java - 如何返回到 Activity 之前的状态？

Question

我创建了一个名为 viewActivity 的 Activity 。它显示Windows系统中的共享文件和文件夹。我正在使用 jcifs.smb 包中的函数 listFiles() 。最初显示共享驱动器。我选择了递归调用 listFiles() 函数。也就是说，当我单击驱动器中的特定文件夹时，会显示该文件的内容。当我再次单击上一个文件夹内的文件夹时，也会显示其内容。这里的问题是，当我按下 Android 中的后退按钮时，它会调用上一个 Activity，而不是返回到上一个文件夹。那么如何实现这个功能呢？

 //my package
package com.android.accesspc;

import java.net.MalformedURLException;
import jcifs.smb.NtlmPasswordAuthentication;
import jcifs.smb.SmbException;
import jcifs.smb.SmbFile;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.ScrollView;
import android.widget.Toast;

public class viewActivity extends Activity{

int id=0;
SmbFile previous=null;
int count=0;
void list(SmbFile obj)
{
    ScrollView sv = new ScrollView(this);
    LinearLayout layout=new LinearLayout(this);
    layout.setOrientation(0x00000001);
    try
    {
        SmbFile a[]=obj.listFiles();
        for(final SmbFile m:a)
        {
            if(!m.isHidden())
            {
                Button btn = new Button(this); 
                btn.setId(id); 
                if(m.isDirectory())
                {
                    btn.setText(m.getName().replace("/","")); 
                    btn.setTextSize((float)20);
                    btn.setOnClickListener(new 
                    View.OnClickListener()
                    {
                        public void onClick(View v) 
                        {
                previous=m;//used to hold previous smb object
                count++;//takes count of no of folders pressed 
                            list(m);
                        }
                    });
                }
                else
                {
                    btn.setText(m.getName()); 
                }
                layout.addView(btn);
                id++;
            }
        }
        sv.addView(layout);
        setContentView(sv);
    }
    catch(SmbException e)
    {
Toast displayMsg=Toast.makeText(this,"cannot list files",Toast.LENGTH_SHORT);
        displayMsg.show();
    }
}

String ip,name,password;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view);

    ip="192.168.0.100";//my ip address
    name="abc";//my windows username
    password="abcd";//my windows password

    SmbFile dir=null;
    String url= "smb://" + ip + "/";
NtlmPasswordAuthentication auth = new NtlmPasswordAuthentication(null, name, password);
    try 
    {
        dir = new SmbFile(url, auth);
    } 
    catch (MalformedURLException e1) 
    {
    Toast displayMsg=Toast.makeText(this,"Network error",Toast.LENGTH_SHORT);
        displayMsg.show();
    }
    //used to list files and folders of smb object initially
    list(dir);
}

@Override
public void onBackPressed() {
    // TODO Auto-generated method stub
    if(!(count==0))
    {
        //if count is not 0,that means the user has clicked a folder
    //we have "previous" holding previous smb value which  has to be called now
        list(previous);
    }
    else
    {
        //the default behaviour
        super.onBackPressed();
    }
}

}

Answer 1

重写 super.onBackPressed()

 @Override
 public boolean onBackPressed(){

 //your code
 }

应该适用于 2.3.3