com.google.plus.samples.photohunt.tasks.FetchJsonTaskLoader.java Source code

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Here is the source code for com.google.plus.samples.photohunt.tasks.FetchJsonTaskLoader.java

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/*
 * Copyright (C) 2012 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.plus.samples.photohunt.tasks;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.Type;
import java.net.HttpURLConnection;
import java.net.URL;

import android.content.Context;
import android.support.v4.content.AsyncTaskLoader;
import android.text.TextUtils;
import android.util.Log;

import com.google.gson.Gson;
import com.google.plus.samples.photohunt.HttpUtils;
import com.google.plus.samples.photohunt.auth.AuthUtil;

/**
 * Loads photos from the photohunt backend.
 */
public class FetchJsonTaskLoader<T> extends AsyncTaskLoader<T> {

    private static final String TAG = FetchJsonTaskLoader.class.getSimpleName();

    private final String mUrl;
    private T mResult;

    protected Type mReturnType;

    protected Exception mException;

    public FetchJsonTaskLoader(Context context, String url) {
        super(context);
        mUrl = url;
    }

    public FetchJsonTaskLoader(Context context, String url, Type returnType) {
        this(context, url);

        mReturnType = returnType;
    }

    @Override
    protected void onStartLoading() {
        super.onStartLoading();

        if (mResult != null) {
            deliverResult(mResult);
        } else if (!TextUtils.isEmpty(mUrl)) {
            forceLoad();
        } else {
            deliverResult(null);
        }
    }

    @Override
    protected void onStopLoading() {
        cancelLoad();
    }

    @Override
    public T loadInBackground() {
        T result = null;

        try {
            result = fetchData();
        } catch (Exception e) {
            if (!isReset()) {
                mException = e;
            }
        }

        return result;
    }

    protected T fetchData() throws IOException {
        HttpURLConnection urlConnection = null;

        try {
            URL url = new URL(mUrl);

            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setUseCaches(true);
            urlConnection.setRequestMethod("GET");

            AuthUtil.setAuthHeaders(urlConnection);

            return onPostFetch(HttpUtils.getContent(urlConnection.getInputStream()));
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
    }

    @SuppressWarnings("unchecked")
    protected T onPostFetch(ByteArrayOutputStream content) throws IOException {
        try {
            String response = new String(content.toByteArray(), "UTF-8");
            Log.v(TAG, "Fetched " + mUrl + ": " + response);
            if (!TextUtils.isEmpty(response) && mReturnType != null) {
                return (T) new Gson().fromJson(response, mReturnType);
            }
        } catch (Exception jsonException) {
            Log.e(TAG, "Unable to parse the json response from: " + mUrl, jsonException);
            mException = jsonException;
        }

        return null;
    }

    public String getUrl() {
        return mUrl;
    }
}