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BarcodeGraphicTracker.java

/*
 * Copyright (C) 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 com.google.android.gms.samples.vision.barcodereader;

import android.content.Context;
import android.support.annotation.UiThread;

import com.google.android.gms.samples.vision.barcodereader.ui.camera.GraphicOverlay;
import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.Tracker;
import com.google.android.gms.vision.barcode.Barcode;

/**
 * Generic tracker which is used for tracking or reading a barcode (and can really be used for
 * any type of item).  This is used to receive newly detected items, add a graphical representation
 * to an overlay, update the graphics as the item changes, and remove the graphics when the item
 * goes away.
 */
public class BarcodeGraphicTracker extends Tracker<Barcode> {
    private GraphicOverlay<BarcodeGraphic> mOverlay;
    private BarcodeGraphic mGraphic;

private BarcodeUpdateListener mBarcodeUpdateListener;

/**
     * Consume the item instance detected from an Activity or Fragment level by implementing the
     * BarcodeUpdateListener interface method onBarcodeDetected.
     */
    public interface BarcodeUpdateListener {
        @UiThread
        void onBarcodeDetected(Barcode barcode);
    }

BarcodeGraphicTracker(GraphicOverlay<BarcodeGraphic> mOverlay, BarcodeGraphic mGraphic,
                          Context context) {
        this.mOverlay = mOverlay;
        this.mGraphic = mGraphic;
        if (context instanceof BarcodeUpdateListener) {
            this.mBarcodeUpdateListener = (BarcodeUpdateListener) context;
        } else {
            throw new RuntimeException("Hosting activity must implement BarcodeUpdateListener");
        }
    }

/**
     * Start tracking the detected item instance within the item overlay.
     */
    @Override
    public void onNewItem(int id, Barcode item) {
        mGraphic.setId(id);
        mBarcodeUpdateListener.onBarcodeDetected(item);
    }

/**
     * Update the position/characteristics of the item within the overlay.
     */
    @Override
    public void onUpdate(Detector.Detections<Barcode> detectionResults, Barcode item) {
        mOverlay.add(mGraphic);
        mGraphic.updateItem(item);
    }

/**
     * Hide the graphic when the corresponding object was not detected.  This can happen for
     * intermediate frames temporarily, for example if the object was momentarily blocked from
     * view.
     */
    @Override
    public void onMissing(Detector.Detections<Barcode> detectionResults) {
        mOverlay.remove(mGraphic);
    }

/**
     * Called when the item is assumed to be gone for good. Remove the graphic annotation from
     * the overlay.
     */
    @Override
    public void onDone() {
        mOverlay.remove(mGraphic);
    }
}