本文主要介绍如何写数据到sd卡,这里主要到的技术是Environment中的方法.
1.
2.实现代码:
/datasave/src/com/amos/datasave/savePasswordService.java
//写数据到sdcard
public void savePasswordToSDCard(String name, String password) {
// android 2.1 /sdcard/xx.txt
// android 2.2 /mnt/sdcard/xx.txt
// self_define /excard/xx.txt // File externalStorageDirectory = Environment.getExternalStorageDirectory();
// String path = externalStorageDirectory.getPath();
// System.out.println("path:" + path); // 要存储的内容
String content = name + ":" + password; Log.d(tag, "检验sdcard是否可用?");
//判断sdcard是否存在?
if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
Log.d(tag, "sdcard不可用!");
Toast.makeText(context, "没有找到SDCard!", Toast.LENGTH_LONG);
return ;
}; try {
// File file = new File("/sdcard/qqpassword.txt");
// File file = new File(path + "/qqpassword2.txt");
File file = new File(Environment.getExternalStorageDirectory(), "/qqpassword2.txt");
FileOutputStream fos = new FileOutputStream(file);
fos.write(content.getBytes());
fos.flush();
fos.close();
} catch (Exception e) {
e.printStackTrace();
} }
在android2.1及以前版本中,其sdcard目录在根目录,2.2,2.3以后其sdcard目录就变成了/mnt/sdcard了,以及一些厂商自定义的android系统,可能也会把sdcard的名称改的各不相同.这里如果还是用绝对路径,那么程序的兼容性将会大大降低.这里主要用到了Enviroment类.
android.os.Environment
其主要方法有:
- getRootDirectory()---->/ 获取根目录
- getDataDirectory()---->/data 获取data目录
- getExternalStorageDirectory()--->/sdcard 获取sd卡目录
- getDownloadCacheDirectory()--->/cache 获取下载文件的缓存目录
- getExternalStorageState--->sdcard的状态,removed,unmounted,checking,nofs,mounted,mounted_ro,shared,unmountable,bad_removal
完整的savePasswordService.java文件为:
package com.amos.datasave; import java.io.File;
import java.io.FileOutputStream; import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast; @SuppressLint("WorldWriteableFiles")
public class savePasswordService {
private Context context; private String tag = "savePasswordService"; public savePasswordService(Context context) {
this.context = context;
} public void savePasswordToFile(String name, String password) {
// 这里设置文件的权限
String content = name + ":" + password;
Log.d(tag, "设置文件的读写权限");
try {
FileOutputStream fileOutput = context.openFileOutput("LoginTestConfig.txt", Context.MODE_WORLD_READABLE | Context.MODE_WORLD_WRITEABLE);
fileOutput.write(content.getBytes());
fileOutput.flush();
fileOutput.close();
} catch (Exception e) {
Log.d(tag, "设置文件的读写权限失败!");
e.printStackTrace();
}
}
//写数据到sdcard
public void savePasswordToSDCard(String name, String password) {
// android 2.1 /sdcard/xx.txt
// android 2.2 /mnt/sdcard/xx.txt
// self_define /excard/xx.txt // File externalStorageDirectory = Environment.getExternalStorageDirectory();
// String path = externalStorageDirectory.getPath();
// System.out.println("path:" + path); // 要存储的内容
String content = name + ":" + password; Log.d(tag, "检验sdcard是否可用?");
//判断sdcard是否存在?
if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
Log.d(tag, "sdcard不可用!");
Toast.makeText(context, "没有找到SDCard!", Toast.LENGTH_LONG);
return ;
}; try {
// File file = new File("/sdcard/qqpassword.txt");
// File file = new File(path + "/qqpassword2.txt");
File file = new File(Environment.getExternalStorageDirectory(), "/qqpassword2.txt");
FileOutputStream fos = new FileOutputStream(file);
fos.write(content.getBytes());
fos.flush();
fos.close();
} catch (Exception e) {
e.printStackTrace();
} } }
如何获取sdcard的大小?
StatFs statFs = new StatFs(Environment.getExternalStorageDirectory().getPath());
long blockSize = statFs.getBlockSize();
long blockCount = statFs.getBlockCount();
long sdCardSize = blockSize*blockCount;
Log.d(tag,""+sdCardSize );
这里使用的是Environment中的方法获取到sdcard的路径,然后将其路径通过StatFs类,该类主要获取指定文件路径下的文件信息(filesystem info).
获取其块大小,块数量.