File 类的操作：
1.首先需要添加相关权限：
代码语言：javascript复制 <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：
代码语言：javascript复制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
代码语言：javascript复制//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
代码语言：javascript复制 /**
* 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("rn");//换行
writer.write(content);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if(writer != null){
writer.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}3.readFromFile()
代码语言：javascript复制//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()
代码语言：javascript复制//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();
}
}
}总结
以上所述是小编给大家介绍的Android studio 将字符串写入本地的操作方法，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对ZaLou.Cn网站的支持！
