Question

可能出现的错误是什么？每次运行应用程序时，活动都不会启动并强制关闭。我是否需要在try和catch块中进行一些更改，还是其他的东西......？

import org.example.emergencyhandler.R;

import android.R.string;
import android.app.Activity;
import android.app.ListActivity;
import android.content.res.Resources.NotFoundException;
import android.os.Bundle;
 public class Main extends ListActivity {
String arr[] = { "Medical Emergency", "example1", "example2", "example3",
        "example4", "example5", "example6", "example7", "example8",
        "example9" };

protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // ListView listview=(ListView)findViewById(R.id.lv);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(Main.this, android.R.layout.simple_list_item_2, arr);
    setListAdapter(adapter);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {

    super.onListItemClick(l, v, position, id);

    String toast=arr[position]; 
    try {
        Toast.makeText(getApplicationContext(), toast + "clicked", Toast.LENGTH_SHORT)

        .show();

    } catch (NotFoundException e) { e.printStackTrace(); }
    }
}

上述类的logcat ：：

  1.06-25 15:33:36.992: D/AndroidRuntime(24847): Shutting down VM
  2.06-25 15:33:36.992: W/dalvikvm(24847): threadid=1: thread exiting with uncaught  exception<br/>   (group=0x40018578)
  3.06-25 15:33:37.046: E/AndroidRuntime(24847): FATAL EXCEPTION: main
  4.06-25 15:33:37.046: E/AndroidRuntime(24847): java.lang.RuntimeException: Unable to instantiate<br/> activity<br/> ComponentInfo{org.example.emergencyhandler/org.example.emergencyhandler.Main}:<br/> java.lang.ClassNotFoundException: org.example.emergencyhandler.Main in loader <br/>dalvik.system.PathClassLoader[/data/app/org.example.emergencyhandler-1.apk]
  5.06-25 15:33:37.046: E/AndroidRuntime(24847):    at<br/> android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1573)
  6.06-25 15:33:37.046: E/AndroidRuntime(24847):    at<br/> android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
  7.06-25 15:33:37.046: E/AndroidRuntime(24847):    at <br/>android.app.ActivityThread.access$1500(ActivityThread.java:117)
  8.06-25 15:33:37.046: E/AndroidRuntime(24847):    at<br/> android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
  9.06-25 15:33:37.046: E/AndroidRuntime(24847):    at <br/>android.os.Handler.dispatchMessage(Handler.java:99)
  10.06-25 15:33:37.046: E/AndroidRuntime(24847):   at android.os.Looper.loop(Looper.java:130)<br/>
  11.06-25 15:33:37.046: E/AndroidRuntime(24847):   at android.app.ActivityThread.main(ActivityThread.java:3687)
  12.06-25 15:33:37.046: E/AndroidRuntime(24847):   at java.lang.reflect.Method.invokeNative(Native Method)
  13.06-25 15:33:37.046: E/AndroidRuntime(24847):   at java.lang.reflect.Method.invoke(Method.java:507)
  14.06-25 15:33:37.046: E/AndroidRuntime(24847):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
  15.06-25 15:33:37.046: E/AndroidRuntime(24847):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
  16.06-25 15:33:37.046: E/AndroidRuntime(24847):   at dalvik.system.NativeStart.main(Native  Method)
  17.06-25 15:33:37.046: E/AndroidRuntime(24847): Caused by: java.lang.ClassNotFoundException:<br/> org.example.emergencyhandler.Main in loader dalvik.system.PathClassLoader[/data/app/org.example.emergencyhandler-1.apk]<br/>
  18.06-25 15:33:37.046: E/AndroidRuntime(24847):   at <br/>dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
  19.06-25 15:33:37.046: E/AndroidRuntime(24847):   at <br/>java.lang.ClassLoader.loadClass(ClassLoader.java:551 )
  20.06-25 15:33:37.046: E/AndroidRuntime(24847):   at<br/> java.lang.ClassLoader.loadClass(ClassLoader.java:511)
  21.06-25 15:33:37.046: E/AndroidRuntime(24847):   at <br/>android.app.Instrumentation.newActivity(Instrumentation.java:1021)
  22.06-25 15:33:37.046: E/AndroidRuntime(24847):   at<br/> android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1565)
  23.06-25 15:33:37.046: E/AndroidRuntime(24847):   ... 11 more

上述申请的清单文件：：

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="19" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="org.example.emergencyhandler.Main"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Answer 1

要对列表中的选择作出反应，请将OnItemClickListener设置为listview

    listView.setOnItemClickListener(new OnItemClickListener() {
     @Override
     public void onItemClick(AdapterView<?> parent, View view,
      int position, long id) {
      Toast.makeText(getApplicationContext(),
        "Click ListItem Number " + position, Toast.LENGTH_LONG)
         .show();
      }
      });

Answer 2

试试这段代码

 public class MainActivity extends ListActivity {

String[] arr = new String[] { "Medical Emergency", "example1", "example2",  "example3",
        "example4", "example5", "example6", "example7", "example8",
        "example9" };

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);


  ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this,    android.R.layout.simple_list_item_1, arr);
   setListAdapter(adapter);
}


  @Override
  protected void onListItemClick(ListView l, View v, int position, long id) {
  String item = (String) getListAdapter().getItem(position);
 Toast.makeText(this, item + " clicked", Toast.LENGTH_LONG).show();
  }

 }

list活动没有在android中启动

2 个答案: