Android：單擊按鈕以檢查是否存在並保存文件

Question

我希望該應用程序可以實現以下功能1.將文件名放入ediTtext 2.按開始按鈕，如果文件存在，則寫入文件，如果不存在，則創建文件3.按停止按鈕，過程將停止並editText的內容將返回到文件名。

我已經完成了保存文件的部分，但是不知道如何檢查是否存在：P，希望可以得到一些代碼作為參考！ 謝謝！

這是保存文件的代碼：

        ////////////////////////////////////
private String TAG = "MyActivity";
private WifiManager wifiManager;
List<ScanResult> list;
private Runnable runnable;
private Handler handler;




@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_wifi_list);        
    handler=new Handler();
    runnable=new Runnable() {
        @Override
        public void run() {
            init();
            handler.postDelayed(this, 3000);
        }
    }; 

    handler.post(runnable);
}




private void init() {
    wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    list = wifiManager.getScanResults();
    ListView listView = (ListView) findViewById(R.id.listView);     
    String wifiInfo = "";
    if (list == null) {
        Toast.makeText(this, "wifi is closed！", Toast.LENGTH_LONG).show();
    }else {
        for (int i = 0; i<list.size();i++){
            ScanResult scanResult = list.get(i);
            String bssid = scanResult.BSSID;
            String ssid = scanResult.SSID;
            int strength = Math.abs(scanResult.level);
            wifiInfo = wifiInfo + String.format("%25s,%20s,%5d\n", bssid,ssid,strength);

        }
        listView.setAdapter(new NewAdapter(this,list));
    }
    writeToFile(wifiInfo,"WifiList_Info.txt");
    Toast toast = Toast.makeText(this, "new record", Toast.LENGTH_SHORT);
    toast.setGravity(Gravity.CENTER, 0, 0);
    toast.show();
}



private void writeToFile(String data,String fileName){

    File file = null;
    OutputStream output = null;
    byte buffer[] = null;   

       try{ 

        File path = Environment.getExternalStorageDirectory();
        file = new File(path,fileName);
        if(!file.exists())
            file.createNewFile();
        output = new FileOutputStream(file, true);
        buffer = data.getBytes();
        output.write(buffer);
        output.flush();
        output.close();        
           } 
          catch(Exception e){              e.printStackTrace(); 
          } 
}



 public void onClick_startEvent(View view) {
     EditText editText = (EditText)findViewById(R.id.et1);
     editText.setText("writing into the file", TextView.BufferType.NORMAL);
}

}

Answer 1

用於檢查文件是否存在：

File tempFile = null;

tempFile = new File(filePath);
if(!tempFile.exists())
    //do your work

Answer 2

File myFile = new File(your_file_path);


if(myFile.exists())
   {

           // file exists
    }


else

{

   // file doesn't exists, so create a new file here.

}