Android实现复制Assets文件到SD卡

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);
  }

}

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

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
      }
    });