Android--文件存储操作(一)

    //将一段文本内容保存到文件中:
    //在onDestory() 里面调用save()方法.此方法写在了super.onDestory() 下面.
 　　//openFileOutput --> FileOutputStream  --> OutputStreamReader -->  BufferedReader
    public void save() {
        String data = "Data to save";
        FileOutputStream out = null;
        BufferedWriter writer = null;
        try {
            out = mContext.openFileOutput("data", Context.MODE_PRIVATE);//需要FileNot错误.
            writer = new BufferedWriter(new OutputStreamWriter(out)); //构建一个outputStreamWriter.接着由构建了一个BufferedWriter()
            writer.write(data);//需要IO错误
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (writer != null) {
                try {
                    writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //在下一次打开的时候,从文件中读取数据
　　// openFileinput --> FileInputStream --> InputStreamReader --> BufferedReader
　　// 前两个  file  一直在 input 前面
    public String load() {
        FileInputStream in = null;
        BufferedReader reader = null;
        StringBuilder sb = new StringBuilder();
        try {
            in = mContext.openFileInput("data");        //需要fileNOt错误
            reader = new BufferedReader(new InputStreamReader(in));
            String line = "";
            while ((line = reader.readLine()) != null) {  //需要IO错误
                sb.append(line);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sb.toString();
    }

//写入到内置存储空间
    public void write(View view) {
        String inputString = inputText.getText().toString();
        if (inputString == null || "".equals(inputString.trim())) {
            Toast.makeText(mContext, "请输入需要写入的内容，不能为空", Toast.LENGTH_SHORT).show();
            return;
        }
        FileOutputStream fos = null;
        try {
            if (appendBtn.isChecked()) {
                fos = mContext.openFileOutput(fileName, Context.MODE_APPEND);
            } else {
                fos = mContext.openFileOutput(fileName, Context.MODE_PRIVATE);
            }
            fos.write(inputString.getBytes());      //向文件里写入内容
            Toast.makeText(mContext, "内容写入完毕！", Toast.LENGTH_SHORT).show();
        } catch (FileNotFoundException e) {
            Toast.makeText(mContext, "文件没有找到，请检查文件路径", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            Toast.makeText(mContext, "写入过程中出现错误 IO", Toast.LENGTH_SHORT).show();
        }
    }

    //读取内置存储空间
    public void readFromSDCard(View view) {
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            String path = Environment.getExternalStorageDirectory() + File.separator + fileName;
            File file = new File(path);
            StringBuilder sBuilder = new StringBuilder("");
            byte[] buffer = new byte[256];
            int hasRead = 0;

            try {
                RandomAccessFile raf = new RandomAccessFile(file, "rw");
                while ((hasRead = raf.read(buffer)) != -1) {
                    sBuilder.append(new String(buffer, 0, hasRead));
                }
                outputText.setText(sBuilder);
                raf.close();
            } catch (FileNotFoundException e) {
                Toast.makeText(mContext, "文件没有找到，请检查文件路径", Toast.LENGTH_SHORT).show();
            } catch (IOException e) {
                Toast.makeText(mContext, "写入过程中出现错误 IO", Toast.LENGTH_SHORT).show();
            }
        }
    }