Question

我正在创建一个应用程序，您可以在其中输入日期，时间，往返地点以及跟踪里程数的任何注释。在我的AddActivity.java中，您输入信息。然后，BufferedWriter将此信息写入txt文件。在我的EditActivity.java（附件）中，文本应自动从文件中读取，然后在EditText中显示给用户。当我运行一个模拟器时，文本显示正常。当我在导出后在手机上运行它时，文本＆＃34;无法检索＆＃34;显示意味着try / catch块中的BufferedReader未成功运行。我在这里错过了什么？谢谢！

    package com.reese.mileagelog;


    import java.io.BufferedReader;
    import java.io.BufferedWriter;
    import java.io.File;
    import java.io.FileNotFoundException;
    import java.io.FileReader;
    import java.io.FileWriter;
    import java.io.IOException;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.Toast;

    public class EditActivity extends Activity implements View.OnClickListener {

Button addBut;
Button editBut;
Button emailBut;
EditText editText;
String currentText;
Button delete;
public String current;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit);
    editText=(EditText)findViewById(R.id.edit1);
    delete = (Button)findViewById(R.id.delete);
    delete.setOnClickListener(this);
    editText.setText(getCurrentText());
    Toast.makeText(getBaseContext(), getCurrentText(), Toast.LENGTH_LONG).show();
    }



@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}




@Override
public void onClick(View v) {
    switch(v.getId())
    {
        case R.id.delete:
            deleteText();

            editText.setText(getCurrentText());
            break;

    }
}
public void deleteText(){
    BufferedWriter bufferedWriter;
    try {
        bufferedWriter = new BufferedWriter(new FileWriter(new 
        File(getFilesDir()+File.separator+"MileageLog.txt")));
        bufferedWriter.write("");
        bufferedWriter.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public String getCurrentText()
{
    String currentText ="Could not retrieve";

    try {
        BufferedReader bufferedReader;
        bufferedReader = new BufferedReader(new FileReader(new 
                File(getFilesDir()+File.separator+"MileageLog.txt")));
        String read;
        StringBuilder builder = new StringBuilder("");

        while((read = bufferedReader.readLine()) != null){
        builder.append(read);
        }
        currentText = builder.toString();
        editText.setText(currentText);
        bufferedReader.close();
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return currentText;
}

    }

Answer 1

很难说没有更多信息，但我最好的猜测是你的应用程序正在安装在SD卡（外部存储设备）而不是内置设备上。发生这种情况时，您需要一个特殊的权限来编写文件，您可以在AndroidManifest.xml：

中添加这些文件

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

如果您宁愿避免此权限，请确保不将android:installLocation设置为preferExternal

Android在模拟器中写入文件但在实际手机上没有

1 个答案: