android app 内部文件路径

 public class MainActivity extends Activity {
 
     final String FILE_NAME = "crazyit.bin";
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
 
         final EditText et1 = (EditText) findViewById(R.id.edt1);
         final EditText et2 = (EditText) findViewById(R.id.edt2);
 
         Button btnWrite = (Button) findViewById(R.id.btnIn);
         btnWrite.setOnClickListener(new OnClickListener() {
 
             @Override
             public void onClick(View v) {
                 write(et1.getText().toString());
                 et1.setText("");
             }
         });
         Button btnRead = (Button) findViewById(R.id.btnOut);
         btnRead.setOnClickListener(new OnClickListener() {
 
             @Override
             public void onClick(View v) {
                 et2.setText(read());
             }
         });
 
     }
 
     /**
      * 写入到/data/data/[包名]/files 路径下
      *
      * @param content
      */
     private void write(String content) {
         try {
             FileOutputStream fos = openFileOutput(FILE_NAME, Context.MODE_APPEND);
             PrintStream ps = new PrintStream(fos);
             ps.println(content);
             ps.close();
 
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         }
     }
 
     /**
      * /data/data/[包名]/files 路径下读取文件
      *
      * @return
      */
     private String read() {
         try {
 
             FileInputStream fis = openFileInput(FILE_NAME);
             byte[] buff = new byte[];
             int hasRead = ;
             StringBuilder sb = new StringBuilder("");
             while ((hasRead = fis.read(buff)) > ) {
                 sb.append(new String(buff, , hasRead));
             }
             fis.close();
             return sb.toString();
 
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
 
         return null;
     }
 
 }