在android 6.0以前，你可以只关注外置存储是否挂载即可，并且可以直接在sdcard目录下创建“xxx”文件夹保存下载的文件（例如下载一张图片a.jpg到sdcar“xxx”文件夹下，我们只需要在清单文件中配置对sdcard读写权限，就可以设置下载路径“mnt/sdcard/xxx/a.jpg”）。但是从6.0以后，也就是M系统后，还需要判断是否有读写权限，只有具备这些权限才可以读写外置存储。并且要通过这个方法：Environment.getExternalStorageDirectory（）获取路径：/storage/emulated/0 默认存在，声明权限则可读写（6.0和以后系统还需要向用户申请同意才可以）。 下面直接上代码： Java代码：
package com.hc.android6.download; import android.os.Environment; import android.os.Handler; import android.os.Message; import android.os.SystemClock; import android.support.v7.app.ActionBarActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.ProgressBar; import android.widget.Toast; import org.hpg.weather.download.R; import java.io.File; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import java.net.URL; import java.net.URLConnection; public class MainActivity extends ActionBarActivity { private final int TODOWN = 1; private static final String TAG = "hc"; private File file1; private int contentLength; private Handler mhandler = new Handler() { @Override public void handleMessage(Message msg) { switch (msg.what) { case TODOWN: // 设置下载进度条的进度 if (file1.length() == contentLength) { Toast.makeText(getApplicationContext(), "下载完成", Toast.LENGTH_SHORT).show(); // 隐藏进度条 mprogressBar.setVisibility(View.GONE); } else { setmprogressbar(); } break; } } }; private void setmprogressbar() { mprogressBar.setProgress((int) file1.length()); } String hcUrl = "http://p1.so.qhmsg.com/t016269623a51ead026.jpg"; private Button button; private ProgressBar mprogressBar; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = (Button) findViewById(R.id.download); mprogressBar = (ProgressBar) findViewById(R.id.progressBar); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { new Thread(new Runnable() { @Override public void run() { download(); } }).start(); } }); } //下载 private void download() { Message message = new Message(); message.what = TODOWN; try { URL url = new URL(hcUrl); //打开连接 URLConnection conn = url.openConnection(); //打开输入流 InputStream is = conn.getInputStream(); //获得长度 contentLength = conn.getContentLength(); mprogressBar.setMax(contentLength); Log.e(TAG, "contentLength = " + contentLength); //创建文件夹 HC，在存储卡下 String dirName = Environment.getExternalStorageDirectory() + "/HC/"; File file = new File(dirName); //不存在创建 if (!file.exists()) { file.mkdir(); } //下载后的文件名 String fileName = dirName + "hcdown.jpg"; file1 = new File(fileName); if (file1.exists()) { file1.delete(); } //创建字节流 byte[] bs = new byte[1024]; int len; OutputStream os = new FileOutputStream(fileName); //写数据 while ((len = is.read(bs)) != -1) { os.write(bs, 0, len); mhandler.sendEmptyMessage(TODOWN); SystemClock.sleep(100); } //完成后关闭流 Log.e(TAG, "download-finish"); Log.e(TAG, file1.length() + ""); os.close(); is.close(); } catch (Exception e) { e.printStackTrace(); } } }xml布局文件
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.hc.android6.download.MainActivity"> <Button android:layout_marginTop="10dp" android:id="@+id/download" android:text="开始下载图片" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <ProgressBar android:layout_below="@+id/download" android:layout_marginTop="10dp" style="?android:attr/progressBarStyleHorizontal" android:layout_width="match_parent" android:layout_height="5dp" android:id="@+id/progressBar" /> </RelativeLayout>