Question

美好的一天！请具体帮助我。我已经读过有关解决此问题的方法，但是我看不出如何将其应用于自己。

07-13 18：55：28.339 3850-3850 / com.zheil.zodiac E / Android运行时：致命异常：主要流程：com.zheil.zodiac，PID：3850 java.lang.RuntimeException：无法实例化活动ComponentInfo {com.zheil.zodiac / com.zheil.zodiac.FirstFragment}： java.lang.ClassCastException：com.zheil.zodiac.FirstFragment不能为强制转换为android.app.Activity 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2608）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2767）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1514）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:163）在android.app.ActivityThread.main（ActivityThread.java:6221）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:904）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:794）造成原因：java.lang.ClassCastException：com.zheil.zodiac.FirstFragment无法转换为android.app.Activity 在android.app.Instrumentation.newActivity（Instrumentation.java:1079）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2598）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2767）在android.app.ActivityThread.-wrap12（ActivityThread.java）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1514）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:163）在android.app.ActivityThread.main（ActivityThread.java:6221）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:904）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:794）

片段：

package com.zheil.zodiac;


import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class FirstFragment extends Fragment {
    private TextView textView2;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_first, container, false);
        textView2 = (TextView) view.findViewById(R.id.textView2);
        String textFromActivity = getArguments().getString("1");
        textView2.setText(textFromActivity);

        return view;
    }
}

部分代码的主要活动：

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Создадим новый фрагмент
        Fragment fragment = null;
        Class fragmentClass = null;

        // Handle navigation view item clicks here.
        int id = item.getItemId();

        switch (id) {
            case R.id.nav_camera:
                // Handle the camera action
                fragmentClass = FirstFragment.class;
                break;
            case R.id.nav_gallery:
                fragmentClass = SecondFragment.class;
                break;
            case R.id.nav_slideshow:

                break;
            case R.id.nav_manage:

                break;
            case R.id.nav_share:

                break;
        }

        try {
            assert fragmentClass != null;
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Вставляем фрагмент, заменяя текущий фрагмент
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.container, fragment).commit();
        // Выделяем выбранный пункт меню в шторке
        item.setChecked(true);
        // Выводим выбранный пункт в заголовке
        setTitle(item.getTitle());

        Bundle bundle = new Bundle();
        bundle.putString("1", String.valueOf(getMapLastIntent().get("aries")));
        fragment.setArguments(bundle);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

Answer 1

请在您的片段类中添加实例

 public static YourFragment newInstance() {
        return new YourFragment();
    }

Answer 2

无需创建Class实例并进行类型转换，只需执行

  @SuppressWarnings("StatementWithEmptyBody")
        @Override
        public boolean onNavigationItemSelected(MenuItem item) {          
            Fragment fragment = null;    
            int id = item.getItemId();    
            switch (id) {
                case R.id.nav_camera:                    
                    fragment = new FirstFragment();
                    break;
                case R.id.nav_gallery:
                    fragment = SecondFragment();
                    break;
                case R.id.nav_slideshow:

                    break;
                case R.id.nav_manage:

                    break;
                case R.id.nav_share:

                    break;
            }                                
            FragmentManager fragmentManager = getSupportFragmentManager();
            Bundle bundle = new Bundle();
            bundle.putString("1",String.valueOf(getMapLastIntent().get("aries")));
            fragment.setArguments(bundle);
            fragmentManager.beginTransaction().replace(R.id.container, fragment).commit();       
            item.setChecked(true);        
            setTitle(item.getTitle());

            DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
            drawer.closeDrawer(GravityCompat.START);
            return true;
        }
    }

无法将片段强制转换为android.app.Activity（私有大小写）

2 个答案: