如何在Android上运行时检查用户是否授予了权限？

我创建了一个简单的 Android 活动，充当拨号盘。 它有一个电话号码的编辑文本和一个呼叫按钮 这是代码：（android 6.0 marshmallow）

public class Main2Activity extends AppCompatActivity {
EditText num;
Button call;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    num = (EditText) findViewById(R.id.num);
    call = (Button) findViewById(R.id.call);
    call.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try {
                // request permission if not granted
                if (ActivityCompat.checkSelfPermission(Main2Activity.this, Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(Main2Activity.this, new String[]{Manifest.permission.CALL_PHONE}, 123);
                    // i suppose that the user has granted the permission
                    Intent in = new Intent(Intent.ACTION_CALL, Uri.parse("tel:" + num.getText().toString()));
                    startActivity(in);
                 // if the permission is granted then ok
                } else {
                    Intent in = new Intent(Intent.ACTION_CALL, Uri.parse("tel:" + num.getText().toString()));
                    startActivity(in);
                }
            }
            // catch the exception if I try to make a call and the permission is not granted
            catch (Exception e){
            }
        }
    });
}

}

当我运行我的应用程序时，我遇到了这些问题

• 如果我单击调用按钮并授予权限，则只有再次单击才会调用意图

• 我不知道如何检查是否已授予权限

使用 onRequestPermissionResult，它处理用户按下的操作ALLOW and DENY，只需在“如果用户按允许”的条件下调用意图即可：

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode) {
        case 123: {
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                //If user presses allow
                Toast.makeText(Main2Activity.this, "Permission granted!", Toast.LENGTH_SHORT).show();
                Intent in = new Intent(Intent.ACTION_CALL, Uri.parse("tel:" + num.getText().toString()));
                startActivity(in);
            } else {
                //If user presses deny
                Toast.makeText(Main2Activity.this, "Permission denied", Toast.LENGTH_SHORT).show();
            }
            break;
        }
    }
}

希望这可以帮助。