數組總是返回空

Question

我正在製作一個Android應用程序，用於從文件夾中讀取文件，從中生成數組，然後在地圖上繪製數組的緯度+經度點。我起初在一個單獨的程序中開發了數組返回方法作爲void方法（它的功能正確）。我對它做的唯一更改是我使它返回數組，以便Android應用程序可以使用它。不過，我總是收到武力。經過一些調試後，我發現我的方法每次都返回'null'（我設置了一個if語句，如果數組爲空，則顯示一個屏幕顯示「FAIL！」 - 並且該應用程序始終顯示「FAIL！」） 。

我檢查以確保文件位於正確的位置 - 它的確是。不過，我不確定程序爲什麼返回null。下面是我的一些代碼：

package net.learn2develop.GoogleMaps; 

import java.io.BufferedReader; 
import java.io.File; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import java.util.List; 
import java.util.StringTokenizer; 

import com.google.android.maps.GeoPoint; 
import com.google.android.maps.MapActivity; 
import com.google.android.maps.MapController; 
import com.google.android.maps.MapView; 
import com.google.android.maps.Overlay; 
import com.google.android.maps.MapView.LayoutParams; 

import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Canvas; 
import android.graphics.Point; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.LinearLayout; 


public class MapsActivity extends MapActivity 
{  
    MapView mapView; 
    MapController mc; 
    GeoPoint p; 
    GeoPoint p2; 
    GeoPoint p99; 

/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    // Map code goes here..... 


    // Add points from ReadCsv.java 
    File fileToUse = new File("/Users/csrobot/Desktop/TrainingData/Training4.csv"); 
    String[][] bump = getArray(fileToUse); 
    if(bump == null){ 
     setContentView(R.layout.deleteme); 
    } 
//  for(int i = 0; i < bump.length; i++) { 
//   String coordinates99[] = {bump[i][0], bump[i][1]}; 
//   double lat99 = Double.parseDouble(coordinates99[0]); 
//   double lng99 = Double.parseDouble(coordinates99[1]); 
//   p99 = new GeoPoint(
//     (int) (lat99 * 1E6), 
//     (int) (lng99 * 1E6)); 
//   MapOverlay mapOverlay99 = new MapOverlay(); 
//   List<Overlay> listOfOverlays99 = mapView.getOverlays(); 
//   listOfOverlays99.add(mapOverlay99); 
//  } 

    mapView.invalidate(); 
} 

@Override 
protected boolean isRouteDisplayed() { 
    return false; 
} 

public String[][] getArray(File file) { 

    try { 
     int row = 0; 
     int col = 0; 
     String[][] numbers=new String[5258][16]; 

     BufferedReader bufRdr; 
     bufRdr = new BufferedReader(new FileReader(file)); 
     String line = null; 

     //read each line of text file 
     while((line = bufRdr.readLine()) != null) { 
      StringTokenizer st = new StringTokenizer(line,","); 
      col=0; 

      while (st.hasMoreTokens()) { 
       //get next token and store it in the array 
       numbers[row][col] = st.nextToken(); 
       col++; 
      } 
      row++; 
     } 

     // ... Here is the code that will make the array 
        // ... 

     //close the file 
     bufRdr.close(); 

     return arrayOfBumps; 

    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } catch(Exception e) { 
       // System.out.println("The following error occurred "+e); 
    } 
    return null; 

} 

所以這是我的活動樣子。

07-28 09:11:10.962: ERROR/AndroidRuntime(13014): FATAL EXCEPTION: main 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014): java.lang.RuntimeException: Unable to start activity ComponentInfo{net.learn2develop.GoogleMaps/net.learn2develop.GoogleMaps.MapsActivity}: java.lang.NullPointerException 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.os.Looper.loop(Looper.java:123) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at java.lang.reflect.Method.invoke(Method.java:521) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at dalvik.system.NativeStart.main(Native Method) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014): Caused by: java.lang.NullPointerException 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at net.learn2develop.GoogleMaps.MapsActivity.onCreate(MapsActivity.java:89) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
07-28 09:11:10.962: ERROR/AndroidRuntime(13014):  ... 11 more 

因此，誰能幫助我在這裏：添加「如果（凹凸== NULL）」語句，並取消註釋的「for」循環跟隨它以前我logcat的？我已經在這裏呆了幾天，但仍然無法弄清楚。

Answer 1

File fileToUse = new File("/Users/csrobot/Desktop/TrainingData/Training4.csv");

這是NullPointerException的來源。

文件的路徑必須以這種形式/data/data/yourpackagename/somefolder/yourfile

你不能做到這一點是這樣的。該文件必須存儲在模擬器/電話數據存儲器內。您必須將文件推送到仿真器數據，例如將您的csv文件移動到assets/raw resource，然後將其加載到InputStreamReader對象中並執行您計劃要執行的操作。從assets文件夾或res/raw文件夾中搜索更多開放文件的示例