Android类FileDownloadList分析

先上代码，再来分析

public class FileDownloadList {
 
 
 private Context mContext;
 
 private baseRequestLims fileRequest = null;
 
 private alertDialog progressDialog = null;
 
 private ProgressBar mProgress;
 
 private TextView mProgressPercent;
 
 private File localFile = null;
 
 private DownLoadReceiver receiver;
 
 private long fileLength = -1L;
 
 private boolean castFlag = false;
 
 private boolean showDialog = false;
 
 private Runnable mCallback = null;
 
 private Handler mHandler = new Handler(){
  @Override
  public void handleMessage(Message msg) {
   super.handleMessage(msg);
   int tempSize = (int)localFile.length();
   if(tempSize < fileLength){
//文件下载中
 if(showDialog){
//显示了进度条的情况下,更新进度条
   int progress = (int)((Double.valueOf(tempSize) / Double.valueOf(fileLength)) * 100);
   mProgress.setProgress(tempSize);
   mProgressPercent.setText(progress + "%");
 }
      }else{
//下载文件完毕
    if(castFlag){//如已注册广播，注销广播
      mContext.unregisterReceiver(receiver);
      castFlag = false;  
    }
    if(showDialog){
     mProgress.setProgress((int)fileLength);
     mProgressPercent.setText("100%");
     progressDialog.dismiss();
    }
   
    if(mCallback != null){
     try{
      Thread.sleep(500);
      mCallback.run();
     }catch (Exception e) {
      e.printStackTrace();
     }
    }
   }
  }
 };
 
 
 
 
 public FileDownloadList(Context context, boolean showDialog){
  mContext = context;
  this.showDialog = showDialog;
  fileRequest = new baseRequestLims(context,ClientServiceType.FILE_DOWN);
  fileRequest.setMethodType(baseRequestLims.METHOD_TYPE_POST);
  fileRequest.setContext(mContext);
    
 }
  public baseRequestLims getFileRequest(){
  return fileRequest;
 }
 
 
 public void downloadFile(String fileName, String saveDir, String saveName, Runnable callback){
  if(callback != null){
   mCallback = callback;
  }
  
  File saveDirFile = new File(saveDir);
  
  //judge the save dir path exist or not 
  if(!saveDirFile.exists()){
   saveDirFile.mkdirs();
  }
  localFile = new File(saveDir,saveName);
  
  if(localFile.isDirectory()){
   new alertDialog.Builder(mContext).setTitle("提示").setMessage("the save file is directory").show();
   return;
  }
  if(fileRequest.getServiceType()==null){
   fileRequest.setServiceType(ClientServiceType.FILE_DOWN);
  }
  fileRequest.addParameter("fpath", fileName);
  fileRequest.addParameter("fname", saveName);
  fileRequest.setStreamPath(localFile.getAbsolutePath());
  fileRequest.setStream(true);
  if(localFile.exists()){
   if(localFile.length() == 0){
    invokeFile(fileRequest);
   }else{
    //文件存在直接打开
    if(showDialog)
     buildProgressDialog().show();
    mHandler.sendMessage(mHandler.obtainMessage());
   }
  }else{
   invokeFile(fileRequest);
  }
 }
 
 
 private void invokeFile(final baseRequestLims request){
  try{
   if(showDialog){
    buildProgressDialog().show();
   }
   receiver = new DownLoadReceiver();
   IntentFilter filter = new IntentFilter();
   filter.addAction("SAVE_DOWNLOAD_FILE");
   mContext.registerReceiver(receiver, filter);
   castFlag = true;
   //下载的子线程
   new Thread(){
    @Override
    public void run() {
     super.run();
     HttpHelper.invoke(request);
    }
   }.start();
  }catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 
 private alertDialog buildProgressDialog(){
  alertDialog.Builder builder = new Builder(mContext);
  builder.setTitle("正在下载文件,请稍候...");
  RelativeLayout container = new RelativeLayout(mContext);
  mProgress = new ProgressBar(mContext);
  mProgress.setId("progress".hashCode());
  BeanUtils.setFieldValue(mProgress, "mOnlyIndeterminate", Boolean.valueOf(false));
  mProgress.setIndeterminate(false);
  LayerDrawable layerDrawable = (LayerDrawable)mContext.getResources().getDrawable(android.R.drawable.progress_horizontal);
  ClipDrawable clipDrawable = (ClipDrawable)layerDrawable.getDrawable(2);
  clipDrawable.setColorFilter(Color.parseColor("#32B5E5"), Mode.SRC_IN);
  mProgress.setProgressDrawable(layerDrawable);
  mProgress.setPadding(0, 0, 0, 0);
  mProgress.setIndeterminateDrawable(
    mContext.getResources().getDrawable(android.R.drawable.progress_indeterminate_horizontal));
  mProgressPercent = new TextView(mContext);
  mProgressPercent.setId("percent".hashCode());
  mProgressPercent.setText("0%");
  mProgressPercent.setTextSize(18);
  
  int containerPadding = DimensionUtils.dip2Px(mContext, 10);
  container.setPadding(containerPadding, containerPadding, containerPadding, containerPadding);
  
  LayoutParams progressLayoutParams = new LayoutParams(
    LayoutParams.MATCH_PARENT, DimensionUtils.dip2Px(mContext, 4));
  progressLayoutParams.addRule(RelativeLayout.CENTER_VERTICAL);
  progressLayoutParams.addRule(RelativeLayout.LEFT_OF, mProgressPercent.getId());
  mProgress.setLayoutParams(progressLayoutParams);
  
  LayoutParams percentLayoutParams = new LayoutParams(
    LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
  percentLayoutParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
  percentLayoutParams.addRule(RelativeLayout.CENTER_VERTICAL);
  mProgressPercent.setLayoutParams(percentLayoutParams);
  
  container.addView(mProgressPercent);
  container.addView(mProgress);
  builder.setView(container);
  builder.setNegativeButton("取消", new onClickListener() { 
   @Override
   public void onClick(DialogInterface dialog, int which) {
    dialog.dismiss();
   }
  });
  
  progressDialog = builder.create();
  return progressDialog;
 }
 
 class DownLoadReceiver extends BroadcastReceiver{
  @Override
  public void onReceive(Context context, Intent intent) {
   //显示进度条
   fileLength = intent.getLongExtra("FILE_LENGTH", -1);
   if(showDialog){
    mProgress.setMax((int)fileLength);
   }
   //更新进度条的线程
   new Thread(){
    @Override
    public void run() {
     super.run();
     while(true){
      try{
Thread.sleep(500);
      }catch (Exception e) {
e.printStackTrace();
      }
      mHandler.sendMessage(mHandler.obtainMessage());
      //获取下载文件的大小
      int loadedSize = (int)localFile.length();
      if(loadedSize >= fileLength){
break;
      }
     }
    }
   }.start();
  }
 }
 
 public DownLoadReceiver getReciver()
 {
  return receiver;
 }
}

它的逻辑：

创建一个FileDownloadList对象后，就可以直接使用该下述方法来实现下载功能。

downloadFile(String fileName, String saveDir, String saveName, Runnable callback)

在实现上是这么个意思：

1.在当前上下文，开启下载线程。当获取到要下载的文件的大小时，发送一个广播过来（这部分没有展示在上述代码中）。

2.在当前上下文中，注册一个广播监听器，监听广播标识为SAVE_DOWNLOAD_FILE的广播。首次监听到发出来的广播后，首次发送过来的广播，包含了要下载的文件的大小信息，然后就每隔5毫秒检测本地文件的大小，直到本地文件的大小(loadedSize)大于等于要下载的文件(fileLength)大小时，退出该循环。

在不断检测的过程中，通过mHandler.sendMessage(mHandler.obtainMessage()); ，让UI线程更新进度条。

下载线程，会不断将服务器返回的数据流，写到本地文件中，所以，本地文件的大小会不断变化，直到，它的大小跟要下载的文件的大小相等时，就退出这个不断检测本地文件大小的线程。

其它没有在上述代码中表现出来的内容(在其它部分的代码中)：

1.在invokeFile( final baseRequestLims request)方法中,开了一个如下的下载线程.该下载线程,会将服务器返回的文件流,写到本地文件(localFile)中;然后，它还会发送一个标识为SAVE_DOWNLOAD广播，包含的信息有要下载文件的文件大小fileLength。

//下载的子线程
   new Thread(){
    @Override
    public void run() {
     super.run();
     HttpHelper.invoke(request);
    }
   }.start();

上述代码存在的问题：

1.上下文，使用的是某个Activity，如果发生系统调用了该Activity的onDestroy()时，下载线程还没有完成，也就意味着，loadedSize的大小还是小于fileLength。从而，那个不断检测本地文件大小的线程就一直在执行着。

即是检测本地文件大小的线程和下载线程还在执行着：

检测本地文件大小的线程：

new Thread(){
    @Override
    public void run() {
     super.run();
     while(true){
      try{
Thread.sleep(500);
      }catch (Exception e) {
e.printStackTrace();
      }
      mHandler.sendMessage(mHandler.obtainMessage());
      //获取下载文件的大小
      int loadedSize = (int)localFile.length();
      if(loadedSize >= fileLength){
break;
      }
     }
    }
   }.start();

下载线程：

new Thread(){
 @Override
 public void run() {
   super.run();
   HttpHelper.invoke(request);
 }
      }.start();

那么，会出现什么问题呢？

1).我可以确定的就是，mContext会出现泄漏。

2). DownLoadReceiver不能正常被取消注册。

分析，待续。