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我正在使用 MainActivity 来管理几个片段的显示。我有一个 showFragment 方法，它遍历我的片段数组并显示/隐藏它们，并相应地设置回栈。问题是每当我按下返回按钮时，HomeFrag 就会显示出来，所有其他碎片都堆积在下面。我从文档中得到的印象是后退按钮将撤消最后一个事务（在提交之前添加的任何内容）。谁能解释为什么这可能会导致这种意外行为？这是我的主要活动。片段都定义在activity_main.xml中：

    public class MainActivity extends MenuBaseActivity {
    private static final int HOME = 0;
    private static final int WRITE = 1;
    private static final int UPLOAD = 2;
    private static final int SHARE = 3;
    private static final int SNAP = 4;
    private static final int POSITION = 5;

    private static final int FRAGMENT_COUNT = POSITION + 1;

    /** The current fragment being displayed **/
    private int mCurrentFragment = -1;

    private Fragment[] fragments = new Fragment[FRAGMENT_COUNT];

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        FragmentManager fm = getSupportFragmentManager();

        fragments[HOME] = fm.findFragmentById(R.id.homeFrag);
        fragments[WRITE] = fm.findFragmentById(R.id.writeFrag);
        fragments[UPLOAD] = fm.findFragmentById(R.id.uploadFrag);
        fragments[SHARE] = fm.findFragmentById(R.id.shareFrag);
        fragments[SNAP] = fm.findFragmentById(R.id.snapFrag);
        fragments[POSITION] = fm.findFragmentById(R.id.positionFrag);

        // If no fragments are currently being displayed, show the home frag
        if(mCurrentFragment == -1) {
            showFragment(0,true);
        }


    }

    /*
     * Handles the click event for all navigation buttons (navOnClick) in the fragments.
     */
    //TODO: Tag navigation with text strings instead of integers
    public void navOnClick(View v) {

        Object objectTag = v.getTag();
        int tag = Integer.valueOf(objectTag.toString());
        showFragment(tag, true);
    }


    public void showFragment(int fragmentIndex, boolean addToBackStack) {

        Log.v(Constants.getLogTag(), "Main: fragmentIndex:" + fragmentIndex + " backstack:" + addToBackStack);

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        //ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right);

        for (int i = 0; i < fragments.length; i++) {
            if (i == fragmentIndex) {
                ft.show(fragments[i]);
              } else {
                ft.hide(fragments[i]);
            }
        }

        if (addToBackStack) {
            Log.v(Constants.getLogTag(), "Main: Adding to backstack");
            ft.addToBackStack(null);
        }

        //Update the current fragment identifier
        mCurrentFragment = fragmentIndex;

        ft.commit();
    }


}
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1 回答 1

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我没有亲自测试过，但请告诉我这是如何工作的。

我实际上决定保留数组，以便我们可以在活动第一次启动时正确隐藏每个片段。我只更改了一些应该可以解决您的问题的小东西。无需每次循环隐藏每个片段。您应该每次只需要隐藏当前片段。

public class MainActivity extends MenuBaseActivity {
    private static final int HOME = 0;
    private static final int WRITE = 1;
    private static final int UPLOAD = 2;
    private static final int SHARE = 3;
    private static final int SNAP = 4;
    private static final int POSITION = 5;

    /** The current fragment being displayed **/
    private int mCurrentFragment = HOME;

    private Fragment[] fragments = new Fragment[FRAGMENT_COUNT];

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();

        fragments[HOME] = fm.findFragmentById(R.id.homeFrag);
        fragments[WRITE] = fm.findFragmentById(R.id.writeFrag);
        fragments[UPLOAD] = fm.findFragmentById(R.id.uploadFrag);
        fragments[SHARE] = fm.findFragmentById(R.id.shareFrag);
        fragments[SNAP] = fm.findFragmentById(R.id.snapFrag);
        fragments[POSITION] = fm.findFragmentById(R.id.positionFrag);

        // Hide all of the fragments except for the home fragment
        for (int i = WRITE; i < fragments.length; i++) {
            ft.hide(fragments[i]);
        }

        ft.commit();
    }

    /*
     * Handles the click event for all navigation buttons (navOnClick) in the fragments.
     */
    //TODO: Tag navigation with text strings instead of integers
    public void navOnClick(View v) {

        Object objectTag = v.getTag();
        int tag = Integer.valueOf(objectTag.toString());
        showFragment(tag, true);
    }


    public void showFragment(int fragmentIndex, boolean addToBackStack) {

        Log.v(Constants.getLogTag(), "Main: fragmentIndex:" + fragmentIndex + " backstack:" + addToBackStack);

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();

        // I changed this part too. You will probably want to implement it this way
        // if you want to also see an animation when hitting the back button. I will
        // leave it up to you as an exercise to figure out how the other animator
        // files should be constructed
        ft.setCustomAnimations(R.animator.slide_in_right, R.animator.slide_out_left, 
                               R.animator.slide_in_left, R.animator.slide_out_right); 

        ft.hide(fragments[mCurrentFragment]);
        ft.show(fragments[fragmentIndex]);

        if (addToBackStack) {
            Log.v(Constants.getLogTag(), "Main: Adding to backstack");
            ft.addToBackStack(null);
        }

        //Update the current fragment identifier
        mCurrentFragment = fragmentIndex;

        ft.commit();
    }
}
于 2013-08-01T19:56:58.557 回答