Android外部SD卡的读取

package com.kevin.writeorreadfile1_1;

import android.app.Activity;
import android.bluetooth.le.ScanFilter;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.media.MediaScannerConnection;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Scanner;

/**
 * 保存并读取数据
 * 1.确保外部SD卡可用Environment.getExternalStorageState()；
 * 2.获取SD卡的根路径
 * 3.写入权限    
 * <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
 * <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"></uses-permission>
 * 4.读取
 */
public class MainActivity extends Activity implements View.OnClickListener {
    private boolean state = true;
    private  File file;
    private ImageView img;
    private Button keepBtn,readBtn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化控件
        keepBtn = (Button) findViewById(R.id.btn_keep_file);
        readBtn = (Button) findViewById(R.id.btn_read_file);
        img = (ImageView) findViewById(R.id.out_img);

        //点击事件
        keepBtn.setOnClickListener(this);
        readBtn.setOnClickListener(this);

        //确保SD卡可用
        String storageState = Environment.getExternalStorageState();//获取SD卡的状态
        if(storageState.equals(Environment.MEDIA_MOUNTED)){
            Log.i("TAG","当前SD卡可用");
        }else {
            state = false;
        }
    }

    @Override
    public void onClick(View view) {
            switch (view.getId()){
                case R.id.btn_keep_file://点击保存
                    if(state){
                        saveImg();
                    }
                    break;
                case R.id.btn_read_file://点击读取
                    if(state){
                        showImg();
                    }
                    break;
            }
    }
    //
    public void saveImg(){
        BufferedInputStream is = null;
        BufferedOutputStream os = null;
        try {
            File storageDirectory = Environment.getExternalStorageDirectory();
            file = new File(storageDirectory,"YangKai.jpg");
            //读取项目中的图片
            InputStream inputStream = getResources().openRawResource(R.drawable.yangkai_photo);
            OutputStream outputStream = new FileOutputStream(file);
            //缓存机制
            is = new BufferedInputStream(inputStream);
            os = new BufferedOutputStream(outputStream);
            //读写操作
            int length = 0 ;
            byte[] bytes = new byte[1024];
            while ((length = is.read(bytes)) != -1){
                os.write(bytes,0,length);
                os.flush();//刷新操作
            }
            Toast.makeText(this,"图片已保存",Toast.LENGTH_SHORT).show();
            ScanFile(file.getPath());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if ( is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (os != null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //扫描进入图片
    private void ScanFile(String path) {

        MediaScannerConnection.scanFile(this,new String[]{path},null,null);
    }

    //显示图片
    public void showImg(){
        //从文件中读取出来
        Bitmap bitmap = BitmapFactory.decodeFile(file.getPath());
        img.setImageBitmap(bitmap);
    }
}