第四章--探究碎片

1.碎片的使用

• 建议引用support.v4包
• 事物替换

 @Bind(R.id.leftfragment_btn)  Button  leftfragment_btn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        ButterKnife.bind(this);
        leftfragment_btn.setOnClickListener(this);
        replaceFragment(new RightFragment());

    }
    
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.leftfragment_btn:
                replaceFragment(new AnotherRightFragment());
                break;
        }
    }

    private void replaceFragment(Fragment fragment) {
        FragmentManager  fragmentManager=getSupportFragmentManager();
        FragmentTransaction  transaction=fragmentManager.beginTransaction();
        transaction.replace(R.id.right_layout,fragment);
        transaction.addToBackStack(null);    //碎片中模拟返回栈
        transaction.commit();
    }
    

2.碎片的生命周期

Paste_Image.png

注：建立一个demo，进行碎片的替换，在生命周期函数中打印一下日志，即可明白；

public class RightFragment extends android.support.v4.app.Fragment {
    private static  final  String  TAG="RightFragment";

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.i(TAG,"onAttach");
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i(TAG,"onCreate");

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        Log.i(TAG,"onCreateView");
        View  view=inflater.inflate(R.layout.right_fragment,container,false);
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.i(TAG,"onActivityCreated");

    }

    @Override
    public void onStart() {
        super.onStart();
        Log.i(TAG,"onStart");

    }

    @Override
    public void onResume() {
        super.onResume();
        Log.i(TAG,"onResume");

    }

    @Override
    public void onPause() {
        super.onPause();
        Log.i(TAG,"onPause");

    }

    @Override
    public void onStop() {
        super.onStop();
        Log.i(TAG,"onStop");

    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.i(TAG,"onDestroyView");

    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG,"onDestroy");

    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.i(TAG,"onDetach");

    }
}

3. 限定符

• large限定符：res下新建一个layout-large资源文件夹，新建mainactivity.xml 在平板和手机上，会自动加载不同的对应的布局，完成适配，解决单双页判定。 限定符大小：small，normal，large，xlarge () ； 分辨率：ldpi, mdpi, hdpi, xhdpi ; 方向： land （横屏） ，port（竖屏）；
• 最小宽度限定符：res下新建一个layout-sw600dp资源文件夹， 大于600dp加载此文件下的布局；小于600dp,加载默认的layout中的布局。

4.碎片的最佳实践--简易版的新闻应用