parse("model.sfb"))
        }
    }
    fun onResolveOkPressed(dialogVal: String) {
        val shortCode = dialogVal.toInt()
        val cloudAnchorId = storageManager.getCloudAnchorID(this, shortCode)
        val resolvedAnchor = arFragment.arSceneView.session?.resolveCloudAnchor(cloudAnchorId)
        cloudAnchor(resolvedAnchor)
        placeObject(arFragment, cloudAnchor!!, Uri.parse("model.sfb"))
        snackbarHelper.showMessage(this, "Now resolving anchor...")
        appAnchorState = AppAnchorState.RESOLVING
    }
    fun onUpdateFrame(frameTime: FrameTime) {
        checkUpdatedAnchor()
    }

@Synchronized
    private fun checkUpdatedAnchor() {
        if (appAnchorState != AppAnchorState.HOSTING && appAnchorState != AppAnchorState.RESOLVING)
            return
        val cloudState: CloudAnchorState = cloudAnchor?.cloudAnchorState!!
        if (appAnchorState == AppAnchorState.HOSTING) {
            if (cloudState.isError) {
                snackbarHelper.showMessageWithDismiss(this, "Error hosting anchor...")
                appAnchorState = AppAnchorState.NONE
            } else if (cloudState == CloudAnchorState.SUCCESS) {
                val shortCode = storageManager.nextShortCode(this)
                storageManager.storeUsingShortCode(this, shortCode, cloudAnchor?.cloudAnchorId)
                snackbarHelper.showMessageWithDismiss(this, "Anchor hosted: $shortCode")
                appAnchorState = AppAnchorState.HOSTED
            }
        } else if (appAnchorState == AppAnchorState.RESOLVING) {
            if (cloudState.isError) {
                snackbarHelper.showMessageWithDismiss(this, "Error resolving anchor...")
                appAnchorState = AppAnchorState.NONE
            } else if (cloudState == CloudAnchorState.SUCCESS) {
                snackbarHelper.showMessageWithDismiss(this, "Anchor resolved...")
                appAnchorState = AppAnchorState.RESOLVED
            }
        }
    }
private fun cloudAnchor(newAnchor: Anchor?) {
        cloudAnchor?.detach()
        cloudAnchor = newAnchor
        appAnchorState = AppAnchorState.NONE
        snackbarHelper.hide(this)
    }
    private fun placeObject(fragment: ArFragment, anchor: Anchor, model: Uri) {
        ModelRenderable.Builder()
            .setSource(fragment.context, model)
            .build()
            .thenAccept { renderable ->
                addNodeToScene(fragment, anchor, renderable)
            }
            .exceptionally {
                val builder = AlertDialog.Builder(this)
                builder.setMessage(it.message).setTitle("Error!")
                val dialog = builder.create()
                dialog.show()
                return@exceptionally null
            }
    }
    private fun addNodeToScene(fragment: ArFragment, anchor: Anchor, renderable: ModelRenderable) {
        val node = AnchorNode(anchor)
        val transformableNode = TransformableNode(fragment.transformationSystem)
        transformableNode.renderable = renderable
        transformableNode.setParent(node)
        fragment.arSceneView.scene.addChild(node)
        transformableNode.select()
    }
}

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