安卓fragment transaction add方法报错

这个问题百度了很多能用的很少！

原来看的B站的视频教程比较老了参数不匹配！我记一下安卓studio3.1的方法

切换fragment 前都先要 FragmentManager manager=getSupportFragmentManager（）  //这个是 android.support.v4.app.FragmentManager;

然后FragmentTransaction transaction=manager.beginTransaction();  之后执行  transaction.replace(fragment 的id); 最后  transaction.commit();

感觉一般主窗口载入窗口你会Add一个fragment  之后点击切换的时候 程序就会崩溃！！！！  你要在载入你fragment  前面加入 transaction=manager.beginTransaction();不管你载入那个fragment  都加这一句

代码如下写的很low 凑合看

主窗口代码

package com.stdu.myllogin;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView zhanghaodenglu;
private TextView dongtaimimadenglu;
private FragmentManager manager;
private FragmentTransaction transaction;
private  YanZhengMaFragment yanZhengMaFragment;
private   LoginFragment loginFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
       loginFragment=new LoginFragment();
        manager= getSupportFragmentManager();
      transaction=manager.beginTransaction();
      transaction.replace(R.id.login_frea,loginFragment);
      transaction.commit();

      zhanghaodenglu=findViewById(R.id.zhanghao_login);
      dongtaimimadenglu=findViewById(R.id.mima_login);
      zhanghaodenglu.setOnClickListener(listener);
      dongtaimimadenglu.setOnClickListener(listener);
        yanZhengMaFragment=new YanZhengMaFragment();
        loginFragment=new LoginFragment();

    }

    private View.OnClickListener listener=new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            switch (view.getId())
            { case R.id.mima_login:

                hideFragment(transaction);

                //transaction.remove(loginFragment);
                transaction=manager.beginTransaction();//这里一定要再写一遍 否则会出错
                transaction.replace(R.id.login_frea,yanZhengMaFragment);
                transaction.commit();
              //  Toast.makeText(MainActivity.this,"验证码登陆测试",Toast.LENGTH_SHORT).show();
                break;
                case  R.id.zhanghao_login:
                    hideFragment(transaction);

                    transaction=manager.beginTransaction();//这里一定要再写一遍 否则会出错
                    transaction.replace(R.id.login_frea,loginFragment);
                    transaction.commit();
                    //Toast.makeText(MainActivity.this,"账号登陆测试",Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    };

    private void hideFragment(FragmentTransaction transaction) {
        if (loginFragment != null) {
            
            transaction.remove(loginFragment);
        }
        if (yanZhengMaFragment != null) {
            
            transaction.remove(yanZhengMaFragment);
        }
    }
}

　　布局界面不写了看看我的哈皮运行截图吧