我的应用程序基本上是一个简单的待办事项列表-用户可以添加项目，将其选中并删除。通过长按或双击列表项来进行删除。在启动屏幕上选择了哪个手势（不要问，这是大学的事情）。添加和检查项目非常有效，长按即可删除。但是，我无法双击工作。我在手势检测方面做了大量工作，作为一个实验，我现在试图简单地使该应用程序检测到我单击/轻击ListView中的一个项目。我不明白为什么我无法使它正常工作，因为长按可以完美工作。
我的主要活动TodoActivity：
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.view.GestureDetectorCompat;
import android.os.*;
import android.widget.*;
import android.view.*;
import android.view.View.*;
import java.util.ArrayList;
public class TodoActivity extends AppCompatActivity implements
GestureDetector.OnGestureListener,
GestureDetector.OnDoubleTapListener{
private GestureDetectorCompat mDetector;
Button addButton;
EditText textEditor;
DbHelper dbHelper;
ListView listView;
ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_todo);
addButton = findViewById(R.id.add_button);
textEditor = findViewById(R.id.entry_input);
dbHelper = new DbHelper(this);
listView = findViewById(R.id.list_view);
showItemList();
addButton.setOnClickListener(new OnClickListener(){
public void onClick(View view){
String text = textEditor.getText().toString();
if (!text.equals("")){
textEditor.setText("");
dbHelper.insertNewItem(text);
showItemList();
} else {
}
}
});
listView.setOnItemClickListener(new ListView.OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
//code never reaches this point
System.out.println("++++++ Tap on item detected ++++++");
}
});
}
public void deleteListItem(View view) {
TextView tv = view.findViewById(R.id.item_text);
String itemText = String.valueOf((tv).getText());
dbHelper.deleteItem(itemText);
showItemList();
}
private void showItemList() {
ArrayList<String> itemList = dbHelper.getTodoList();
if(adapter==null) {
adapter = new ArrayAdapter<>(this, R.layout.listitems, R.id.item_text, itemList);
listView.setAdapter(adapter);
}
else {
adapter.clear();
adapter.addAll(itemList);
adapter.notifyDataSetChanged();
}
}
}
dbhelper，以备您复制：
package com.example.p10_studio_version;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
public class DbHelper extends SQLiteOpenHelper {
public static final String DB_NAME = "ToDoDB";
public static final String TABLE_NAME = "ItemsToDo";
public static final String COLUMN_NAME = "Items";
public static final int DB_VERSION = 1;
public DbHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String query = String.format("CREATE TABLE %s (ID INTEGER PRIMARY KEY AUTOINCREMENT, %s TEXT NOT NULL);", TABLE_NAME, COLUMN_NAME);
db.execSQL(query);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String query = String.format("DELETE TABLE IF EXISTS %s", TABLE_NAME);
db.execSQL(query);
onCreate(db);
}
public void insertNewItem(String item) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values= new ContentValues();
values.put(COLUMN_NAME, item);
db.insertWithOnConflict(TABLE_NAME, null, values, SQLiteDatabase.CONFLICT_REPLACE);
db.close();
}
public void deleteItem(String item) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_NAME, COLUMN_NAME + " = ?", new String[]{item});
db.close();
}
public ArrayList<String> getTodoList() {
ArrayList<String> todoList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.query(TABLE_NAME, new String[]{COLUMN_NAME}, null, null, null, null, null);
while (c.moveToNext()) {
int index = c.getColumnIndex(COLUMN_NAME);
todoList.add(c.getString(index));
}
c.close();
db.close();
return todoList;
}
}
activity_todo.xml：
<?xml version="1.0" encoding="utf-8"?>
<!--<androidx.constraintlayout.widget.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=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>-->
<androidx.constraintlayout.widget.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"
android:background="#DEDFE2"
tools:context="com.example.p10_studio_version.TodoActivity"
android:id="@+id/relativeLayout">
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:layout_marginBottom="10dp"
android:gravity="center"
android:text="@string/title_text"
android:textSize="50sp"
app:layout_constraintBottom_toTopOf="@+id/list_view"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="10dp"
android:layout_marginRight="10dp"
android:background="#80DF675D"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/title"
android:descendantFocusability="blocksDescendants"
android:focusable="false"
android:focusableInTouchMode="false" />
<EditText
android:id="@+id/entry_input"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginEnd="5dp"
android:layout_marginRight="5dp"
android:layout_marginBottom="8dp"
android:autofillHints="hi"
android:background="#B3FFFFFF"
android:gravity="bottom"
android:inputType="text"
android:padding="10dp"
app:layout_constraintBottom_toTopOf="@+id/add_button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<Button
android:id="@+id/add_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="50dp"
android:layout_marginBottom="20dp"
android:background="#DF675C"
android:text="@string/button_text"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.606"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent" />
<ImageView
android:id="@+id/doubletap_anim"
android:layout_width="126dp"
android:layout_height="126dp"
android:layout_marginStart="36dp"
android:layout_marginLeft="36dp"
android:layout_marginTop="332dp"
android:visibility="gone"
app:background="@drawable/animation_double"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="@id/list_view" />
<ImageView
android:id="@+id/longtap_anim"
android:layout_width="126dp"
android:layout_height="126dp"
android:layout_marginStart="68dp"
android:layout_marginLeft="68dp"
android:layout_marginTop="332dp"
android:visibility="gone"
app:background="@drawable/animation_long"
app:layout_constraintStart_toEndOf="@id/doubletap_anim"
app:layout_constraintTop_toTopOf="@id/list_view" />
</androidx.constraintlayout.widget.ConstraintLayout>
listitems.xml：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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:id="@+id/relativeLayout2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:longClickable="true"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
android:descendantFocusability="blocksDescendants" >
<CheckBox
android:id="@+id/checkBox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginBottom="8dp"
android:gravity="center"
android:scaleX="2"
android:scaleY="2"
android:text="@null"
android:translationX="12dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/item_text"
app:layout_constraintTop_toTopOf="parent"
android:focusable="false"
android:focusableInTouchMode="false" />
<TextView
android:id="@+id/item_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:foregroundGravity="center_horizontal"
android:gravity="left|center_vertical"
android:paddingLeft="10dp"
android:paddingTop="5dp"
android:paddingRight="10dp"
android:paddingBottom="5dp"
android:textSize="20sp"
app:layout_constraintHeight_min="50dp"
app:layout_constraintStart_toEndOf="@+id/checkBox"
tools:layout_conversion_wrapHeight="71"
tools:layout_conversion_wrapWidth="258"
tools:layout_editor_absoluteY="10dp"
tools:ignore="MissingConstraints"
android:focusable="false"
android:focusableInTouchMode="false" />
</androidx.constraintlayout.widget.ConstraintLayout>