Android實現復制Assets文件到SD卡

2019-10-21 21:32:15

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Assets文件介紹

assets文件夾里面的文件都是保持原始的文件格式，需要用AssetManager以字節流的形式讀取文件。

1. 先在Activity里面調用getAssets() 來獲取AssetManager引用。
2. 再用AssetManager的open(String fileName, int accessMode) 方法則指定讀取的文件以及訪問模式就能得到輸入流InputStream。
3. 然后就是用已經open file 的inputStream讀取文件，讀取完成后記得inputStream.close() 。
4. 調用AssetManager.close() 關閉AssetManager。

封裝類

代碼遵循單例模式，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 文件夾下的目錄      copyAssetsToDst(context, srcPath + File.separator + fileName, dstPath + File.separator + fileName);     } else { // assets 文件夾      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); }}

調用代碼

如果你需要將如圖所示的apks下的文件復制到SD卡的app/apks目錄下，則這樣調用：

Android,復制,Assets,SD卡

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

###如果你需要收到文件復制完成的時的回調，則使用如下代碼：

FileUtils.getInstance(Context context).copyAssetsToSD("apks","app/apks").setFileOperateCallback(new FileUtils.FileOperateCallback() { @Override  public void onSuccess() {  // TODO: 文件復制成功時，主線程回調   }   @Override   public void onFailed(String error) {    // TODO: 文件復制失敗時，主線程回調   }  });

代碼說明

在上面代碼中，通過單例模式傳入一個context獲得FileUtils實例，通過實例去調用copyAssetsToSD()方法，方法參數：