外部储存篇

实习第二周，这是第一篇实习总结

以前也不少使用File储存，这不刚来公司，就被一个小小的Demo困了一下午，下午上班前，经理让我读取外网IP，IMEI，然后退出程序，进来再次读取，判断和上次读取的数据是否相同

自然读取IP和IMEI网上就有大把教程，我这里就不缀述，这里是来归纳外部储存的一些使用心得

自己分了类型

1.每次储存都覆盖上一次文件。

2.每一次储存都把数据追加到上一次文件上。

大伙可以根据需求自行选择，我把代码贴上来

覆盖篇

public class MainActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toast.makeText(MainActivity.this, readOldIMEI(), Toast.LENGTH_SHORT).show();

}
//获得读写公用的外部储存路径
/**
*
* @param fileName
* 文件名
* @return
*/
private File mCacheFile;
private String directoryName="text";//目录名
public File getFile(String fileName) {
if (mCacheFile == null) {
mCacheFile = new File(Environment.getExternalStorageDirectory(), directoryName);

}
File file2 = new File(mCacheFile, fileName);
if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
//判断目录或目录文件是否存在
if (!mCacheFile.exists()) {
mCacheFile.mkdirs();//创建目录
}
try {
file2.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
return file2;
}
String newIMEI="84545454654564";
//将数据写入外部储存
private void saveIMEI(String newIMEI) {
File file2 = getFile("IMEI");
if (file2.exists()) {
try {
FileOutputStream fos = new FileOutputStream(file2);
fos.write(newIMEI.getBytes());
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
saveIMEI(newIMEI);
}
/**
*
* @return 读取上次IMEI
*/
private String readOldIMEI() {
File file2 = getFile("IMEI");
String text = null;
if (file2.exists()) {
FileInputStream fis;
try {
fis = new FileInputStream(file2);
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
text = br.readLine();
br.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return text;
}

}追加篇
public class MainActivity extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toast.makeText(MainActivity.this, Readerimei(), Toast.LENGTH_SHORT).show();

}

public void saveimei(String content)

{

try {
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){

//获取SD卡的目录
File sdCardDir = Environment.getExternalStorageDirectory();
File targetFile = new File(sdCardDir.getCanonicalPath() + "/resultimei.txt");
//以指定文件创建RandomAccessFile对象
RandomAccessFile raf = new RandomAccessFile(targetFile, "rw");
//将文件记录指针移动到最后
raf.seek(targetFile.length());
//输出文件内容
raf.write(content.getBytes());
raf.close();
}
} catch (Exception e) {
e.printStackTrace();
}

}
public String Readerimei() {
try {

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
Toast.makeText(MainActivity.this, "SD卡存在", Toast.LENGTH_SHORT).show();
//获得SD卡对应的存储目录
File sdCardDir = Environment.getExternalStorageDirectory();
String str = sdCardDir.getCanonicalPath() + "resultimei.txt";
//获取指定文件对应的输入流
FileInputStream fis = new FileInputStream(sdCardDir.getCanonicalPath() + "/resultimei.txt");
//将指定输入流包装成BufferReader
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
StringBuilder sb = new StringBuilder("");
String line = null;
//循环读取文件内容
while((line = br.readLine()) != null){
sb.append(line);
}
br.close();
return sb.toString();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
String IMEI="844646546546546\n";
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
saveimei(IMEI);
}

}

还有很多方法，自己就总结这两种供以后使用了