Android之再谈文件操作和SDcard读写

1>读写SDCard数据要权限如下。

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 / xFileOutputStream 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() {@Overridepublic 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();}}});    }}

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