将不可见的CheckBox设置为在ListView

时间：2018-01-10 18:15:41

标签： android

我在ListView中有一个具有自定义适配器的复选框。复选框最初是不可见的，但是当用户单击“添加”按钮将项目添加到ListView时，我想将其中的一定数量设置为可见。可见的复选框的数量取决于用户输入，例如，如果用户键入多个集合为5，则将有5个可用于ListView项目的复选框。我在自定义适配器类中有一个名为showCheckBoxes（）的方法，并在数据库中发生数据更改时在主活动中调用它。我在自定义适配器类中实例化了我的复选框，但是如果我在主活动的onStart（）中调用showCheckboxes（），我会得到setVisibility（）方法的空指针异常。如果我在自定义适配器类的getView（）中调用showCheckBoxes（），应用程序运行时没有错误，但复选框仍然不可见。

logcat的：

01-10 12:52:58.711 11470-11470/com.josh2.mygains E/AndroidRuntime: FATAL EXCEPTION: main
                                                               Process: com.josh2.mygains, PID: 11470
                                                               java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.CheckBox.setVisibility(int)' on a null object reference
                                                                   at com.josh2.mygains.ExerciseList.showCheckBoxes(ExerciseList.java:91)
                                                                   at com.josh2.mygains.WorkoutActivity$3.onDataChange(WorkoutActivity.java:102)
                                                                   at com.google.android.gms.internal.to.zza(Unknown Source:13)
                                                                   at com.google.android.gms.internal.vj.zzHX(Unknown Source:2)
                                                                   at com.google.android.gms.internal.vp.run(Unknown Source:65)
                                                                   at android.os.Handler.handleCallback(Handler.java:789)
                                                                   at android.os.Handler.dispatchMessage(Handler.java:98)
                                                                   at android.os.Looper.loop(Looper.java:164)
                                                                   at android.app.ActivityThread.main(ActivityThread.java:6809)
                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                   at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

自定义适配器类（尝试通过在getView（）中调用showCheckBoxes（）来设置可见复选框）：

public class ExerciseList extends ArrayAdapter<Exercise> {
private Activity context;
List<Exercise> exercises;

private CheckBox checkBox1;
private CheckBox checkBox2;
private CheckBox checkBox3;
private CheckBox checkBox4;
private CheckBox checkBox5;
private CheckBox checkBox6;

public ExerciseList(Activity context, List<Exercise> exercises) {
    super(context, R.layout.layout_exercise_list, exercises);
    this.context = context;
    this.exercises = exercises;
}

public void updateExerciseList(List<Exercise> exercises) {
    this.exercises = exercises;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    LayoutInflater inflater = context.getLayoutInflater();
    View listViewItem = inflater.inflate(R.layout.layout_exercise_list, null, true);

    TextView nameTextView = listViewItem.findViewById(R.id.nameTextView);
    TextView setsTextView = listViewItem.findViewById(R.id.setsTextView);
    TextView repsTextView = listViewItem.findViewById(R.id.repsTextView);
    TextView restTextView = listViewItem.findViewById(R.id.restTextView);

    checkBox1 = listViewItem.findViewById(R.id.checkBox1);
    checkBox2 = listViewItem.findViewById(R.id.checkBox2);
    checkBox3 = listViewItem.findViewById(R.id.checkBox3);
    checkBox4 = listViewItem.findViewById(R.id.checkBox4);
    checkBox5 = listViewItem.findViewById(R.id.checkBox5);
    checkBox6 = listViewItem.findViewById(R.id.checkBox6);

    Exercise exercise = exercises.get(position);

    if(exercise != null && exercise.getName() != null) {
        nameTextView.setText(exercise.getName());
    }
    if(exercise != null) {
        setsTextView.setText("Sets: " + String.valueOf(exercise.getSets()));
    }
    if(exercise != null) {
        repsTextView.setText("Reps: " + String.valueOf(exercise.getReps()));
    }
    if(exercise != null) {
        restTextView.setText("Rest time: " + String.valueOf(exercise.getRestTime()) + " mins");
    }

    try {
        int sets = Integer.parseInt(setsTextView.getText().toString());
        showCheckBoxes(sets);
    } catch(NumberFormatException e) {
        e.printStackTrace();
    }

    return listViewItem;
}

public void showCheckBoxes(int sets) {
    if(sets == 1) {
        checkBox1.setVisibility(View.VISIBLE);
    } else if(sets == 2) {
        checkBox1.setVisibility(View.VISIBLE);
        checkBox2.setVisibility(View.VISIBLE);
    } else if(sets == 3) {
        checkBox1.setVisibility(View.VISIBLE);
        checkBox2.setVisibility(View.VISIBLE);
        checkBox3.setVisibility(View.VISIBLE);
    } else if(sets == 4) {
        checkBox1.setVisibility(View.VISIBLE);
        checkBox2.setVisibility(View.VISIBLE);
        checkBox3.setVisibility(View.VISIBLE);
        checkBox4.setVisibility(View.VISIBLE);
    } else if(sets == 5) {
        checkBox1.setVisibility(View.VISIBLE);
        checkBox2.setVisibility(View.VISIBLE);
        checkBox3.setVisibility(View.VISIBLE);
        checkBox4.setVisibility(View.VISIBLE);
        checkBox5.setVisibility(View.VISIBLE);
    } else if(sets == 6) {
        checkBox1.setVisibility(View.VISIBLE);
        checkBox2.setVisibility(View.VISIBLE);
        checkBox3.setVisibility(View.VISIBLE);
        checkBox4.setVisibility(View.VISIBLE);
        checkBox5.setVisibility(View.VISIBLE);
        checkBox6.setVisibility(View.VISIBLE);
    } /*else {
        Toast.makeText(WorkoutActivity.this, "Please enter an amount of sets between 1 and 6.", Toast.LENGTH_LONG).show();
    }*/
}

}

主要活动（尝试通过在onStart（）中调用showCheckBoxes（）设置可见复选框）：

public class WorkoutActivity extends AppCompatActivity {

String day;
TextView workoutDayTV;

EditText exerciseNameET;
EditText setsET;
EditText repsET;
EditText restTimeET;
Button addButton;

ExerciseList exerciseAdapter;
ArrayList<Exercise> exercises;
ListView exerciseList;

DatabaseReference dbExercises;

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

    dbExercises = FirebaseDatabase.getInstance().getReference("exercises");

    Intent intent = getIntent();
    day = intent.getStringExtra("day");

    exerciseNameET = findViewById(R.id.exerciseNameET);
    setsET = findViewById(R.id.setsET);
    repsET = findViewById(R.id.repsET);
    restTimeET = findViewById(R.id.restTimeET);
    addButton = findViewById(R.id.addButton);
    workoutDayTV = findViewById(R.id.workoutDayTV);
    exerciseList = findViewById(R.id.exerciseList);

    exercises = new ArrayList<>();

    exerciseAdapter = new ExerciseList(WorkoutActivity.this, exercises);
    exerciseList.setAdapter(exerciseAdapter);

    workoutDayTV.setText(day + " Workout Schedule");
    addButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            addExercise();
        }
    });

    exerciseList.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView<?> adapterView, View view, int position, long l) {
            Exercise exercise = exercises.get(position);
            showExerciseDialog(exercise, exercise.getId(), exercise.getName());
            return true;
        }
    });
}

@Override
protected void onStart() {
    super.onStart();
    dbExercises.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            exercises.clear();
            for(DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                Exercise exercise = postSnapshot.getValue(Exercise.class);
                if(day.equals(exercise.getDay())) {
                    exercises.add(exercise);
                    try {
                        exerciseAdapter.showCheckBoxes(exercise.getSets());
                    } catch(NumberFormatException e) {
                        e.printStackTrace();
                    }
                }
            }
            exerciseAdapter.updateExerciseList(exercises);
            exerciseAdapter.notifyDataSetChanged();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

private void addExercise() {
    String name = exerciseNameET.getText().toString();
    try {
        int sets = Integer.parseInt(setsET.getText().toString());
        int reps = Integer.parseInt(repsET.getText().toString());
        int restTime = Integer.parseInt(restTimeET.getText().toString());

        if((!TextUtils.isEmpty(name)) && (!TextUtils.isEmpty(setsET.getText().toString())) && (!TextUtils.isEmpty(repsET.getText().toString())) && (!TextUtils.isEmpty(restTimeET.getText().toString()))) {
            String id = dbExercises.push().getKey();
            Exercise exercise = null;
            if(day.equals("Monday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Monday");
            } else if(day.equals("Tuesday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Tuesday");
            } else if(day.equals("Wednesday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Wednesday");
            } else if(day.equals("Thursday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Thursday");
            } else if(day.equals("Friday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Friday");
            } else if(day.equals("Saturday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Saturday");
            } else if(day.equals("Sunday")) {
                exercise = new Exercise(id,name,sets,reps,restTime,"Sunday");
            }
            dbExercises.child(id).setValue(exercise);
            exerciseNameET.setText("");
            setsET.setText("");
            repsET.setText("");
            restTimeET.setText("");
        }
    } catch(NumberFormatException e) {
        Toast.makeText(this, "All fields are required. Please complete the missing fields.", Toast.LENGTH_LONG).show();
        e.printStackTrace();
    }
}

private void updateExercise(String id, String name, int sets, int reps, int restTime, String day) {
    DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference("exercises").child(id);
    Exercise exercise = new Exercise(id, name, sets, reps, restTime, day);
    dbRef.setValue(exercise);
}

private boolean deleteExercise(String id) {
    DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference("exercises").child(id);
    dbRef.removeValue();
    return true;
}

private void showExerciseDialog(final Exercise exercise, final String id, String name) {
    AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    LayoutInflater inflater = getLayoutInflater();
    View dialogView = inflater.inflate(R.layout.exercise_dialog, null);
    dialog.setView(dialogView);

    final EditText exerciseNameET = dialogView.findViewById(R.id.exerciseNameET);
    final EditText setsET = dialogView.findViewById(R.id.setsET);
    final EditText repsET = dialogView.findViewById(R.id.repsET);
    final EditText restTimeET = dialogView.findViewById(R.id.restTimeET);
    Button updateButton = dialogView.findViewById(R.id.updateButton);
    Button deleteButton = dialogView.findViewById(R.id.deleteButton);

    dialog.setTitle(name);
    dialog.setMessage("Update or delete this exercise.");
    final AlertDialog alertDialog = dialog.create();
    alertDialog.show();

    updateButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String name = exerciseNameET.getText().toString();
            try {
                int sets = Integer.parseInt(setsET.getText().toString());
                int reps = Integer.parseInt(repsET.getText().toString());
                int restTime = Integer.parseInt(restTimeET.getText().toString());
                if((!TextUtils.isEmpty(name)) && (!TextUtils.isEmpty(setsET.getText().toString())) && (!TextUtils.isEmpty(repsET.getText().toString())) && (!TextUtils.isEmpty(restTimeET.getText().toString()))) {
                    updateExercise(id,name,sets,reps,restTime,exercise.getDay());
                    alertDialog.dismiss();
                }
            } catch(NumberFormatException e) {
                Toast.makeText(getApplicationContext(), "All fields are required. Please complete the missing fields.", Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }
        }
    });

    deleteButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            deleteExercise(id);
            alertDialog.dismiss();
        }
    });
}

}

列表视图项XML：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:descendantFocusability="blocksDescendants" >

<LinearLayout
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="0.5"
    android:orientation="vertical">

    <TextView
        android:id="@+id/nameTextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="23sp" />

    <TextView
        android:id="@+id/setsTextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="15sp" />

    <TextView
        android:id="@+id/repsTextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="15sp" />

    <TextView
        android:id="@+id/restTextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="15sp" />
</LinearLayout>

<LinearLayout
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="0.25"
    android:orientation="vertical">

    <CheckBox
        android:id="@+id/checkBox1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 1"
        android:visibility="invisible" />

    <CheckBox
        android:id="@+id/checkBox2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 2"
        android:visibility="invisible" />

    <CheckBox
        android:id="@+id/checkBox3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 3"
        android:visibility="invisible" />
</LinearLayout>

<LinearLayout
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="0.25"
    android:orientation="vertical">

    <CheckBox
        android:id="@+id/checkBox4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 4"
        android:visibility="invisible" />

    <CheckBox
        android:id="@+id/checkBox5"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 5"
        android:visibility="invisible" />

    <CheckBox
        android:id="@+id/checkBox6"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Set 6"
        android:visibility="invisible" />
</LinearLayout>

0 个答案:

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