子线程Handler.sendMessage 报错：Attempt to invoke virtual method 'boolean android.os.Handler.sendMessage

原因一：检查是否定义handler, 需要定义handler来接受sendMessage 发送的数据，具体代码如下：

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private Handler handler; handler = new Handler() {             @Override             public void handleMessage(Message msg) {                           }        }

 

原因二：参考https://blog.csdn.net/Rodulf/article/details/50910356