Android开始之 扩展存储sdcard

//访问sdcar需要授权WRITE_EXTERNAL_STORAGE

    //---------------------写-----------------------
    public boolean saveFileToSdcard(String fileName, byte[] data) {
        boolean flag = false;
        // 先判断sdcard的状态；
        String state = Environment.getExternalStorageState();
        // 表示sdcard挂载在手机上，并且可以读写
        FileOutputStream outputStream = null;
        // 获得sdcard的根目录/mnt/sdcard/.....
        File root = Environment.getExternalStorageDirectory();

        if (state.equals(Environment.MEDIA_MOUNTED)) {
            // File file =new File(root, fileName);//在sdcard根目录上创建一个文件
            File file = new File(root.getAbsolutePath() + "/txt");// 创建一个TXT文件夹再存
            if (!file.exists()) {
                file.mkdirs();
            }
            try {
                // outputStream=new FileOutputStream(file);
                outputStream = new FileOutputStream(new File(file, fileName));
                outputStream.write(data, 0, data.length);
                flag = true;
            } catch (Exception e) {
                // TODO: handle exception
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (Exception e2) {
                        // TODO: handle exception
                        e2.printStackTrace();
                    }

                }

            }

        }
        return flag;
    }

-------------测试------------------------

public void save(){
        FileService service=new FileService();
        service.saveFileToSdcard("aa.txt", "zy520".getBytes());
    
    }

----------------------------------

//----------------------------------读文件内容-----------------------
    public String readContextFromSdcard(String fileName) {
        File root=Environment.getExternalStorageDirectory();
        FileInputStream inputStream=null;
        ByteArrayOutputStream outputStream=new ByteArrayOutputStream();
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File file = new File(root.getAbsolutePath() + "/txt/");    
            File file2=new File(file, fileName);
            int len=0;
            byte[]data=new byte[1024];
            
            
            if (file2.exists()) {
                try {
                    inputStream=new FileInputStream(file2);    
                while((len=inputStream.read(data))!=-1){
                    outputStream.write(data, 0, len);
                    
                
                }
                return new String(outputStream.toByteArray());
                } catch (Exception e) {
                    // TODO: handle exception
                    e.printStackTrace();
                }finally{
                    if (inputStream!=null) {
                        try {
                            inputStream.close();
                        } catch (Exception e2) {
                            // TODO: handle exception
                            e2.printStackTrace();
                        }
                        
                    }
                }
            
            }
        }
        
        return null;
    }

------------测试--------------------

    public void read(){
        FileService service=new FileService();
        String msg =service.readContextFromSdcard("aa.txt");
        System.out.println("---->>"+msg);
        
        
    }

-------------下载图片到sdcard再从sdcard中读出来----------------------------

public class ImageCache {
    public static String saveImageCache(String fileName, byte[] data) {

        File file = Environment.getExternalStorageDirectory();
        FileOutputStream outputStream = null;
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            try {
                outputStream = new FileOutputStream(new File(file, fileName));
                outputStream.write(data, 0, data.length);
                
                return file.getAbsolutePath()+"/"+fileName;
            } catch (Exception e) {
                // TODO: handle exception
                e.printStackTrace();
            }finally{
                if (outputStream!=null) {
                try {
                    outputStream.close();
                } catch (Exception e2) {
                    // TODO: handle exception
                    e2.printStackTrace();
                }
                }
            }
        }

        return null;
    }
}

---------------------------------------------

public class MainActivity extends ActionBarActivity {
    private Button button;
    private ImageView imageView;
    private ProgressDialog dialog;
    private String path ="https://www.baidu.com/img/bd_logo1.png";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_main);
        dialog = new ProgressDialog(this);
        dialog.setTitle("提示");
        dialog.setMessage("load.....");
        button = (Button) findViewById(R.id.button1);
        imageView = (ImageView) findViewById(R.id.imageView1);
        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                new MyTask().execute(path);
            }
        });

    }

    class MyTask extends AsyncTask<String, Void, byte[]> {
        private String imageName;
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            dialog.show();
        }

        @Override
        protected byte[] doInBackground(String... params) {
            // TODO Auto-generated method stub
            try {
                String name=params[0];
                //截取图片名称：bd_logo1.png
                imageName=name.substring(name.lastIndexOf("/")+1, name.length());
            } catch (Exception e) {
                // TODO: handle exception
            }
            
            return HttpUtils.getImage(params[0]);
        }

        @Override
        protected void onPostExecute(byte[] result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            if (result != null) {
                Bitmap bitmap=BitmapFactory.decodeByteArray(result, 0, result.length);
                imageView.setImageBitmap(bitmap);
                ImageCache.saveImageCache(imageName, result);

            } else {
                imageView.setImageResource(R.drawable.ic_launcher);
            }

            dialog.dismiss();
        }

    }

public class HttpUtils {
public static byte[] getImage(String path){
    byte[]data=null;
    HttpClient httpClient=new DefaultHttpClient();
    HttpPost post =new HttpPost(path);
    try {
            HttpResponse response=httpClient.execute(post);
    
    if (response.getStatusLine().getStatusCode()==200) {
        data=EntityUtils.toByteArray(response.getEntity());
    }
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }finally{
        httpClient.getConnectionManager().shutdown();
    }

    
    return data;
}
}

、、------------------------------------------------------

//---------------保存指定的SDcard目录----------
    public void saveFileToSdcardBySuff(String fileName,byte [] data){
        
        //保存文件的目录
        File file=null;
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            if (fileName.endsWith(".mp3")) {
                file=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
                
            }else if (fileName.endsWith(".jpg")||fileName.endsWith(".png")||fileName.endsWith(".gif")) {
                file=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
            }else if (fileName.endsWith(".mp4")||fileName.endsWith(".3gp")) {
                file=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES);
                
            }else {
                file=Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
            }
        }
        FileOutputStream outputStream=null;
        try {
            outputStream=new FileOutputStream(new File(file,fileName));
            outputStream.write(data,0, data.length);
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }finally{
            try {if (outputStream!=null) {
                outputStream.close();
            }
                
            } catch (Exception e2) {
                // TODO: handle exception
            }
            
        }
        
    }

------------------------------测试---------------------------------------

public void save2(){
        FileService service=new FileService();
        service.saveFileToSdcardBySuff("aa.txt", "zy520".getBytes());
    
    }
    

---------------------------删除----------------------------------------

public boolean deleteFileFromSdcard(String folder,String fileName){
    boolean flag=false;
    File file=Environment.getExternalStorageDirectory();
    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
        File exitfile=new File(file.getAbsolutePath()+"/"+folder+"/"+fileName);
        if (exitfile.exists()) {
            flag=exitfile.delete();
            
        }
    }
    
    
    return flag;
    
}

----------------测试-------------------------

public void del(){
        FileService service=new FileService();
        boolean flag =service.deleteFileFromSdcard("txt","aa.txt");
        System.out.println("---->>"+flag);
        
        
    }