Android之再谈文件操作和SDcard读写

1>读写SDCard数据要权限如下。

<!-- 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"/>

2>读写service如下

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); } }

3>控制层如下。要判断手机是否存在sd卡，并且是否写保护。

public class MainActivity extends Activity { private static final String TAG = "MainActivity"; private FileService fileService; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); fileService = new FileService(this); Button button = (Button) this.findViewById(R.id.button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { EditText filenameText = (EditText) findViewById(R.id.filename); EditText contentText = (EditText) findViewById(R.id.filecontent); String filename = filenameText.getText().toString(); String content = contentText.getText().toString(); try { //判断sdcard是否存在于手机上，并且可以进行读写访问 if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ fileService.saveToSDCard(filename, content); Toast.makeText(MainActivity.this, R.string.success, 1).show(); }else{ Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show(); } } catch (Exception e) { Log.e(TAG, e.toString()); Toast.makeText(MainActivity.this, R.string.error, 1).show(); } } }); } }