Hello. I'm Wataku, a server-side programmer who is studying programming at a certain school. : relaxed: Let's develop Android this time as well. Since there are various ways to display list views on Android, I myself have become confused, so I would like to sleep with the devil.
--A person who can write Java somehow. --Someone who is ambiguous in Android development but can do it a little.
○ Listener class when tapping the list view: ** onItemClickListener ** Implement the interface.
* This interface is a member interface of the AdapterView class
○ List setting method
setOnItemClickListener(Insert the member interface that implements onItemClickListener)
** 1) Event handler: onItemClick () ** 4 arguments
1.AdapterView<?> parent
->The entire tapped ListView
2.View view
->One line of tapped screen parts
3.int position
->Tapped line number
* Starting from 0
4.long id
->Primary key value when ListView is generated based on DB data
* If DB is not used, the same value as the above position
** 2) Data acquisition ** ○ The data of the tapped line can be obtained using parent and position.
(String)parent.getItemAtPosition(position)
private class ListItemClickListener implements AdapterView.OnItemClickListener {
public void onItemClick(AdapterView<?> parent, View view, int position, long l) {
String item = (String)parent.getItemAtPosition(position);
Toast.makeText(ListClickSampleActivity.this, show, Toast.LENGTH_SHORT).show();
}
}
** 1) Create with xml **
activity_list_click_sample.xml
<?xml version="1.0" encoding="utf-8"?>
<ListView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/lvMenu"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:entries="@array/lv_menu"/>
string.xml
<?xml version="1.0" encoding="UTF-8" ?>
<resources>
<string name="app_name">List selection sample</string>
<string-array name="lv_menu">
<item>Fried chicken</item>
<item>Hamburger set meal</item>
<item>Ginger-grilled set meal</item>
<item>Steak set meal</item>
<item>Stir-fried vegetables set meal</item>
<item>Twice-cooked meat set meal</item>
<item>Mapo tofu set meal</item>
<item>Tonkatsu set meal</item>
<item>Minced cutlet set meal</item>
<item>Chicken and set meal</item>
<item>Croquette set meal</item>
<item>Grilled fish set meal</item>
<item>Yakiniku set meal</item>
<item>Weak meat and strong food</item>
</string-array>
</resources>
ListClickSampleActivity.java
public class ListClickSampleActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_click_sample);
ListView lvMenu = findViewById(R.id.lvMenu);
lvMenu.setOnItemClickListener(ListItemClickListener);
}
AdapterView.OnItemClickListener ListItemClickListener = new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long l) {
String item = (String)parent.getItemAtPosition(position);
String show = "Set meal of your choice:" + item;
Toast.makeText(ListClickSampleActivity.this, show, Toast.LENGTH_SHORT).show();
}
};
}
** 2) Create with Java code **
<?xml version="1.0" encoding="utf-8"?>
<ListView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/lvPref"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
PrefListActivity.java
public class PrefListActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pref_list);
ListView lvPref = findViewById(R.id.lvPref);
List<String> prefList = createPrefectureList();
ArrayAdapter<String> adapter = new ArrayAdapter<>(PrefListActivity.this, android.R.layout.simple_list_item_1, prefList);
lvPref.setAdapter(adapter);
lvPref.setOnItemClickListener(new ListItemClickListener());
}
/**
*A method to generate a state list.
* @return State list object.
*/
private List<String> createPrefectureList() {
List<String> prefList = new ArrayList<>();
prefList.add("Hokkaido");
prefList.add("Aomori Prefecture");
prefList.add("Iwate Prefecture");
prefList.add("Miyagi Prefecture");
prefList.add("Akita");
prefList.add("Yamagata Prefecture");
prefList.add("Fukushima Prefecture");
prefList.add("Ibaraki Prefecture");
prefList.add("Tochigi Prefecture");
prefList.add("Gunma Prefecture");
prefList.add("Saitama");
prefList.add("Chiba");
prefList.add("Tokyo");
prefList.add("Kanagawa Prefecture");
prefList.add("Niigata Prefecture");
prefList.add("Toyama Prefecture");
prefList.add("Ishikawa Prefecture");
prefList.add("Fukui prefecture");
prefList.add("Yamanashi Prefecture");
prefList.add("Nagano Prefecture");
prefList.add("Gifu Prefecture");
prefList.add("Shizuoka Prefecture");
prefList.add("Aichi prefecture");
prefList.add("Mie Prefecture");
prefList.add("Shiga Prefecture");
prefList.add("Kyoto");
prefList.add("Osaka");
prefList.add("Hyogo prefecture");
prefList.add("Nara Prefecture");
prefList.add("Wakayama Prefecture");
prefList.add("Tottori prefecture");
prefList.add("Shimane Prefecture");
prefList.add("Okayama Prefecture");
prefList.add("Hiroshima Prefecture");
prefList.add("Yamaguchi Prefecture");
prefList.add("Tokushima Prefecture");
prefList.add("Kagawa Prefecture");
prefList.add("Ehime Prefecture");
prefList.add("Kochi Prefecture");
prefList.add("Fukuoka Prefecture");
prefList.add("Saga Prefecture");
prefList.add("Nagasaki Prefecture");
prefList.add("Kumamoto Prefecture");
prefList.add("Oita Prefecture");
prefList.add("Miyazaki prefecture");
prefList.add("Kagoshima prefecture");
prefList.add("Okinawa Prefecture");
return prefList;
}
/**
*A member class that describes what happens when a list is selected.
*Transfer the process to the second screen.
*/
private class ListItemClickListener implements AdapterView.OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String prefName = (String) parent.getItemAtPosition(position);
Intent intent = new Intent(PrefListActivity.this, PrefEditActivity.class);
intent.putExtra("selectedPrefNo", position);
intent.putExtra("selectedPrefName", prefName);
startActivity(intent);
}
}
}
Use the ** SimpleCursorAdapter ** class. → Use when you want to create a list view based on the data in the DB. 6 arguments
1.context
2.R-value that represents the layout of each row in the list view
＊simple_list_view_item_1 is usually good.
3.Cursor object
4.String[] :Array of column names
5.int[] :Array of R-values of screen parts
6.0 is fine
How to display (register) this in the list view -> Use the ** setAdapter ** method of the ListView class
MemoListActivity.java
public class MemoListActivity extends AppCompatActivity {
private ListView _lvMemoList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_memo_list);
_lvMemoList = findViewById(R.id.lvMemoList);
_lvMemoList.setOnItemClickListener(new ListItemClickListener());
}
@Override
protected void onResume() {
super.onResume();
DatabaseHelper helper = new DatabaseHelper(MemoListActivity.this);
SQLiteDatabase db = helper.getWritableDatabase();
Cursor cursor = DataAccess.findAll(db);
String[] from = {"title"};
int[] to = {android.R.id.text1};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(MemoListActivity.this, android.R.layout.simple_list_item_1, cursor, from, to, 0);
_lvMemoList.setAdapter(adapter);
}
}
ʻonResume: Method to refresh the screen `
Use ** SimpleAdapter **. row To customize each row in the list view, do the following: ** 1) Prepare a layout .xml file for one line ** -> How to write xml file is the same as normal layout file
res/layout/row.xml
<LinearLayout ... >
<ImageView ... />
<TextView ... />
<TextView ... />
<TextView ... />
</LinearLayout>
* File name can be anything
** 2) Specify the R value of the file in 1) in the argument that specifies the layout when newing the adapter. ** **
(ex.)
new.SimpleAdapter( ..., _list, R.layout.row, ... );
** 3) In the int array of the argument to when newing the adapter class, specify the R value of id described in the file of 1). ** **
(ex.)
int[] to = {R.id.tvMenuName, R.id.tvMenuPrice}
ViewBinder
** (1) What is ViewBinder **
You can use row.xml to customize the layout that precedes the list view.
Then, how to change the display contents of each line according to the data?
Create your own process to assign from data to to screen parts by combining from-to (creating ViewBinder), the procedure is as follows.
** 1) Create a class that implements the SimpleAdapter.ViewBinder interface. -> Private member class is fine **
** 2) Describe the data allocation process to the screen parts in the setViewValue () method of this class. (See below) **
** 3) Pass a new version of this class to the setViewBinder () method of the adapter class **
(ex.)
private class CustomViewBinder implement SimpleAdapter.ViewBinder {
@Override
public boolean setViewValue() {
Describe the data allocation of screen parts in each line here
}
}
adapter.setViewBinder(new CustomViewBinder());
** (2) Argument of setViewValue () ** The argument of the method of setViewValue () is the following three.
1. View view :Screen parts in one line.
2. Object data :The data to assign to the first argument above.
3. String textReprosentation :A string of the contents of the second argument. If the second argument is null
White space string.
** (3) Processing pattern in setViewValue () ** In setViewValue (), branch using the id of the argument view, and describe the process using the argument data. → The switch statement is convenient.
public booelan setViewValue ( .... ) {
int viewId = view.getId();← Get id
switch( viewId ) {← Branch processing according to id(switch)
case R . id . imPhoneType :← R value because it is a comparison between ids
ImageView imPhoneType = ( ImageView ) view;
int phoneType = ( Integer ) data;
Then do whatever you want.
return true;
case .....
}
return false
}
In the setViewValue () method, if you write your own process to embed data in the view, that is, write return true at the end of each case. In addition, write return false at the end of the method. → Based on this return value, it is judged whether to embed data on the os side.
** (4) For SimpleCursorAdapter ** Even in the case of SimpleCursorAdapter, the processing of setViewValue () of ViewBinder is the same as that of SimpleAdapter.
view . getId()Branch the value of with a switch. However, the arguments are the following three.
1. View view :Screen parts in one line of the list.
2. Cursor cursor :A cursor object that contains data for one row of the target list.
3. int columnIndex :The column index of the data to be assigned to the first argument above.
When the data in the DB that is the original data of the list view is updated, it is necessary to retrieve the data from the DB and display it again.
○ The following source code.
SimpleCursorAdapter adapter = ( SimpleCursorAdapter ) _lvPhones . getAdapter();
adapter . changeCursor( cursor );← Swap the cursor. New cursor
(note) If you want to set the adapter with `ʻonCreate () and set (replace) the cursor with onResume (), you can pass null as the argument cursor when you new SimpleCursorAdapter in onCreate (). ``
public class CustomizedListView2Activity extends AppCompatActivity {
/**
*List data to be displayed in the list view.
*/
private List<Map<String, Object>> _list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_customized_list_view2);
_list = createList();
String[] from = {"phoneType", "phoneNo", "phoneSex"};
int[] to = {R.id.imPhoneType, R.id.tvPhoneNo, R.id.tvSex};
SimpleAdapter adapter = new SimpleAdapter(CustomizedListView2Activity.this, _list, R.layout.row, from, to);
adapter.setViewBinder(new CustomViewBinder());
ListView lvPhones = findViewById(R.id.lvPhones);
lvPhones.setAdapter(adapter);
}
/**
*A method that generates the list data displayed in the list view.
*
* @return The generated list data.
*/
private List<Map<String, Object>> createList() {
List<Map<String, Object>> list = new ArrayList<>();
for (int i = 1; i <= 30; i++) {
int phoneType = (int) (3 * Math.random()) + 1;
int phoneNoInt = (int) (99999999 * Math.random());
int phoneSexInt = (int) (10*Math.random() + 1);
String phoneNo = "090" + String.format("%08d", phoneNoInt);
int phoneSex = 1;
if(phoneSexInt <= 5) {
phoneSex = 0;
}
Map<String, Object> map = new HashMap<>();
map.put("phoneType", phoneType);
map.put("phoneNo", phoneNo);
map.put("phoneSex", phoneSex);
list.add(map);
}
return list;
}
/**
*List view custom view binder class.
*/
private class CustomViewBinder implements SimpleAdapter.ViewBinder {
@Override
public boolean setViewValue(View view, Object data, String textRepresentation) {
int viewId = view.getId();
switch(viewId) {
case R.id.imPhoneType:
ImageView imPhoneType = (ImageView) view;
int phoneType = (Integer) data;
switch(phoneType) {
case 2:
imPhoneType.setImageResource(android.R.drawable.ic_menu_crop);
break;
case 3:
imPhoneType.setImageResource(android.R.drawable.ic_menu_myplaces);
break;
default:
imPhoneType.setImageResource(android.R.drawable.ic_menu_call);
break;
}
return true;
case R.id.tvPhoneNo:
TextView tvPhoneNo = (TextView) view;
String phoneNo = (String) data;
tvPhoneNo.setText(phoneNo);
return true;
case R.id.tvSex:
TextView tvSex = (TextView) view;
int phoneSex = (Integer) data;
String sex = "♂";
if(phoneSex == 0) {
sex = "♀";
}
tvSex.setText(sex);
return true;
}
return false;
}
}
}
public class CustomizedListView3Activity extends AppCompatActivity {
private ListView _lvPhones;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_customized_list_view3);
_lvPhones = findViewById(R.id.lvPhones);
String[] from = {"phone_type", "phone_no", "phone_sex"};
int[] to = {R.id.imPhoneType, R.id.tvPhoneNo, R.id.tvSex};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(CustomizedListView3Activity.this, R.layout.row, null, from, to, 0);
adapter.setViewBinder(new CustomViewBinder());
_lvPhones.setAdapter(adapter);
}
@Override
public void onResume() {
super.onResume();
setNewCursor();
}
/**
*A method that updates the cursor in the cursor adapter.
*/
private void setNewCursor() {
DatabaseHelper helper = new DatabaseHelper(CustomizedListView3Activity.this);
SQLiteDatabase db = helper.getWritableDatabase();
Cursor cursor = DataAccess.findAll(db);
SimpleCursorAdapter adapter = (SimpleCursorAdapter) _lvPhones.getAdapter();
adapter.changeCursor(cursor);
}
/**
*List view custom view binder class.
*
* @author Shinzo SAITO
*/
private class CustomViewBinder implements SimpleCursorAdapter.ViewBinder {
@Override
public boolean setViewValue(View view, Cursor cursor, int columnIndex) {
int viewId = view.getId();
switch(viewId) {
case R.id.imPhoneType:
ImageView imPhoneType = (ImageView) view;
int phoneType = cursor.getInt(columnIndex);
switch(phoneType) {
case 2:
imPhoneType.setImageResource(android.R.drawable.ic_menu_crop);
break;
case 3:
imPhoneType.setImageResource(android.R.drawable.ic_menu_myplaces);
break;
default:
imPhoneType.setImageResource(android.R.drawable.ic_menu_call);
break;
}
return true;
case R.id.tvPhoneNo:
TextView tvPhoneNo = (TextView) view;
String phoneNo = cursor.getString(columnIndex);
tvPhoneNo.setText(phoneNo);
return true;
case R.id.tvSex:
TextView tvSex = (TextView) view;
int phoneSex = cursor.getInt(columnIndex);
String sex = "♂";
if(phoneSex == 0) {
sex = "♀";
}
tvSex.setText(sex);
return true;
}
return false;
}
}
}
that's all. I've summarized the list view on Android. If you have any suggestions such as something wrong, please contact us. Thank you for reading to the end.
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