我正在构建一个Android应用程序，用sftp从linux主机（Raspberry Pi）获取.jpg文件。以下是我的代码。但是当我按下按钮时，它会保持Connection Error。
MainActivity.java
package com.example.picture_controller_2;
import android.graphics.drawable.Drawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.app.Activity;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.ChannelSftp;
import com.jcraft.jsch.SftpException;
import android.view.View;
import android.os.AsyncTask;
import android.widget.ImageView;
import android.widget.Toast;
public class Button2Activity extends AppCompatActivity {
private ImageView iv1;
private Drawable ddd;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_button2);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
public void show_picture_func (View v) {
iv1 = (ImageView) findViewById(R.id.imageView1);
String SFTPHOST = "192.168.0.1";
int SFTPPORT =22;
String SFTPUSER = "pi";
String SFTPPASS = "raspberry";
String SFTPWORKINGDIR = "/home/pi/imgs/";
Session session = null;
Channel channel = null;
ChannelSftp channelSftp = null;
try {
JSch jsch = new JSch();
session = jsch.getSession(SFTPUSER, SFTPHOST, SFTPPORT);
session.setPassword(SFTPPASS);
session.setConfig("StrictHostKeyChecking", "no");
session.setTimeout(1000);
session.connect();
channel = session.openChannel("sftp");
channel.connect();
channelSftp = (ChannelSftp) channel;
channelSftp.cd(SFTPWORKINGDIR);
byte[] buffer = new byte[1024];
BufferedInputStream bis = new BufferedInputStream(channelSftp.get("/home/pi/imgs/AAP.jpg"));
Drawable ddd = Drawable.createFromStream(bis,"ddd");
Toast.makeText(getApplicationContext(), "Connection OK", Toast.LENGTH_LONG).show();
} catch (Exception ex) {
Toast.makeText(getApplicationContext(), "Connection Error", Toast.LENGTH_LONG).show();
ex.printStackTrace();
}
iv1.setImageDrawable(ddd);
Toast.makeText(getApplicationContext(), "Picture Success", Toast.LENGTH_LONG).show();
}
}
那么，我错过了什么？
UPDATE1
按下按钮时，以下是logcat消息：
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: android.os.NetworkOnMainThreadException
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1315)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:111)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at java.net.SocketOutputStream.write(SocketOutputStream.java:157)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at com.jcraft.jsch.IO.put(IO.java:64)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at com.jcraft.jsch.Session.connect(Session.java:256)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at com.jcraft.jsch.Session.connect(Session.java:183)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at ir.sapna_co.adalux_controller_2.Button2Activity.show_picture_func(Button2Activity.java:65)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at java.lang.reflect.Method.invoke(Native Method)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
11-09 18:26:59.008 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.view.View.performClick(View.java:5646)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.view.View$PerformClick.run(View.java:22459)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.os.Handler.handleCallback(Handler.java:761)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.os.Handler.dispatchMessage(Handler.java:98)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.os.Looper.loop(Looper.java:156)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at android.app.ActivityThread.main(ActivityThread.java:6531)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at java.lang.reflect.Method.invoke(Native Method)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:941)
11-09 18:26:59.009 16361-16361/ir.sapna_co.adalux_controller_2 W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:831)
11-09 18:26:59.012 16361-16361/ir.sapna_co.adalux_controller_2 I/HwPointEventFilter: do not support AFT because of no config
11-09 18:26:59.058 16361-16361/ir.sapna_co.adalux_controller_2 I/HwPointEventFilter: do not support AFT because of no config
答案 0 :(得分：1)
将show_picture_func的网络代码包含在AsyncTask内，并在onPostExecute方法中执行您的UI内容：
public void show_picture_func (View v) {
new AsyncTask<Void, Void, Void>() {
Drawable ddd = null;
protected Void doInBackground(Void... unused) {
// Background Code
String SFTPHOST = "192.168.0.1";
int SFTPPORT =22;
String SFTPUSER = "pi";
String SFTPPASS = "raspberry";
String SFTPWORKINGDIR = "/home/pi/imgs/";
Session session = null;
Channel channel = null;
ChannelSftp channelSftp = null;
try {
JSch jsch = new JSch();
session = jsch.getSession(SFTPUSER, SFTPHOST, SFTPPORT);
session.setPassword(SFTPPASS);
session.setConfig("StrictHostKeyChecking", "no");
session.setTimeout(1000);
session.connect();
channel = session.openChannel("sftp");
channel.connect();
channelSftp = (ChannelSftp) channel;
channelSftp.cd(SFTPWORKINGDIR);
byte[] buffer = new byte[1024];
BufferedInputStream bis = new BufferedInputStream(channelSftp.get("/home/pi/imgs/AAP.jpg"));
ddd = Drawable.createFromStream(bis,"ddd");
} catch (Exception ex) {
ex.printStackTrace();
}
return null;
}
protected void onPostExecute(Void unused) {
// Post Code
iv1.setImageDrawable(ddd);
Toast.makeText(getApplicationContext(), "Picture Success", Toast.LENGTH_LONG).show();
}
}.execute();
}