java - Listview 在 Activity 上不可见

问题描述

在单击浮动操作按钮时动态添加列表项后，我在 Activity 上看不到我的列表视图。当我单击floatingActionButton 时，会打开一个接受我输入的新活动，单击保存按钮后ReminderActivity 会打开，但未显示在列表中添加的输入。

我的动机是listView每次从ReminderInputDataActivity获取数据后添加一个新项目，当我单击浮动操作按钮时会打开。

public class ReminderActivity extends AppCompatActivity {

    private ListView lvReminder;
    private FloatingActionButton floatingActionButton;
    private ArrayList<Reminder> reminders;
    public static final String REMINDER_INPUT = "reminder_input";
    private ReminderCustomAdapter reminderListAdapter;

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

        reminders = new ArrayList<>();
        lvReminder = (ListView) findViewById(R.id.lvReminder);
        Intent getIntent = getIntent();
        String[] reminderInput = getIntent.getStringArrayExtra(REMINDER_INPUT);
        if (reminderInput != null) {
            reminders.add(new Reminder(reminderInput[0], reminderInput[1], reminderInput[2]));
        }
        reminderListAdapter = new ReminderCustomAdapter(this, R.layout.listview_reminder, reminders);
        lvReminder.setAdapter(reminderListAdapter);

        floatingActionButton = (FloatingActionButton) findViewById(R.id.fab);
        floatingActionButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent intent = new Intent(ReminderActivity.this, ReminderInputDataActivity.class);
                startActivity(intent);
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (reminderListAdapter != null) {
            reminderListAdapter.notifyDataSetChanged();
        }
    }
}

public class Reminder {

    private String title;
    private String date;
    private String time;

    public Reminder() {
    }

    public Reminder(String title, String date, String time) {
        this.title = title;
        this.date = date;
        this.time = time;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }
}

public class ReminderInputDataActivity extends AppCompatActivity {

    private EditText etReminderTitle;
    private Button btDate, btTime;
    public static final String REMINDER_INPUT = "reminder_input";

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

        etReminderTitle = (EditText) findViewById(R.id.etReminderTitle);
        btDate = (Button) findViewById(R.id.btReminderDate);
        btTime = (Button) findViewById(R.id.btReminderTime);
        btDate.setText(new SimpleDateFormat("E, dd MMM yyyy", Locale.getDefault()).format(new Date()));
        btTime.setText(new SimpleDateFormat("HH:mm:ss", Locale.getDefault()).format(new Date()));
        Button btRemSave = (Button) findViewById(R.id.btRemSave);
        Button btRemCancel = (Button) findViewById(R.id.btRemCancel);

        final Intent intent = new Intent(ReminderInputDataActivity.this, ReminderActivity.class);
        btRemSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String[] userInput = new String[3];
                userInput[0] = etReminderTitle.getText() != null ? etReminderTitle.getText().toString() : "";
                userInput[1] = btDate.getText().toString();
                userInput[2] = btTime.getText().toString();
                Bundle bundle = new Bundle();
                bundle.putStringArray(REMINDER_INPUT, userInput);
                intent.putExtras(bundle);
                startActivity(intent);
            }
        });

        btRemCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(intent);
            }
        });
    }
}

public class ReminderCustomAdapter extends BaseAdapter {

    private final Context mContext;
    private int resource;
    private ArrayList<Reminder> reminderList;

    public ReminderCustomAdapter(Context mContext, int resource, ArrayList<Reminder> reminderList) {
        this.mContext = mContext;
        this.resource = resource;
        this.reminderList = reminderList;
    }

    @Override
    public int getCount() {
        return 0;
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(resource, null);
        TextView tvInputRemTitle = (TextView) view.findViewById(R.id.tvInputRemTitle);
        TextView tvInputRemDate = (TextView) view.findViewById(R.id.tvInputRemDate);
        TextView tvInputRemTime = (TextView) view.findViewById(R.id.tvInputRemTime);

        Reminder reminder = reminderList.get(position);
        tvInputRemTitle.setText(reminder.getTitle());
        tvInputRemDate.setText(reminder.getDate());
        tvInputRemTime.setText(reminder.getTime());
        return view;
    }
}

活动提醒.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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="@+id/lvReminder"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_margin="16dp"
        android:backgroundTint="@color/colorPrimaryDark"
        android:contentDescription="@string/reminder"
        android:src="@android:drawable/ic_input_add"
        app:shapeAppearanceOverlay="@style/fab_3_rounded" />

</RelativeLayout>

listview_reminder.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"
    android:orientation="vertical"
    android:padding="10dp">

    <TextView
        android:id="@+id/tvInputRemTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="Title"
        android:textSize="15sp" />

    <TextView
        android:id="@+id/tvInputRemDate"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvInputRemTitle"
        android:hint="Date" />

    <TextView
        android:id="@+id/tvInputRemTime"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvInputRemTitle"
        android:layout_marginLeft="10dp"
        android:layout_toRightOf="@+id/tvInputRemDate"
        android:hint="Time" />

</RelativeLayout>

我是 android 新手并开始创建一个基本项目，对于上述问题，我观看了一些视频并浏览了文章，但无法在这里找到问题。

请帮忙。提前致谢！

标签： javaandroidandroid-layout

解决方案

问题是由于此代码

    final Intent intent = new Intent(ReminderInputDataActivity.this, ReminderActivity.class);
    btRemSave.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String[] userInput = new String[3];
            userInput[0] = etReminderTitle.getText() != null ? etReminderTitle.getText().toString() : "";
            userInput[1] = btDate.getText().toString();
            userInput[2] = btTime.getText().toString();
            Bundle bundle = new Bundle();
            bundle.putStringArray(REMINDER_INPUT, userInput);
            intent.putExtras(bundle);
            startActivity(intent);
        }
    });

在这里，您ReminderActivity再次开始调用onCreate此活动的方法，您在其中添加reminders = new ArrayList<>();了重新创建没有数据的数组列表。为避免这种情况，您可以实施两种解决方案。

实施interface。
StartActivityForResult.

最简单的解决方案是StartActivityForResult. 例如，

Intent intent = new Intent(ReminderActivity.this,ReminderInputDataActivity.class);  
                startActivityForResult(intent, 2); 

and in the same activity implement the callback.

@Override  
   protected void onActivityResult(int requestCode, int resultCode, Intent data)  
   {
    super.onActivityResult(requestCode, resultCode, data);  
    // check if the request code is same as what is passed  here it is 2  
    if(requestCode==2)  
    {  
     String message=data.getStringExtra("MESSAGE");   
     textView1.setText(message);  
     }  
 }

从 ReminderInputDataActivity 像这样将数据发送回此类。

  Intent intent=new Intent();  
                intent.putExtra("MESSAGE",message);  
                setResult(2,intent);  
                finish();//finishing activity

java - Listview 在 Activity 上不可见

问题描述

解决方案

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