java - 将onClickListener与ListView中的CheckBoxes一起使用

Question

因此，我一直在尝试在切换复选框时进行注册。到目前为止，我还没有运气。 onClickListener是否适合这种情况？当我尝试使用它时，出现一个错误。

MainActivity.java

  private static final String TAG = "MainActivity";
    private HabitHelper mHelper;
    private ListView mHabitView;
    private ArrayAdapter<String> mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mHelper = new HabitHelper(this);
        mHabitView = (ListView) findViewById(R.id.habitList);

        FloatingActionButton myFab = (FloatingActionButton) findViewById(R.id.addHabit);
        CheckedTextView chkBox = (CheckedTextView) findViewById(R.id.habitItem);

        myFab.setOnClickListener(this);


        chkBox.setOnClickListener(this);

        updateUI();
    }

    public void onClick (View v){

        final EditText habitText = new EditText(this);
        AlertDialog dialog = new AlertDialog.Builder(this)
                .setTitle("Add a new habit")
                .setMessage("What habit would you like to start working on?")
                .setView(habitText)
                .setPositiveButton("Add", new DialogInterface.OnClickListener(){
            @Override
                    public void onClick(DialogInterface dialog, int which) {
                String habit = String.valueOf(habitText.getText());
                SQLiteDatabase db = mHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                values.put(HabitContract.HabitEntry.COLUMN_NAME_TITLE, habit);
                db.insertWithOnConflict(HabitContract.HabitEntry.TABLE, null, values, SQLiteDatabase.CONFLICT_REPLACE);
                db.close();
                updateUI();

            }
        })
                .setNegativeButton("Cancel", null)
                .create();
                dialog.show();

    }


    public class CheckBoxClick implements AdapterView.OnItemClickListener{

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
            CheckedTextView ctv = (CheckedTextView)arg1.findViewById(R.id.habitItem);
            if (ctv.isChecked()){
                Toast.makeText(MainActivity.this, "You have completed your habit for the day", Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(MainActivity.this, "Make sure you complete your task before checking me!", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void updateUI(){
        ArrayList<String> habitList = new ArrayList<>();
        SQLiteDatabase db = mHelper.getReadableDatabase();
        Cursor cursor = db.query(HabitContract.HabitEntry.TABLE, new String[]{HabitContract.HabitEntry._ID, HabitContract.HabitEntry.COLUMN_NAME_TITLE}, null, null, null, null, null);
        while (cursor.moveToNext()){
            int idx = cursor.getColumnIndex(HabitContract.HabitEntry.COLUMN_NAME_TITLE);
            habitList.add(cursor.getString(idx));
        }
        if (mAdapter == null){
            mAdapter = new ArrayAdapter<>(this, R.layout.item_habit, R.id.habitItem, habitList);
            mHabitView.setAdapter(mAdapter);
        }
        else {
            mAdapter.clear();
            mAdapter.addAll(habitList);
            mAdapter.notifyDataSetChanged();
        }
        cursor.close();
        db.close();
    }

    private void deleteHabit(View view){
        View parent = (View) view.getParent();
        TextView habitTextView = (TextView) parent.findViewById(R.id.habitItem);
        String habit = String.valueOf(habitTextView.getText());
        SQLiteDatabase db = mHelper.getWritableDatabase();
        db.delete(HabitContract.HabitEntry.TABLE, HabitContract.HabitEntry.COLUMN_NAME_TITLE + " = ?", new String[] {habit});
        db.close();
        updateUI();
    }}

activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.jonathan.myapplication.MainActivity"
    tools:layout_editor_absoluteY="81dp"
    tools:layout_editor_absoluteX="0dp">


    <ListView
        android:id="@+id/habitList"
        android:layout_width="0dp"
        android:layout_height="0dp"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintRight_creator="1"
        tools:layout_constraintBottom_creator="1"
        android:layout_marginStart="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginEnd="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="8dp"
        tools:layout_constraintLeft_creator="1"
        android:layout_marginBottom="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/addHabit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:clickable="true"
        app:fabSize="mini"
        app:srcCompat="@android:drawable/ic_input_add"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintRight_toRightOf="parent"
        tools:ignore="RtlHardcoded" />
</android.support.constraint.ConstraintLayout>

item_habit.xml

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


    <CheckedTextView
        android:id="@+id/habitItem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_vertical"
        android:checkMark="?android:attr/listChoiceIndicatorMultiple"
        android:padding="5dp"
        android:checked="false"
        android:clickable="true"
        android:focusable="true"
        android:text=""
        />

</RelativeLayout>

错误

java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.jonathan.myapplication / com.example.jonathan.myapplication.MainActivity}：java.lang.NullPointerException：尝试调用虚拟方法'void android.widget.CheckedTextView。在空对象引用上的setOnClickListener（android.view.View $ OnClickListener）'
                                                                                  在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2817）
                                                                                  在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2892）
                                                                                  在android.app.ActivityThread.-wrap11（未知来源：0）
                                                                                  在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1593）
                                                                                  在android.os.Handler.dispatchMessage（Handler.java:105）
                                                                                  在android.os.Looper.loop（Looper.java:164）
                                                                                  在android.app.ActivityThread.main（ActivityThread.java:6541）
                                                                                  在java.lang.reflect.Method.invoke（本机方法）
                                                                                  在com.android.internal.os.Zygote $ MethodAndArgsCaller.run（Zygote.java:240）
                                                                                  在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:767）
                                                                               引起原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“ void android.widget.CheckedTextView.setOnClickListener（android.view.View $ OnClickListener）”
                                                                                  在com.example.jonathan.myapplication.MainActivity.onCreate（MainActivity.java:50）
                                                                                  在android.app.Activity.performCreate（Activity.java:6975）
                                                                                  在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1213）
                                                                                  在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2770）
                                                                                  在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2892）
                                                                                  在android.app.ActivityThread.-wrap11（未知来源：0）
                                                                                  在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1593）
                                                                                  在android.os.Handler.dispatchMessage（Handler.java:105）
                                                                                  在android.os.Looper.loop（Looper.java:164）
                                                                                  在android.app.ActivityThread.main（ActivityThread.java:6541）
                                                                                  在java.lang.reflect.Method.invoke（本机方法）
                                                                                  在com.android.internal.os.Zygote $ MethodAndArgsCaller.run（Zygote.java:240）
                                                                                  在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:767）

Answer 1

您没有为Lis​​tView创建视图，而CheckedTestView不在布局内。

您尝试为其设置侦听器的位置实际上应该在将创建CheckedTestViews的ListAdapter内。

我看到，您使用了CursorAdapter，可以检查单击次数，然后进入listView槽：

 listView.setOnItemClickListener(new OnItemClickListener(){/**/});

但是，您必须删除chb.setOnClickListener（this），因为它们是列表中的项目，而不是布局中的单个视图。