Volleyを無理矢理file schemeに対応してみる

NetworkImageView#setImageUrl(String, ImageLoader)はfileスキームに未対応なので扱えるように改造してみました

BasicNetwork#performRequest()メソッドをOverrideしてfile schemeの場合はFileInputStream経由でデータを取得するようにしたらあっさりできました。

CustomNetwork.java

package com.example.volleysample;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Collections;

import org.apache.http.HttpStatus;

import android.net.Uri;
import android.util.Log;

import com.android.volley.NetworkError;
import com.android.volley.NetworkResponse;
import com.android.volley.Request;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.BasicNetwork;
import com.android.volley.toolbox.ByteArrayPool;
import com.android.volley.toolbox.HttpStack;
import com.example.volleysample.BuildConfig;

public class CustomNetwork extends BasicNetwork {
    private static final String TAG = CustomNetwork.class.getSimpleName();

    public CustomNetwork(HttpStack stack) {
        super(stack);
    }

    public CustomNetwork(HttpStack stack, ByteArrayPool pool) {
        super(stack, pool);
    }

    @Override
    public NetworkResponse performRequest(Request<?> request)
            throws VolleyError {
        // file schemeの場合は自前で処理
        Uri uri = Uri.parse(request.getUrl());
        if (uri != null && "file".equals(uri.getScheme())) {
            return performFileRequest(uri);
        }

        // file scheme以外の処理は親クラスに丸投げ
        return super.performRequest(request);
    }

    private NetworkResponse performFileRequest(Uri uri) throws VolleyError {
        File file = new File(uri.getPath());
        NetworkResponse response;
        if (file.exists()) {
            byte[] data = readBytes(file);
            response = new NetworkResponse(data);
        } else {
            // 404エラーを返す
            if (BuildConfig.DEBUG)
                Log.w(TAG, "performFileRequest: file not found: " + file);
            response = new NetworkResponse(HttpStatus.SC_NOT_FOUND, null,
                    Collections.<String, String> emptyMap(), false);
        }
        return response;
    }

    private byte[] readBytes(File file) throws VolleyError {
        if (BuildConfig.DEBUG) Log.d(TAG, "readBytes: reading data from " + file);
        byte[] data = null;
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            InputStream in = null;
            try {
                in = new FileInputStream(file);
                byte[] buf = new byte[1024];
                int len = 0;
                while ((len = in.read(buf, 0, buf.length)) >= 0) {
                    out.write(buf, 0, len);
                }
                data = out.toByteArray();
                if (BuildConfig.DEBUG) Log.d(TAG, "readBytes: read " + data.length + " bytes.");
            } finally {
                if (in != null) in.close();
                if (out != null) out.close();
            }
        } catch (IOException e) {
            if (BuildConfig.DEBUG) Log.w(TAG, "readBytes: failed to read data", e);
            throw new NetworkError(e);
        }
        return data;
    }
}

実際に使う場合にはRequestQueueのコンストラクターにCustomNetworkのインスタンスを渡します。

    public static RequestQueue createRequestQueue(Context context, HttpStack stack, int maxCacheSizeInBytes) {
        File cacheDir = new File(context.getCacheDir(), DEFAULT_CACHE_DIR);

        String userAgent = "volley/0";
        try {
            String packageName = context.getPackageName();

            PackageInfo info = context.getPackageManager().getPackageInfo(packageName, 0);
            userAgent = packageName + "/" + info.versionCode;
        } catch (NameNotFoundException e) {
        }

        if (stack == null) {
            if (Build.VERSION.SDK_INT >= 9) {
                stack = new HurlStack();
            } else {
                // Prior to Gingerbread, HttpUrlConnection was unreliable.
                // See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
                stack = new HttpClientStack(AndroidHttpClient.newInstance(userAgent));
            }
        }

//        Network network = new BasicNetwork(stack);
        Network network = new CustomNetwork(stack); // ここだけ修正

        RequestQueue queue = new RequestQueue(new DiskBasedCache(cacheDir, maxCacheSizeInBytes), network);
        queue.start();

        return queue;
    }