文章

Fragment 最佳实践

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作者 jk2K 2 分钟阅读

初始化 Fragment

对于不需要接收参数的Fragment，只需要实现

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public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)

方法即可

传参给 Fragment

Fragment需要提供一个静态的创建方法, 通常叫做newInstance

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public class DemoFragment extends Fragment {
    public static DemoFragment newInstance(String someTitle) {
        DemoFragment demoFragment = new DemoFragment();
        args.putString("someTitle", someTitle);
        demoFragment.setArguments(args);
        return demoFragment;
    }
    
    ...
}

你可以这样获取参数

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public class DemoFragment extends Fragment {
    ... 
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
       // Get arguments
       String someTitle = getArguments().getString("someTitle", "");
    }
    
    ...
}

你可以这样来调用DemoFragment

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DemoFragment.newInstance("测试").show(getSupportFragmentManager(), "DemoFragment");

Activity 与 Fragment 之间的通讯

方法1

在Fragment里通过getActivity()来直接调用Activity里面的方法 例如

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((MainActivity) getActivity()).doPositiveClick();

方法2

Activity通过实现Fragment里的接口来与Fragment进行交互 例如

第一步

NewsItemFragment定义OnNewsItemSelectedListener接口

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public class NewsItemFragment extends Fragment {
    OnNewsItemSelectedListener mCallback;

    // Container Activity must implement this interface
    public interface OnNewsItemSelectedListener {
        public void onNewsItemSelected(int position);
    }
    
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        
        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (OnNewsItemSelectedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnNewsItemSelectedListener");
        }
    }
    
    ...
}

第二步

NewsItemFragment调用onNewsItemSelected方法

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Override
public void onListItemClick(ListView l, View v, int position, long id) {
    // Send the event to the host activity
    mCallback.onNewsItemSelected(position);
}

第三步

MainActivity里实现OnNewsItemSelectedListener接口

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public class MainActivity extends AppCompatActivity implements NewsItemFragment.OnNewsItemSelectedListener
{
    ...
    
    @Override
    public void onNewsItemSelected(int position)
    {
        //Do something with the position value passed back
        Toast.makeText(activity, "Clicked "+ position, Toast.LENGTH_LONG).show();
        
    }
}

方法2比方法1更复杂，但是在某些情况下可能必须要这样实现

注意

  • Fragment之间不可直接进行通讯，需通过Activity来控制

参考文档

技术
android
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