android之 檔案IO

[Context方法本應用資料檔案夾]

public FileInputStream openFileInput(String name)
throws FileNotFoundException

public FileOutputStream openFileOutput(String name, int mode)
throws FileNotFoundException

package org.crazyit.io;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.PrintStream;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;public class FileTest extends Activity{final String FILE_NAME = "crazyit.bin";@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);System.out.println(new StringBuilder("a").append("b").append("c").toString());// 擷取兩個按鈕Button read = (Button) findViewById(R.id.read);Button write = (Button) findViewById(R.id.write);// 擷取兩個文字框final EditText edit1 = (EditText) findViewById(R.id.edit1);final EditText edit2 = (EditText) findViewById(R.id.edit2);// 為write按鈕綁定事件監聽器write.setOnClickListener(new OnClickListener(){@Overridepublic void onClick(View source){// 將edit1中的內容寫入檔案中write(edit1.getText().toString());edit1.setText("");}});read.setOnClickListener(new OnClickListener(){@Overridepublic void onClick(View v){// 讀取指定檔案中的內容，並顯示出來edit2.setText(read());}});}private String read(){try{// 開啟檔案輸入資料流FileInputStream fis = openFileInput(FILE_NAME);byte[] buff = new byte[1024];int hasRead = 0;StringBuilder sb = new StringBuilder("");// 讀取檔案內容while ((hasRead = fis.read(buff)) > 0){sb.append(new String(buff, 0, hasRead));}// 關閉檔案輸入資料流fis.close();return sb.toString();}catch (Exception e){e.printStackTrace();}return null;}private void write(String content){try{// 以追加模式開啟檔案輸出資料流FileOutputStream fos = openFileOutput(FILE_NAME, MODE_APPEND);// 將FileOutputStream封裝成PrintStreamPrintStream ps = new PrintStream(fos);// 輸出檔案內容ps.println(content);// 關閉檔案輸出資料流ps.close();}catch (Exception e){e.printStackTrace();}}}

應用程式的資料檔案預設儲存在/data/data//files目錄下。

[讀寫SD卡上檔案]

private String read(){try{// 如果手機插入了SD卡，而且應用程式具有訪問SD的許可權if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){// 擷取SD卡對應的儲存目錄File sdCardDir = Environment.getExternalStorageDirectory();// 擷取指定檔案對應的輸入資料流FileInputStream fis = new FileInputStream(sdCardDir.getCanonicalPath() + FILE_NAME);// 將指定輸入資料流封裝成BufferedReaderBufferedReader br = new BufferedReader(new InputStreamReader(fis));StringBuilder sb = new StringBuilder("");String line = null;// 迴圈讀取檔案內容while ((line = br.readLine()) != null){sb.append(line);}// 關閉資源br.close();return sb.toString();}}catch (Exception e){e.printStackTrace();}return null;}private void write(String content){try{// 如果手機插入了SD卡，而且應用程式具有訪問SD的許可權if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){// 擷取SD卡的目錄File sdCardDir = Environment.getExternalStorageDirectory();File targetFile = new File(sdCardDir.getCanonicalPath() + FILE_NAME);// 以指定檔案建立 RandomAccessFile對象RandomAccessFile raf = new RandomAccessFile(targetFile, "rw");// 將檔案記錄指標移動到最後raf.seek(targetFile.length());// 輸出檔案內容raf.write(content.getBytes());// 關閉RandomAccessFileraf.close();}}catch (Exception e){e.printStackTrace();}}