数据储存方式

    1.SharedPreferences的存储

package com.zking.administrator.g160628_android15_data;

import android.content.Context;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class LoginActivity extends AppCompatActivity {

    private EditText et_login_uname;
    private EditText et_login_upass;
    private SharedPreferences sp;
    private SharedPreferences.Editor editor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        et_login_uname = (EditText) findViewById(R.id.et_login_uname);
        et_login_upass = (EditText) findViewById(R.id.et_login_upass);
        sp = getSharedPreferences("loginInfo", Context.MODE_PRIVATE);
        editor = sp.edit();

        //获取数据
        String uname=sp.getString("uname","");//从SharedPreferences里获取数据
        String upass=sp.getString("upass","");
        et_login_uname.setText(uname);
        et_login_upass.setText(upass);
    }
    public void login(View view){
        String uname=et_login_uname.getText().toString();
        String upass=et_login_upass.getText().toString();
        editor.putString("uname",uname);//保存到SharedPreferences中
        editor.putString("upass",upass);
        //细节：
        editor.commit();
    }
}

2.I-0读写内部存储、外部存储的文件数据

package com.zking.administrator.g160628_android15_data;

import android.content.Context;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private EditText et_main_content;
    private EditText et_main_name;
    private String sdCard;

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

        //获取手机内存卡的路径
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            sdCard = Environment.getExternalStorageDirectory().getAbsolutePath();
        }
    }
    public void save(View view){
        String content=et_main_content.getText().toString();
        String fileName=et_main_name.getText().toString();
        //io
        //写，输出流
        try {
            FileOutputStream fos=new FileOutputStream(sdCard+"/"+fileName);
            fos.write(content.getBytes());
            fos.close();
            Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void read(View view){
        String fileName=et_main_name.getText().toString();
        //读：输入流
        try {
            FileInputStream fis=new FileInputStream(sdCard+"/"+fileName);
            byte buf[]=new byte[1024];
            int len=0;
            StringBuffer s=new StringBuffer();
            while((len= fis.read(buf))!=-1){
                s.append(new String(buf,0,len));
            }
            et_main_content.setText(s);
            fis.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}