当我尝试插入日期和时间选择器时，为什么我的应用程序不断崩溃？ [英] Why does my app keep crashing when i try to insert a date and time picker?

问题描述

我一般都是android和编码的新手。我试图在我的代码中插入一个Android时间和日期选择器，但是当我尝试这样做时它会不断崩溃。任何人都可以帮我出来

  public class NewEvent extends Activity {
 
 private static int RESULT_LOAD_IMAGE = 1 ; 
 
私人EventHandler处理程序; 
 
 private String picturePath =; 
 
 private String name; 
 private String place; 
 private String date; 
 private String time; 
私人字符串照片; 
 
 DatePicker datepicker; //对象datepicker 
 int年，月，日; //声明年，月和日的变量
 TimePicker timepicker; //对象为timepicker 
 
 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.new_event）; 
 
 handler = new EventHandler（getApplicationContext（））; 
 
 // datepicker =（DatePicker）findViewById（R.id.datePicker）; //从layout 
 // timepicker =（TimePicker）findViewById（R.id.timePicker）获取datepicker属性; //从布局
获取timepicker属性timepicker.setIs24HourView（true）; //将timepicker设置为24小时时钟视图
按钮按钮=（Button）findViewById（R.id.button1）; //按钮显示日期戳值
按钮button1 =（Button）findViewById（R.id.button2）; //按钮显示timepicker值
 
 
 
 ImageView iv_user_photo =（ImageView）findViewById（R.id.iv_user_photo）; 
 iv_user_photo.setOnClickListener（new OnClickListener（）{
 
 @Override 
 public void onClick（View arg0）{
 
 Intent intent = new Intent（Intent .ACTION_PICK，android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI）; 
 
 startActivityForResult（intent，RESULT_LOAD_IMAGE）; 
 
} 
}）; 
 
 
按钮btn_add =（Button）findViewById（R.id.btn_add）; 
 btn_add.setOnClickListener（new OnClickListener（）{
 
 @Override 
 public void onClick（View arg0）{
 
 EditText et_name =（EditText）findViewById （R.id.et_name）; 
 name = et_name.getText（）。toString（）; 
 
 EditText et_place =（EditText）findViewById（R.id.et_place）; 
 place = et_place.getText（）。toString（）; 
 
 EditText et_date =（EditText）findViewById（R.id.et_date）; 
 date = et_date.getText（）。toString ）; 
 
 EditText et_time =（EditText）findViewById（R.id.et_time）; 
 time = et_time.getText（）。toString（）; 
 
 ImageView iv_photograph =（ImageView）findViewById（R.id.iv_user_photo）; 
 photograph = picturePath; 
 
事件事件=新事件（）; 
 event.setName（name）; 
 event.setPlace（place）; 
 event.setDate（date）; 
 event.setTime（time）; 
 event.setPhotograph（照片）; 
 
 Boolean added = handler.addEventDetails（event）; 
 if（added）{
 Intent intent = new Intent（NewEvent.this，MainEvent.class）; 
 startActivity（intent）; 
} else {
 Toast.makeText（getApplicationContext（），Event data not added。Please try again，Toast.LENGTH_LONG）.show（）; 
} 
 
 
} 
}）; 
 
 button.setOnClickListener（new View.OnClickListener（）{
 @Override 
 public void onClick（View v）{
 // TODO自动生成的方法存根
 //显示datepicker值弹出通知
 Toast.makeText（getBaseContext（），Date：
 +（datepicker.getMonth（）+ 1）+/+ datepicker.getDayOfMonth （）
 +/+ datepicker.getYear（），Toast.LENGTH_LONG）.show（）;} 
}）; 
 //点击按钮开始timepicker事件
 button1.setOnClickListener（new View.OnClickListener（）{
 @Override 
 public void onClick（View v）{
 / / TODO自动生成的方法stub 
 //显示timepicker值弹出通知
 Toast.makeText（getBaseContext（），Time Selected：+ timepicker.getCurrentHour（）+：
 + timepicker.getCurrentMinute（），Toast.LENGTH_SHORT）.show（）; 
} 
}）; 
 
 
 
 
 
 
 @Override 
 protected void onActivityResult（int requestCode，int resultCode，Intent data）{
 
 super.onActivityResult（requestCode，resultCode，data）; 
 
 if（requestCode == RESULT_LOAD_IMAGE&&& resultCode == RESULT_OK&& null！= data）{
 Uri imageUri = data.getData（）; 
 String [] filePathColumn = {MediaStore.Images.Media.DATA}; 
 
游标cursor = getContentResolver（）。query（imageUri，
 filePathColumn，null，null，null）; 
 cursor.moveToFirst（）; 
 
 int columnIndex = cursor.getColumnIndex（filePathColumn [0]）; 
 picturePath = cursor.getString（columnIndex）; 
 cursor.close（）; 
 
 ImageView imageView =（ImageView）findViewById（R.id.iv_user_photo）; 
 imageView.setImageBitmap（BitmapFactory.decodeFile（picturePath））; 
 
} 
} 
 
} 
  

这是我的xml：

 <？xml version =1.0encoding =utf-8？> 
< RelativeLayout xmlns：android =http://schemas.android.com/apk/res/android
 android：layout_width =match_parent
 android：layout_height =match_parent 
 android：orientation =vertical
 android：padding =10dp> 
 
< TextView 
 android：id =@ + id / tv_new_event_title
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =添加新事件
 android：textAppearance =？android：attr / textAppearanceLarge
 android：layout_alignParentTop =true/> 
 
 
< Button 
 android：id =@ + id / btn_add
 android：layout_width =match_parent
 android：layout_height = wrap_content
 android：text =添加事件
 android：layout_alignParentBottom =true/> 
 
< ScrollView 
 android：layout_width =match_parent
 android：layout_height =match_parent
 android：layout_below =@ id / tv_new_event_title
 android：layout_above =@ id / btn_add> 
< LinearLayout 
 android：layout_width =fill_parent
 android：layout_height =wrap_content
 android：orientation =vertical> 
< ImageView 
 android：id =@ + id / iv_user_photo
 android：src =@ drawable / add_user_icon
 android：layout_width =100dp
 android：layout_height =100dp/> 
 
< TextView 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =Event：/> 
 
< EditText 
 android：id =@ + id / et_name
 android：layout_width =match_parent
 android：layout_height =wrap_content
 android：ems =10
 android：inputType =text> 
< requestFocus /> 
< / EditText> 
 
 
< TextView 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =Place：/ > 
 
< EditText 
 android：id =@ + id / et_place
 android：layout_width =match_parent
 android：layout_height =wrap_content
 android：ems =10
 android：inputType =text> 
< requestFocus /> 
< / EditText> 
 
< TextView 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =Date：/> 
 
< EditText 
 android：id =@ + id / et_date
 android：layout_width =match_parent
 android：layout_height =wrap_content
 android：ems =10
 android：inputType =date/> 
 
< Button 
 android：id =@ + id / button
 style =？android：attr / buttonStyleSmall
 android：layout_width =wrap_content 
 android：layout_height =wrap_content
 android：text =Button/> 
< requestFocus /> 
 
< TextView 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =Time：/> 
 
< EditText 
 android：id =@ + id / et_time
 android：layout_width =match_parent
 android：layout_height =wrap_content
 android：ems =10
 android：inputType =time/> 
 
< Button 
 android：id =@ + id / button1
 style =？android：attr / buttonStyleSmall
 android：layout_width =wrap_content 
 android：layout_height =wrap_content
 android：text =Button1/> 
 
 
< requestFocus /> 
 
< / LinearLayout> 
< / ScrollView> 
 
< / RelativeLayout> 
  

这是我的LogCat：

  08-25 11：57：44.144：E / AndroidRuntime（554）：FATAL EXCEPTION：main 
 08-25 11：57：44.144：E / AndroidRuntime（554）：java。 lang.RuntimeException：无法启动活动ComponentInfo {com.chris.hockeymanagemtapp / com.chris.hockeymanagemtapp.NewEvent}：java.lang.NullPointerException 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:1647）
 08-25 11：57：44.144：E / AndroidRuntime（554）：在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:1663） 
 08-25 11：57：44.144：E / AndroidRuntime（554）：android.app.ActivityThread.access $ 1500（ActivityThread.java:117）
 
 08-25 11:57 ：44.144：E / AndroidRuntime（554）：android.app.ActivityThread $ H.handleMessage（ActivityThread.java:931）
 
 08-25 11：57：44.144：E / AndroidRuntime（554） ：在android.os.Handler.dispatchMessage（Handler.java:99）
 
 08-25 11：57：44.144：E / Andr oidRuntime（554）：在android.os.Looper.loop（Looper.java:123）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在android.app.ActivityThread .main（ActivityThread.java:3683）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：java.lang.reflect.Method.invokeNative（Native Method）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在java.lang.reflect.Method.invoke（Method.java:507）
 
 08-25 11 ：57：44.144：E / AndroidRuntime（554）：com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:839）
 
 08-25 11：57：44.144： E / AndroidRuntime（554）：at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:597）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在dalvik.system.NativeStart.main（本地方法）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：引起：java.lang.NullPointerException 
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在com.chris.hockeymanagemtapp.NewEvent.onCreate（NewEvent.java:60）
 
 08-25 11:57： 44。 144：E / AndroidRuntime（554）：在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1047）
 
 08-25 11：57：44.144：E / AndroidRuntime（554）：在android .app.ActivityThread.performLaunchActivity（ActivityThread.java:1611）
 08-25 11：57：44.144：E / AndroidRuntime（554）：... 11更多
  / pre> 
 
解决方案
在您的OnCreate方法中执行此操作：
 
 
 
 DatePicker dt =（DatePicker）findViewById（R.id.yourDatePickerId）; 
 
 
 
正如Anuj所说，您需要在使用之前对其进行初始化
 
I am a novice with android and coding in general. I am trying to insert an android time and date picker into my code however it keeps crashing when I attempt to do so. Can anyone please help me out
    public class NewEvent extends Activity {    

        private static int RESULT_LOAD_IMAGE = 1;

        private EventHandler handler;

        private String picturePath = "";

        private String name;
        private String place;
        private String date;
        private String time;
        private String photograph;

        DatePicker datepicker; // object for datepicker
        int year , month , day;  // declaring variables for year, month and day
        TimePicker timepicker; // object for timepicker



        @Override
        protected void onCreate(Bundle savedInstanceState) {

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

            handler = new EventHandler(getApplicationContext());

            //datepicker = (DatePicker) findViewById(R.id.datePicker); // Obtain datepicker attributes from layout
               //timepicker = (TimePicker) findViewById(R.id.timePicker); //Obtain timepicker attributes from layout
                timepicker.setIs24HourView(true);    //setting timepicker to 24 hr clock view
               Button button = (Button) findViewById(R.id.button1); // button to display datepicker value
                Button button1 = (Button) findViewById(R.id.button2);  // button to display timepicker value



            ImageView iv_user_photo = (ImageView) findViewById(R.id.iv_user_photo);
            iv_user_photo.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {

                    Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);

                    startActivityForResult(intent, RESULT_LOAD_IMAGE);              

                }
            });


            Button btn_add = (Button) findViewById(R.id.btn_add);
            btn_add.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {

                    EditText et_name = (EditText) findViewById(R.id.et_name);
                    name = et_name.getText().toString();

                    EditText et_place = (EditText) findViewById(R.id.et_place);
                    place = et_place.getText().toString();

                    EditText et_date = (EditText) findViewById(R.id.et_date);
                    date = et_date.getText().toString();

                    EditText et_time = (EditText) findViewById(R.id.et_time);
                    time = et_time.getText().toString();

                    ImageView iv_photograph = (ImageView) findViewById(R.id.iv_user_photo);
                    photograph = picturePath;

                    Event event = new Event();
                    event.setName(name);
                    event.setPlace(place);
                    event.setDate(date);
                    event.setTime(time);
                    event.setPhotograph(photograph);

                    Boolean added = handler.addEventDetails(event);
                    if(added){
                        Intent intent = new Intent(NewEvent.this, MainEvent.class);
                        startActivity(intent);
                    }else{
                        Toast.makeText(getApplicationContext(), "Event data not added. Please try again", Toast.LENGTH_LONG).show();
                    }


                }
            });

            button.setOnClickListener(new View.OnClickListener() { 
                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
    // displaying datepicker value as pop up notification
                    Toast.makeText(getBaseContext(), "Date : "
                    + (datepicker.getMonth() + 1) +"/"+datepicker.getDayOfMonth()
                            +"/"+datepicker.getYear(), Toast.LENGTH_LONG).show();            }
            });
    // On clicking button start timepicker event
            button1.setOnClickListener(new View.OnClickListener() { 
            @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
    // displaying timepicker value as pop up notification
                Toast.makeText(getBaseContext(),"Time Selected : "+timepicker.getCurrentHour()+":"
                        +timepicker.getCurrentMinute(), Toast.LENGTH_SHORT).show();
    }
            });



            }


        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {

            super.onActivityResult(requestCode, resultCode, data);

            if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
                Uri imageUri = data.getData();
                String[] filePathColumn = { MediaStore.Images.Media.DATA };

                Cursor cursor = getContentResolver().query(imageUri,
                        filePathColumn, null, null, null);
                cursor.moveToFirst();

                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                picturePath = cursor.getString(columnIndex);
                cursor.close();

                ImageView imageView = (ImageView) findViewById(R.id.iv_user_photo);
                imageView.setImageBitmap(BitmapFactory.decodeFile(picturePath));

            }
        }

    }
Here is my xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" 
    android:padding="10dp">    

    <TextView
        android:id="@+id/tv_new_event_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add New Event"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:layout_alignParentTop="true" />


    <Button
        android:id="@+id/btn_add"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add Event"
        android:layout_alignParentBottom="true" />

    <ScrollView        
        android:layout_width="match_parent"
        android:layout_height="match_parent" 
        android:layout_below="@id/tv_new_event_title"
        android:layout_above="@id/btn_add">
        <LinearLayout 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
            <ImageView 
                android:id="@+id/iv_user_photo"
                android:src="@drawable/add_user_icon"
                android:layout_width="100dp"
                android:layout_height="100dp"/>

            <TextView               
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Event:" />

            <EditText
                android:id="@+id/et_name"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ems="10"
                android:inputType="text" >      
                <requestFocus />
            </EditText>


             <TextView              
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Place:" />

            <EditText
                android:id="@+id/et_place"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ems="10"
                android:inputType="text" >      
                <requestFocus />
            </EditText>

             <TextView              
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Date:" />

            <EditText
                android:id="@+id/et_date"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ems="10"
                android:inputType="date" />

            <Button
                android:id="@+id/button"
                style="?android:attr/buttonStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Button" />
            <requestFocus />

            <TextView               
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Time:" />

            <EditText
                android:id="@+id/et_time"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ems="10"
                android:inputType="time" />

            <Button
                android:id="@+id/button1"
                style="?android:attr/buttonStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Button1" />


                <requestFocus />

        </LinearLayout>
    </ScrollView>

</RelativeLayout>
Here is my LogCat:
08-25 11:57:44.144: E/AndroidRuntime(554): FATAL EXCEPTION: main
08-25 11:57:44.144: E/AndroidRuntime(554): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.chris.hockeymanagemtapp/com.chris.hockeymanagemtapp.NewEvent}: java.lang.NullPointerException
08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.os.Handler.dispatchMessage(Handler.java:99)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.os.Looper.loop(Looper.java:123)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread.main(ActivityThread.java:3683)

08-25 11:57:44.144: E/AndroidRuntime(554):  at java.lang.reflect.Method.invokeNative(Native Method)

08-25 11:57:44.144: E/AndroidRuntime(554):  at java.lang.reflect.Method.invoke(Method.java:507)

08-25 11:57:44.144: E/AndroidRuntime(554):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)

08-25 11:57:44.144: E/AndroidRuntime(554):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)

08-25 11:57:44.144: E/AndroidRuntime(554):  at dalvik.system.NativeStart.main(Native Method)

08-25 11:57:44.144: E/AndroidRuntime(554): Caused by: java.lang.NullPointerException

08-25 11:57:44.144: E/AndroidRuntime(554):  at com.chris.hockeymanagemtapp.NewEvent.onCreate(NewEvent.java:60)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)

08-25 11:57:44.144: E/AndroidRuntime(554):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-25 11:57:44.144: E/AndroidRuntime(554):  ... 11 more

解决方案
Inside your OnCreate method do this:

DatePicker dt = (DatePicker) findViewById(R.id.yourDatePickerId);

As Anuj said, you need to initialize it before using it

                        
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