Android 将手机号码保存在文件中

我开发了一个android应用程序，用户可以通过手机号码注册。我希望我的应用程序保存电话号码，以便下次用户打开应用程序时，无需再次输入电话号码，类似于Whatsapp。。 这是我的代码，但它不起作用，每次打开应用程序时我都必须输入电话号码，而且，在将此代码添加到我的应用程序后，应用程序变得又重又慢

  if (android.os.Build.VERSION.SDK_INT > 9) 
  {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
                .permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }
    try {
        TelephonyManager tMgr = (TelephonyManager) getApplicationContext()
                .getSystemService(Context.TELEPHONY_SERVICE);
        mPhoneNumber = tMgr.getLine1Number().toString();
    } catch (Exception e) {
        String EE = e.getMessage();
    }
    if (mPhoneNumber == null) {
    try {
        fOut = openFileOutput("textfile.txt", MODE_WORLD_READABLE);

        fIn = openFileInput("textfile.txt");
        InputStreamReader isr = new InputStreamReader(fIn);
        char[] inputBuffer = new char[50];
        if (isr.read(inputBuffer) == 0) {

        }

    } catch (IOException ioe) {
        ioe.printStackTrace();
    }

    AlertDialog.Builder alert = new AlertDialog.Builder(this);
    alert.setTitle("Warrning");
    alert.setMessage("Please Set Your Phone number");
    final EditText input = new EditText(this);
    alert.setView(input);
    alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int whichButton) {
            mPhoneNumber = input.getText().toString();
            try {
                fIn = openFileInput("textfile.txt");
                InputStreamReader isr = new InputStreamReader(fIn);
                char[] inputBuffer = new char[50];
                if (isr.read(inputBuffer) == 0) {
                    OutputStreamWriter osw = new OutputStreamWriter(fOut);
                    // ---write the string to the file---
                    osw.write(mPhoneNumber);
                    osw.flush();
                    osw.close();
                    // ---display file saved message---
                    Toast.makeText(getBaseContext(),
                            "Phone number saved successfully!",
                            Toast.LENGTH_SHORT).show();
                    // ---clears the EditText---
                    input.setText("");
                } else {
                    int charRead;
                    while ((charRead = isr.read(inputBuffer)) > 0) {
                        // ---convert the chars to a String---
                        String readString = String.copyValueOf(inputBuffer,
                                0, charRead);
                        mPhoneNumber = readString;
                        inputBuffer = new char[50];
                    }
                    // ---set the EditText to the text that has been
                    // read---

                    Toast.makeText(getBaseContext(),
                            "Phone number read successfully!",
                            Toast.LENGTH_SHORT).show();
                }

            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
            int UserServiceId = CallLogin(mPhoneNumber);
            if (UserServiceId > 0) {
                Intent Service = new Intent(MainScreeen.this,
                        RecipeService.class);
                Service.putExtra("UserId", UserServiceId);
                startService(Service);
            } else {
                Intent Reg = new Intent(MainScreeen.this,
                        Regsteration.class);
                Reg.putExtra("PhoneNumber", mPhoneNumber);
                startActivity(Reg);
            }
        }
    });
    alert.show();
    } else {

        int UserServiceId = CallLogin(mPhoneNumber);
        if (UserServiceId > 0) {
            Intent Service = new Intent(MainScreeen.this,
                    RecipeService.class);
            Service.putExtra("UserId", UserServiceId);
            startService(Service);
        } else {
            Intent Reg = new Intent(MainScreeen.this, Regsteration.class);
            Reg.putExtra("PhoneNumber", mPhoneNumber);
            startActivity(Reg);
        }
    } 

---

请帮我弄清楚

在这段代码中：

if (mPhoneNumber == null) {
try {
    fOut = openFileOutput("textfile.txt", MODE_WORLD_READABLE);
    fIn = openFileInput("textfile.txt");

您打开文件进行输出，这将销毁您已经写入的任何内容。稍后，当您尝试读取此文件时，一切都太晚了

而且，这里的代码太多了。不要重新发明轮子。您不需要一次读取一个字符的文件。如果您只想将字符串写入文件，然后再将其读回，请使用

DataInputStream

和

DataOutputStream

，您可以直接使用

readUTF（）

和

writeUTF（）

读取/写入字符串。下面是一个读取该文件的简单示例：

    DataInputStream in = new DataInputStream(openFileInput("textfile.txt"));
    String contents = in.readUTF();

要写入文件，请使用：

    DataOuputStream out = new DataOutputStream(openFileOutput("textfile.txt", 0));
    out.writeUTF(phoneNumber);

---

显然，您需要添加try/catch块和处理异常，并确保在

finally

块中关闭流，但如果这样做，您将得到更少的代码。

为了帮助您，我给出了我的活动示例，以便读取和写入文件中的数据：

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class StoreDataActivity extends Activity {

    private static final String TAG = "ExerciceActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.main);

        writeFileOnDisk("toto.txt", "Bienvenue chez Android");

        String content = readFileOnDisk("toto.txt");
        Log.v(TAG, "content=" + content);
    }

    private void writeFileOnDisk(String filename, String data) {

        try {
            FileOutputStream fos = openFileOutput(filename, this.MODE_PRIVATE);
            fos.write(data.getBytes());
            fos.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    private String readFileOnDisk(String filename) {

        int inChar;
        StringBuffer buffer = new StringBuffer();

        try {
            FileInputStream fis = this.openFileInput(filename);
            while ((inChar = fis.read()) != -1) {
                buffer.append((char) inChar);
            }
            fis.close();

            String content = buffer.toString();

            return content;

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }