我正在做一份调查表，这意味着一个片段代表一个问题。一个问题包含一些可以属于不同类型的字段，例如文本字段，额定字段...
这些字段在片段的ListView中呈现为行。它们被实现为复合视图，因为我需要对字段进行其他处理。
问题是，当我通过自定义适配器呈现行时，会抛出 InflateException 异常：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: cz.rusna.clinical_questionnaire, PID: 9141
android.view.InflateException: <merge /> can be used only with a valid ViewGroup root and attachToRoot=true
at android.view.LayoutInflater.inflate(LayoutInflater.java:475)
at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
at cz.rusna.clinical_questionnaire.views.adapters.TestRunnerAdapter.getView(TestRunnerAdapter.java:80)
at android.widget.AbsListView.obtainView(AbsListView.java:2347)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
at android.widget.ListView.fillFromTop(ListView.java:759)
at android.widget.ListView.layoutChildren(ListView.java:1673)
at android.widget.AbsListView.onLayout(AbsListView.java:2151)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.support.constraint.ConstraintLayout.onLayout(ConstraintLayout.java:1915)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:443)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2086)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1843)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
xms活动如下：
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_runner_test"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".views.activities.TestRunnerActivity">
<FrameLayout
android:id="@+id/test_runner_frame_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</android.support.constraint.ConstraintLayout>
片段布局如下：
<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/fragment_test_runner"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".views.fragments.TestRunnerFragment">
</ListView>
片段 onCreateView 如下：
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
ListView listView = (ListView) inflater.inflate(R.layout.fragment_test_runner, container, false);
listView.setAdapter(new TestRunnerAdapter(mCurrent.getQuestionFields(), getContext()));
return listView;
}
适配器代码如下：
public class TestRunnerAdapter extends BaseAdapter {
private List<QuestionField> mQuestionFields;
private Context mContext;
public TestRunnerAdapter(List<QuestionField> fields, Context context) {
mQuestionFields = fields;
mContext = context;
}
@Override
public int getCount() {
return mQuestionFields.size();
}
@Override
public QuestionField getItem(int position) {
return mQuestionFields.get(position);
}
@Override
public int getItemViewType(int position) {
QuestionField questionField = mQuestionFields.get(position);
if (questionField.getFieldType() == FieldType.TEXT) {
return 0;
} else if (questionField.getFieldType() == FieldType.RATED) {
return 1;
} else {
return 2;
}
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public int getViewTypeCount() {
return 3;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = convertView;
int type = getItemViewType(position);
QuestionField questionField = mQuestionFields.get(position);
if (view == null) {
LayoutInflater inflater = LayoutInflater.from(mContext);
if (type == 0) {
view = inflater.inflate(R.layout.text_field, parent, false);
TextFieldData textFieldData = (TextFieldData) questionField.getFieldData();
((TextFieldView)view).setTextField(textFieldData.getText());
} else if (type == 1) {
view = inflater.inflate(R.layout.rated_field, parent, false);
RatedFieldData ratedFieldData = (RatedFieldData) questionField.getFieldData();
((RatedFieldView)view).setRatedField(ratedFieldData);
} else {
view = inflater.inflate(R.layout.unrated_field, parent, false);
}
}
return view;
}
}
复合视图的示例。
public class TextFieldView extends LinearLayout {
private TextView mTextView;
public TextFieldView(Context context) {
this(context, null);
}
public TextFieldView(Context context, AttributeSet attributes) {
this(context, attributes, 0);
}
public TextFieldView(Context context, AttributeSet attributes, int defStyleAttr) {
super(context, attributes, defStyleAttr);
init(context);
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public TextFieldView(Context context, AttributeSet attributes, int defStyleAttr, int defStyleRes) {
super(context, attributes, defStyleAttr, defStyleRes);
init(context);
}
private void init(Context context) {
LayoutInflater.from(context).inflate(R.layout.text_field, this);
mTextView = (TextView) findViewById(R.id.text);
}
public void setTextField(String text) {
mTextView.setText(text);
}
}
及其xml：
<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="18dp"
android:gravity="center_vertical" />
</merge>
在适配器类的 getView 方法中，这些代码在行上呈现这些视图时失败：
view = inflater.inflate(R.layout.text_field, parent, false);