为什么我不能在 Android 中使用 SimpleAdapter 单击 ListView 中的按钮？

Question

我是 Android 新手。我之前也发布了这个问题，但没有找到合适的答案。我的要求是在使用SimpleAdapter 生成的Listview 中使Button 可点击。我不想使用CustomAdapter、BaseAdapter 或任何其他适配器。我不想将我的 Activty 扩展为SimpleAdapter。我的代码和错误日志如下。如果有人有任何解决方案，请逐步向我解释。谢谢。

MainActivity.java

 public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayList<HashMap<String, String>>val1=new ArrayList<HashMap<String,String>>(); 
    HashMap<String, String>val=new HashMap<String,String>();
    val.put("a","a");
    val.put("c","c");
    val.put("b","b");
    val1.add(val);

     final ListView l=(ListView)findViewById(R.id.listView1);
     ListAdapter k=new SimpleAdapter(this,val1,R.layout.mytask,new String[]{"TaskId","heading","status"},new int[]{R.id.View1,R.id.View2,R.id.ViewStatus});

     Button b=(Button)findViewById(R.id.mytask);
     b.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Toast.makeText(MainActivity.this,"save",Toast.LENGTH_SHORT).show();
        }
    });
        l.setAdapter(k);




}

错误日志：

  04-07 01:43:07.075: E/AndroidRuntime(2113): FATAL EXCEPTION: main
  04-07 01:43:07.075: E/AndroidRuntime(2113): Process: com.example.s, PID: 2113
  04-07 01:43:07.075: E/AndroidRuntime(2113): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.s/com.example.s.MainActivity}: java.lang.NullPointerException
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.app.ActivityThread.access$800(ActivityThread.java:135)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.os.Handler.dispatchMessage(Handler.java:102)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.os.Looper.loop(Looper.java:136)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at android.app.ActivityThread.main(ActivityThread.java:5017)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at java.lang.reflect.Method.invokeNative(Native Method)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at java.lang.reflect.Method.invoke(Method.java:515)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  04-07 01:43:07.075: E/AndroidRuntime(2113):   at dalvik.system.NativeStart.main(Native Method)
 04-07 01:43:07.075: E/AndroidRuntime(2113): Caused by: java.lang.NullPointerException
 04-07 01:43:07.075: E/AndroidRuntime(2113):    at com.example.s.MainActivity.onCreate(MainActivity.java:34)
 04-07 01:43:07.075: E/AndroidRuntime(2113):    at android.app.Activity.performCreate(Activity.java:5231)
 04-07 01:43:07.075: E/AndroidRuntime(2113):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
 04-07 01:43:07.075: E/AndroidRuntime(2113):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
 04-07 01:43:07.075: E/AndroidRuntime(2113):    ... 11 more

mytask.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical" 

>

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginTop="18dp"
    android:text="Task Name:"

    android:textSize="15dp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/View1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:text="TextView"

    android:textSize="15dp"
    android:textStyle="bold"
    android:visibility="invisible" />

<TextView
    android:id="@+id/View2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/textView1"
    android:layout_alignBottom="@+id/textView1"
    android:layout_marginLeft="31dp"
    android:layout_toRightOf="@+id/textView1"
    android:text="TextView"

    android:textSize="15dp"
    android:textStyle="bold"
    android:visibility="visible" />

<TextView
    android:id="@+id/ViewStatus"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/View2"
    android:layout_alignBottom="@+id/View2"
    android:layout_alignParentRight="true"
    android:text="Pending"

    android:textSize="15dp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/ViewStatus"
    android:layout_alignBottom="@+id/ViewStatus"
    android:layout_marginRight="14dp"
    android:layout_toLeftOf="@+id/ViewStatus"
    android:text="Status:"

    android:textSize="15dp"
    android:textStyle="bold" />

<Button
    android:id="@+id/mytask"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/textView1"
    android:text="Button" />

 </RelativeLayout>

activity_main.xml

 <ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginLeft="106dp"
    android:layout_marginTop="124dp" >
</ListView>

Answer 1

activity_main.xml 没有 ID 为 mytask 的 Button。所以不能在 MainActivtiy 中初始化 Button。

Button 属于 mytask.xml 覆盖 getView 并在那里有按钮侦听器。

http://developer.android.com/reference/android/widget/SimpleAdapter.html

编辑：

   SimpleAdapter k=new SimpleAdapter(this,val1,R.layout.mytask,new String[]{"a","c","b"},new int[]{R.id.View1,R.id.View2,R.id.ViewStatus})
    {
        @Override
        public View getView (int position, View convertView, ViewGroup parent)
        {
            View v = super.getView(position, convertView, parent);

             Button b=(Button)v.findViewById(R.id.mytask);
             b.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {
                    // TODO Auto-generated method stub
                    Toast.makeText(MainActivity.this,"save",Toast.LENGTH_SHORT).show();
                }
            });
            return v;
        }


    };

编辑：因为你不相信这是快照

Answer 2

将此属性android:descendantFocusability="blocksDescendants" 写入您的mytask.xml 相对布局中。

并在主要活动中将a,c,b 替换为"TaskId","heading","status"。