AndroidStudio——数据存储之SD卡存储

SaveToSdCardActivity代码：

public class SaveToSdCardActivity extends AppCompatActivity { private Button save, read, delete; private EditText content; private TextView show; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_save_to_sd_card); save = (Button) findViewById(R.id.save); read = (Button) findViewById(R.id.read); delete = (Button) findViewById(R.id.delete); content = (EditText) findViewById(R.id.content); show = (TextView) findViewById(R.id.show); save.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { saveFile(); } }); read.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { show.setText(readFile()); } }); delete.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { removeFile(); } }); } //保存文件到sd卡 public void saveFile() { FileOutputStream fos = null; //获取SD卡状态 String state = Environment.getExternalStorageState(); //判断SD卡是否就绪 if (!state.equals(Environment.MEDIA_MOUNTED)) { Toast.makeText(this, "请检查SD卡", Toast.LENGTH_SHORT).show(); return; } //取得SD卡根目录 File file = Environment.getExternalStorageDirectory(); try { Log.d("======SD卡根目录：", "" + file.getCanonicalPath().toString()); //File myFile=new File(file.getCanonicalPath()+"/sd.txt"); /* 输出流的构造参数1：可以是File对象 也可以是文件路径 输出流的构造参数2：默认为False=>覆盖内容； true=>追加内容 */ fos = new FileOutputStream(file.getCanonicalPath() + "/sd.txt"); // fos = new FileOutputStream(file.getCanonicalPath() + "/sd.txt",true); //fos=new FileOutputStream(myFile); String str = content.getText().toString(); fos.write(str.getBytes()); Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show(); } catch (IOException e) { e.printStackTrace(); } finally { if (fos != null) { try { fos.close(); fos.flush(); } catch (IOException e) { e.printStackTrace(); } } } } //从SD卡读取文件 public String readFile() { //读的时候要用字符流 万一里面有中文 BufferedReader reader = null; FileInputStream fis = null; StringBuilder sbd = new StringBuilder(); String state = Environment.getExternalStorageState(); if (!state.equals(Environment.MEDIA_MOUNTED)) { Toast.makeText(this, "SD卡未就绪", Toast.LENGTH_SHORT).show(); return ""; } File root = Environment.getExternalStorageDirectory(); try { fis = new FileInputStream(root + "/sd.txt"); reader = new BufferedReader(new InputStreamReader(fis)); String row = ""; while ((row = reader.readLine()) != null) { sbd.append(row); } } catch (FileNotFoundException e) { Toast.makeText(this, "文件不存在", Toast.LENGTH_SHORT).show(); //e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } } return sbd.toString(); } //删除SD卡文件 public void removeFile() { String state = Environment.getExternalStorageState(); if (!state.equals(Environment.MEDIA_MOUNTED)) { Toast.makeText(this, "SD卡未就绪", Toast.LENGTH_SHORT).show(); return; } //取得SD卡根目录 File root = Environment.getExternalStorageDirectory(); File myFile=new File(root+"/sd.txt"); //File myFile=new File(root,"sd.txt"); if (myFile.exists()) { myFile.delete(); Toast.makeText(this,"文件已删除",Toast.LENGTH_SHORT).show(); }else { Toast.makeText(this,"文件不存在",Toast.LENGTH_SHORT).show(); } } }

activity_save_to_sd_card布局文件：

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.dell.jreduch008.SaveToSdCardActivity"> <EditText android:id="@+id/content" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="请输入内容" android:layout_alignParentStart="true" android:layout_alignParentTop="true" /> <Button android:id="@+id/save" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="保存" android:layout_below="@+id/content" android:layout_alignParentStart="true" /> <Button android:id="@+id/read" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="读取" android:layout_above="@+id/show" android:layout_centerHorizontal="true" /> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/show" android:layout_below="@id/save"/> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="删除" android:id="@+id/delete" android:layout_above="@+id/show" android:layout_alignParentEnd="true" /> </RelativeLayout>