数据存储-读取外部数据

导航栏Tools->"Android"->"Android Device Monitor"->File Explorer->mnt->sdcard

这是一个指向目录  

MainActivity.class:

privateStringfilename="test";

caseR.id.writBtn:

File myfile=newFile(sdcard,"this is my file.txt");

if(!sdcard.exists()){

Toast.makeText(getApplicationContext(),"当前设备不具备SD卡目录",Toast.LENGTH_LONG).show();

return;

}try{

myfile.createNewFile();

Toast.makeText(getApplicationContext(),"创建目录已完成",Toast.LENGTH_LONG).show();

FileOutputStream fos =newFileOutputStream(myfile);

OutputStreamWriter osw =newOutputStreamWriter(fos,"UTF-8");

osw.write(et.getText().toString());

osw.flush();

osw.close();

fos.close();

Toast.makeText(getApplicationContext(),"文件写入完成",Toast.LENGTH_LONG).show();

}catch(IOException e) {

e.printStackTrace();

}

break;

caseR.id.readBtn:

File myfiles=newFile(sdcard,"this is my file.txt");

if(myfiles.exists()) {

FileInputStream fis =null;

try{

fis =newFileInputStream(myfiles);

InputStreamReader isr =newInputStreamReader(fis,"UTF-8");

char[] input =new char[fis.available()];

isr.read(input);

isr.close();

fis.close();

String inString =newString(input);

show.setText(inString);

}catch(FileNotFoundException e) {

e.printStackTrace();

}catch(UnsupportedEncodingException e) {

e.printStackTrace();

}catch(IOException e) {

e.printStackTrace();

}

}

break;

注意在AndroidManifest.xml中 添加SD权限

完成效果图：