Question

在我的应用中，我有SearchView，点击后会在ExpandableListView内打开Fragment，显示搜索查询的一些结果。现在我有一个问题，每次我点击searchIcon应用程序崩溃。

MainActivity.Java：

public class MainActivity extends AppCompatActivity implements SearchView.OnQueryTextListener
{

    private ExpListAdapter listAdapter;
    private ExpandableListView expList;
    private ArrayList<parentClass> parentList = new ArrayList<>();

    private boolean b = true;
    sql sqlo = new sql();



   @Override
   protected void onCreate (Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
       setSupportActionBar(toolbar);

       Intent sIntent = getIntent();
       if (Intent.ACTION_SEARCH.equals(sIntent.getAction())) {
           String query = sIntent.getStringExtra(SearchManager.QUERY);


       }}


    public void searchClick(MenuItem item){
        Fragment frag = new Results();

        FragmentTransaction ft  = getSupportFragmentManager().beginTransaction();

        ft.replace(R.id.FragFaecher,frag).commit();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);


        SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
        SearchView searchView = (SearchView) menu.findItem(R.id.search).getActionView();

        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
        searchView.setIconifiedByDefault(false);
        searchView.setOnQueryTextListener(this);

       searchView.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
           @Override
           public void onViewAttachedToWindow(View v) {

           }

           @Override
           public void onViewDetachedFromWindow(View v) {
            Fragment frag = new FaecherFrag();
               FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
               ft.replace(R.id.FragFaecher,frag).commit();
           }
       });



        return true;
    }


        public void displayList(ExpandableListView expList){
        if(b){populateList();}

        listAdapter = new ExpListAdapter(MainActivity.this,parentList);
        expList.setAdapter(listAdapter);
        b = false;
    }

    private void populateList(){
        String[] cThema = sqlo.getAlleThemen(this);
        String[] cFormel = sqlo.getAlleFormeln(this);
        int cThemaLength = cThema.length;
        int cFormelLength = cFormel.length;
        childClass Child;

        ArrayList<childClass> childList = new ArrayList<>();

        for (int i=0; i<cThemaLength;i++){Child = new childClass(cThema[i]);childList.add(Child);}
        parentClass Parent = new parentClass("Themen",childList);
        parentList.add(Parent);

        childList = new ArrayList<>();

        for (int i=0;i<cFormelLength;i++){Child = new childClass(cFormel[i]);childList.add(Child);}
        Parent = new parentClass("Formeln",childList);

        parentList.add(Parent);

    }

    @Override
    public boolean onQueryTextSubmit(String query) {

        return false;
    }

    @Override
    public boolean onQueryTextChange(String query) {

        return false;
    }
}

ExpListAdapter.Java：

public class ExpListAdapter extends BaseExpandableListAdapter {

    private Context context;
    private ArrayList<parentClass> parentList;
    private ArrayList<parentClass> originalList;

    public ExpListAdapter(Context context, ArrayList<parentClass> parentList){
        this.context = context;
        this.parentList = new ArrayList<>();
        this.parentList.addAll(parentList);
        this.originalList = new ArrayList<>();
        this.originalList.addAll(parentList);
    }

    @Override
    public int getGroupCount() {
        return parentList.size();
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        ArrayList<childClass> childList = parentList.get(groupPosition).getChildList();
        return childList.size();
    }

    @Override
    public Object getGroup(int groupPosition) {
        return parentList.get(groupPosition);
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        ArrayList<childClass> childList = parentList.get(groupPosition).getChildList();
        return childList.get(childPosition);
    }

    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {

        return childPosition;
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }



    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
        childClass child = (childClass) getChild(groupPosition,childPosition);
        if (convertView == null){
            LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.child_row,null);
        }
        TextView name = (TextView) convertView.findViewById(R.id.name);
        name.setText(child.getName().trim());

        return convertView;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup Parent) {
        parentClass parent = (parentClass) getGroup(groupPosition);
        if(convertView == null){
            LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.parent_row,null);

        }
        TextView heading = (TextView) convertView.findViewById(R.id.heading);
        heading.setText(parent.getName().trim());
        return convertView;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    public void filterData(String query){

    }
}

片段：

public class Results extends Fragment {

    ExpandableListView expList;

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

        View rootView = inflater.inflate(R.layout.fragment_results, container, false);

        return rootView;

    }

    public void onStart(){
        super.onStart();
        expList = (ExpandableListView) getView().findViewById(R.id.expList);
        MainActivity ma = new MainActivity();
        ma.displayList(expList);
    }
}

我得到错误＆＃34; java.lang.IllegalStateException：在onCreate（）＆＃34;之前，活动不可用的系统服务在getGroupView（）方法上。但如果我没有弄错，我已经打电话给我的MainActivity onCreate。那么为什么会出现这种错误？

致命的例外：主要处理：formelhelfer5_10.formelhelfer5_10，PID：2301 java.lang.IllegalStateException：onCreate（）之前不能用于活动的系统服务在android.app.Activity.getSystemService（Activity.java:5581） at formelhelfer5_10.formelhelfer5_10.ExpListAdapter.getGroupView（ExpListAdapter.java:86）在android.widget.ExpandableListConnector.getView（ExpandableListConnector.java:446）在android.widget.AbsListView.obtainView（AbsListView.java:2360）在android.widget.ListView.measureHeightOfChildren（ListView.java:1326）在android.widget.ListView.onMeasure（ListView.java:1233）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1464）在android.widget.LinearLayout.measureVertical（LinearLayout.java:758）在android.widget.LinearLayout.onMeasure（LinearLayout.java:640）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.view.View.measure（View.java:19731）在android.widget.RelativeLayout.measureChildHorizontal（RelativeLayout.java:715）在android.widget.RelativeLayout.onMeasure（RelativeLayout.java:461）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.support.design.widget.CoordinatorLayout.onMeasureChild（CoordinatorLayout.java:668）在android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild（HeaderScrollingViewBehavior.java:90）在android.support.design.widget.AppBarLayout $ ScrollingViewBehavior.onMeasureChild（AppBarLayout.java:1192）在android.support.design.widget.CoordinatorLayout.onMeasure（CoordinatorLayout.java:733）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.support.v7.widget.ContentFrameLayout.onMeasure（ContentFrameLayout.java:135）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1464）在android.widget.LinearLayout.measureVertical（LinearLayout.java:758）在android.widget.LinearLayout.onMeasure（LinearLayout.java:640）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1464）在android.widget.LinearLayout.measureVertical（LinearLayout.java:758）在android.widget.LinearLayout.onMeasure（LinearLayout.java:640）在android.view.View.measure（View.java:19731）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6120）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在com.android.internal.policy.DecorView.onMeasure（DecorView.java:687）在android.view.View.measure（View.java:19731）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2271）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1358）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1607）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1246）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6301）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java:871）在android.view.Choreographer.doCallbacks（Choreographer.java:683）在android.view.Choreographer.doFrame（Choreographer.java:619）在android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:857）在android.os.Handler.handleCallback（Handler.java:751） 09-06 13：13：20.688 2301-2301 / formelhelfer5_10.formelhelfer5_10 E / AndroidRuntime：at android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6077） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:865）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:755）

Answer 1

MainActivity ma = new MainActivity();
ma.displayList(expList);

永远不要使用new实例化活动。此类实例未针对您使用Activity的任何内容进行初始化，例如用作可以访问系统服务的Context。

在片段中，您可以使用getActivity()访问附加的托管活动。使用它而不是实例化新活动。

Answer 2

使用此：

View.inflate(ctx, R.layout.parent_row, null);

在这里：

 @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup Parent) {
        parentClass parent = (parentClass) getGroup(groupPosition);
        if(convertView == null){
            convertView = View.inflate(ctx, R.layout.parent_row, null); 

        }
        TextView heading = (TextView) convertView.findViewById(R.id.heading);
        heading.setText(parent.getName().trim());
        return convertView;
    }

Answer 3

1）如图所示laalto - 从不使用new实例化活动。

更改

 public void onStart(){
    super.onStart();
    expList = (ExpandableListView) getView().findViewById(R.id.expList);
    MainActivity ma = new MainActivity();
    ma.displayList(expList);
}

带

 public void onStart(){
    super.onStart();
    expList = (ExpandableListView) getView().findViewById(R.id.expList);
    MainActivity ma = (MainActivity) getActivity();
    ma.displayList(expList);
}

2）创建如此深度的依赖

并不是一个好主意

在Expandable ListView

3 个答案: