android - fragment ListView view.setBackgroundColor(Color.GREEN);

Question

我有一个从字符串数组填充的 fragment ListView 。 我所追求的是当我点击选定的行时它变成绿色并保持绿色。 只要您不滚动，我所拥有的就可以使用。当您滚动未被选中的行时，背景就会发生变化。 据我了解，这是由于 ListView 回收其 View 的方式所致。 我花了很多时间尝试不同的方法来阻止这种情况的发生，但我缺乏关于如何做到这一点的知识。

public class AreaListFragment extends ListFragment {

private static final String STATE_ACTIVATED_POSITION = "activated_position";
private Callbacks mCallbacks = sDummyCallbacks;
private CentreDataContent mContent;
private int mActivatedPosition = ListView.INVALID_POSITION;

public interface Callbacks {
    public void onItemSelected(String id);
}

private static Callbacks sDummyCallbacks = new Callbacks() {
    @Override
    public void onItemSelected(String id) {
    }
};

public AreaListFragment() {
}

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

    if (mContent == null) {
        Resources res = getResources();
        mContent = new CentreDataContent(R.integer.UnknownID,
                                         res.getStringArray(R.array.undefinedArea),
                                         res.getStringArray(R.array.undefinedChecklist));

        setListAdapter(new ArrayAdapter<CentreDataContent.CentreArea>(
            getActivity(),
            android.R.layout.simple_list_item_activated_1,
            android.R.id.text1,
            CentreDataContent.AREAS));
    }
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);      
    // Restore the previously serialized activated item position.
    if (savedInstanceState != null
            && savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)) {
        setActivatedPosition(savedInstanceState.getInt(STATE_ACTIVATED_POSITION));
    } 
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    // Activities containing this fragment must implement its callbacks.
    if (!(activity instanceof Callbacks)) {
        throw new IllegalStateException("Activity must implement fragment's callbacks.");
    }

    mCallbacks = (Callbacks) activity;
}

@Override
public void onDetach() {
    super.onDetach();
    mCallbacks = sDummyCallbacks;
}

@Override
public void onListItemClick(ListView listView, View view, int position, long id) {
    super.onListItemClick(listView, view, position, id);
    view.setBackgroundColor(Color.GREEN);

    mCallbacks.onItemSelected(CentreDataContent.AREAS.get(position).id.toString());

}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if (mActivatedPosition != ListView.INVALID_POSITION) {
        // Serialize and persist the activated item position.
        outState.putInt(STATE_ACTIVATED_POSITION, mActivatedPosition);
    }
}

/**
 * Turns on activate-on-click mode. When this mode is on, list items will be
 * given the 'activated' state when touched.
 */
public void setActivateOnItemClick(boolean activateOnItemClick) {
    // When setting CHOICE_MODE_SINGLE, ListView will automatically
    // give items the 'activated' state when touched.
    getListView().setChoiceMode(activateOnItemClick
            ? ListView.CHOICE_MODE_SINGLE
            : ListView.CHOICE_MODE_NONE);
}

private void setActivatedPosition(int position) {
    if (position == ListView.INVALID_POSITION) {
        getListView().setItemChecked(mActivatedPosition, false);
    } else {
        getListView().setItemChecked(position, true);
    }

    mActivatedPosition = position;
}

我是 android 的新手，正在努力学习。所以这方面的任何帮助都会很棒 非常感谢

Answer 1

您真正想要做的是创建一个背景状态可绘制对象，它会根据行的状态发生变化。

例如

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:drawable="@drawable/list_pressed_holo" android:state_activated="true"/>
</selector>

正如您在此处看到的那样，当状态变为 activated 时，特定的 drawable 被显示

所以当您点击列表中的项目时，您所要做的就是

listview.setItemChecked(position, true);

这将导致布局中的 Root View 被设置为激活并更改背景。

现在您还必须通过跟踪并在按下新行时关闭激活状态来管理您检查的上一行

listview.setItemChecked(lastPosition, false);

您当然可以将 ListView 设置为 CHOICE_MODE_SINGLE而且您不必担心管理上一个点击的项目。

listview.setChoiceMode(ListView.CHOICE_MODE_SINGLE);