如何在安装期间将文件从资产复制到SD卡

Question

我无法将文件从资源文件夹复制到SD卡。我怎么能做到这一点？或者有没有办法将文件从资产或任何其他文件夹复制到应用程序的安装的SD卡？ 这是我的代码：

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.os.Bundle;
import android.app.Activity;
import android.content.res.AssetManager;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.app.NavUtils;

public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    CopyAssets();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

private void CopyAssets() { 
    AssetManager assetManager = getAssets(); 
    String[] files = null; 
    try { 
        files = assetManager.list(""); 
    } catch (IOException e) { 
        Log.e("tag", e.getMessage()); 
    } 
    for(String filename : files) { 
        InputStream in = null; 
        OutputStream out = null; 
        try { 
          in = assetManager.open(filename); 
          out = new FileOutputStream("/sdcard/" + filename); 
          copyFile(in, out); 
          in.close(); 
          in = null; 
          out.flush(); 
          out.close(); 
          out = null; 
        } catch(Exception e) { 
            Log.e("tag", e.getMessage()); 
        }        
    } 
} 
private void copyFile(InputStream in, OutputStream out) throws IOException { 
    byte[] buffer = new byte[1024]; 
    int read; 
    while((read = in.read(buffer)) != -1){ 
      out.write(buffer, 0, read); 
    } 
}


}

Answer 1

您不应该硬编码存储目录。使用 Environment.getExternalStorageDirectory（）

String destFile = Environment.getExternalStorageDirectory().toString().concat("/ans");
try {

        File f2 = new File(destFile);
        InputStream in = getAssets().open("try.xml");
        OutputStream out = new FileOutputStream(f2);

        byte[] buf = new byte[1024];
        int len;
        while ((len = in.read(buf)) > 0) {
            out.write(buf, 0, len);
        }
        in.close();
        out.close();
        System.out.println("File copied.");
    } catch (FileNotFoundException ex) {
        System.out
                .println(ex.getMessage() + " in the specified directory.");

    } catch (IOException e) {
        System.out.println(e.getMessage());
    }

在清单中添加权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Answer 2

要在SD卡中写入文件，您必须授予清单

的权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

你呢？

Answer 3

将此代码添加到您的onCreate。因此，安装后第一次启动应用程序时，将资产复制到SD卡，然后再次进入应用程序时调用它。

        SharedPreferences score = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
    Editor score_inc = score.edit();
    int counter = score.getInt("counter",0);
    float font_size = score.getFloat("font_size",20.0f);
    if(counter==0)
    {
        //Put your function to copy files here
        score_inc.putInt("counter", ++counter);
        score_inc.commit();
        Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT).show();
    }