爲什麼「新文件（路徑）」不適用於Android 6.0

Question

public void GetFiles(String Path, String Extension, boolean IsIterative) 
    { 
     File[] files = new File(Path).listFiles(); 
     Map<String , String> map ; 
     for (int i = 0; i < files.length; i++) 
     { 
      File f = files[i]; 
      if (f.isFile()) 
      { 
       if (f.getPath().substring(f.getPath().length() - Extension.length()).equals(Extension)) 
       { 
        map = new HashMap<String, String>(); 
        map.put("img", f.getPath()); 
        map.put("name", f.getName()); 
        lstPics.add(map); 
       } 
       if (!IsIterative) 
        break; 
      } 
      else if (f.isDirectory() && f.getPath().indexOf("/.") == -1) 
       GetFiles(f.getPath(), Extension, IsIterative); 
     } 
    } 

爲什麼它在Android 4.4中運行良好，並在android 6.0中發生錯誤？ java.lang.NullPointerException：試圖獲得空數組的長度 我使用samsung注4運行android 4.4.4 我使用nexus 5運行andoroid 6.0。

10-21 11:55:03.891 23515 23515 E AndroidRuntime: java.lang.NullPointerException: Attempt to get length of null array 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at qjizho.vrlauncher.Launcher.GetFiles(Launcher.java:137) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at qjizho.vrlauncher.Launcher$1.onItemClick(Launcher.java:58) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.widget.AdapterView.performItemClick(AdapterView.java:310) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.widget.AbsListView.performItemClick(AbsListView.java:1145) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.widget.AbsListView$PerformClick.run(AbsListView.java:3042) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.widget.AbsListView$3.run(AbsListView.java:3879) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.os.Looper.loop(Looper.java:148) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5417) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
10-21 11:55:03.891 23515 23515 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Answer 1

這是因爲您沒有存儲權限，並且在默認情況下未授予Android M存儲空間。

請發佈您的目標SDK是什麼？你也問過AndroidManifest.xml中的存儲權限嗎？

public void GetFiles(String Path, String Extension, boolean IsIterative) 
     { 
      File[] files = new File(Path).listFiles(); <== This particular line is working fine no issue 
      Map<String , String> map ; 
      for (int i = 0; i < files.length; i++) <== this line is giving the Null Pointer Exception because since you don't have storage permission, so files are coming null. 
      { 
       File f = files[i]; 
       if (f.isFile()) 
       { 
        if (f.getPath().substring(f.getPath().length() - Extension.length()).equals(Extension)) 
        { 
         map = new HashMap<String, String>(); 
         map.put("img", f.getPath()); 
         map.put("name", f.getName()); 
         lstPics.add(map); 
        } 
        if (!IsIterative) 
         break; 
       } 
       else if (f.isDirectory() && f.getPath().indexOf("/.") == -1) 
        GetFiles(f.getPath(), Extension, IsIterative); 
      } 
     }