File存储—内部存储

1、内部存储，手机内存，是ROM，不是RAM，存储在手机自带的内存中
作用：在手机的内部存储空间，存储程序的私有数据
存储位置：data/data/包名/files/文件名

创建输出，输入流
FileOutputStream fos = openFileOutput(文件名，模式（MODE_PRIVATE）);

FileINputStream fis= openfileInput(文件名);
案例一：

public class MainActivity extends Activity {

 private EditText etContent;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  etContent = (EditText) findViewById(R.id.et_content);
 }

 // 保存
 public void save(View v) {
  String content = etContent.getText().toString();
  // 创建输出流，保存文件
  // 参数1：文件名
  // 参数2：操作模式，选择私有
  try {
   FileOutputStream fos = openFileOutput("content.txt",
     Context.MODE_PRIVATE);
   fos.write(content.getBytes());
   fos.close();
   Toast.makeText(this, "保存成功！", 1).show();
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

 // 读取
 public void read(View v) {
  try {
   FileInputStream fis = openFileInput("content.txt");
   byte[] b = new byte[fis.available()];
   fis.read(b);

   String info = new String(b);
   etContent.setText(info);
   fis.close();
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }
}
案例二：文件名以对话框的形式显示，可以供用户选择读取的是哪个问价中的数据

public class MainActivity extends Activity {

 private EditText etContent;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  etContent = (EditText) findViewById(R.id.et_content);
 }

 public void save(View v) {
  String content = etContent.getText().toString();

  SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
  String fileName = sdf.format(new Date()) + ".txt";
  try {
   FileOutputStream fos = openFileOutput(fileName,
     Context.MODE_PRIVATE);
   fos.write(content.getBytes());
   fos.close();
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 }

 public void read(View v) {
  // 返回文件名的数组
  String[] files = fileList();

  // 创建适配器
  final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
    android.R.layout.simple_dropdown_item_1line, files);
  // 创建对话框，显示所有的文件名
  new AlertDialog.Builder(this).setTitle("请选择")
    .setAdapter(adapter, new OnClickListener() {

     @Override
     public void onClick(DialogInterface dialog, int which) {
      // TODO Auto-generated method stub
      String fileName = adapter.getItem(which);

      try {
       FileInputStream fis = openFileInput(fileName);
       byte[] b = new byte[fis.available()];
       fis.read(b);
       fis.close();
       String info = new String(b);
       etContent.setText(fileName + "--" + info);

      } catch (Exception e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
      }

     }
    }).create().show();
 }
}

2、外部存储，sdcard