if( str_driversig != null && str_driversig.length()>0 && !str_driversig.contentEquals(null))
{
}else
{
Toast.makeText(context,"Please give Driver Signature",Toast.LENGTH_SHORT).show();
}
这里str_driversig变量vaue像..... / .... / signature / 81046.png
始终显示以下错误:
UncaughtException: java.lang.NullPointerException: Null reference used for synchronization (monitor-enter)
at java.lang.String.contentEquals(String.java:958)
at com.main.exam.ui.driverchecklist.AddDriverChecklist.save_driver_checklist(AddDriverChecklist.java:1318)
at com.main.exam.ui.driverchecklist.AddDriverChecklist.onClick(AddDriverChecklist.java:367)
at android.view.View.performClick(View.java:6261)
at android.widget.TextView.performClick(TextView.java:11185)
at android.view.View$PerformClick.run(View.java:23752)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408)
答案 0 :(得分:0)
您正在尝试检查数据字符串是否等于null,而不是!str_driversig.contentEquals("null")
而不是!str_driversig.contentEquals(null)
。在您的情况下null
导致NPE。