SD卡存储

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_write"
android:text="写入文件" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="btn_read"
android:text="读取文件" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/tv_show"
android:text="显示" />

二、Java

写主函数，注意导包 （Alt+Enter）

public void btn_write (View view){
String state= Environment.getExternalStorageState();
if(state.equals(Environment.MEDIA_MOUNTED)){
File SDPath=Environment.getExternalStorageDirectory();
File file=new File(SDPath,"data.txt");
String data="Success!";
FileOutputStream fos;
try {
fos=new FileOutputStream(file);
fos.write(data.getBytes());
fos.close();
} catch (Exception e) {
e.printStackTrace();
}
}

}
public void btn_read (View view){
String state=Environment.getExternalStorageState();
if (state.equals(Environment.MEDIA_MOUNTED)){
File SDPath=Environment.getExternalStorageDirectory();
File file=new File(SDPath,"data.txt");
FileInputStream fis;
try {
fis=new FileInputStream(file);
BufferedReader br=new BufferedReader(new InputStreamReader(fis));
String data=br.readLine();
TextView textView=(TextView)findViewById(R.id.tv_show);
textView.setText(data);
fis.close();
} catch (Exception e) {
e.printStackTrace();
}

}

}

三、在清单文件的<manifest>节点下配置权限信息

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>