將多個字符串寫入文件並添加新行

Question

我正在構建一個基本應用程序，您可以從微調器中選擇一種顏色並單擊「保存」。如果您要查找的顏色不在微調框中，請按下按鈕，然後將其輸入到EditText中。 我試圖讓它可以寫入所選的微調器/編輯文本顏色和「colors.txt」文件中的日期。目前，沒有任何錯誤，但是當我在Android上啓動應用程序時，它立即崩潰。

Colorchooser.java

package com.example.scalendar; 

import java.io.IOException; 
import java.io.OutputStreamWriter; 
import android.os.Bundle; 
import android.app.Activity; 
import android.content.Context; 
import android.util.Log; 
import android.view.Menu; 

public class Colorchooser extends Activity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_colorchooser); 
    } 


    public void writetoFile(String str) { 
     try { 
      OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("colors.txt", Context.MODE_PRIVATE)); 
      outputStreamWriter.write("colorstring , datestring"); 
      outputStreamWriter.close(); 
     } 
     catch (IOException e) { 
      Log.e("Exception", "File write failed: " + e.toString()); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.colorchooser, menu); 
     return true; 
    } 
}` 

這裏是我的strings.xml文件

<?xml version="1.0" encoding="utf-8"?> 
<resources> 

    <string name="app_name">SCalendar</string> 
    <string name="action_settings">Settings</string> 
    <string name="color_prompt">What was todays color?</string> 
    <string name="SaveButtonText">Save To Calendar</string> 
    <string name="textfieldhint">Enter color</string> 
    <string name="otherbuttontext">Color not listed</string> 
    <string name="othercolorexplanationtext">Dont see the color here? Click the button below and type it yourself.</string> 


    <string-array name="color_arrays"> 
     <item>Select a color:</item> 
     <item>Purple</item> 
     <item>Orange</item> 
     <item>Green</item> 
     <item>Red</item> 
     <item>Blue</item> 
     <item>Pink</item> 
     <item>Brown</item> 
     <item>Yellow</item> 
     <item>Black</item> 
     <item>White</item> 
    </string-array> 

      <string name="colorstring"> 
       colorSpinner = findViewById(R.id.colorSpinner) 
       colorSpinner.getSelectedItem().toString() 
      </string> 

      <string name="datestring"> 
      SimpleDateFormat formatter = new SimpleDateFormat("dd_MM_yyyy"); 
      Date now = new Date(); 
      String fileName = formatter.format(now).toString(); 
      </string> 


</resources>` 

這是我的Mainactivity.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context="Colorchooser" > 

<Spinner 
    android:id="@+id/colorSpinner" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_alignParentTop="true" 
    android:layout_centerHorizontal="true" 
    android:entries="@array/color_arrays" 
    android:prompt="@string/color_prompt" /> 

<TextView 
    android:id="@+id/othercolorexplaination" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignLeft="@+id/colorSpinner" 
    android:layout_below="@+id/colorSpinner" 
    android:layout_marginTop="15dp" 
    android:text="@string/othercolorexplanationtext" 
    android:textAppearance="?android:attr/textAppearanceMedium" /> 

<Button 
    android:id="@+id/ButtonSave" 
    style="@style/AppTheme" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:layout_alignLeft="@+id/othercolorexplaination" 
    android:layout_alignParentBottom="true" 
    android:layout_marginBottom="62dp" 
    android:onClick="writetoFile(String getcolor)" 
    android:text="@string/SaveButtonText" /> 

<EditText 
    android:id="@+id/othercolor" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:layout_alignLeft="@+id/ButtonSave" 
    android:layout_below="@+id/otherbutton" 
    android:layout_marginTop="42dp" 
    android:ems="10" 
    android:focusable="false" 
    android:hint="@string/textfieldhint" 
    android:inputType="textEmailAddress" > 
</EditText> 

<Button 
    android:id="@+id/otherbutton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@+id/othercolorexplaination" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="24dp" 
    android:onClick="othercolor.focusableInTouchMode(true)" 
    android:text="@string/otherbuttontext" /> 
</RelativeLayout>` 

Answer 1

看來你有一些重大對Java字符串與字符串變量var之間關係的誤解iables，和字符串變量VS字符串資源：

1. 此：

   outputStreamWriter.write("colorstring , datestring"); 
   

   將永遠寫 「colorstring，datestring」 到您的文件，那麼該文件將是這樣的：

   colorstring, datestring 
   colorstring, datestring 
   colorstring, datestring 
   

2. 你不能指望你的字符串資源中的Java代碼被執行：

   <string name="colorstring"> 
        colorSpinner = findViewById(R.id.colorSpinner) 
        colorSpinner.getSelectedItem().toString() 
   </string> 
   

   您資源中的字符串爲Constants。在運行時沒有辦法改變它們。