我想从服务器下载图像并保存到模拟器中的SD卡中。
首先，我必须获取JSON String图像并传递下载服务器URL以供下载并保存到SD卡中。
我在运行时遇到NullPointerException错误。
请有人帮助我。
这是我的代码
public void getAllImagePath_List() {
String strUrl_GetAll_Activity = "http://xxx/xxx/xxx.svc/xxx/xx/"+str_UserId+"/xx/"+xxx+"/xxx/"+xxx;
Log.e("strUrl_GetAll_Activity ", " = " + strUrl_GetAll_Activity);
InputStream inputStream = null;
try {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse httpResponse = httpclient.execute(new HttpGet(strUrl_GetAll_Activity));
inputStream = httpResponse.getEntity().getContent();
if (inputStream != null)
strResult = convertInputStreamToString(inputStream);
else
strResult = "Did not work!";
String jsonStr = strResult;
try {
JSONObject jsonObj = new JSONObject(jsonStr);
String jsonResult = jsonObj.toString().trim();
Log.e("jsonResult ", " = " + jsonResult);
JSONObject getAllActivity_List = jsonObj.getJSONObject("Get_ALL_ActivityListResult");
Log.e("getAllActivity_List ", " = " + getAllActivity_List.toString());
String strSync = getAllActivity_List.getString("Sync_Time");
Log.e("strSync ", " = " + strSync.toString());
JSONArray jarr = getAllActivity_List.getJSONArray("ActivityObjectList");
Log.e("jarr ", " = " + jarr.toString());
SQLiteDatabase mDb = dbhelper.getWritableDatabase();
int imageNum = 0;
BufferedOutputStream bos;
imagesArray = new String[jarr.length()];
for (int j = 0; j < jarr.length(); j++)
{
JSONObject jobjVessels = jarr.getJSONObject(j);
str_imgList_imageaudioPath = jobjVessels.getString("imageaudioPath");
Log.e("", "" + str_imgList_imageaudioPath);
String str_ImageUrl = "http://xxx/xxx/xxx.svc/DownloadFile/FileName/"+str_imgList_imageaudioPath;
downloadUrl(str_ImageUrl);
Log.e("Downloaded Completed","!!!!!");
}
}
catch (JSONException je)
{
je.printStackTrace();
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
private Bitmap downloadUrl(String strUrl) throws IOException{
Bitmap bitmap=null;
InputStream iStream = null;
try{
URL url = new URL(strUrl);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.connect();
iStream = urlConnection.getInputStream();
bitmap = BitmapFactory.decodeStream(iStream);
Log.e("bitmap while url", "downloading " + bitmap.toString());
saveBitmap(bitmap);
}catch(Exception e){
Log.e("Exception while url", "downloading " + e.toString());
}finally{
iStream.close();
}
return bitmap;
}
void saveImage(Bitmap bmp) {
File filename;
try {
String path = Environment.getExternalStorageDirectory().toString();
Log.i("in save()", "after mkdir");
new File(path + "jsonObj_Images").mkdirs();
filename = new File(path + "jsonObj_Images");
Log.i("in save()", "after file");
FileOutputStream out = new FileOutputStream(filename);
Log.i("in save()", "after outputstream");
bmp.compress(Bitmap.CompressFormat.JPEG, 90, out);
Log.e("bmp "," = "+bmp);
out.flush();
out.close();
Log.i("in save()", "after outputstream closed");
MediaStore.Images.Media.insertImage(getContentResolver(),
filename.getAbsolutePath(), filename.getName(),
filename.getName());
//bt.setText("Saved...");
Toast.makeText(getApplicationContext(),
"File is Saved in " + filename, Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}
这是我的Logcat错误
08-04 12:28:06.424 4350-4402/? E/Downloaded Completed﹕ !!!!!
08-04 12:28:06.424 4350-4402/? E/﹕ 3_20150623145579002.png
08-04 12:28:06.704 4350-4402/? E/im connected﹕ Download
08-04 12:28:07.215 4350-4402/? I/in save()﹕ after mkdir
08-04 12:28:07.225 4350-4402/? I/in save()﹕ after file
08-04 12:28:07.254 4350-4402/? W/System.err﹕ java.io.FileNotFoundException: /mnt/sdcard/mvc/jsonObj_Images: open failed: EACCES (Permission denied)
08-04 12:28:07.284 4350-4402/? W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:416)
08-04 12:28:07.295 4350-4402/? W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
08-04 12:28:07.314 4350-4354/? D/dalvikvm﹕ GC_CONCURRENT freed 1276K, 73% free 6523K/23608K, paused 4ms+9ms, total 84ms
08-04 12:28:07.314 4350-4402/? W/System.err﹕ at java.io.FileOutputStream.<init>(FileOutputStream.java:73)
08-04 12:28:07.314 4350-4402/? W/System.err﹕ at com.example.tazeen.classnkk.AllPosts_Page.saveImage(AllPosts_Page.java:287)
08-04 12:28:07.314 4350-4402/? W/System.err﹕ at com.example.tazeen.classnkk.AllPosts_Page.downloadFile(AllPosts_Page.java:270)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at com.example.tazeen.classnkk.AllPosts_Page.getAllImagePath_List(AllPosts_Page.java:236)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at com.example.tazeen.classnkk.AllPosts_Page$GetImageDetails.doInBackground(AllPosts_Page.java:173)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at com.example.tazeen.classnkk.AllPosts_Page$GetImageDetails.doInBackground(AllPosts_Page.java:156)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at android.os.AsyncTask$2.call(AsyncTask.java:287)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at java.util.concurrent.FutureTask.run(FutureTask.java:234)
08-04 12:28:07.324 4350-4402/? W/System.err﹕ at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
08-04 12:28:07.334 4350-4402/? W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
08-04 12:28:07.334 4350-4402/? W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
08-04 12:28:07.334 4350-4402/? W/System.err﹕ at java.lang.Thread.run(Thread.java:856)
08-04 12:28:07.334 4350-4402/? W/System.err﹕ Caused by: libcore.io.ErrnoException: open failed: EACCES (Permission denied)
08-04 12:28:07.344 4350-4402/? W/System.err﹕ at libcore.io.Posix.open(Native Method)
08-04 12:28:07.344 4350-4402/? W/System.err﹕ at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
08-04 12:28:07.344 4350-4402/? W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:400)
提前致谢。
答案 0 :(得分：0)
您不应该使用JSON下载图像，我建议您使用以下代码。你必须发送相应的网址。为了我的工作正常，您收到图像并将其保存在Bitmap类型的变量中。然后你必须将它保存到你的SD。我建议你使用一个独特的文件夹，用mkdirs函数以编程方式创建它。问候
好！！
class GetFromServer extends AsyncTask<String, Void, Bitmap>
{
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(FotoEmergenteControlador.this);
pDialog.setMessage("Por Favor, Espere...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Bitmap doInBackground(String... params) {
String httpAdress = params[0];
Bitmap imagenObtenida=null;
try {
URL ImgUrl = new URL(httpAdress);
HttpURLConnection conn = (HttpURLConnection) ImgUrl.openConnection();
conn.connect();
imagenObtenida = BitmapFactory.decodeStream(conn.getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
return imagenObtenida;
}
@Override
protected void onPostExecute(Bitmap result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
pDialog.dismiss();
contentImage.setImageBitmap(result);
}
}
答案 1 :(得分：0)
不要忘记在AndroidManifest.xml上声明正确的权限！
在您的情况下，您需要android.permission.WRITE_EXTERNAL_STORAGE。类似的东西：
<manifest>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application>
<!-- ... -->
</application>
</manifest>
然后，检查外部存储器是否已安装。
/* Checks if external storage is available for read and write */
public boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
return false;
}
另外，更改这些行
String path = Environment.getExternalStorageDirectory().toString();
// ...
new File(path + "jsonObj_Images").mkdirs();
filename = new File(path + "jsonObj_Images");
到
String folderName = "jsonObj_Images";
String fileName = "YourFile.jpg";
String path = Environment.getExternalStorageDirectory().getAbsolutePath();
File root = new File(path + File.separator + folderName);
if (!root.mkdirs()) {
Log.w("TAG","Folder not created!");
}
File file = new File (root,fileName);
// ...
FileOutputStream out = new FileOutputStream(file);
Log.i("in save()", "after outputstream");
bmp.compress(Bitmap.CompressFormat.JPEG, 90, out);
Log.e("bmp "," = "+bmp);
out.flush();
out.close();