用toast消息在android中的Listview

Question

我试图在列表视图中显示项目

• 并且列表行的onclick显示一个toast消息

• 我有错误

我能够在列表视图中显示元素,但点击列表项我得到错误

---

MainActivity.java

public class MainActivity extends Activity {

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

        String Names[]={"Mango","Banana","grapes"};

        ListView LV=(ListView) findViewById(R.id.listView1);

        ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,R.layout.list_item,R.id.textView1,Names);

        LV.setAdapter(adapter);

        LV.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> arg0, View v, int arg2,
                    long arg3) {
                // TODO Auto-generated method stub
                Toast.makeText(getApplicationContext(), ((TextView) v).getText(), Toast.LENGTH_SHORT).show();
            }
        });
    }
}

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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_gravity="center"
        android:padding="5dp"
        android:text="TextView"
        android:textStyle="italic|bold" />

</LinearLayout>

activity_main.xml中

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/listView1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="1" >
    </ListView>

</LinearLayout>

LOG

08-19 18:29:18.621: D/AndroidRuntime(692): Shutting down VM
08-19 18:29:18.621: W/dalvikvm(692): threadid=1: thread exiting with uncaught exception (group=0x40015560)
08-19 18:29:18.921: E/AndroidRuntime(692): FATAL EXCEPTION: main
08-19 18:29:18.921: E/AndroidRuntime(692): java.lang.ClassCastException: android.widget.LinearLayout
08-19 18:29:18.921: E/AndroidRuntime(692):  at com.example.listviews.MainActivity$1.onItemClick(MainActivity.java:34)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.widget.AdapterView.performItemClick(AdapterView.java:284)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.widget.ListView.performItemClick(ListView.java:3513)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:1812)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.os.Handler.handleCallback(Handler.java:587)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.os.Handler.dispatchMessage(Handler.java:92)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.os.Looper.loop(Looper.java:123)
08-19 18:29:18.921: E/AndroidRuntime(692):  at android.app.ActivityThread.main(ActivityThread.java:3683)
08-19 18:29:18.921: E/AndroidRuntime(692):  at java.lang.reflect.Method.invokeNative(Native Method)
08-19 18:29:18.921: E/AndroidRuntime(692):  at java.lang.reflect.Method.invoke(Method.java:507)
08-19 18:29:18.921: E/AndroidRuntime(692):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-19 18:29:18.921: E/AndroidRuntime(692):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-19 18:29:18.921: E/AndroidRuntime(692):  at dalvik.system.NativeStart.main(Native Method)
08-19 18:29:23.481: I/Process(692): Sending signal. PID: 692 SIG: 9
08-19 18:35:01.833: D/AndroidRuntime(726): Shutting down VM
08-19 18:35:01.833: W/dalvikvm(726): threadid=1: thread exiting with uncaught exception (group=0x40015560)
08-19 18:35:01.851: E/AndroidRuntime(726): FATAL EXCEPTION: main
08-19 18:35:01.851: E/AndroidRuntime(726): java.lang.ClassCastException: android.widget.LinearLayout
08-19 18:35:01.851: E/AndroidRuntime(726):  at com.example.listviews.MainActivity$1.onItemClick(MainActivity.java:34)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.widget.AdapterView.performItemClick(AdapterView.java:284)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.widget.ListView.performItemClick(ListView.java:3513)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:1812)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.os.Handler.handleCallback(Handler.java:587)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.os.Handler.dispatchMessage(Handler.java:92)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.os.Looper.loop(Looper.java:123)
08-19 18:35:01.851: E/AndroidRuntime(726):  at android.app.ActivityThread.main(ActivityThread.java:3683)
08-19 18:35:01.851: E/AndroidRuntime(726):  at java.lang.reflect.Method.invokeNative(Native Method)
08-19 18:35:01.851: E/AndroidRuntime(726):  at java.lang.reflect.Method.invoke(Method.java:507)
08-19 18:35:01.851: E/AndroidRuntime(726):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-19 18:35:01.851: E/AndroidRuntime(726):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-19 18:35:01.851: E/AndroidRuntime(726):  at dalvik.system.NativeStart.main(Native Method)

有关克服这一点的任何想法

Answer 1

正如您从logcat中看到的那样,您正在获得类强制转换异常,因为您正在尝试将线性布局(对于您的listitem)转换为TextView的根视图(在本例中为View v).

你应该做的是如下:

LV.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> arg0, View v, int arg2,
                long arg3) {
            //here v is your ListItem's layout.
            TextView tv = (TextView) v.findViewById(R.id.textView1);
            Toast.makeText(getApplicationContext(), tv.getText().toString(), Toast.LENGTH_SHORT).show();
        }
    });