我想通过提供ftp的主机名来访问位于FTP服务器上的文件夹中的文件，并将其显示在我使用android studio开发的应用程序中。它应该是动态的，也就是说它应该反映在我给出特定URL的文件夹内完成的所有更改，即如果删除或插入某些内容，它应该反映在应用程序中。我无法连接到FTP服务器，我的应用程序崩溃。以下是我的应用程序的代码。请查看代码并帮助我。 感谢。
这是我的MainActivity.java:-
package com.example.nishant.ftp1;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import org.apache.commons.net.PrintCommandListener;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPConnectionClosedException;
import org.apache.commons.net.ftp.FTPReply;
import org.apache.commons.net.ftp.FTPSClient;
import java.io.IOException;
import java.io.PrintWriter;
import org.apache.commons.net.ftp.FTPClient;
import java.io.InputStream;
import java.net.SocketException;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FTPClient ftpClient = new FTPClient();
try {
ftpClient.connect("ftp.drivehq.com");
ftpClient.enterLocalPassiveMode();
Log.v("ttt", "connected");
ftpClient.setFileType(FTPClient.ASCII_FILE_TYPE);
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, "done", Toast.LENGTH_SHORT).show();
}
});
ftpClient.disconnect();
/*Workbook wb = Workbook.getWorkbook(inStream);
Sheet s = wb.getSheet(0);
int row = s.getRows();
int col = s.getColumns();
for (int i = 0; i < row; i++) {
for(int c = 0, c< col; c++){
Cell z = s.getCell(c, i);
String content = z.getContents();
}
}*/
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
logcat错误：
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 E/Zygote: MountEmulatedStorage()
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 E/Zygote: v2
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 I/SELinux: Function: selinux_compare_spd_ram , priority [2] , priority version is VE=SEPF_SAMSUNG-SGH-I337_5.0.1-1_0039
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 E/SELinux: [DEBUG] get_category: variable seinfo: default sensitivity: NULL, cateogry: NULL
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 I/art: Late-enabling -Xcheck:jni
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 I/libpersona: KNOX_SDCARD checking this for 10240
01-24 12:45:09.643 7023-7023/com.example.nishant.ftp1 I/libpersona: KNOX_SDCARD not a persona
01-24 12:45:09.773 7023-7023/com.example.nishant.ftp1 D/ResourcesManager: creating new AssetManager and set to /data/app/com.example.nishant.ftp1-1/base.apk
01-24 12:45:10.013 7023-7023/com.example.nishant.ftp1 I/InstantRun: starting instant run server: is main process
01-24 12:45:10.253 7023-7023/com.example.nishant.ftp1 W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
01-24 12:45:10.664 7023-7023/com.example.nishant.ftp1 D/AndroidRuntime: Shutting down VM
01-24 12:45:10.674 7023-7023/com.example.nishant.ftp1 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nishant.ftp1, PID: 7023
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.nishant.ftp1/com.example.nishant.ftp1.MainActivity}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2702)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2767)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1449)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1147)
at java.net.InetAddress.lookupHostByName(InetAddress.java:418)
at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
at java.net.InetAddress.getByName(InetAddress.java:305)
at org.apache.commons.net.SocketClient.connect(SocketClient.java:202)
at org.apache.commons.net.SocketClient.connect(SocketClient.java:306)
at com.example.nishant.ftp1.MainActivity.onCreate(MainActivity.java:40)
at android.app.Activity.performCreate(Activity.java:6289)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2655)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2767)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1449)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5951)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
01-24 12:50:11.007 7023-7023/com.example.nishant.ftp1 I/Process: Sending signal. PID: 7023 SIG: 9
build.gradle：
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
defaultConfig {
applicationId "com.example.nishant.ftp1"
minSdkVersion 15
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
implementation files('libs/commons-net-3.6.jar')
}
activity_main.xml中
答案 0 :(得分：0)
你应该写一个方法getCurrentFileNames（）获取文件名并在mobile文件夹中搜索并返回当前存储文件的列表。你还应该编写另一个方法DownloafFileFromServer（String fileName），它接受一个文件名，如果文件存在于服务器中它应该下载它，如果不存在，它应该删除它在移动文件夹中。
List<String> fileNames = getCurrentFileNames();
String inputfileName;
for(String fileName:fileNames){
if(!inputfileName.equals(fileName){
DownloadFileFromServer(inputfileName);
break;
}
}
public void DownloadFileFromServer(String fileName){
OkHttpClient client = new OkHttpClient();]
String url = "http://hostname.com/folder/fileName"
Request request = new Request.Builder().url(url).build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws
IOException {
try {
DownloadFileFromUrl(response, fileName);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
DownloadFileFromUrl(Response res, String fileName){
InputStream is = null;
FileOutputStream fos = null;
File f = new File(Environment.getExternalStorageDirectory() +
"/folder/" + fileName);
if(res.code == 200){
try {
if (f.exists())
f.delete();
fos = new FileOutputStream(f);
is = res.body().byteStream();
byte[] buffer = new byte[1024];
int rd;
long count = 0;
while ((rd = is.read(buffer, 0, buffer.length)) > 0) {
fos.write(buffer, 0, rd);
count += rd;
}
is.close();
fos.flush();
fos.close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
//deleted in server
else if(res.code == 404){
if (f.exists())
//delete in mobile folder as well
f.delete();
}
}
答案 1 :(得分：0)
您可以使用Asynctask类来解决问题。你可以在这里找到代码：