Android ListFragment android.widget.LinearLayout 无法转换为 android.widget.TextView答案

【问题标题】：Android ListFragment android.widget.LinearLayout cannot be cast to android.widget.TextViewAndroid ListFragment android.widget.LinearLayout 无法转换为 android.widget.TextView
【发布时间】：2016-02-26 12:21:06
【问题描述】：

我正在将我的活动更改为我的一个应用程序的片段，并遇到了以下错误。错误中没有说明导致错误的原因，但我将其缩小到以下片段。

我还遇到了另一个奇怪的错误，当一个项目被添加到列表中时，它的复选框不能被勾选，直到活动被离开并再次重新进入？有没有办法让复选框在添加到列表后立即删除，而不必离开并再次回来？

谁能给我解释一下这个错误？

片段

import android.app.Dialog;
import android.support.v4.app.ListFragment;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Spinner;


public class ShoppingList extends ListFragment{

    private Cursor cursor;
    private static int measurementValue;
    private static String unitValue;

    private String name;
    private String unit;
    private int measurement;
    private int currMeasurement;
    private int newMeasure;


    public ShoppingList() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        final View rootView = inflater.inflate(R.layout.fragment_shopping, container, false);

        final DBMain db = new DBMain(getActivity());

        db.open();

        cursor = db.getAllItems();
        String[] values = new String[cursor.getCount()];
        cursor.moveToFirst();
        for(int i = 0; i < cursor.getCount(); i++)
        {
            String row = cursor.getString(cursor.getColumnIndex("name"));
            values[i] = row;
            cursor.moveToNext();
        }

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
                R.layout.shopping_list_row, values);
        setListAdapter(adapter);

        FloatingActionButton filterButton = (FloatingActionButton) rootView.findViewById(R.id.addButton);
        filterButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
            // custom ingredient_dialog
            final Dialog dialog = new Dialog(getActivity());
            dialog.setContentView(R.layout.shopping_dialog);
            dialog.setTitle("Add Item");

            final EditText item = (EditText) dialog.findViewById(R.id.item);

            final Spinner measurement = (Spinner) dialog.findViewById(R.id.measurement);
            measurement.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
                final String measurementValue = measurement.getSelectedItem().toString();
                int finalMeasurement = Integer.parseInt(measurementValue);
                ShoppingList.measurementValue = finalMeasurement;
                }

                @Override
                public void onNothingSelected(AdapterView<?> parentView) {

                }

                });

                final Spinner unit = (Spinner) dialog.findViewById(R.id.unit);
                unit.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {
                    String finalUnit = unit.getSelectedItem().toString();
                    unitValue = finalUnit;
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> parentView) {
                    }

                    });

                    Button dialogButtonOk = (Button) dialog.findViewById(R.id.dialogButtonOK);
                    // if button is clicked, close the custom ingredient_dialog
                    dialogButtonOk.setOnClickListener(new View.OnClickListener() {
                                                    @Override
                                                    public void onClick(View v) {
                        String newItem = item.getText().toString();
                        db.open();
                        db.insertItem(newItem, measurementValue, unitValue);
                        Cursor cursor = db.getAllItems();

                        //String[] columns = new String[] {db.KEY_NAME, db.KEY_CODE, db.KEY_ROWID};
                        String[] columns = new String[]{db.KEY_ITEM_NAME, db.KEY_MEASUREMENT, db.KEY_UNIT};

                        int[] to = new int[]{R.id.ingredientName, R.id.ingredientMeasurement, R.id.ingredientUnit};

                        final SimpleCursorAdapter myCursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.shopping_list_row, cursor, columns, to, 0);

                        //final ListView shoppingList = (ListView) rootView.findViewById(R.id.shoppingList);
                        //shoppingList.setAdapter(myCursorAdapter);
                        setListAdapter(myCursorAdapter);
                        dialog.dismiss();
                            }
                        });

                        Button dialogButtonNext = (Button) dialog.findViewById(R.id.dialogButtonNext);
                        // if button is clicked, close the custom ingredient_dialog
                        dialogButtonNext.setOnClickListener(new View.OnClickListener() {
                                                    @Override
                                                    public void onClick(View v) {
                        String newItem = item.getText().toString();
                        db.open();
                        db.insertItem(newItem, measurementValue, unitValue);
                        item.setText("");
                        Cursor cursor = db.getAllItems();

                        //String[] columns = new String[] {db.KEY_NAME, db.KEY_CODE, db.KEY_ROWID};
                        String[] columns = new String[]{db.KEY_ITEM_NAME, db.KEY_MEASUREMENT, db.KEY_UNIT};

                        int[] to = new int[]{R.id.ingredientName, R.id.ingredientMeasurement, R.id.ingredientUnit};

                        final SimpleCursorAdapter myCursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.shopping_list_row, cursor, columns, to, 0);

                        //final ListView shoppingList = (ListView) rootView.findViewById(R.id.shoppingList);
                        //shoppingList.setAdapter(myCursorAdapter);
                        setListAdapter(myCursorAdapter);

                                                    }
                                                });
                         dialog.show();
                                            }
                                        }

                     );

        return rootView;
    }

    public class ShoppingCustomAdapter extends SimpleCursorAdapter implements CompoundButton.OnCheckedChangeListener {

        private Context mContext;
        private Context appContext;
        private int layout;
        private Cursor cr;
        private final LayoutInflater inflater;

        //private Context context = this;
        //DBMain db = new DBMain(context);


        public ShoppingCustomAdapter(Context context, int layout, Cursor c, String[] from, int[] to) {
            super(context, layout, c, from, to);
            this.layout = layout;
            this.mContext = context;
            this.inflater = LayoutInflater.from(context);
            this.cr = c;
        }

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {
            return inflater.inflate(layout, null);
        }

        @Override
        public void bindView(View view, Context context, Cursor cursor) {
            super.bindView(view, context, cursor);
            CheckBox checkBox1 = (CheckBox) view.findViewById(R.id.checkBox1);
            checkBox1.setOnCheckedChangeListener(this);
            int columnIndex = cursor.getColumnIndex("_id");
            int columnvalue = cursor.getInt(columnIndex);
            checkBox1.setTag(columnvalue);
        }

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            int id = (Integer) buttonView.getTag();


            final DBMain db = new DBMain(getActivity());

            db.open();

            //getting information about deleted item from the shopping list
            Cursor item = db.getSingleItem(id);
            item.moveToPosition(-1);
            while(item.moveToNext())
            {
                name = item.getString(item.getColumnIndex("name"));
                measurement = item.getInt(item.getColumnIndex("measurement"));
                unit = item.getString(item.getColumnIndex("unit"));
            }
            item.close();

            //check if item is in Kitchen
            Cursor check = db.getSingleItem(id);

            //if yes, update it
            if(check!=null && check.getCount()>0)
            {
                //get current kitchen measurement
                Cursor measure = db.getKitchenMeasurementID(id);
                measure.moveToPosition(-1);
                while(measure.moveToNext())
                {
                    currMeasurement = measure.getInt(measure.getColumnIndex("measurement"));
                }
                measure.close();
                newMeasure = measurement + currMeasurement;

                db.updateContents(name, newMeasure);
            }
            else
            {

                db.insertContent(name, measurement, unit);
            }

            db.deleteItem(id);
        }
    }

}

片段的 XML

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
>

<ListView
    android:id="@android:id/list"
    android:layout_below="@+id/editText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
</ListView>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/addButton"
    app:backgroundTint="@color/floatingButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|right"
    android:clickable="true"
    android:src="@drawable/ic_tab_add"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true"
    android:layout_marginBottom="63dp"
    android:layout_marginRight="16dp" />


</android.support.design.widget.CoordinatorLayout>

行布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:weightSum="1">

<TextView
    android:id="@+id/ingredientName"
    android:layout_width="wrap_content"
    android:textColor="#000000"
    android:layout_height="wrap_content"
    android:padding="5dp"
    android:hint="wewewe"/>

<TextView
    android:id="@+id/ingredientMeasurement"
    android:textColor="#000000"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@+id/ingredientName"
    android:padding="5dp"
    android:hint="fefefef"/>

<TextView
    android:id="@+id/ingredientUnit"
    android:textColor="#000000"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_toRightOf="@+id/ingredientMeasurement"
    android:padding="5dp"
    android:hint="qqqqq"/>


<CheckBox
    android:id="@+id/checkBox1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="right"
    android:background="#fff"
    android:text=""/>
</LinearLayout>

Logcat 错误

Caused by: java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.TextView

【问题讨论】：

标签： android android-layout android-fragments

【解决方案1】：

你使用ArrayAdapter不正确，问题似乎出在这一行：

ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
                R.layout.shopping_list_row, values);

检查documentation，第二个参数需要布局资源ID，但不是任何资源：

包含 TextView 的布局文件的资源 ID，当实例化视图。

但您的行布局是LinearLayout。

如果你使用更复杂的布局，使用另一个构造函数：

public ArrayAdapter (Context context, int resource, 
                     int textViewResourceId, T[] objects)

您可以使用它的第三个参数在布局中指定TextView。

【讨论】：

感谢您的回复，我仍然不清楚如何修复它，我应该使用公共 ArrayAdapter 并将内容传递到其中，然后将其设置为列表视图吗？
设置数据到适配器，适配器到ListView。您可能希望使用 R.id.ingredientName 作为第三个参数。
如果对您有帮助，请考虑接受（并投票）答案；）

【解决方案2】：

在代码行中

ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),
                R.layout.shopping_list_row, values);
        setListAdapter(adapter);

布局“shopping_list_row”具有 LinearLayout，但数组适配器采用 textview，因此您需要设置父级为 Textview 的布局，或者创建具有自定义行的自定义适配器。

【讨论】：