如何创建一个列表视图，以便点击每个列表项目将打开不同的活动？

Question

我有一个列表视图。我想单击每个列表项目并打开不同的活动。其实，我写了代码，但它不工作。我的编码技能无法处理这个问题。如何用字符串和类对创建Hahmap，然后将其放入ArrayAdapter。任何人都可以给我看代码吗？

ListViewAcivity.java

import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 
import android.widget.Toast; 

import java.util.ArrayList; 
import java.util.HashMap; 

public class ListViewActivity extends Activity { 
    ListView listView ; 

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

     // Get ListView object from xml 
     listView = (ListView) findViewById(R.id.list); 

     // Defined Array values to show in ListView 
     HashMap<String, Class> hashMap=new HashMap<String, Class>(); 


     hashMap.put("A Function", MActivity.class); 
     hashMap.put("B Function",AActivity.class); 
     hashMap.put("c Function",XActivity.class); 
     hashMap.put("D Function",ZActivity.class); 
     hashMap.put("E Function", PActivity.class); 
     hashMap.put("F Function", QActivity.class); 


     // Define a new Adapter 
     // First parameter - Context 
     // Second parameter - Layout for the row 
     // Third parameter - ID of the TextView to which the data is written 
     // Forth - the Array of data 

//错误是在这里...... //此构造函数不能得到解决。 //我不知道如何使用// String，Class对和Array Adapter。

ArrayAdapter<HashMap<String,Class>> adapter = new ArrayAdapter<HashMap<String,Class>>(this, android.R.layout.simple_list_item_1, android.R.id.text1, hashMap); 


     // Assign adapter to ListView 
     listView.setAdapter(adapter); 

     // ListView Item Click Listener 
     listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 

      @Override 
      public void onItemClick(AdapterView<?> parent, View view, 
            int position, long id) { 

       // ListView Clicked item index 
       int itemPosition  = position; 

       // ListView Clicked item value 
       String itemValue = (String) listView.getItemAtPosition(position); 
       switch(itemPosition){ 
        case 0: Intent newActivity = new Intent(ListViewActivity.this, MActivity.class); 
         startActivity(newActivity); 
         break; 
        case 1: Intent newActivity1 = new Intent(ListViewActivity.this, AActivity.class); 
         startActivity(newActivity1); 
         break; 
        case 2: Intent newActivity2 = new Intent(ListViewActivity.this, XActivity.class); 
         startActivity(newActivity2); 
         break; 
        case 3: Intent newActivity3 = new Intent(ListViewActivity.this, ZActivity.class); 
         startActivity(newActivity3); 
         break; 
        case 4: Intent newActivity4 = new Intent(ListViewActivity.this, PActivity.class); 
         startActivity(newActivity4); 
         break; 
        case 5: Intent newActivity5 = new Intent(ListViewActivity.this, QActivity.class); 
         startActivity(newActivity5); 
         break; 


       } 

      } 
      @SuppressWarnings("unused") 
      public void onClick(View v){ 
      }; 
     });} 
} 

main_screen_Activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 
<ListView 
    android:id="@+id/list" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content"></ListView> 

</LinearLayout> 

Answer 1

简单的静态实例。

public class MainActivity extends AppCompatActivity { 

    ListView lv1; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     //Initialize the list view 
     lv1 = (ListView) findViewById(R.id.mainlist); 

     //Add the List data 
     //as the array is stored starting with 0, the Layouts will be having 0th position, Intents being 1 and so on.. 
     String[] sessiontuts = new String[]{"Activity 1", "Activity2"}; 

     //use the Simple array adapter 
     ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,android.R.id.text1,sessiontuts); 

     //now to bind the data to list, just set the adapter we just created to the listview, 
     lv1.setAdapter(adapter); 

     //we need to have click listner on the particular item, 
     //all the items in list will have a position starting from 0 to n, 
     //so, write the intent code to launch particular activity depending on list item position 
     lv1.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> adapterView, View view, int pos, long l) { 
       //using switch case, to check the condition. 
       switch (pos){ 
        case 0: 
         startActivity(new Intent(getApplicationContext(), Act1.class)); 
         break; 
        case 1: 
         startActivity(new Intent(getApplicationContext(), Act2.class)); 
         break; 
       } 
      } 
     }); 
    } 
} 

Answer 2

一种ArrayAdapter期望一个阵列或对象来显示的列表。所以你需要提供一个数组/列表

是什么让你认为它可以处理地图？列表/数组表示事物的序列;而地图则代表了某种东西到其他东西的映射。

换句话说：你不能传递一个地图对象。

只需传递一个包含要显示的字符串的列表或数组（“Medical Reminders”，...）。

但是有那张地图有价值;你只需要改变你的代码位：

首先，你可以使用键映射为输入的创建一个ArrayAdapter，像这样的时候：

List<String> arrayItems = new ArrayList<>(hashMap.keySet()); 

，然后在onClickItem()你做不是需要检索索引 - 因为你已经有了那张告诉你哪个类属于哪个字符串的地图！含义：ListView为您提供所选项目字符串和hashMap将所有可能的字符串映射到相应的活动类别！

所以，你可以扔掉你的整个“开关”的代码，而是做这样的事情：为你所要求的功能

String itemValue = (String) listView.getItemAtPosition(position); 
Class classForSelectedValue = hashMap.get(itemValue); 
Intent activity = new Intent(ListViewActivity.this, classForSelectedValue);