将数据保存到文件中

1、首先由openFileOutput()方法得到FileOutputStream对象；
由FileOutputStream创建OutputStreamWrite对象；由OutputStreamWrite创建BuffereWrite对象。大概的流程如下：

public void saveFile(){
    FileOutputStream fos = openFileOutput("文件名",MODE_PRIVATE);
    OutputStreamWrite osw = new OutputStreamWrite(fos);
    BuffereWrite bw = new BuffereWrite(osw);
bw.write(data);
}

2、由openFileInput得到FileInputStream对象；由FileInputStream得到InputStreamReader对象；由InputStreamReader得到BuffereReader对象。TextUtils.isEmpty(）这个方法可以对字符串进行两种空之判断。当值是null或者空字符串时，返回true。

String data = load();
if(!TextUtils.isEmpty(data)){
            editText.setText(data);
            editText.setSelection(data.length());
            Toast.makeText(this, "读取成功", Toast.LENGTH_SHORT).show();
        }
public String readFile(){
    FileInputStream fis = openFileInput("文件名");
    InputStreamReader isr = new InputStreamReader(fis);
    BuffereReader br = new BuffereReader(isr);
    StringBulder sb = new StringBulder();
String s = "";
while((s = br.readLine) != null){
        sb.append(s);
    }
return sb.toString();
}