在存储中保存文本的权限 android 不起作用

Question

我已经为用户构建了示例应用程序来编写一些文本并将其保存在内部存储中。

格式为 TXT 或 pdf。 我已经尝试过 android Kitkat sdk 19 并且它工作正常但是当我尝试使用最新的 android 9 时我被拒绝无法将文本保存在内部存储中

编辑：我想知道是否必须手动创建我的文件文件夹

我错过了什么？

安卓清单

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

主要活动

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

       mSaveTextBtn.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            mText = mResultEt.getText().toString().trim();
            if(mText.isEmpty()){
                Toast.makeText(MainActivity.this, "write text First...", Toast.LENGTH_SHORT).show();
            }
            else{
                if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
                    if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
                    == PackageManager.PERMISSION_GRANTED){
                        String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
                        requestPermissions(permissions,WRITE_EXTERNAL_STORAGE_CODE);
                    }else {
                        saveToTxtFile(mText);
                    }
                }else {
                    saveToTxtFile(mText);
                }
            }

        }
    }); 

}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch (requestCode){
        case WRITE_EXTERNAL_STORAGE_CODE: {
            if (grantResults.length > 0 && grantResults[0]
                    == PackageManager.PERMISSION_GRANTED) {
                //permission granted save data
                saveToTxtFile(mText);
            } else {
                //permission denied
                Toast.makeText(this, "Storage Permission required to store", Toast.LENGTH_SHORT).show();
            }
        }
        break;
    }
}

private void saveToTxtFile(String mText){
    //get current time for file name
    String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
            Locale.getDefault()).format(System.currentTimeMillis());
    try{
        //path tp storage
        File path = Environment.getExternalStorageDirectory();
        //create folder named "My file"
        File dir = new File( path + "/My Files/");
        dir.mkdirs();
        //file name
        String fileName = "MyFile_" + timestamp + ".txt";

        File file = new File (dir, fileName);

        //used to store characater in file
        FileWriter fw = new FileWriter(file.getAbsoluteFile());
        BufferedWriter bw = new BufferedWriter(fw);
        bw.write(mText);
        bw.close();

        //show file name and path where file saved
        Toast.makeText(this, fileName+"is saved to\n" +dir, Toast.LENGTH_SHORT).show();

    }catch (Exception e){
        //if anything goes wrong
        Toast.makeText(this, e.getMessage(), Toast.LENGTH_SHORT).show();
    }
}

Answer 1

正如Shashanth和kashyap所建议的那样。

这只是一种解决方法，但它有效。

我已经添加了

android:requestLegacyExternalStorage="true"

到我的AndroidManifest.xml文件中的<application>元素。

并改变了线路

File path = Environment.getExternalStorageDirectory();

到

File path = new File(getExternalFilesDir(null).getAbsolutePath());

Answer 2

在您的MainActivity您应该检查是否授予权限，然后使用!=运算符。

if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
                        == PackageManager.PERMISSION_GRANTED) {}

这一行应该是——

if(checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
                    != PackageManager.PERMISSION_GRANTED){}