Android App将数据写入内部存储和外部存储的示例

public class MainActivity extends Activity {  private TextView show;  private EditText et;  private String filename = "test";  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    show = (TextView) findViewById(R.id.show);    et = (EditText) findViewById(R.id.et);    findViewById(R.id.write).setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View v) {        try {          FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);          //FileOutputStream是字节流，如果是写文本的话，需要进一步把FileOutputStream包装 UTF-8是编码          OutputStreamWriter osw = new OutputStreamWriter(fos, "UTF-8");          //写          osw.write(et.getText().toString());          osw.flush();          fos.flush();          osw.close();          fos.close();        } catch (FileNotFoundException e) {          e.printStackTrace();        } catch (UnsupportedEncodingException e) {          // TODO Auto-generated catch block          e.printStackTrace();        } catch (IOException e) {          // TODO Auto-generated catch block          e.printStackTrace();        }      }    });      findViewById(R.id.read).setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View v) {        try {          FileInputStream fis = openFileInput(filename);          //当输入输出都指定字符集编码的时候，就不会出现乱码的情况          InputStreamReader isr = new InputStreamReader(fis, "UTF-8");          //获取文件的可用长度，构建一个字符数组          char[] input = new char[fis.available()];          isr.read(input);          isr.close();          fis.close();          String readed = new String(input);          show.setText(readed);        } catch (FileNotFoundException e) {          e.printStackTrace();        } catch (UnsupportedEncodingException e) {          // TODO Auto-generated catch block          e.printStackTrace();        } catch (IOException e) {          // TODO Auto-generated catch block          e.printStackTrace();        }      }    });        }  }

// 创建一个URL对象，该对象包含一个IP地址，urlStr指的是网络IP地址 url = new URL(urlStr); // 通过URL对象，来创建一个HttpURLConnection对象HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();

InputStream input = urlConn.getInputStream();

//在AndroidManifest.xml配置文件中加入权限信息 <uses-permission android:name="android.permission.INTERNET"/>

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);

Environment.getExternalStorageDirectory();

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

public class FileUtils {  private String SDPATH;  public String getSDPATH(){    return SDPATH;  }  //构造函数，得到SD卡的目录，这行函数得到的目录名其实是叫"/SDCARD"  public FileUtils() {    SDPATH = Environment.getExternalStorageDirectory() +"/";  }  //在SD卡上创建文件  public File createSDFile(String fileName) throws IOException{    File file = new File(SDPATH + fileName);    file.createNewFile();    return file;  }  //在SD卡上创建目录  public File createSDDir(String dirName){    File dir = new File(SDPATH + dirName);    dir.mkdir();    return dir;  }  //判断SD卡上的文件夹是否存在  public boolean isFileExist(String fileName){    File file = new File(SDPATH + fileName);    return file.exists();  }  //将一个InputStream里面的数据写入到SD卡中  //将input写到path这个目录中的fileName文件上  public File write2SDFromInput(String path, String fileName, InputStream input){    File file = null;     OutputStream output = null;     try{       createSDDir(path);       file = createSDFile(path + fileName);       //FileInputStream是读取数据，FileOutputStream是写入数据，写入到file这个文件上去      output = new FileOutputStream(file);       byte buffer [] = new byte[4 * 1024];       while((input.read(buffer)) != -1){         output.write(buffer);       }       output.flush();     }     catch(Exception e){       e.printStackTrace();     }     finally{       try{         output.close();       }       catch(Exception e){         e.printStackTrace();       }     }     return file;   } }