Question

我在MainActivity的onCreate中初始化接口SMSListener，但在重写的onReceive函数中它是null。我在onReceive中错误地使用了公共接口变量吗？每当我在重写函数之外测试它时，我已正确初始化变量。

SmsReceiver：

public class SmsReceiver extends BroadcastReceiver {
    public interface OnCustomReceiveSMS {
        void OnReceiveSMS(String inNumber, String inText);
    }
    public OnCustomReceiveSMS SMSListener;

    //constructor
    public SmsReceiver(){
        this.SMSListener = null;
    }

    //register sms listener
    public void SetCustomEventListener(OnCustomReceiveSMS eventListener){
        this.SMSListener = eventListener;
        this.SMSListener.OnReceiveSMS("test1", "test2");
    }

    @Override
    public void onReceive(Context context, Intent intent) {
         //THIS IS ALWAYS FALSE EVEN AFTER INITIALIZED
         if(this.SMSListener != null){
            Toast.makeText(context, "SMSListener is NOT null", Toast.LENGTH_SHORT).show();
            this.SMSListener.OnReceiveSMS("test3", "test4");
         }else{
            Toast.makeText(context, "SMSListener is NULL", Toast.LENGTH_SHORT).show();
         }
    }
}

MainActivity：

public class MainActivity extends AppCompatActivity {
    SmsReceiver smsReceiverObj;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //initialize SMS receiver and register event listener
        this.smsReceiverObj = new SmsReceiver();
        this.smsReceiverObj.SetCustomEventListener(new SmsReceiver.OnCustomReceiveSMS() {
            @Override
            public void OnReceiveSMS(String inNumber, String inText) {
                Toast.makeText(getApplicationContext(), "test event listener fired", Toast.LENGTH_SHORT).show();
            }
        });
   }
}

SetCustomEventListener（test1，test2）中的第一个测试在初始化接口变量后立即正常工作。当我在onReceive函数中尝试使用它时，我总是得到“SMSListener is NULL”调试消息。

Answer 1

问题可能是粘性的broadcast，它会在您onReceive之前调用setCustomEventListener方法，更好的方法是在构造函数中初始化它

public class SmsReceiver extends BroadcastReceiver {
    public interface OnCustomReceiveSMS {
        void OnReceiveSMS(String inNumber, String inText);
    }
    public OnCustomReceiveSMS SMSListener;

    //constructor
    public SmsReceiver(OnCustomReceiveSMS eventListener){
        this.SMSListener = eventListener;
        this.SMSListener.OnReceiveSMS("test1", "test2");
    }

    @Override
    public void onReceive(Context context, Intent intent) {
         //THIS IS ALWAYS FALSE EVEN AFTER INITIALIZED
         if(this.SMSListener != null){
            Toast.makeText(context, "SMSListener is NOT null", Toast.LENGTH_SHORT).show();
            this.SMSListener.OnReceiveSMS("test3", "test4");
         }else{
            Toast.makeText(context, "SMSListener is NULL", Toast.LENGTH_SHORT).show();
         }
    }
}

在你的活动中

this.smsReceiverObj = new SmsReceiver(new SmsReceiver.OnCustomReceiveSMS() {
            @Override
            public void OnReceiveSMS(String inNumber, String inText) {
                Toast.makeText(getApplicationContext(), "test event listener fired", Toast.LENGTH_SHORT).show();
            }
        });

修改

问题是你试图在Manifest中注册它，从清单中删除receiver并在MainActivity内注册它，它会像魅力一样工作

this.smsReceiverObj = new SmsReceiver(new SmsReceiver.OnCustomReceiveSMS() { @Override public void OnReceiveSMS(String inNumber, String inText) { Toast.makeText(getApplicationContext(), "test event listener fired", Toast.LENGTH_SHORT).show(); } }); registerReceiver(this.smsReceiverObj,new IntentFilter());

重写OnReceive中的空本地变量

1 个答案: