安卓对话框错误

Question

我做了DatePicker和TimePicker。有了它们，我可以设置对话框必须出现的时间。当我按下按钮设置警报时，一切都很好，但是当对话框必须出现时，另一个对话框出现文本“不幸的是程序已停止”。有人可以告诉我我的代码哪里有问题吗？

主要 Activity :

package in.wptrafficanalyzer.servicealarmdemo;

    import java.util.GregorianCalendar;

    import android.app.Activity;
    import android.app.AlarmManager;
    import android.app.PendingIntent;
    import android.content.Intent;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.DatePicker;
    import android.widget.TimePicker;
    import android.widget.Toast;


    public class MainActivity extends Activity {

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

            OnClickListener setClickListener = new OnClickListener() {

                @Override
                public void onClick(View v) {
                    /** This intent invokes the activity DemoActivity, which in turn opens the AlertDialog window */
                    Intent i = new Intent("in.wptrafficanalyzer.servicealarmdemo.demoactivity");

                    /** Creating a Pending Intent */
                    PendingIntent operation = PendingIntent.getActivity(getBaseContext(), 0, i, Intent.FLAG_ACTIVITY_NEW_TASK);

                    /** Getting a reference to the System Service ALARM_SERVICE */
                    AlarmManager alarmManager = (AlarmManager) getBaseContext().getSystemService(ALARM_SERVICE);

                    /** Getting a reference to DatePicker object available in the MainActivity */
                    DatePicker dpDate = (DatePicker) findViewById(R.id.dp_date);

                    /** Getting a reference to TimePicker object available in the MainActivity */
                    TimePicker tpTime = (TimePicker) findViewById(R.id.tp_time);

                    int year = dpDate.getYear();
                    int month = dpDate.getMonth();
                    int day = dpDate.getDayOfMonth();
                    int hour = tpTime.getCurrentHour();
                    int minute = tpTime.getCurrentMinute();

                    /** Creating a calendar object corresponding to the date and time set by the user */
                    GregorianCalendar calendar = new GregorianCalendar(year,month,day, hour, minute);

                    /** Converting the date and time in to milliseconds elapsed since epoch */
                    long alarm_time = calendar.getTimeInMillis();

                    /** Setting an alarm, which invokes the operation at alart_time */
                    alarmManager.set(AlarmManager.RTC_WAKEUP  , alarm_time , operation);

                    /** Alert is set successfully */
                    Toast.makeText(getBaseContext(), "Alarm is set successfully",Toast.LENGTH_SHORT).show();

                }
            };      

            OnClickListener quitClickListener = new OnClickListener() {         
                @Override
                public void onClick(View v) {
                    finish();
                }
            };

            Button btnSetAlarm = ( Button ) findViewById(R.id.btn_set_alarm);
            btnSetAlarm.setOnClickListener(setClickListener);

            Button btnQuitAlarm = ( Button ) findViewById(R.id.btn_quit_alarm);
            btnQuitAlarm.setOnClickListener(quitClickListener);

        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            getMenuInflater().inflate(R.menu.activity_main, menu);
            return true;
        }
    }

警报演示:

package in.wptrafficanalyzer.servicealarmdemo;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.view.WindowManager.LayoutParams;


public class AlertDemo extends DialogFragment {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        /** Turn Screen On and Unlock the keypad when this alert dialog is displayed */
        getActivity().getWindow().addFlags(LayoutParams.FLAG_TURN_SCREEN_ON | LayoutParams.FLAG_DISMISS_KEYGUARD);


        /** Creating a alert dialog builder */
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

        /** Setting title for the alert dialog */
        builder.setTitle("Alarm");

        /** Setting the content for the alert dialog */
        builder.setMessage("An Alarm by AlarmManager");

        /** Defining an OK button event listener */
        builder.setPositiveButton("OK", new OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                /** Exit application on click OK */
                getActivity().finish();
            }                       
        });

        /** Creating the alert dialog window */
        return builder.create();
    }

    /** The application should be exit, if the user presses the back button */ 
    @Override
    public void onDestroy() {       
        super.onDestroy();
        getActivity().finish();
    }

}

演示 Activity :

package in.wptrafficanalyzer.servicealarmdemo;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.WindowManager.LayoutParams;
import android.widget.Toast;

public class DemoActivity extends FragmentActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {        
        super.onCreate(savedInstanceState); 

        /** Creating an Alert Dialog Window */
        AlertDemo alert = new AlertDemo();

        /** Opening the Alert Dialog Window */
        alert.show(getSupportFragmentManager(), "AlertDemo");       
    }
}

日志:

07-18 15:01:40.740: E/AndroidRuntime(429): FATAL EXCEPTION: main
07-18 15:01:40.740: E/AndroidRuntime(429): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{in.wptrafficanalyzer.servicealarmdemo/in.wptrafficanalyzer.servicealarmdemo.DemoActivity}: java.lang.ClassNotFoundException: in.wptrafficanalyzer.servicealarmdemo.DemoActivity in loader dalvik.system.PathClassLoader[/data/app/in.wptrafficanalyzer.servicealarmdemo-1.apk]
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.os.Looper.loop(Looper.java:123)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-18 15:01:40.740: E/AndroidRuntime(429):  at java.lang.reflect.Method.invokeNative(Native Method)
07-18 15:01:40.740: E/AndroidRuntime(429):  at java.lang.reflect.Method.invoke(Method.java:521)
07-18 15:01:40.740: E/AndroidRuntime(429):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-18 15:01:40.740: E/AndroidRuntime(429):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-18 15:01:40.740: E/AndroidRuntime(429):  at dalvik.system.NativeStart.main(Native Method)
07-18 15:01:40.740: E/AndroidRuntime(429): Caused by: java.lang.ClassNotFoundException: in.wptrafficanalyzer.servicealarmdemo.DemoActivity in loader dalvik.system.PathClassLoader[/data/app/in.wptrafficanalyzer.servicealarmdemo-1.apk]
07-18 15:01:40.740: E/AndroidRuntime(429):  at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
07-18 15:01:40.740: E/AndroidRuntime(429):  at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
07-18 15:01:40.740: E/AndroidRuntime(429):  at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-18 15:01:40.740: E/AndroidRuntime(429):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)

Answer 1

类加载器正在寻找它没有找到的 DemoActivity 。确保 DemoActivity 类在项目中可用。

也代替:

Intent i = new Intent("in.wptrafficanalyzer.servicealarmdemo.demoactivity");

你应该使用:

Intent i = new Intent(getBaseContext(),DemoActivity.class);