在完成初学者教程之后，我最后结合了一堆课程来创建一个计时器应用程序，这需要花费一些时间并在时间过后播放媒体。该应用程序运行良好...昨天。我不记得改变什么，但是当我今天尝试调试时，应用程序会加载到我的手机，安装和崩溃。我收到大量错误消息，我不明白：
02-28 15:12:58.864: E/AndroidRuntime(26257): FATAL EXCEPTION: main
02-28 15:12:58.864: E/AndroidRuntime(26257): java.lang.RuntimeException: Unable to start activity ComponentInfo{digital.clock.activity/digital.clock.activity.DigitalActivity}: java.lang.NullPointerException
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.os.Handler.dispatchMessage(Handler.java:99)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.os.Looper.loop(Looper.java:130)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread.main(ActivityThread.java:3683)
02-28 15:12:58.864: E/AndroidRuntime(26257): at java.lang.reflect.Method.invokeNative(Native Method)
02-28 15:12:58.864: E/AndroidRuntime(26257): at java.lang.reflect.Method.invoke(Method.java:507)
02-28 15:12:58.864: E/AndroidRuntime(26257): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-28 15:12:58.864: E/AndroidRuntime(26257): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-28 15:12:58.864: E/AndroidRuntime(26257): at dalvik.system.NativeStart.main(Native Method)
02-28 15:12:58.864: E/AndroidRuntime(26257): Caused by: java.lang.NullPointerException
02-28 15:12:58.864: E/AndroidRuntime(26257): at digital.clock.activity.DigitalActivity.onCreate(DigitalActivity.java:74)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-28 15:12:58.864: E/AndroidRuntime(26257): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
02-28 15:12:58.864: E/AndroidRuntime(26257): ... 11 more
我的主要活动看起来像......
package digital.clock.activity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.app.AlarmManager;
import android.app.PendingIntent;
import java.util.ArrayList;
import android.gesture.Gesture;
import android.gesture.GestureLibraries;
import android.gesture.GestureLibrary;
import android.gesture.GestureOverlayView;
import android.gesture.Prediction;
import android.gesture.GestureOverlayView.OnGesturePerformedListener;
public class DigitalActivity extends Activity
{
private GestureLibrary gLib;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
gLib = GestureLibraries.fromRawResource(this, R.raw.gestures);
if (!gLib.load())
{
Toast.makeText(this, "Could not load Gesture Library", Toast.LENGTH_LONG).show();
finish();
}
GestureOverlayView gestures = (GestureOverlayView) findViewById(R.id.gestures);
final OnGesturePerformedListener handleGestureListener = new OnGesturePerformedListener()
{
@Override
public void onGesturePerformed(GestureOverlayView gestureView, Gesture gesture)
{
ArrayList<Prediction> predictions = gLib.recognize(gesture);
// one prediction needed
if (predictions.size() > 0)
{
Prediction prediction = predictions.get(0);
// checking prediction
if (prediction.score > 1.0)
{
// and action
timerAlert2();
}
}
}
};
gestures.addOnGesturePerformedListener(handleGestureListener);
//Create button and do something with intents...
Button Activity2 = (Button) findViewById(R.id.Button01);
Activity2.setOnClickListener(new View.OnClickListener()
{
public void onClick (View view)
{
Intent replyIntent = new Intent();
setResult(RESULT_OK, replyIntent);
finish();
}
});
Button startTimer = (Button) findViewById(R.id.startTimer);
startTimer.setOnClickListener(new View.OnClickListener()
{
public void onClick (View view)
{
timerAlert(view);
}
});
Button stopAlarm = (Button) findViewById(R.id.stopAlarm);
stopAlarm.setOnClickListener(new View.OnClickListener()
{
public void onClick (View view)
{
stopService(new Intent(getBaseContext(), MediaPlayerService.class));
}
});
}
public void timerAlert (View view)
{
//Declare the EditText object
EditText textField = (EditText) findViewById(R.id.timeInSeconds);
//Get user-entered number and convert to string
int i = Integer.parseInt(textField.getText().toString());
//Declare intent object
Intent timerIntent = new Intent(this, TimerBroadcastReceiver.class);
//Create PendingIntent and set parameters (context, code, intent object to use, constants)
PendingIntent myPendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 0, timerIntent, 0);
//Create AlarmManager and assign it the ALARM_SERVICE
AlarmManager myAlarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
//set AlarmManager parameters (type, TriggerTime, Operation)
//RTC_WAKEUP will wake up the phone for the alarm, RTC will activate the alarm next time the phone wakes
myAlarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (i * 1000), myPendingIntent);
Toast.makeText(this, "Alarm is set for " + i + " seconds!", Toast.LENGTH_LONG).show();
}
public void timerAlert2 ()
{
int i = 5;
//Declare intent object
Intent timerIntent = new Intent(this, TimerBroadcastReceiver.class);
//Create PendingIntent and set parameters (context, code, intent object to use, constants)
PendingIntent myPendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), 0, timerIntent, 0);
//Create AlarmManager and assign it the ALARM_SERVICE
AlarmManager myAlarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
//set AlarmManager parameters (type, TriggerTime, Operation)
//RTC_WAKEUP will wake up the phone for the alarm, RTC will activate the alarm next time the phone wakes
myAlarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + (i * 60000), myPendingIntent);
Toast.makeText(this, "Alarm is set for " + i + " minutes!", Toast.LENGTH_LONG).show();
}
}
答案 0 :(得分：0)
似乎没有找到你的按钮:(它在试图访问你在第73行实例化的按钮的行上崩溃了：Button01）。
搜索你的项目，它应该有一个名为res的子目录，其中应该有一个名为main.xml的文件。在其中你应该找到一个元素
<Button
android:id="@+id/button01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
您应该验证您的项目是否包含此文件并在其中包含该行。如果您仍然遇到问题，请清理您的项目，以便更正。