在Android中从sdcard中检索文件

在我的应用程序中，我从SD卡中检索文件，检查后是.jpg oe .png图片我在文件数组中存储文件的路径。但是我得到NullPointerException也存在文件路径。以下代码有什么问题。请帮助在Android中从sdcard中检索文件

File[] image; 
    File f = new File("/sdcard/download");//or Environment.getExternalStorageDirectory().getPath() 
     File[] files = f.listFiles(); 

     int j=0; 
     for(int i = 0; i < files.length; i++,j++) { 
      File file1 = files[i]; 

      String myfile = file1.getPath().substring(file1.getPath().lastIndexOf("/")+1,file1.getPath().length()).toLowerCase(); 
      System.out.println("file is : "+files[i]); 
      if(myfile.endsWith(".jpeg")||myfile.endsWith(".png")|| myfile.endsWith(".gif") || myfile.endsWith(".jpg")) 
      { 
       System.out.println("file is : "+files[i]); 
       image[j]=files[i];//here i'm getting exception 
       } 
      }

者除外

02-15 19:28:36.463: E/AndroidRuntime(12918): FATAL EXCEPTION: main 
02-15 19:28:36.463: E/AndroidRuntime(12918): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.my.zproject/com.my.zproject.ImportFile}: java.lang.NullPointerException 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.os.Handler.dispatchMessage(Handler.java:99) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.os.Looper.loop(Looper.java:123) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.ActivityThread.main(ActivityThread.java:4627) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at java.lang.reflect.Method.invokeNative(Native Method) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at java.lang.reflect.Method.invoke(Method.java:521) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at dalvik.system.NativeStart.main(Native Method) 
02-15 19:28:36.463: E/AndroidRuntime(12918): Caused by: java.lang.NullPointerException 
02-15 19:28:36.463: E/AndroidRuntime(12918): at com.my.zproject.ImportFile.onCreate(ImportFile.java:76) 
02-15 19:28:36.463: E/AndroidRuntime(12918): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)

来源

2013-02-15 yuva ツ

发布错误日志 – Nickolaus 2013-02-15 14:09:53

另外，不要硬编码的SD卡。改为使用环境类 – 2013-02-15 14:10:18

我发布了错误日志 – 2013-02-15 14:14:09

您需要初始化数组image这样

File[] image; 
File f = new File("/sdcard/download");//or Environment.getExternalStorageDirectory().getPath() 
    File[] files = f.listFiles(); 
    image = new File[files.length] 
    int j=0;

来源

2013-02-15 14:14:21

在Android中从sdcard中检索文件

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