Android实现复制Assets文件到SD卡

Assets文件介绍

assets文件夹里面的文件都是保持原始的文件格式，需要用AssetManager以字节流的形式读取文件。

1. 先在Activity里面调用getAssets() 来获取AssetManager引用。
2. 再用AssetManager的open(String fileName, int accessMode) 方法则指定读取的文件以及访问模式就能得到输入流InputStream。
3. 然后就是用已经open file 的inputStream读取文件，读取完成后记得inputStream.close() 。
4. 调用AssetManager.close() 关闭AssetManager。

封装类

代码遵循单例模式，例如：

import android.content.Context;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

/**
 * Created by shenhua on 1/17/2017.
 * Email shenhuanet@126.com
 */
public class FileUtils {

 private static FileUtils instance;
 private static final int SUCCESS = 1;
 private static final int FAILED = 0;
 private Context context;
 private FileOperateCallback callback;
 private volatile boolean isSuccess;
 private String errorStr;

 public static FileUtils getInstance(Context context) {
  if (instance == null)
   instance = new FileUtils(context);
  return instance;
 }

 private FileUtils(Context context) {
  this.context = context;
 }

 private Handler handler = new Handler(Looper.getMainLooper()) {
  @Override
  public void handleMessage(Message msg) {
   super.handleMessage(msg);
   if (callback != null) {
    if (msg.what == SUCCESS) {
     callback.onSuccess();
    }
    if (msg.what == FAILED) {
     callback.onFailed(msg.obj.toString());
    }
   }
  }
 };

 public FileUtils copyAssetsToSD(final String srcPath, final String sdPath) {
  new Thread(new Runnable() {
   @Override
   public void run() {
    copyAssetsToDst(context, srcPath, sdPath);
    if (isSuccess)
     handler.obtainMessage(SUCCESS).sendToTarget();
    else
     handler.obtainMessage(FAILED, errorStr).sendToTarget();
   }
  }).start();
  return this;
 }

 public void setFileOperateCallback(FileOperateCallback callback) {
  this.callback = callback;
 }

 private void copyAssetsToDst(Context context, String srcPath, String dstPath) {
  try {
   String fileNames[] = context.getAssets().list(srcPath);
   if (fileNames.length > 0) {
    File file = new File(Environment.getExternalStorageDirectory(), dstPath);
    if (!file.exists()) file.mkdirs();
    for (String fileName : fileNames) {
     if (!srcPath.equals("")) { // assets 文件夹下的目录
      copyAssetsToDst(context, srcPath + File.separator + fileName, dstPath + File.separator + fileName);
     } else { // assets 文件夹
      copyAssetsToDst(context, fileName, dstPath + File.separator + fileName);
     }
    }
   } else {
    File outFile = new File(Environment.getExternalStorageDirectory(), dstPath);
    InputStream is = context.getAssets().open(srcPath);
    FileOutputStream fos = new FileOutputStream(outFile);
    byte[] buffer = new byte[1024];
    int byteCount;
    while ((byteCount = is.read(buffer)) != -1) {
     fos.write(buffer, 0, byteCount);
    }
    fos.flush();
    is.close();
    fos.close();
   }
   isSuccess = true;
  } catch (Exception e) {
   e.printStackTrace();
   errorStr = e.getMessage();
   isSuccess = false;
  }
 }

 public interface FileOperateCallback {
  void onSuccess();

  void onFailed(String error);
 }

}

调用代码

如果你需要将如图所示的apks下的文件复制到SD卡的app/apks目录下，则这样调用：

FileUtils.getInstance(Context context).copyAssetsToSD("apks","app/apks");

###如果你需要收到文件复制完成的时的回调，则使用如下代码：

FileUtils.getInstance(Context context).copyAssetsToSD("apks","app/apks").setFileOperateCallback(new FileUtils.FileOperateCallback() {
 @Override
  public void onSuccess() {
  // TODO: 文件复制成功时，主线程回调
   }

   @Override
   public void onFailed(String error) {
    // TODO: 文件复制失败时，主线程回调
   }
  });

代码说明

在上面代码中，通过单例模式传入一个context获得FileUtils实例，通过实例去调用copyAssetsToSD()方法，方法参数：