java - 运行时异常 : Unable to instantiate activity

Question

我收到一条错误消息:RuntimeException:无法实例化 Activity - 但我不确定为什么会发生这种情况。非常感谢任何建议。

当尝试执行以下源代码时:

package com.example.httpgetandroidexample;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.DefaultHttpClient;

import com.androidexample.httpgetexample.R;


import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class HttpGetAndroidExample<AsyncronoustaskAndroidExample> extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        final Button GetServerData = (Button) findViewById(R.id.GetServerData);

        GetServerData.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {

                // Server Request URL
                String serverURL = "http://androidexample.com/media/webservice/getPage.php";

                // Create Object and call AsyncTask execute Method
                new LongOperation().execute(serverURL);

            }
        });    

    }


    // Class with extends AsyncTask class
    private class LongOperation  extends AsyncTask<String, Void, Void> {

        private final HttpClient Client = new DefaultHttpClient();
        private String Content;
        private String Error = null;
        private ProgressDialog Dialog = new ProgressDialog(HttpGetAndroidExample.this);

        TextView uiUpdate = (TextView) findViewById(R.id.output);

        protected void onPreExecute() {
            // NOTE: You can call UI Element here.

            //UI Element
            uiUpdate.setText("Output : ");
            Dialog.setMessage("Downloading source..");
            Dialog.show();
        }

        // Call after onPreExecute method
        protected Void doInBackground(String... urls) {
            try {

                // Call long running operations here (perform background computation)
                // NOTE: Don't call UI Element here.

                // Server url call by GET method
                HttpGet httpget = new HttpGet(urls[0]);
                ResponseHandler<String> responseHandler = new BasicResponseHandler();
                Content = Client.execute(httpget, responseHandler);

            } catch (ClientProtocolException e) {
                Error = e.getMessage();
                cancel(true);
            } catch (IOException e) {
                Error = e.getMessage();
                cancel(true);
            }

            return null;
        }

        protected void onPostExecute(Void unused) {
            // NOTE: You can call UI Element here.

            // Close progress dialog
            Dialog.dismiss();

            if (Error != null) {

                uiUpdate.setText("Output : "+Error);

            } else {

                uiUpdate.setText("Output : "+Content);

             }
        }

    }
}


07-16 11:48:37.622: D/ActivityThread(21370): setTargetHeapUtilization:0.25
07-16 11:48:37.622: D/ActivityThread(21370): setTargetHeapIdealFree:8388608
07-16 11:48:37.622: D/ActivityThread(21370): setTargetHeapConcurrentStart:2097152
07-16 11:48:37.642: W/dalvikvm(21370): threadid=1: thread exiting with uncaught exception (group=0x41ba7438)
07-16 11:48:37.652: E/AndroidRuntime(21370): FATAL EXCEPTION: main
07-16 11:48:37.652: E/AndroidRuntime(21370): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.androidexample.httpgetexample/com.androidexample.httpgetexample.HttpGetAndroidExample}: java.lang.ClassNotFoundException: com.androidexample.httpgetexample.HttpGetAndroidExample
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2012)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread.access$700(ActivityThread.java:139)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1224)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.os.Looper.loop(Looper.java:137)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread.main(ActivityThread.java:4918)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at java.lang.reflect.Method.invokeNative(Native Method)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at java.lang.reflect.Method.invoke(Method.java:511)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at dalvik.system.NativeStart.main(Native Method)
07-16 11:48:37.652: E/AndroidRuntime(21370): Caused by: java.lang.ClassNotFoundException: com.androidexample.httpgetexample.HttpGetAndroidExample
07-16 11:48:37.652: E/AndroidRuntime(21370):    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
07-16 11:48:37.652: E/AndroidRuntime(21370):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2003)
07-16 11:48:37.652: E/AndroidRuntime(21370):    ... 11 more

Answer 1

list 文件中您的 Activity 的类名称错误，它使用了错误的包名称。

它似乎正在使用:

com.androidexample.httpgetexample.HttpGetAndroidExample

而你的类(class)是

com.example.httpgetandroidexample.HttpGetAndroidExample