java - Android:SimpleDateFormat 给出 API 错误

Question

我在 Android 上使用 SimpleDateFormat。我用 API 24 测试了它，它有效。当我尝试在 API 16 上使用它时，它崩溃了。 我在互联网上搜索过，发现有人说这可能是因为错误的导入语句( import android.icu.text.SimpleDateFormat )，但我已经在使用 import java.text.SimpleDateFormat 了。 .

我的代码(在 onclickButton 上崩溃):

import java.text.SimpleDateFormat;

public class MainActivity extends AppCompatActivity {

SimpleDateFormat sdf;
String date;

    public void onclickButton (View view) {

        Calendar c = Calendar.getInstance();
        sdf = new SimpleDateFormat("dd MM YYYY");
        sdf.setTimeZone(TimeZone.getTimeZone("Europe/Berlin"));
        date = sdf.format(c.getTime());
    }
...
}

堆栈跟踪:

W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xb111d228)
E/AndroidRuntime: FATAL EXCEPTION: main
              java.lang.IllegalStateException: Could not execute method for android:onClick
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                  at android.view.View.performClick(View.java:4084)
                  at android.view.View$PerformClick.run(View.java:16966)
                  at android.os.Handler.handleCallback(Handler.java:615)
                  at android.os.Handler.dispatchMessage(Handler.java:92)
                  at android.os.Looper.loop(Looper.java:137)
                  at android.app.ActivityThread.main(ActivityThread.java:4745)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:511)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                  at dalvik.system.NativeStart.main(Native Method)
               Caused by: java.lang.reflect.InvocationTargetException
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:511)
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                  at android.view.View.performClick(View.java:4084) 
                  at android.view.View$PerformClick.run(View.java:16966) 
                  at android.os.Handler.handleCallback(Handler.java:615) 
                  at android.os.Handler.dispatchMessage(Handler.java:92) 
                  at android.os.Looper.loop(Looper.java:137) 
                  at android.app.ActivityThread.main(ActivityThread.java:4745) 
                  at java.lang.reflect.Method.invokeNative(Native Method) 
                  at java.lang.reflect.Method.invoke(Method.java:511) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
                  at dalvik.system.NativeStart.main(Native Method) 
               Caused by: java.lang.IllegalArgumentException: Unknown pattern character 'Y'
                  at java.text.SimpleDateFormat.validateFormat(SimpleDateFormat.java:268)
                  at java.text.SimpleDateFormat.validatePattern(SimpleDateFormat.java:323)
                  at java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:369)
                  at java.text.SimpleDateFormat.<init>(SimpleDateFormat.java:253)
                  at com.jonathan_tilly.adventskalender.MainActivity.onclickButton(MainActivity.java:34)
                  at java.lang.reflect.Method.invokeNative(Native Method) 
                  at java.lang.reflect.Method.invoke(Method.java:511) 
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                  at android.view.View.performClick(View.java:4084) 
                  at android.view.View$PerformClick.run(View.java:16966) 
                  at android.os.Handler.handleCallback(Handler.java:615) 
                  at android.os.Handler.dispatchMessage(Handler.java:92) 
                  at android.os.Looper.loop(Looper.java:137) 
                  at android.app.ActivityThread.main(ActivityThread.java:4745) 
                  at java.lang.reflect.Method.invokeNative(Native Method) 
                  at java.lang.reflect.Method.invoke(Method.java:511) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
                  at dalvik.system.NativeStart.main(Native Method) 

感谢任何帮助!

Answer 1

可能这是因为您在类之外声明变量。尝试:

import java.text.SimpleDateFormat;

public class MainActivity extends AppCompatActivity {

    SimpleDateFormat sdf;
    String date;

    public void onclickButton (View view) {

        Calendar c = Calendar.getInstance();
        sdf = new SimpleDateFormat("dd MM yyyy");
        sdf.setTimeZone(TimeZone.getTimeZone("Europe/Berlin"));
        date = sdf.format(c.getTime());
    }
...

}