SD卡读取写入

package com.example.administrator.myapplication.activity;

import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.example.administrator.myapplication.R;
import com.example.administrator.myapplication.entity.SDCard;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class SdCardActivity extends AppCompatActivity {
    Button writeBtn;
    Button readBtn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sd_card);
        inno();
    }

    private void inno() {
        writeBtn = (Button) findViewById(R.id.write);
        writeBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                WriteToSD();
            }
        });
        readBtn = (Button) findViewById(R.id.read);
        readBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ReadFormSD();
            }
        });
    }

    //保存文件到SD卡
    private void WriteToSD(){
        ObjectOutputStream oos = null;
        //Environment.getExternalStorageState获取外部存储的状态
        String state = Environment.getExternalStorageState();
        //外部存储正常  如果SD卡存在
        if (state.equals(Environment.MEDIA_MOUNTED)){
            //获取外部存储的根路径
            File root = Environment.getExternalStorageDirectory();
            //在SD卡下创建新的文件夹
            File TargetDir = new File(root,super.getPackageName());
            //若不存在，创建文件夹
            if (!TargetDir.exists()){
                TargetDir.mkdir();
            }
            try {
                oos = new ObjectOutputStream(new FileOutputStream(new File(TargetDir+"SDCard.txt")));
                SDCard sdCard = new SDCard("王倩","是大二的!");
                oos.writeObject(sdCard);
                Toast.makeText(getApplication(),"写入SD卡成功！",Toast.LENGTH_SHORT).show();
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                try {
                    oos.flush();
                    oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }else {
            Toast.makeText(getApplication(),"没有找到SD卡",Toast.LENGTH_SHORT).show();
        }
    }

    //从SD卡读取文件
    private void ReadFormSD(){
        String state = Environment.getExternalStorageState();
        if (state.equals(Environment.MEDIA_MOUNTED)){
            File root = Environment.getExternalStorageDirectory();
            File TargetDir = new File(root,super.getPackageName());
            if (TargetDir.exists()){
                try {
                    ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File(TargetDir+"SDCard.txt")));
                    SDCard sdCard = (SDCard) ois.readObject();
                    Toast.makeText(SdCardActivity.this,sdCard.getName()+" "+sdCard.getIntroduce(),Toast.LENGTH_SHORT).show();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}