Question

当前的一名普通学生和我创建了一个比萨饼项目的列表视图，并且我使用simple_list_item_checked布局对列表中的每个项目都有一个复选框。我想做的就是写一个文本视图，说“您已经选择了”，然后选择了复选框中的项目。

这是我的XML代码：

<?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">

    <ListView
        android:id="@+id/listView"
        android:layout_width="398dp"
        android:layout_height="398dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toTopOf="@+id/button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="46dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"
        android:text="Print Selected Items"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="124dp"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

这是我的Java代码：

package com.example.tut4_3;

import androidx.appcompat.app.AppCompatActivity;
import android.app.LauncherActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    ListView listView;
    Button button;
    TextView tx;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tx = (TextView)findViewById(R.id.textView);
        listView = (ListView)findViewById(R.id.listView);
        listView.setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE);
        String[] array = {"Ham And Pineapple","Seafood","Meat Lovers","Italian"};
        ArrayAdapter<String> arrayAdapter
                = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_checked,array);
       listView.setAdapter(arrayAdapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                int pos = position;
                Toast.makeText(getApplicationContext(),"your selection is "+parent.getItemAtPosition(pos),
                        Toast.LENGTH_SHORT).show();
            }
        });



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

我当前的输出：列表视图是正确的，我可以单击复选框，但是现在单击按钮后，我要打印单击了哪些项目。

Answer 1

首先，您必须初始化用于初始化所有其他元素的按钮：

        button = (Button)findViewById(R.id.button);

然后在onClickListener中遍历所有项目并挑选出已选中的项目。然后，我得到选中的Item并将其值添加到outputString：

    SparseBooleanArray checked = listView.getCheckedItemPositions();
    String outputText = "";
    for (int i = 0; i < listView.getAdapter().getCount(); i++) {
        if (checked.get(i)) {
            outputText += arrayAdapter.getItem(i) + ", ";
        }
    }

最后，您必须将String设置为TextView的文本：

    tx.setText(outputText);

所有Java文件中的所有内容都应如下所示：

package com.example.tut4_3;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    ListView listView;
    Button button;
    TextView tx;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tx = (TextView)findViewById(R.id.textView);
        button = (Button)findViewById(R.id.button);
        listView = (ListView)findViewById(R.id.listView);
        listView.setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE);
        String[] array = {"Ham And Pineapple","Seafood","Meat Lovers","Italian"};
        final ArrayAdapter<String> arrayAdapter
                = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_checked,array);
        listView.setAdapter(arrayAdapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                int pos = position;
                Toast.makeText(getApplicationContext(),"your selection is "+parent.getItemAtPosition(pos),
                        Toast.LENGTH_SHORT).show();
            }
        });



        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SparseBooleanArray checked = listView.getCheckedItemPositions();
                String outputText = "";
                for (int i = 0; i < listView.getAdapter().getCount(); i++) {
                    if (checked.get(i)) {
                        outputText += arrayAdapter.getItem(i) + ", ";
                    }
                }
                tx.setText(outputText);
            }
        });
    }
}

通过列表视图中的复选框查看选择了哪些项目

1 个答案: