Java 无法将图像保存到SD卡
我尝试下载带有此代码的图像并保存它: 在这方面:Java 无法将图像保存到SD卡,java,android,Java,Android,我尝试下载带有此代码的图像并保存它: 在这方面: OutputStream os =new FileOutputStream(f); 我在emulator上进行了尝试。我的应用程序出现异常,没有保存到此路径的权限: java.io.FileNotFoundException: /mnt/sdcard/InterFlora/1221618532: open failed: EACCES (Permission denied) 我还要加上这一行: <uses-permission andr
OutputStream os =new FileOutputStream(f);
我在emulator上进行了尝试。我的应用程序出现异常,没有保存到此路径的权限:
java.io.FileNotFoundException: /mnt/sdcard/InterFlora/1221618532: open failed: EACCES (Permission denied)
我还要加上这一行:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
试试这个方法。。
导入java.io.BufferedInputStream;
导入java.io.File;
导入java.io.FileOutputStream;
导入java.io.InputStream;
导入java.io.OutputStream;
导入java.net.URL;
导入java.net.URLConnection;
导入android.app.Activity;
导入android.app.Dialog;
导入android.app.ProgressDialog;
导入android.content.Context;
导入android.content.Intent;
导入android.net.Uri;
导入android.os.AsyncTask;
导入android.os.Bundle;
导入android.util.Log;
导入android.view.view;
导入android.view.view.OnClickListener;
导入android.widget.Button;
公共类主要扩展活动{
/**在首次创建活动时调用*/
公共静态最终整型对话框\u下载\u进度=0;
专用按钮startBtn;
private ProgressDialog mProgressDialog;
/**在首次创建活动时调用*/
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
startBtn=(按钮)findViewById(R.id.startBtn);
setOnClickListener(新的OnClickListener(){
公共void onClick(视图v){
startDownload();
}
});
}
私有void startDownload(){
字符串url=”http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";
新建DownloadFileAsync().execute(url);
}
@凌驾
受保护的对话框onCreateDialog(int id){
开关(id){
案例对话框\u下载\u进度:
mProgressDialog=新建进度对话框(此);
设置消息(“下载文件…”);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_水平);
mProgressDialog.setCancelable(假);
mProgressDialog.show();
返回mProgressDialog;
违约:
返回null;
}
}
类DownloadFileAsync扩展AsyncTask{
@凌驾
受保护的void onPreExecute(){
super.onPreExecute();
showDialog(对话框下载进度);
}
@凌驾
受保护的字符串背景(字符串…aurl){
整数计数;
试一试{
URL=新URL(aurl[0]);
URLConnection conexion=url.openConnection();
conexion.connect();
int lenghtOfFile=conexion.getContentLength();
Log.d(“ANDRO_ASYNC”,“文件长度:“+lenghtOfFile”);
FileOutputStream对象;
InputStream输入=新的BufferedInputStream(url.openStream());
//obj=openFileOutput(“来自波兰格但斯克的一些照片”,Context.MODE\u PRIVATE);
字符串路径=“/sdcard/”;/“/data/data/com.server/”;
OutputStream output=新文件OutputStream(路径+“some_photo_from_gdansk_poland.jpg”);//obj
字节数据[]=新字节[1024];
长总计=0;
而((计数=输入。读取(数据))!=-1){
总数+=计数;
出版进度(“+(int)((总计*100)/长度文档));
输出.写入(数据,0,计数);
}
output.flush();
output.close();
input.close();
}捕获(例外e){}
返回null;
}
受保护的void onProgressUpdate(字符串…进度){
Log.d(“ANDRO_ASYNC”,progress[0]);
mProgressDialog.setProgress(Integer.parseInt(progress[0]));
}
@凌驾
受保护的void onPostExecute(字符串未使用){
dismissDialog(对话框下载进度);
}
}
}
并添加android.permission.WRITE\u外部存储
您检测外部存储位置的方法比Munish Kapoor的答案要好,因为/sdcard并不总是正确的文件夹路径
但之后,您确定/myfolder作为文件夹存在吗。您应该创建一个指向该位置的文件,并对其调用mkdirs来创建它
然后,将文件保存在内部。尝试此操作以获取文件夹(如果不存在,则创建该文件夹),然后使用f file变量,就像在代码中所做的那样:
File cacheDirectory;
if ( android.os.Environment.getExternalStorageState().equals( android.os.Environment.MEDIA_MOUNTED ))
cacheDirectory = new File( android.os.Environment.getExternalStorageDirectory(), "myFolder/" );
else
cacheDirectory = this.getCacheDir();
if( !cacheDirectory.exists() )
cacheDirectory.mkdirs();
File f = new File( cacheDirectory, "my_file.jpg" );
阅读getCacheDir()
的链接:
将此行添加到manifest.xml成功
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
您应该将android.permission.WRITE\u EXTERNAL\u STORAGE权限添加到清单文件中显示您的清单以及添加此行的位置我认为您应该首先创建包含目录我按照我在帖子中所说的创建它,也许在模拟器中是不同的?顺便问一下,mkdirs返回什么?我只是检查了一下,然后在exist检查后创建了dir,然后再次尝试此代码exist检查告诉您dir不再存在您可能在android上弄乱了linux文件系统。这种情况有时会发生。取出卡,删除文件夹/mnt/sdcard,然后重新启动,将卡放回原处。您应该会看到SD卡的内容,然后重试代码。我在这里收到空指针错误:android.os.Environment.getExternalStorageDirectory()。。知道它为什么会来吗?如何解决这个问题?确认这一点以及阅读许可对我来说很有效
Try this works..
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class main extends Activity {
/** Called when the activity is first created. */
public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
private Button startBtn;
private ProgressDialog mProgressDialog;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
startBtn = (Button)findViewById(R.id.startBtn);
startBtn.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
startDownload();
}
});
}
private void startDownload() {
String url = "http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";
new DownloadFileAsync().execute(url);
}
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DIALOG_DOWNLOAD_PROGRESS:
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setMessage("Downloading file..");
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(false);
mProgressDialog.show();
return mProgressDialog;
default:
return null;
}
}
class DownloadFileAsync extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
showDialog(DIALOG_DOWNLOAD_PROGRESS);
}
@Override
protected String doInBackground(String... aurl) {
int count;
try {
URL url = new URL(aurl[0]);
URLConnection conexion = url.openConnection();
conexion.connect();
int lenghtOfFile = conexion.getContentLength();
Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);
FileOutputStream obj;
InputStream input = new BufferedInputStream(url.openStream());
//obj=openFileOutput("some_photo_from_gdansk_poland.jpg", Context.MODE_PRIVATE);
String Path="/sdcard/";//"/data/data/com.server/";
OutputStream output = new FileOutputStream(Path+"some_photo_from_gdansk_poland.jpg");//obj
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
publishProgress(""+(int)((total*100)/lenghtOfFile));
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
} catch (Exception e) {}
return null;
}
protected void onProgressUpdate(String... progress) {
Log.d("ANDRO_ASYNC",progress[0]);
mProgressDialog.setProgress(Integer.parseInt(progress[0]));
}
@Override
protected void onPostExecute(String unused) {
dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
}
}
}
and add android.permission.WRITE_EXTERNAL_STORAGE
File cacheDirectory;
if ( android.os.Environment.getExternalStorageState().equals( android.os.Environment.MEDIA_MOUNTED ))
cacheDirectory = new File( android.os.Environment.getExternalStorageDirectory(), "myFolder/" );
else
cacheDirectory = this.getCacheDir();
if( !cacheDirectory.exists() )
cacheDirectory.mkdirs();
File f = new File( cacheDirectory, "my_file.jpg" );
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />