Android中文件存储分为两类,一类在文件系统中,一类在存储在SDCard中
1.文件系统内
public class FileActivity extends Activity {
@Override public void onCreate(Bundle savedInstanceState) {
...
FileOutputStream outStream = this.openFileOutput("itcast.txt", Context.MODE_PRIVATE);
outStream.write("传智播客".getBytes());
outStream.close();
}
}
openFileOutput()方法的第一参数用于指定文件名称,不能包含路径分隔符“/” ,如果文件不存在,Android 会自动创建它。创建的文件保存在/data/data/<package name>/files目录,如: /data/data/cn.itcast.action/files/itcast.txt ,通过点击Eclipse菜单“Window”-“Show View”-“Other”,在对话窗口中展开android文件夹,选择下面的File Explorer视图,然后在File Explorer视图中展开/data/data/<package name>/files目录就可以看到该文件。
openFileOutput()方法的第二参数用于指定操作模式,有四种模式,分别为:
Context.MODE_PRIVATE = 0
Context.MODE_APPEND = 32768
Context.MODE_WORLD_READABLE = 1
Context.MODE_WORLD_WRITEABLE = 2
2.SDCard中
配置AndroidManifest.xml
<!-- 在SDCard中创建与删除文件权限 --> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> <!-- 往SDCard写入数据权限 --> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
写SDCard
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ File sdCardDir = Environment.getExternalStorageDirectory();//获取SDCard目录 File saveFile = new File(sdCardDir, “itcast.txt”); FileOutputStream outStream = new FileOutputStream(saveFile); outStream.write("传智播客".getBytes()); outStream.close(); }
总结:文件读写类
public class FileService { private Context context; public FileService(Context context) { this.context = context; } /** * 以私有文件保存内容 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void saveToSDCard(String filename, String content) throws Exception{ File file = new File(Environment.getExternalStorageDirectory(), filename); FileOutputStream outStream = new FileOutputStream(file); outStream.write(content.getBytes()); outStream.close(); } /** * 以私有文件保存内容 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void save(String filename, String content) throws Exception{ FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_PRIVATE); outStream.write(content.getBytes()); outStream.close(); } /** * 以追加方式保存内容 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void saveAppend(String filename, String content) throws Exception{// ctrl+shift+y / x FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_APPEND); outStream.write(content.getBytes()); outStream.close(); } /** * 保存内容,注:允许其他应用从该文件中读取内容 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void saveReadable(String filename, String content) throws Exception{ FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_READABLE); outStream.write(content.getBytes()); outStream.close(); } /** * 保存内容,注:允许其他应用往该文件写入内容 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void saveWriteable(String filename, String content) throws Exception{ FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_WRITEABLE); outStream.write(content.getBytes()); outStream.close(); } /** * 保存内容,注:允许其他应用对该文件读和写 * @param filename 文件名称 * @param content 文件内容 * @throws Exception */ public void saveRW(String filename, String content) throws Exception{ FileOutputStream outStream = context.openFileOutput(filename, Context.MODE_WORLD_READABLE+ Context.MODE_WORLD_WRITEABLE); outStream.write(content.getBytes()); outStream.close(); } /** * 读取文件内容 * @param filename 文件名称 * @return * @throws Exception */ public String readFile(String filename) throws Exception{ FileInputStream inStream = context.openFileInput(filename); byte[] buffer = new byte[1024]; int len = 0; ByteArrayOutputStream outStream = new ByteArrayOutputStream(); while( (len = inStream.read(buffer))!= -1){ outStream.write(buffer, 0, len); } byte[] data = outStream.toByteArray();//得到文件的二进制数据 outStream.close(); inStream.close(); return new String(data); } }