Java 日期及日期;时间应用程序没有';开始
我制作了一个应用程序,你可以点击一个按钮,它应该在Java 日期及日期;时间应用程序没有';开始,java,android,datetime,Java,Android,Datetime,我制作了一个应用程序,你可以点击一个按钮,它应该在EditText字段中显示当前日期和时间。问题是,应用程序在启动时崩溃。有人能帮我吗 package de.example.datumzeit; 公共类MainActivity扩展活动实现OnClickListener{ EditText etdate, ettime; String mytime, mydate; @Override public void onCreate(Bundle savedInstanceState) { s
EditText
字段中显示当前日期和时间。问题是,应用程序在启动时崩溃。有人能帮我吗
package de.example.datumzeit;
公共类MainActivity扩展活动实现OnClickListener{
EditText etdate, ettime;
String mytime, mydate;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button datum_einfügen = (Button) findViewById(R.id.btngo);
etdate = (EditText) findViewById(R.id.etdate);
ettime = (EditText) findViewById(R.id.ettime);
datum_einfügen.setOnClickListener(this);
// time
mytime = java.text.DateFormat.getTimeInstance().format(Calendar.getInstance().getTime());
// date
mydate =java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
}
@Override
public void onClick(View view){
etdate.setText(mydate);
ettime.setText(mytime);
}
}
LogCat:
03-25 10:30:38.298: E/AndroidRuntime(25676): FATAL EXCEPTION: main
03-25 10:30:38.298: E/AndroidRuntime(25676): Process: de.example.datum_zeit, PID: 25676
03-25 10:30:38.298: E/AndroidRuntime(25676): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{de.example.datum_zeit/de.example.datum_zeit.MainActivity}: java.lang.NullPointerException
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.access$900(ActivityThread.java:161)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.os.Looper.loop(Looper.java:157)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.main(ActivityThread.java:5356)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 10:30:38.298: E/AndroidRuntime(25676): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
03-25 10:30:38.298: E/AndroidRuntime(25676): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
03-25 10:30:38.298: E/AndroidRuntime(25676): at dalvik.system.NativeStart.main(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): Caused by: java.lang.NullPointerException
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.Activity.findViewById(Activity.java:1965)
03-25 10:30:38.298: E/AndroidRuntime(25676): at de.example.datum_zeit.MainActivity.<init>(MainActivity.java:26)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.Class.newInstanceImpl(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.Class.newInstance(Class.java:1208)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2222)
03-25 10:30:38.298: E/AndroidRuntime(25676): ... 11 more
03-25 10:30:38.298:E/AndroidRuntime(25676):致命异常:main
03-25 10:30:38.298:E/AndroidRuntime(25676):进程:de.example.datum_zeit,PID:25676
03-25 10:30:38.298:E/AndroidRuntime(25676):java.lang.RuntimeException:无法实例化活动组件信息{de.example.datum_zeit/de.example.datum_zeit.MainActivity}:java.lang.NullPointerException
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.ActivityThread.access$900(ActivityThread.java:161)
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.os.Handler.dispatchMessage(Handler.java:102)上
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.os.Looper.loop(Looper.java:157)上
03-25 10:30:38.298:E/AndroidRuntime(25676):位于android.app.ActivityThread.main(ActivityThread.java:5356)
03-25 10:30:38.298:E/AndroidRuntime(25676):位于java.lang.reflect.Method.Invokenactive(本机方法)
03-25 10:30:38.298:E/AndroidRuntime(25676):位于java.lang.reflect.Method.invoke(Method.java:515)
03-25 10:30:38.298:E/AndroidRuntime(25676):在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
03-25 10:30:38.298:E/AndroidRuntime(25676):位于com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
03-25 10:30:38.298:E/AndroidRuntime(25676):在dalvik.system.NativeStart.main(本机方法)
03-25 10:30:38.298:E/AndroidRuntime(25676):由以下原因引起:java.lang.NullPointerException
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.Activity.findViewById(Activity.java:1965)
03-25 10:30:38.298:E/AndroidRuntime(25676):在de.example.datum_zeit.MainActivity.(MainActivity.java:26)
03-25 10:30:38.298:E/AndroidRuntime(25676):位于java.lang.Class.newInstanceImpl(本机方法)
03-25 10:30:38.298:E/AndroidRuntime(25676):位于java.lang.Class.newInstance(Class.java:1208)
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.Instrumentation.newActivity(Instrumentation.java:1079)上
03-25 10:30:38.298:E/AndroidRuntime(25676):在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2222)
03-25 10:30:38.298:E/AndroidRuntime(25676):。。。还有11个
这个
EditText etdate = (EditText) findViewById(R.id.etdate);
EditText ettime = (EditText) findViewById(R.id.ettime);
在任何方法之外
将布局内容设置为“活动”后,需要进行初始化
EditText etdate;
EditText ettime;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
etdate = (EditText) findViewById(R.id.etdate);
ettime = (EditText) findViewById(R.id.ettime);
这应该适合您:
package de.example.datumzeit;
public class MainActivity extends Activity implements OnClickListener {
EditText etdate, ettime;
String mytime, mydate;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button datum_einfügen = (Button) findViewById(R.id.btngo);
datum_einfügen.setOnClickListener(this);
etdate = (EditText) findViewById(R.id.etdate);
ettime = (EditText) findViewById(R.id.ettime);
// time
mytime = java.text.DateFormat.getTimeInstance().format(Calendar.getInstance().getTime());
// date
mydate =java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
}
@Override
public void onClick(View view){
etdate.setText(mydate);
ettime.setText(mytime);
}
}
etdate
和ettime
的初始化应该采用类似于onCreate
的方法。首先,我建议您浏览数字格式化程序的文档
愿下面的一个能帮助你
public static final SimpleDateFormat MMM_DD_YYYY_HH_MM_12_HOURS = new SimpleDateFormat("MMM dd, yyyy hh:mm a");
public static final SimpleDateFormat DD_MM_YYYY_HH_MM_12_HOURS = new SimpleDateFormat("dd/MM/yyyy hh:mm a");
为此创建一个实例。您应该移动
EditText etdate = (EditText) findViewById(R.id.etdate);
EditText ettime = (EditText) findViewById(R.id.ettime);
在onCreate()方法中。还要使EditText变量为全局变量
EditText etdate ,ettime
在onCreate()方法中
更新:
03-25 10:30:38.298: E/AndroidRuntime(25676): FATAL EXCEPTION: main
03-25 10:30:38.298: E/AndroidRuntime(25676): Process: de.example.datum_zeit, PID: 25676
03-25 10:30:38.298: E/AndroidRuntime(25676): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{de.example.datum_zeit/de.example.datum_zeit.MainActivity}: java.lang.NullPointerException
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.access$900(ActivityThread.java:161)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.os.Looper.loop(Looper.java:157)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.main(ActivityThread.java:5356)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 10:30:38.298: E/AndroidRuntime(25676): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
03-25 10:30:38.298: E/AndroidRuntime(25676): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
03-25 10:30:38.298: E/AndroidRuntime(25676): at dalvik.system.NativeStart.main(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): Caused by: java.lang.NullPointerException
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.Activity.findViewById(Activity.java:1965)
03-25 10:30:38.298: E/AndroidRuntime(25676): at de.example.datum_zeit.MainActivity.<init>(MainActivity.java:26)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.Class.newInstanceImpl(Native Method)
03-25 10:30:38.298: E/AndroidRuntime(25676): at java.lang.Class.newInstance(Class.java:1208)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
03-25 10:30:38.298: E/AndroidRuntime(25676): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2222)
03-25 10:30:38.298: E/AndroidRuntime(25676): ... 11 more
把这个拿走
mytime = java.text.DateFormat.getTimeInstance().format(Calendar.getInstance().getTime());
// date
mydate =java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
来自onCreate()方法。您也需要将堆栈跟踪带到此处,否则我们无法帮助您将所有UI初始化代码移动到
onCreate()方法中。
我这样做了,但仍然不起作用。Logcat仍然是samethanks,谢谢你的帮助,但它不起作用。启动时仍会闪烁。现在再次检查答案。它工作正常!这是活动中的一个错误。谢谢!
@Override
public void onClick(View view){
if(view.getId()==R.id.btngo)
mytime = java.text.DateFormat.getTimeInstance().format(Calendar.getInstance().getTime());
// date
mydate =java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());
etdate.setText(mydate);
ettime.setText(mytime);
}
}
mytime = java.text.DateFormat.getTimeInstance().format(Calendar.getInstance().getTime());
// date
mydate =java.text.DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime());