java.lang.RuntimeException: Can not toast on a thread that has not called Looper.prepare()终极解决方案

大家好，又见面了，我是你们的朋友全栈君。

源代码：

Thread thread = new Thread(() -> { 
   
    MySQLUtil mySQLUtil = new MySQLUtil(this);
    mySQLUtil.getConnection("cce-18");
    ArrayList<String> res = null;
    res = mySQLUtil.getMajorGpaRank(idMyself, major, finalYear, finalSemester_, course_nature);
    if(res == null) { 
   
         ToastUtil.showMessage(getApplicationContext(), "暂无成绩信息!");
    }else { 
   ...}
});
thread.start();
try { 
   
    thread.join();
} catch (InterruptedException e) { 
   
    e.printStackTrace();
}

网上看了很多解决办法，都是在Toast的前后加上：

Looper.prepare();
ToastUtil.showMessage(getApplicationContext(), "暂无成绩信息!");
Looper.loop();

实验之后发现会卡在原来的界面，正确的解决办法：开一个runOnUiThread，如下所示：

runOnUiThread(() -> { 
   
    ToastUtil.showMessage(getApplicationContext(), "暂无成绩信息!");
});