Android -检查权限

Question

此代码用于测试应用程序在被检查后是否具有权限，如果您有权限，则返回true，否则返回false。

但是当我运行应用程序停止工作时，它就不起作用了，所以我想知道它为什么不能工作，如果代码中缺少了什么：

EDIT2 --提出了一些建议，但仍然没有奏效：

 public class CheckPermission extends Activity {
    private final Context context;
    private static final String MNC = "MNC";
    int permReq = 0;
    String permMan = "";

    public CheckPermission(Context context) {
        this.context = context;
    }

    //perMan can be any code number higher than 0
    public void requestPermission(String permRequested){
        switch (permRequested) {
            case "CAMERA":
                //Request for Camera
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission.CAMERA);
                this.permMan = Manifest.permission.CAMERA;
                break;
            case "INTERNET":
                //Requesr for Internet
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission.INTERNET);
                this.permMan = Manifest.permission.INTERNET;
                break;
            case "STORAGE":
                //Request for group Storage - Read_External_Storage & Write_External_Storage
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.STORAGE);
                this.permMan = Manifest.permission_group.STORAGE;
                break;
            case "MICROPHONE":
                //Request for group Microphone - Record_Audio
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.MICROPHONE);
                this.permMan = Manifest.permission_group.MICROPHONE;
                break;
            case "LOCATION":
                //Request for group Location - Acess_Fine_Location & Acess_Coarse_Location
                this.permReq =  ContextCompat.checkSelfPermission(context, Manifest.permission_group.LOCATION);
                this.permMan = Manifest.permission_group.LOCATION;
                break;
            case "CALL":
                //Requesr for call
                this.permReq = ContextCompat.checkSelfPermission(context, Manifest.permission.CALL_PHONE);
                this.permMan = Manifest.permission.CALL_PHONE;
                break;
            default:
                break;
        }
    }

    public boolean hasPermission( String permRequested){
        final PackageManager pm = context.getPackageManager();

        if(isMNC_Or_Higher()) {
            requestPermission(permRequested);
            Toast.makeText(this.context, "Is MNC - permMan: " + this.permMan + " Perm required: " + permReq, Toast.LENGTH_SHORT).show();

            if (permReq != pm.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{this.permMan}, this.permReq);
                return false;
            }
        }
        return true;
    }

    //check if is 6.0 or higher
    public boolean isMNC_Or_Higher(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            return true;
        }
        return false;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {

        if (requestCode == this.permReq) {
            if (grantResults.length == 1 &&
                    grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permissão concedida", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "Permissão negada", Toast.LENGTH_SHORT).show();
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}

错误：

PID: 25504 java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法的android.content.Context android.content.Contextandroid.content.ContextWrapper.getApplicationContext(ContextWrapper.java:107) at com.dev.kamui.patrulhacomunitaria.CheckPermission.hasPermission(CheckPermission.java:68)在com.dev.kamui.patrulhacomunitaria.Pagina_Principal$1.onClick(Pagina_Principal.java:47) at android.view.View.performClick(View.java:5198)在android.view.View$PerformClick.run(View.java:21147) at android.os.Handler.handleCallback(Handler.java:739)在android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148)在android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(原生方法)在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

需要像这样调用requestPermissions

requestPermissions(this, new String[]{this.permMan}, this.permReq);

如果您希望CheckPermission作为Util类，那么就不需要从Activity继承它。也不需要在this.context构造函数中执行“CheckPermission = context;”。相反，通过hasPermission方法并将上下文发送到requestPermission方法。在ActivityCompat.requestPermissions中也使用它。然后在调用onRequestPermissionsResult的每个活动中实现hasPermission。

Answer 2

活动不应该像您所写的那样具有构造函数。

活动本身是上下文的子类，因此您可以编写this而不是context。

this.permReq = ContextCompat.checkSelfPermission(this, Manifest.permission_group.STORAGE);

Answer 3

在Android6.0和更高版本中，您必须在代码中请求许可。

私有静态最终int PERMISSION_REQUEST_CODE = 1；

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {

    if (checkSelfPermission(Manifest.permission.SEND_SMS)
            == PackageManager.PERMISSION_DENIED) {

        Log.d("permission", "permission denied to SEND_SMS - requesting it");
        String[] permissions = {Manifest.permission.SEND_SMS};

        requestPermissions(permissions, PERMISSION_REQUEST_CODE);

    }
}