package com.example.test_resume;import android.app.Activity;import android.os.Bundle;/** * 在onWindowFocusChanged中操作可以有效避免第一次启动APP和每次从后台启动后加载弹窗时报错Unable to add window * --token null is not valid的bug *  *  * @author NULL *  */public class MainActivity extends Activity {    private boolean isFirstLaunch = false;    private boolean isResume = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        isFirstLaunch = true;    }    @Override    protected void onResume() {        super.onResume();        isResume = true;    }    @Override    public void onWindowFocusChanged(boolean hasFocus) {        super.onWindowFocusChanged(hasFocus);        if (hasFocus) {            if (isFirstLaunch) {                isFirstLaunch = false;                // TODO 第一次启动界面加载完毕后的操作            }            if (isResume) {                isResume = false;                // TODO 每一次从后台打开后界面加载完毕后的操作            }        }    }    /**     * 到后台时要移除添加window的操作     */    @Override    protected void onPause() {        super.onPause();    }}