Android studio 将字符串写入本地的操作

File 类的操作:
1.首先需要添加相关权限:

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

注意6.0以上需要动态申请:

 private  void checkPermission(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//6.0以上

            int permission = ActivityCompat.checkSelfPermission(getApplication(), Manifest.permission.RECEIVE_SMS);
            int permission1 = ActivityCompat.checkSelfPermission(getApplication(), Manifest.permission.WRITE_EXTERNAL_STORAGE);
            if(permission != PackageManager.PERMISSION_GRANTED && permission1 != PackageManager.PERMISSION_GRANTED) {
                Log.e(TAG,"没有获取权限,请申请");
                // 申请一个(或多个)权限,并提供用于回调返回的获取码(用户定义)
                if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                        Manifest.permission.RECEIVE_SMS) && ActivityCompat.shouldShowRequestPermissionRationale(this,
                        Manifest.permission.WRITE_EXTERNAL_STORAGE)) {//这里可以写个对话框之类的项向用户解释为什么要申请权限,并在对话框的确认键后续再次申请权限

                    Log.e(TAG,"提示");
                    ActivityCompat.requestPermissions(this,
                            new String[]{Manifest.permission.RECEIVE_SMS,Manifest.permission.WRITE_EXTERNAL_STORAGE}, CODE_READ_SMS);
                } else {
                    //申请权限,字符串数组内是一个或多个要申请的权限,1是申请权限结果的返回参数,在onRequestPermissionsResult可以得知申请结果

                    Log.e(TAG,"您已禁止");
                    Toast.makeText(MainActivity.this,"没有获取读取手机权限,请到应用中心手动打开该权限",Toast.LENGTH_SHORT).show();

                }
            }else{
                 Log.e(TAG,"获取到了权限");
            }
        }else{
            Log.e(TAG,"获取到了权限");
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode == CODE_READ_SMS){
            if(grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Log.e(TAG,"获取到了权限");
            } else{
                // 没有获取到权限,做特殊处理
                Log.e(TAG,"没有获取到权限");
                Toast.makeText(MainActivity.this,"没有获取读取手机权限,请到应用中心手动打开该权限",Toast.LENGTH_SHORT).show();
            }
        }
    }

2.saveToFile

a)BufferedWriter 追加

//保存文件到sd卡
    public void saveToFile(String content) {
        BufferedWriter out = null;

        //获取SD卡状态
        String state = Environment.getExternalStorageState();
        //判断SD卡是否就绪
        if (!state.equals(Environment.MEDIA_MOUNTED)) {
            Toast.makeText(this, "请检查SD卡", Toast.LENGTH_SHORT).show();
            return;
        }
        //取得SD卡根目录
        File file = Environment.getExternalStorageDirectory();
        try {
            Log.e(TAG, "======SD卡根目录:" + file.getCanonicalPath());
            if(file.exists()){
                LOG.e(TAG, "file.getCanonicalPath() == " + file.getCanonicalPath());
            }
            /*
            输出流的构造参数1:可以是File对象  也可以是文件路径
            输出流的构造参数2:默认为False=>覆盖内容; true=>追加内容
             */
            out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file.getCanonicalPath() + "/readMsg.txt",true)));
            out.newLine();
            out.write(content);
            Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

b)FileWriter追加

 /**
     * 使用FileWriter进行文本内容的追加
     * @param file
     * @param content
     */
    private void addTxtToFileWrite(File file, String content){
        FileWriter writer = null;
        try {
            //FileWriter(file, true),第二个参数为true是追加内容,false是覆盖
            writer = new FileWriter(file, true);
            writer.write("\r\n");//换行
            writer.write(content);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if(writer != null){
                    writer.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

3.readFromFile()

 //从SD卡读取文件
    public String readFromFile() {
        //读的时候要用字符流   万一里面有中文
        BufferedReader reader = null;
        FileInputStream fis;
        StringBuilder sbd = new StringBuilder();
        String state = Environment.getExternalStorageState();
        if (!state.equals(Environment.MEDIA_MOUNTED)) {
            Toast.makeText(this, "SD卡未就绪", Toast.LENGTH_SHORT).show();
            return "";
        }
        File root = Environment.getExternalStorageDirectory();
        try {
            fis = new FileInputStream(root + "/readMsg.txt");
            reader = new BufferedReader(new InputStreamReader(fis));
            String row;
            while ((row = reader.readLine()) != null) {
                sbd.append(row);
            }
        } catch (FileNotFoundException e) {
            Toast.makeText(this, "文件不存在", Toast.LENGTH_SHORT).show();
            //e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sbd.toString();
    }

4.removeFromFile()

//删除SD卡文件
    public void removeFromFile() {
        String state = Environment.getExternalStorageState();
        if (!state.equals(Environment.MEDIA_MOUNTED)) {
            Toast.makeText(this, "SD卡未就绪", Toast.LENGTH_SHORT).show();
            return;
        }
        //取得SD卡根目录
        File root = Environment.getExternalStorageDirectory();
        File myFile=new File(root+"/sd.txt");
        //File myFile=new File(root,"sd.txt");
        if (myFile.exists()) {
            myFile.delete();
            Toast.makeText(this,"文件已删除",Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(this,"文件不存在",Toast.LENGTH_SHORT).show();
        }
    }
}

猜你喜欢

转载自blog.csdn.net/Silence_Sep/article/details/81219337