在android [duplicate]中运行时检查权限时获取NullPointerException

最是人间留不住，朱颜辞镜花辞树。这篇文章主要讲述在android [duplicate]中运行时检查权限时获取NullPointerException相关的知识，希望能为你提供帮助。
这个问题在这里已有答案：

What is a NullPointerException, and how do I fix it? 12个答案

这是MainActivity代码。从MainActivity的onCreate（）方法调用MultiplePermission类的permissionCheck（）方法。

public class MainActivity extends AppCompatActivity {@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); if(Build.VERSION.SDK_INT > = 23){ MultiplePermission multiplePermission = new MultiplePermission(); if(multiplePermission.permissionCheck()){ Toast.makeText(this, "All permission granted", Toast.LENGTH_SHORT).show(); }else{ Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show(); } } } }

MultiplePermission类代码如下。此类的permissionCheck（）方法在运行时检查android权限。如果拒绝任何权限，则关闭整个应用程序。

public class MultiplePermission extends AppCompatActivity { private int PERMISSION_ALL = 1; private String[] PERMISSIONS = { Manifest.permission.RECORD_AUDIO, Manifest.permission.READ_PHONE_STATE, Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.PROCESS_OUTGOING_CALLS }; public boolean permissionCheck() { if (!hasPermissions(this, PERMISSIONS)) {ActivityCompat.requestPermissions(this, PERMISSIONS, PERMISSION_ALL); } return true; }private boolean hasPermissions(Context context,String[] permissions) { for (String permission : permissions) { if (ActivityCompat.checkSelfPermission((Activity)context, permission) != PackageManager.PERMISSION_GRANTED) { return false; } } return true; }@Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { for(int result : grantResults){ if(result != PackageManager.PERMISSION_GRANTED) System.exit(0); } return; } }

这是错误信息。

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.content.Context.checkPermission(java.lang.String, int, int)' on a null object reference at android.content.ContextWrapper.checkPermission(ContextWrapper.java:669) at android.support.v4.content.ContextCompat.checkSelfPermission(ContextCompat.java:453) at testapp.android.vogella.com.permissiontest.MultiplePermission.hasPermissions(MultiplePermission.java:40) at testapp.android.vogella.com.permissiontest.MultiplePermission.permissionCheck(MultiplePermission.java:29) at testapp.android.vogella.com.permissiontest.MainActivity.onCreate(MainActivity.java:16) at android.app.Activity.performCreate(Activity.java:6664) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

答案【在android [duplicate]中运行时检查权限时获取NullPointerException】你永远不应该用Activity开始一个new Object()，它不会得到context参考。
MultiplePermission不应该是Activity，并且在你需要上下文的方法中，通过参数得到它：

public boolean permissionCheck(Activity activity) { if (!hasPermissions(this, PERMISSIONS)) {ActivityCompat.requestPermissions(activity, PERMISSIONS, PERMISSION_ALL); } return true; }