如何在android中逐行閱讀？

Question

我使用此代碼。

try{ 
      // Open the file that is the first 
      // command line parameter 
      FileInputStream fstream = new FileInputStream("config.txt"); 
      // Get the object of DataInputStream 
      DataInputStream in = new DataInputStream(fstream); 
      BufferedReader br = new BufferedReader(new InputStreamReader(in)); 
      while ((br.readLine()) != null) { 
       temp1 = br.readLine(); 
       temp2 = br.readLine(); 

      } 

      in.close(); 
    }catch (Exception e){//Catch exception if any 
    Toast.makeText(getBaseContext(), "Exception", Toast.LENGTH_LONG).show(); 
    } 
    Toast.makeText(getBaseContext(), temp1+temp2, Toast.LENGTH_LONG).show(); 

但這是顯示異常並且不更新temp1和temp2。

Answer 1

你看到的例外 - 我會強烈建議）來捕捉一個特定的類型，例如IOException和b）記錄或顯示消息或堆棧跟蹤，以及c）至少從DDMS角度檢查LogCat中是否使用Eclipse進行編程 - 可能是由於Android沒有找到您的文件config.txt正試圖打開。通常，對於最簡單的情況（例如您的應用程序），使用openFileInput - see the documentation來打開專用於應用程序的文件以獲取詳細信息。

除了例外情況，您的讀取循環有缺陷：您需要在輸入前初始化一個空字符串，並將其填入while的條件中。

String line = ""; 
while ((line = br.readLine()) != null) { 
    // do something with the line you just read, e.g. 
    temp1 = line; 
    temp2 = line; 
} 

但是，如果您只是想將前兩行保存在不同的變量中，則不需要循環。

String line = ""; 
if ((line = br.readLine()) != null) 
    temp1 = line; 
if ((line = br.readLine()) != null) 
    temp2 = line; 

正如其他人已經指出，調用readLine消耗線，因此，如果您config.txt文件僅包含一行代碼消耗它的while條件，然後temp1和temp2得到null分配，因爲沒有更多的文字讀書。如果你想保存你所要做的前兩行

Answer 2

try{ 
     // Open the file that is the first 
     // command line parameter 
     FileInputStream fstream = new FileInputStream("config.txt"); 
     // Get the object of DataInputStream 
     DataInputStream in = new DataInputStream(fstream); 
     BufferedReader br = new BufferedReader(new InputStreamReader(in)); 
     String line = ""; 
     while ((line = br.readLine()) != null) { 
      temp1 = line; 
      temp2 = line; 

     } 

     in.close(); 
}catch (Exception e){//Catch exception if any 
Toast.makeText(getBaseContext(), "Exception", Toast.LENGTH_LONG).show(); 
} 
Toast.makeText(getBaseContext(), temp1+temp2, Toast.LENGTH_LONG).show(); 

Answer 3

br.readLine（）in while已經佔用一行。

試試這個

LineNumberReader reader = new LineNumberReader(new FileReader("config.txt"))); 
    String line; 
    while ((line = reader.readLine()) != null) { 
     //doProcessLine 
    } 

Answer 4

：

try 
{ 
    // Open the file that is the first 
    // command line parameter 
    FileInputStream fstream = new FileInputStream("config.txt"); 
    // Get the object of DataInputStream 
    DataInputStream in = new DataInputStream(fstream); 
    BufferedReader br = new BufferedReader(new InputStreamReader(in)); 
    String line = ""; 
    if((line = br.readLine()) != null) 
     temp1 = line; 
    if((line = br.readLine()) != null) 
     temp2 = line; 
} 
catch(Exception e) 
{ 
    e.printStackTrace(); 
}