如何使用android在phonegap 2.9中检查文件是否存在？

Question

我使用此代码从服务器下载歌曲：

JavaScript File

var fileTransfer = new FileTransfer();
var uri = encodeURI("http://www.abcdefg.it/uploads/"+sound);
var filePath = "/sdcard/download/"+sound;

fileTransfer.download(
    uri,
    filePath,
    function(entry) {
        console.log("download complete: " + entry.fullPath);
    },
    function(error) {

        alert(JSON.stringify(error));

        console.log("download error source " + error.source);
        console.log("download error target " + error.target);
        console.log("upload error code" + error.code);
    },
    false,
    {
        headers: {
            "Authorization": "Basic dGVzdHVzZXJuYW1lOnRlc3RwYXNzd29yZA=="
        }
    }
);

Problem

如果 File Exist 在 sdcard 上设置条件，然后 不下载

如果 not Exist 则 下载

Note

请注意，我使用的是 Phonegap 2.9.0

Request

如果您有任何想法/解决方案，请分享。 谢谢。

Answer 1

使用这个插件：

Java 插件：

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

import org.apache.cordova.api.CallbackContext;
import org.apache.cordova.api.CordovaPlugin;
import org.apache.cordova.api.PluginResult;

public class Downloader extends CordovaPlugin {

    public boolean execute(String action, JSONArray args,
            CallbackContext callbackContext) {

        if (!action.equals("downloadFile")) {
            callbackContext.sendPluginResult(new PluginResult(
                    PluginResult.Status.INVALID_ACTION));
            return true;
        }
        try {

            String fileUrl = args.getString(0);
            String fileName = args.getString(2);
            String dirName = args.getString(1);
            String overwrite = args.getString(3);


            callbackContext.sendPluginResult(this.downloadUrl(fileUrl, dirName,
                    fileName, overwrite, callbackContext));
            return true;

        } catch (JSONException e) {

            e.printStackTrace();
            callbackContext.sendPluginResult(new PluginResult(
                    PluginResult.Status.JSON_EXCEPTION, e.getMessage()));
            return false;

        } catch (InterruptedException e) {
            e.printStackTrace();
            callbackContext.sendPluginResult(new PluginResult(
                    PluginResult.Status.ERROR, e.getMessage()));
            return false;
        }

    }

    private PluginResult downloadUrl(String fileUrl, String dirName,
            String fileName, String overwrite, CallbackContext callbackContext)
            throws InterruptedException, JSONException {

        try {

            Log.d("PhoneGapLog", "Downloading " + fileUrl + " into " + dirName
                    + "/" + fileName);

            File dir = new File(dirName);
            if (!dir.exists()) {
                Log.d("PhoneGapLog", "directory " + dirName + " created");
                dir.mkdirs();
            }

            File file = new File(dirName, fileName);

            if (overwrite.equals("false") && file.exists()) {
                Log.d("DownloaderPlugin", "File already exist");

                JSONObject obj = new JSONObject();
                obj.put("status", 1);
                obj.put("total", 0);
                obj.put("file", fileName);
                obj.put("dir", dirName);
                obj.put("progress", 100);

                return new PluginResult(PluginResult.Status.OK, obj);
            }

            URL url = new URL(fileUrl);
            HttpURLConnection ucon = (HttpURLConnection) url.openConnection();
            ucon.setRequestMethod("GET");
            ucon.connect();

            Log.d("PhoneGapLog", "Download start");

            InputStream is = ucon.getInputStream();
            byte[] buffer = new byte[1024];
            int readed = 0, progress = 0,
            // totalReaded = 0,
            fileSize = ucon.getContentLength();

            FileOutputStream fos = new FileOutputStream(file);

            while ((readed = is.read(buffer)) > 0) {

                fos.write(buffer, 0, readed);
                // totalReaded += readed;

                // int newProgress = (int) (totalReaded*100/fileSize);
                // if (newProgress != progress)
                // progress = informProgress(fileSize, newProgress, dirName,
                // fileName, callbackId);

            }

            fos.close();

            Log.d("PhoneGapLog", "Download finished");

            JSONObject obj = new JSONObject();
            obj.put("status", 1);
            obj.put("total", fileSize);
            obj.put("file", fileName);
            obj.put("dir", dirName);
            obj.put("progress", progress);

            return new PluginResult(PluginResult.Status.OK, obj);

        } catch (FileNotFoundException e) {
            Log.d("PhoneGapLog", "File Not Found: " + e);
            return new PluginResult(PluginResult.Status.ERROR, 404);
        } catch (IOException e) {
            Log.d("PhoneGapLog", "Error: " + e);
            return new PluginResult(PluginResult.Status.ERROR, e.getMessage());
        }
    }
}

js 插件：

cordova.define("cordova/plugin/downloader",
  function(require, exports, module) {
    var exec = require("cordova/exec");
    var Downloader = function () {};

Downloader.prototype.downloadFile = function(fileUrl, dirName, fileName, overwrite, win, fail) {    
    if (overwrite == false)
        overwrite = "false";
    else
        overwrite = "true";
    exec(win, fail, "Downloader", "downloadFile", [ fileUrl, dirName, fileName, overwrite ]);

};
var downloader = new Downloader();
    module.exports = downloader;

});
if (!window.plugins) {
    window.plugins = {};
}
if (!window.plugins.downloader) {
    window.plugins.downloader = cordova.require("cordova/plugin/downloader");
}

像这样使用它：

function downloadFile(fileUrl, dirName, fileName, overwrite) {
    window.plugins.downloader.downloadFile(
        fileUrl, 
        {overwrite : true}, 
        function(res) {
            alert(JSON.stringify(result));
        }, 
        function(error) {
            alert(error);
        }
    );
    window.plugins.downloader.downloadFile(fileUrl, dirName, fileName,overwrite);
    window.plugins.fileOpener.open("file://" + dirName + fileName);
}