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Android类参考---Fragment(二)

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回退堆栈

在Fragment中被编辑的事务能够放在它自己的Activity中回退堆栈内。当用户在该Activity中按下返回按钮时,在回退堆栈中的任何事务在Activity自己被结束之前会被弹出堆栈。

例如,实例化一个带有整数参数的简单的Fragment对象,并且把这个整数显示在它的UI的一个TextView中:

publicstaticclassCountingFragmentextendsFragment{
    int mNum;

    /**
     * Create a new instance of CountingFragment, providing "num"
     * as an argument.
     */
    staticCountingFragment newInstance(int num){
        CountingFragment f =newCountingFragment();

        // Supply num input as an argument.
        Bundle args =newBundle();
        args.putInt("num", num);
        f.setArguments(args);

        return f;
    }

    /**
     * When creating, retrieve this instance's number from its arguments.
     */
    @Override
    publicvoid onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        mNum = getArguments()!=null? getArguments().getInt("num"):1;
    }

    /**
     * The Fragment's UI is just a 易做图 text view showing its
     * instance number.
     */
    @Override
    publicView onCreateView(LayoutInflater inflater,ViewGroup container,
            Bundle savedInstanceState){
        View v = inflater.inflate(R.layout.hello_world, container,false);
        View tv = v.findViewById(R.id.text);
        ((TextView)tv).setText("Fragment #"+ mNum);
        tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
        return v;
    }
}

用下面的方法创建一个新的Fragment实例,用它来替换当前被显示的Fragment实例,并把这种改变发布到回退堆栈上:

void addFragmentToStack(){
    mStackLevel++;

    // Instantiate a new fragment.
    Fragment newFragment =CountingFragment.newInstance(mStackLevel);

    // Add the fragment to the activity, pushing this transaction
    // on to the back stack.
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.replace(R.id.易做图_fragment, newFragment);
    ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
    ft.addToBackStack(null);
    ft.commit();
}

每次调用上面这个方法之后,就会在堆栈上增加一个新的实体,并且按下回退键时,会把它从堆栈中弹出,并给用户返回之前的Activity状态。

 

 

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补充:移动开发 , Android ,
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