android:assets下的文件复制到SD卡

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 由于assets和res下的文件都只可以读不可以写，那么在程序初始化后，将后期需要使用并且需要修改的文件复制到SD卡。下面代码提供一个工具类，将assets下的任意资源复制到SD卡下。

assets下的资源如下图：
这里写图片描述

下面是工具类：
AssetsCopyTOSDcard .java

import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import android.content.Context;import android.content.res.AssetManager;import android.os.Environment;public class AssetsCopyTOSDcard {     Context context;    public AssetsCopyTOSDcard(Context context) {        super();        this.context = context;    }    /**     * @param context     * @param assetpath  asset下的路径     * @param SDpath     SDpath下保存路径     */    public void AssetToSD(String assetpath,String SDpath ){        AssetManager asset=context.getAssets();        //循环的读取asset下的文件，并且写入到SD卡        String[] filenames=null;        FileOutputStream out = null;          InputStream in=null;        try {            filenames = asset.list(assetpath);            if(filenames.length>0){//说明是目录                //创建目录                getDirectory(assetpath);                for(String fileName:filenames){                    AssetToSD(assetpath+"/"+fileName, SDpath+"/"+fileName);                }            }else{//说明是文件，直接复制到SD卡                File SDFlie=new File(SDpath);                String  path=assetpath.substring(0, assetpath.lastIndexOf("/"));                getDirectory(path);                if(!SDFlie.exists()){                    SDFlie.createNewFile();                }                //将内容写入到文件中                in=asset.open(assetpath);                out= new FileOutputStream(SDFlie);                  byte[] buffer = new byte[1024];                int byteCount=0;                while((byteCount=in.read(buffer))!=-1){                    out.write(buffer, 0, byteCount);                }                out.flush();            }        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            try {                out.close();                in.close();                asset.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }    //分级建立文件夹    public void getDirectory(String path){        //对SDpath进行处理，分层级建立文件夹        String[]  s=path.split("/");        String str=Environment.getExternalStorageDirectory().toString();          for (int i = 0; i < s.length; i++) {            str=str+"/"+s[i];            File file=new File(str);            if(!file.exists()){                file.mkdir();            }        }    }}

MainActivity .java

import android.os.Bundle;import android.os.Environment;import android.app.Activity;import android.view.Menu;public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        String path="aaa/a1.txt";        AssetsCopyTOSDcard assetsCopyTOSDcard=new AssetsCopyTOSDcard(getApplicationContext());        assetsCopyTOSDcard.AssetToSD(path,Environment.getExternalStorageDirectory().toString()+"/"+path);    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.main, menu);        return true;    }}

   测试路径：   aaa   Aaa/bbb   Aaa/bbb/ba.txt   Aaa/a1.txt

在编程过程中遇到的两个问题：

open failed: ENOENT (No such file or directory)
open failed: EISDIR (Is a directory)

代码下载：请点击

2015-09-21 错误修改

if(!SDFlie.exists()){                    SDFlie.createNewFile();                }                //将内容写入到文件中                in=asset.open(assetpath);                out= new FileOutputStream(SDFlie);                  byte[] buffer = new byte[1024];                int byteCount=0;                while((byteCount=in.read(buffer))!=-1){                    out.write(buffer, 0, byteCount);                }                out.flush();

修改为：

if(!SDFlie.exists()){                    SDFlie.createNewFile();                    //将内容写入到文件中                in=asset.open(assetpath);                out= new FileOutputStream(SDFlie);                  byte[] buffer = new byte[1024];                int byteCount=0;                while((byteCount=in.read(buffer))!=-1){                    out.write(buffer, 0, byteCount);                }                }                out.flush();

因为当文件存在时，不复制。不修改的情况下，out.close();会报空指针异常。

finally{            try {                out.close();                in.close();                asset.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }

修改为：

finally{            try {                if(out!=null){                    out.close();                    out=null;                    }                if(in!=null){                    in.close();                    in=null;                    }                /**                 * 关闭报错，java.lang.RuntimeException:                  * Unable to start activity ComponentInfo                 * {com.example.wealth/com.example.wealth.UI.main}:                  * java.lang.RuntimeException: Assetmanager has been closed                 *///              if(asset!=null){//                  asset.close();//                  asset=null;//                  }            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }

关于报错解释：请点击。

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