Android数据存储——SharedPreferences及SDCard_sharedpreferences 保存到 sdcard

1、SharedPreferences

Store privateprimitive data in key-value pairs.

保存简单的键值对数据。

2、InternalStorage

Store privatedata on the device memory.

在手机内存中保存不对外共享的信息。

3、ExternalStorage

Store public dataon the shared external storage.

在外部存储设备上保存公共的数据信息。主要指保存在SDCard上。

4、SQLiteDatabases

Store structureddata in a private database.

将结构化的数据保存进数据库。

5、NetworkConnection

Store data on theweb with your own network server.

将数据保存到自己的远程服务器上。

public class MainActivity extends Activity {    
	private ImageView imageView_main_img;    
	private String urlString = "http://t2.baidu.com/it/u=2,1891512358&fm=19&gp=0.jpg";
	@Override    
	protected void onCreate(Bundle savedInstanceState) {    
		super.onCreate(savedInstanceState);    
		setContentView(R.layout.activity_main);    
		imageView_main_img = (ImageView) findViewById(R.id.imageView_main_img);   
		
	}        
	public void clickButton(View view) {    
		switch (view.getId()) {    
		case R.id.button_main_save:    
			new MyTask(this).execute(urlString);    
			break;    
			
		case R.id.button_main_show:    
			String filepath = SDCardHelper.getSDCardPath() + File.separator    + "mydir" + File.separator + "firstimg.jpg";    
			byte[] data = SDCardHelper.loadFileFromSDCard(filepath);    
			if (data != null) {    Bitmap bm = BitmapFactory.decodeByteArray(data, 0, data.length);   
			imageView_main_img.setImageBitmap(bm);    
			} else {    
				Toast.makeText(this, "没有该图片！", Toast.LENGTH_LONG).show();   
				
			}    
			break;  
			
		default:    
			
			break;   
			
		}    
		
	}        
	class MyTask extends AsyncTask<String, Void, byte[]> {    
		private Context context;    
		private ProgressDialog pDialog;        
		public MyTask(Context context) {    
			this.context = context;    
			pDialog = new ProgressDialog(context);   
			pDialog.setIcon(R.drawable.ic_launcher);    
			pDialog.setMessage("图片加载中...");    }        
		
		@Override    
		protected void onPreExecute() {    
			super.onPreExecute();    
			pDialog.show();    
		}        
		@Override   
		protected byte[] doInBackground(String... params) {    
			BufferedInputStream bis = null;    
			ByteArrayOutputStream baos = new ByteArrayOutputStream();    
			try {   
				URL url = new URL(params[0]);    
				HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();    
				httpConn.setDoInput(true);    
				httpConn.connect();        
				if (httpConn.getResponseCode() == 200) {    
					bis = new BufferedInputStream(httpConn.getInputStream());    
					byte[] buffer = new byte[1024 * 8];   
					int c = 0;       
					while ((c = bis.read(buffer)) != -1) {    
						baos.write(buffer, 0, c);    
						baos.flush();    	
					}    
					
					return baos.toByteArray();   
					
				}        
				
			} catch (Exception e) {    
				e.printStackTrace();    
				}    return null;   
				
		}        
		@Override    
		protected void onPostExecute(byte[] result) {   
			super.onPostExecute(result);    
			if (result == null) {    
				Toast.makeText(context, "图片加载失败！", Toast.LENGTH_LONG).show();    
				
			} else {   
				// 将字节数组转成Bitmap，然后将bitmap加载的imageview控件中  
				// Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0,    
				// result.length);    
				// imageView_main_img.setImageBitmap(bitmap);   
				if (SDCardHelper.saveFileToSDCard(result, "mydir",    "firstimg.jpg")) { 
					Toast.makeText(context, "图片保存OK！", Toast.LENGTH_LONG).show();    
					} else {    
						Toast.makeText(context, "图片保存失败！", Toast.LENGTH_LONG).show();
						
					}    
				}    
			pDialog.dismiss();    
			}    
		}        
	@Override    
	public boolean onCreateOptionsMenu(Menu menu) {    
		getMenuInflater().inflate(R.menu.main, menu);    
		return true;    
		}   
	} 
 
		
	}
	}
}

1. listFiles()
2. isFile()
3. isDirectory()
4. getAbsolutePath()
5. getParentFile()
6. 
   

public class MainActivity extends Activity {   private TextView textView_main_currentpath;   private ListView listView_main_fileList;    
  private File currentFile = null;   private File[] arrCurrentFiles = null;    
  @Override   
protected void onCreate(Bundle savedInstanceState) 
{   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);      
      textView_main_currentpath = (TextView) findViewById(R.id.text_main_currentpath);  
      listView_main_fileList = (ListView) findViewById(R.id.listView_main_filelist);     
    if (SDCardHelper.isSDCardMounted()) { 
         currentFile = new File(SDCardHelper.getSDCardPath());   
                 fillListView(currentFile);   } else {   
                       Toast.makeText(MainActivity.this, "SDCARD不存在！", Toast.LENGTH_LONG)   .show();  
 }      listView_main_fileList   .setOnItemClickListener(new OnItemClickListener() {      
    @Override  
     public void onItemClick(AdapterView<?> parent, View view,   int position, long id) {   
                      if (arrCurrentFiles[position].isDirectory()) {   
                              File[] arrSubFiles = arrCurrentFiles[position] .listFiles(); 
           if (arrSubFiles.length == 0) {   Toast.makeText(MainActivity.this, "您点击的是空目录！",   2000).show();   
                    } else {   fillListView(arrCurrentFiles[position]);   
             }      } else {   Toast.makeText(MainActivity.this, "您点击的不是目录！",   
          Toast.LENGTH_LONG).show();   }   }   });      }      public void clickButton(View view) {   switch (view.getId()) {   case R.id.imageView_main_back:   if (!currentFile.getAbsolutePath().equals(   SDCardHelper.getSDCardPath())) {   fillListView(currentFile.getParentFile());   }   break;   default:   break;   }   }      public void fillListView(File file) {   currentFile = file;   arrCurrentFiles = currentFile.listFiles();      List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();   for (int i = 0; i < arrCurrentFiles.length; i++) {   Map<String, Object> map = new HashMap<String, Object>();   if (arrCurrentFiles[i].isDirectory()) {   map.put("imgId", R.drawable.folder);   } else {   map.put("imgId", R.drawable.file);   }   map.put("filename", arrCurrentFiles[i].getName());   list.add(map);   }      SimpleAdapter adapter = new SimpleAdapter(MainActivity.this, list,   R.layout.item_listview_main,   new String[] { "imgId", "filename" }, new int[] {   R.id.imageView_item_listview_type,   R.id.text_item_listview_filename });   listView_main_fileList.setAdapter(adapter);   textView_main_currentpath.setText(currentFile.getAbsolutePath());   }   }