I'm very new to Android Dev/Java and I'm following a tutorial online and trying to create a simple To Do list application for Android. It looks the tutorial is a bit outdated and relies on the DPAD to navigate up and down the list of tasks in order to target a list item and delete it using the "Delete Button" in the applications menu. I am having a hard time trying to figure out how to "select" a list item on click and delete it using the "delete" button. Right now when a click a list item it does nothing, so the application doesn't know which is selected, when I click the delete button. Here is my XML and Java code. Any insight will be very helpful.
XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<EditText
android:id="@+id/textItem"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:ems="10" />
<Button
android:id="@+id/btnAdd"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textItem"
android:layout_below="@+id/textItem"
android:text="@string/add" />
<ListView
android:id="@+id/listItems"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/btnAdd"
android:layout_alignRight="@+id/btnAdd"
android:layout_below="@+id/btnAdd"
android:layout_marginTop="20dp" >
</ListView>
</RelativeLayout>
JAVA
package com.example.todo;
import java.util.ArrayList;
import java.util.Calendar;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnKeyListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements View.OnClickListener, DialogInterface.OnClickListener, OnKeyListener {
EditText textItem;
Button btnAdd;
Button btnDelete;
ListView listItems;
ArrayList<String> toDoItems;
ArrayAdapter<String> aa;
String[] date = {"Movie", "Dinner", "Drinks"};
String[] gym = {"Cardio", "Upper Body", "Lower Body"};
String[] meeting = {"30min Meeting", "1 Hour Meeting", "2 Hour Meeting"};
String[] homework = {"Paper", "Exercise", "Assignment"};
String[] project = {"App", "Web", "Graphic Design"};
String currentMenu;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textItem = (EditText)findViewById(R.id.textItem);
btnAdd = (Button)findViewById(R.id.btnAdd);
btnDelete = (Button)findViewById(R.id.btnDelete);
listItems = (ListView)findViewById(R.id.listItems);
btnAdd.setOnClickListener(this);
textItem.setOnKeyListener(this);
toDoItems = new ArrayList<String>();
aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, toDoItems);
listItems.setAdapter(aa);
/*--Set heading to todays Date--*/
TextView tvDisplayDate = (TextView) findViewById(R.id.heading);
final Calendar c = Calendar.getInstance();
int yy = c.get(Calendar.YEAR);
int mm = c.get(Calendar.MONTH);
int dd = c.get(Calendar.DAY_OF_MONTH);
// set current date into textview
tvDisplayDate.setText(new StringBuilder()
// Month is 0 based, just add 1
.append(mm + 1).append("/").append(dd).append("/").append(yy));
}
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
MenuItem item;
item = menu.add("delete");
item.setIcon(R.drawable.remove);
item = menu.add("date");
item.setIcon(R.drawable.date);
item = menu.add("gym");
item.setIcon(R.drawable.gym);
item = menu.add("meeting");
item.setIcon(R.drawable.meeting);
item = menu.add("homework");
item.setIcon(R.drawable.homework);
item = menu.add("project");
item.setIcon(R.drawable.project);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
if (item.hasSubMenu() == false) {
if (item.getTitle() == "date") {
currentMenu = "date";
this.displayPopup("Date Options", this.date);
}
if (item.getTitle() == "gym") {
currentMenu = "gym";
this.displayPopup("Gym Options", this.gym);
}
if (item.getTitle() == "meeting") {
currentMenu = "meeting";
this.displayPopup("Meeting Options", this.meeting);
}
if (item.getTitle() == "homework") {
currentMenu = "homework";
this.displayPopup("Homework Options", this.homework);
}
if (item.getTitle() == "project") {
currentMenu = "project";
this.displayPopup("Project Options", this.project);
}
if(item.getTitle() == "delete") {
int index = listItems.getSelectedItemPosition();
this.deleteItem(index);
}
}
return true;
}
private void addItem(String item) {
if (item.length() > 0 ) {
Toast.makeText(getApplicationContext(), item+" added", Toast.LENGTH_SHORT).show();
this.toDoItems.add(item);
this.aa.notifyDataSetChanged();
this.textItem.setText("");
}
}
private void deleteItem(int itemId) {
if (itemId >=0) {
String itemName = (String)listItems.getItemAtPosition(itemId);
Toast.makeText(getApplicationContext(), itemName+" delete", Toast.LENGTH_SHORT).show();
this.toDoItems.remove(itemId);
aa.notifyDataSetChanged();
}
}
private void displayPopup(String title, String[] items) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle(title);
builder.setItems(items, this);
builder.show();
}
@Override
public void onClick(View v) {
if (v == this.btnAdd) {
this.addItem(this.textItem.getText().toString());
}
}
@Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_DOWN && keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
this.addItem(this.textItem.getText().toString());
}
return false;
}
@Override
public void onClick(DialogInterface dialog, int item) {
if (currentMenu == "date") this.addItem(date[item]);
if (currentMenu == "gym") this.addItem(gym[item]);
if (currentMenu == "meeting") this.addItem(meeting[item]);
if (currentMenu == "homework") this.addItem(homework[item]);
if (currentMenu == "project") this.addItem(project[item]);
listItems.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
listItems.setSelection(position);
view.setSelected(true);
}
});}
}
The way i see it, you have to options, in both you'll have to use the onItemClick:
the first, is to delete the item when you click on it
listItems.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// remove the item from the array
toDoItems.remove(position);
// call a UI update for the list
aa.notifyDataSetChanged();
}
});
the second, is to store the clicked item position, and then call the delete action once user has clicked on the delete button from the menu.
int selectedItem = -1;
listItems.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//save the clicked item position
// and the when the delete button is pressed, use it.
// keep in mind that this is not that good if you are using recycled list
selectedItem = position; }
});
any way, i would suggest start using an updated tutorial first...
从ListActicity扩展并覆盖onListItemClicked方法。
Selecting and clicking are 2 different things.
Override listview.setOnItemClickListener and set your clicked list item selected. Then your delete will work.
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
listview.setSelection(position);
view.setSelected(true);
}
});
You should try this tutorial to learn more about listview: http://www.vogella.com/tutorials/AndroidListView/article.html
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