java - 为不同的 Activity 调用类中的上下文

Question

我正在检查类(class)内的 SEND_SMS 权限:

public class SendSms extends Activity{
    int requestPerm;

    private void checkPermissionSms(){
        if(ContextCompat.checkSelfPermission(, Manifest.permission.SEND_SMS)
                != PackageManager.PERMISSION_GRANTED){
                   ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.SEND_SMS},
                          requestPerm);                                 //If we don't have the permission, request it here
        }
    }

但是在 checkSelPermission 处，它需要一个上下文，但我不确定它需要什么上下文(甚至不太确定 checkSelfPermission 的上下文)我正在关注:

https://developer.android.com/training/permissions/requesting.html#java

上述方法的调用方式如下:

public static void sendSms(String message){
   // Intent calledSendSMS = getIntent();
    //String message = calledSendSMS.getStringExtra(Intent.EXTRA_TEXT);
 //   PendingIntent pi = PendingIntent.getActivity(this,0, new Intent(this,SendSms.class),0);
    SendSms checkPerm = new SendSms();
    SmsManager sendTheMessage = SmsManager.getDefault();
    String phoneNumber = "5556";
    checkPerm.checkPermissionSms();
    sendTheMessage.sendTextMessage(phoneNumber, null,message,null,null);
}

这个方法是从另一个 Activity 调用的。我确实输入了“this”，但随后出现以下错误:

 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:724)
                      at android.support.v4.content.ContextCompat.checkSelfPermission(ContextCompat.java:430)
                      at com.example.android.footysortit.SendSms.checkPermissionSms(SendSms.java:17)

实际上我想做的就是检查权限并在需要时请求它。

编辑:如果我在实际 Activity 中添加检查权限并使用“this”，它就可以正常工作。那么如何让它传递 Activity 数据呢？

Answer 1

更改此:

SendSms checkPerm = new SendSms();

致:

SendSms checkPerm = new SendSms(this);

SendSms 类 - 您需要创建该类的构造函数

public class SendSms extends Activity {

private Activity mActivity;
private int requestPerm;

public SendSms(Activity mActivity) {
    this.mActivity = mActivity;

}

private void checkPermissionSms() {
    if (ContextCompat.checkSelfPermission(mActivity, Manifest.permission.SEND_SMS) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.SEND_SMS}, requestPerm);
        //If we don't have the permission, request it here
    }
  }
}