Android Studio 中的片段事务错误

Question

我是 Android 编程的菜鸟，我在处理片段时遇到了一个错误，它说我无法从静态上下文中引用非静态方法 (beginTransaction)。代码如下：

public class User extends ActionBarActivity implements AdapterView.OnItemClickListener{

private ActionBarDrawerToggle actionBarDrawerToggle;
private DrawerLayout drawerLayout;
private ListView navList;
private android.support.v4.app.FragmentTransaction fragmentTransaction;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_user);
    //DrawerLayout    (za xml)
    DrawerLayout drawerLayout = (DrawerLayout)findViewById(R.id.drawerlayout);
    ListView navList = (ListView)findViewById(R.id.navlist);
            ArrayList<String> navArray = new ArrayList<String>();
    navArray.add("Latest");
    navArray.add("Popular conversations");
    navArray.add("New Message");
    navArray.add("Settings");
    navArray.add("Log out");
    navList.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_activated_1,navArray);
    navList.setAdapter(adapter);
    navList.setOnItemClickListener(this);

    actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,R.string.opendrawer,R.string.closedrawer);
    drawerLayout.setDrawerListener(actionBarDrawerToggle);
    android.support.v7.app.ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayShowHomeEnabled(true);
    actionBar.setDisplayHomeAsUpEnabled(true);
    android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();
   // delete phps?

    loadSelection(0);
}


// *** Yes, I'm aware of the errors down below..
@Override
private void loadSelection(int i){
navList.setItemChecked(i, true);
 switch(i){
     case 0:
         homefragment homefragment = new homefragment();
         fragmentTransaction = FragmentManager.beginTransaction();
         fragmentTransaction.replace(R.id.fragmentholder, homefragment);
         fragmentTransaction.commit();
         break;
     //ostali slucajevi l8er..

     case 3:
         NewMsg NewMsg = new NewMsg();
         fragmentTransaction = FragmentManager.beginTransaction();      // <-----  ??????????
         fragmentTransaction.replace(R.id.fragmentholder,NewMsg);
         fragmentTransaction.commit();
         break;
    }
}

 protected void onPostCreate(Bundle savedInstanceState) {
     super.onPostCreate(Bundle savedInstanceState);
     actionBarDrawerToggle.syncState();
 }



 @Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_user, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    } else if (id == android.R.id.home) {
        if (drawerLayout.isDrawerOpen(navList)) {
            drawerLayout.closeDrawer(navList);
        } else {
            drawerLayout.openDrawer(navList);
        }
    }
        return super.onOptionsItemSelected(item);

    }


@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

   loadSelection(position);

drawerLayout.closeDrawer(navList);
}
}

编辑：删除链接，添加代码。

Answer 1

这其实和fragment没有关系，而是比较笼统的。 FragmentManager.beginTransaction() 的问题在于 FragmentManager 是对类的静态引用，而您应该将方法调用为类的对象。解决方案是使用

getSupportFragmentManager().beginTransaction();

或者你可以添加

android.support.v4.app.FragmentManager fragmentManager;

到你的类的变量。然后你可以在你的代码中使用你拥有的onCreate 方法

android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();

只使用

fragmentManager = getSupportFragmentManager();

因为你已经声明你的类有变量fragmentManager，所以这很有效。然后在出现错误的代码中，将大写的FragmentManager 替换为fragmentManager。

编辑：阅读代码时出错，后一种方法现在也有效。