要从ModelRenderable列表中选择不同的3D对象，你可以使用以下代码示例：

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import androidx.appcompat.app.AppCompatActivity;
import com.google.ar.core.Anchor;
import com.google.ar.core.HitResult;
import com.google.ar.core.Plane;
import com.google.ar.core.Trackable;
import com.google.ar.sceneform.AnchorNode;
import com.google.ar.sceneform.rendering.ModelRenderable;
import com.google.ar.sceneform.ux.ArFragment;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ArFragment arFragment;
    private List modelRenderables;
    private int currentModelIndex = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        arFragment = (ArFragment) getSupportFragmentManager().findFragmentById(R.id.arFragment);

        modelRenderables = new ArrayList<>();
        modelRenderables.add(getModelRenderable("model1.sfb")); // Add your model filenames here
        modelRenderables.add(getModelRenderable("model2.sfb"));
        modelRenderables.add(getModelRenderable("model3.sfb"));

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                addObjectToScene();
            }
        });
    }

    private void addObjectToScene() {
        if (arFragment.getArSceneView().getArFrame() != null) {
            // Get the center of the screen
            float screenCenterX = arFragment.getArSceneView().getWidth() / 2f;
            float screenCenterY = arFragment.getArSceneView().getHeight() / 2f;

            // Perform a hit test at the center of the screen to check if a plane or feature point was hit
            List hitTest = arFragment.getArSceneView().getArFrame().hitTest(screenCenterX, screenCenterY);
            for (HitResult hit : hitTest) {
                Trackable trackable = hit.getTrackable();
                if (trackable instanceof Plane && ((Plane) trackable).isPoseInPolygon(hit.getHitPose())) {
                    // Create an anchor at the hit location
                    Anchor anchor = hit.createAnchor();
                    AnchorNode anchorNode = new AnchorNode(anchor);
                    anchorNode.setParent(arFragment.getArSceneView().getScene());

                    // Create a new instance of the selected model renderable and attach it to the anchor node
                    ModelRenderable selectedModel = modelRenderables.get(currentModelIndex);
                    currentModelIndex = (currentModelIndex + 1) % modelRenderables.size();
                    selectedModel.setShadowCaster(false);
                    selectedModel.setShadowReceiver(false);
                    anchorNode.setRenderable(selectedModel);
                    break;
                }
            }
        }
    }

    private ModelRenderable getModelRenderable(String filename) {
        ModelRenderable.builder()
                .setSource(this, Uri.parse(filename))
                .build()
                .thenAccept(renderable -> modelRenderables.add(renderable))
                .exceptionally(throwable -> {
                    // Handle loading error
                    return null;
                });
    }
}

在您的布局文件（activity_main.xml）中，添加一个Button和ArFragment：

请确保在AndroidManifest.xml文件中添加ArFragment的相关权限和配置。

这个示例代码会在AR场景中添加一个按钮，点击按钮时会在屏幕中心的平面上添加一个3D对象。每次点击按钮，会切换到不同的3D对象。您需要将3D模型文件（例如model1.sfb）放置在您的项目资源文件夹中，并在getModelRenderable方法中引用正确的文件名。

希望这个示例能帮助到你！