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[1024];
            int hasRead = 0;
            StringBuilder sb = new StringBuilder("");
            while ((hasRead = fis.read(buff)) > 0) {
                sb.append(new String(buff, 0, hasRead));
            }
            fis.close();
            return sb.toString();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

}